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systemd/src/shared/creds-util.c
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Lennart Poettering 5cead3f269 credentials: add policy that can allow key=null creds from the ESP (#42555) 
This PR only sets the default to "relaxed" - I can change the default
to "tofu" if desired. But for that we will also need to update the NEWS
file to ensure everyone is aware of this new default.

---

This PR adds a new `systemd.credentials-boot=` kernel
commandline that allows to control if credentials with
a `null` key are accepted.

The possible options are:
* strict: always insist on tpm encryption
* tofu: allow null encryption in firstboot mode and when no tpm is
available
* relaxed: allow null encryption when sb is off, or no tpm is available
* off: allow null encryption always

The default is `relaxed` which is exactly the behavior we had before.

This replaces the initial idea of using plaintext credentials
at firstboot (thanks to Lennart for this nicer and simpler design).

---

With that we can drop `- firstboot: optionally accept credentials at
firstboot without authentication` from TODO.md
2026-07-10 14:43:12 +02:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <pwd.h>
#include <sys/file.h>
#include <unistd.h>
#include "efivars.h"
#include "time-util.h"
#include "sd-id128.h"
#include "sd-json.h"
#include "sd-varlink.h"
#include "alloc-util.h"
#include "blockdev-util.h"
#include "chattr-util.h"
#include "copy.h"
#include "creds-util.h"
#include "crypto-util.h"
#include "efi-api.h"
#include "env-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "find-esp.h"
#include "format-util.h"
#include "fs-util.h"
#include "initrd-util.h"
#include "io-util.h"
#include "json-util.h"
#include "log.h"
#include "memory-util.h"
#include "mkdir.h"
#include "parse-util.h"
#include "path-util.h"
#include "proc-cmdline.h"
#include "random-util.h"
#include "recurse-dir.h"
#include "sparse-endian.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "tmpfile-util.h"
#include "tpm2-pcr.h"
#include "tpm2-util.h"
#include "user-util.h"
#define PUBLIC_KEY_MAX (UINT32_C(1024) * UINT32_C(1024))
bool credential_name_valid(const char *s) {
/* We want that credential names are both valid in filenames (since that's our primary way to pass
* them around) and as fdnames (which is how we might want to pass them around eventually) */
return filename_is_valid(s) && fdname_is_valid(s);
}
bool credential_glob_valid(const char *s) {
const char *e, *a;
size_t n;
/* Checks if a credential glob expression is valid. Note that this is more restrictive than
* fnmatch()! We only allow trailing asterisk matches for now (simply because we want some freedom
* with automatically extending the pattern in a systematic way to cover for unit instances getting
* per-instance credentials or similar. Moreover, credential globbing expressions are also more
* restrictive than credential names: we don't allow *, ?, [, ] in them (except for the asterisk
* match at the end of the string), simply to not allow ambiguity. After all, we want the flexibility
* to one day add full globbing should the need arise. */
if (isempty(s))
return false;
/* Find first glob (or NUL byte) */
n = strcspn(s, "*?[]");
e = s + n;
/* For now, only allow asterisk wildcards, and only at the end of the string. If it's anything else, refuse. */
if (isempty(e))
return credential_name_valid(s);
if (!streq(e, "*")) /* only allow trailing "*", no other globs */
return false;
if (n == 0) /* Explicitly allow the complete wildcard. */
return true;
if (n > NAME_MAX + strlen(e)) /* before we make a copy on the stack, let's check this is not overly large */
return false;
/* Make a copy of the string without the '*' suffix */
a = strndupa_safe(s, n);
return credential_name_valid(a);
}
static int get_credentials_dir_internal(const char *envvar, const char **ret) {
const char *e;
assert(ret);
e = secure_getenv(envvar);
if (!e)
return -ENXIO;
if (!path_is_absolute(e) || !path_is_normalized(e))
return -EINVAL;
*ret = e;
return 0;
}
int get_credentials_dir(const char **ret) {
return get_credentials_dir_internal("CREDENTIALS_DIRECTORY", ret);
}
int get_encrypted_credentials_dir(const char **ret) {
return get_credentials_dir_internal("ENCRYPTED_CREDENTIALS_DIRECTORY", ret);
}
int open_credentials_dir(void) {
const char *d;
int r;
r = get_credentials_dir(&d);
if (r < 0)
return r;
return RET_NERRNO(open(d, O_CLOEXEC|O_DIRECTORY));
}
int get_system_credentials_dir(const char **ret) {
int r;
assert(ret);
/* Note that for system credentials the environment variable we honour is just for debugging purpose
* (unlike for the per-service credential path env var where it's key part of the protocol). */
r = get_credentials_dir_internal("SYSTEMD_SYSTEM_CREDENTIALS_DIRECTORY", ret);
if (r >= 0 || r != -ENXIO)
return r;
*ret = SYSTEM_CREDENTIALS_DIRECTORY;
return 0;
}
int get_encrypted_system_credentials_dir(const char **ret) {
int r;
assert(ret);
r = get_credentials_dir_internal("SYSTEMD_ENCRYPTED_SYSTEM_CREDENTIALS_DIRECTORY", ret);
if (r >= 0 || r != -ENXIO)
return r;
*ret = ENCRYPTED_SYSTEM_CREDENTIALS_DIRECTORY;
return 0;
}
int read_credential(const char *name, void **ret, size_t *ret_size) {
_cleanup_free_ char *fn = NULL;
const char *d;
int r;
assert(ret);
if (!credential_name_valid(name))
return -EINVAL;
r = get_credentials_dir(&d);
if (r < 0)
return r;
fn = path_join(d, name);
if (!fn)
return -ENOMEM;
return read_full_file_full(
AT_FDCWD, fn,
UINT64_MAX, SIZE_MAX,
READ_FULL_FILE_SECURE,
NULL,
(char**) ret, ret_size);
}
int read_credential_with_decryption(const char *name, void **ret, size_t *ret_size) {
_cleanup_(iovec_done_erase) struct iovec ret_iovec = {};
_cleanup_(erase_and_freep) void *data = NULL;
_cleanup_free_ char *fn = NULL;
size_t sz = 0;
const char *d;
int r;
/* Just like read_credential() but will also look for encrypted credentials. Note that services only
* receive decrypted credentials, hence use read_credential() for those. This helper here is for
* generators, i.e. code that runs outside of service context, and thus has no decrypted credentials
* yet.
*
* Note that read_credential_harder_and_warn() logs on its own, while read_credential() does not!
* (It's a lot more complex and error prone given its TPM2 connectivity, and is generally called from
* generators only where logging is OK).
*
* Error handling is also a bit different: if we can't find a credential we'll return 0 and NULL
* pointers/zero size, rather than -ENXIO/-ENOENT. */
if (!credential_name_valid(name))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid credential name: %s", name);
r = read_credential(name, ret, ret_size);
if (r >= 0)
return 1; /* found */
if (!IN_SET(r, -ENXIO, -ENOENT))
return log_error_errno(r, "Failed to read unencrypted credential '%s': %m", name);
r = get_encrypted_credentials_dir(&d);
if (r == -ENXIO)
goto not_found;
if (r < 0)
return log_error_errno(r, "Failed to determine encrypted credentials directory: %m");
fn = path_join(d, name);
if (!fn)
return log_oom();
r = read_full_file_full(
AT_FDCWD, fn,
UINT64_MAX, SIZE_MAX,
READ_FULL_FILE_SECURE,
NULL,
(char**) &data, &sz);
if (r == -ENOENT)
goto not_found;
if (r < 0)
return log_error_errno(r, "Failed to read encrypted credential data: %m");
if (geteuid() != 0)
r = ipc_decrypt_credential(
name,
now(CLOCK_REALTIME),
getuid(),
&IOVEC_MAKE(data, sz),
CREDENTIAL_ANY_SCOPE,
&ret_iovec);
else
r = decrypt_credential_and_warn(
name,
now(CLOCK_REALTIME),
/* tpm2_device= */ NULL,
/* tpm2_signature_path= */ NULL,
getuid(),
&IOVEC_MAKE(data, sz),
CREDENTIAL_ANY_SCOPE,
&ret_iovec);
if (r < 0)
return r;
if (ret)
*ret = TAKE_PTR(ret_iovec.iov_base);
if (ret_size)
*ret_size = ret_iovec.iov_len;
return 1; /* found */
not_found:
if (ret)
*ret = NULL;
if (ret_size)
*ret_size = 0;
return 0; /* not found */
}
int read_credential_strings_many_internal(
const char *first_name, char **first_value,
...) {
_cleanup_free_ void *b = NULL;
bool all = true;
int r, ret = 0;
assert(first_value);
/* Reads a bunch of credentials into the specified buffers. If the specified buffers are already
* non-NULL frees them if a credential is found. Only supports string-based credentials
* (i.e. refuses embedded NUL bytes).
*
* 0 is returned when some or all credentials are missing.
*/
if (!first_name)
return 0;
r = read_credential(first_name, &b, NULL);
if (r == -ENXIO) /* No creds passed at all? Bail immediately. */
return 0;
if (r == -ENOENT)
all = false;
else if (r < 0)
RET_GATHER(ret, r);
else
free_and_replace(*first_value, b);
va_list ap;
va_start(ap, first_value);
for (;;) {
_cleanup_free_ void *bb = NULL;
const char *name;
char **value;
name = va_arg(ap, const char *);
if (!name)
break;
value = ASSERT_PTR(va_arg(ap, char **));
r = read_credential(name, &bb, NULL);
if (r == -ENOENT)
all = false;
else if (r < 0)
RET_GATHER(ret, r);
else
free_and_replace(*value, bb);
}
va_end(ap);
return ret < 0 ? ret : all;
}
int read_credential_bool(const char *name) {
_cleanup_free_ void *data = NULL;
int r;
r = read_credential(name, &data, NULL);
if (r < 0)
return IN_SET(r, -ENXIO, -ENOENT) ? 0 : r;
return parse_boolean(data);
}
int get_credential_user_password(const char *username, char **ret_password, bool *ret_is_hashed) {
_cleanup_(erase_and_freep) char *creds_password = NULL;
_cleanup_free_ char *cn = NULL;
int r;
assert(ret_password);
assert(ret_is_hashed);
/* Try to pick up the password for this account via the credentials logic */
cn = strjoin("passwd.hashed-password.", username);
if (!cn)
return -ENOMEM;
r = read_credential(cn, (void**) &creds_password, NULL);
if (r == -ENOENT) {
free(cn);
cn = strjoin("passwd.plaintext-password.", username);
if (!cn)
return -ENOMEM;
r = read_credential(cn, (void**) &creds_password, NULL);
if (r < 0)
log_debug_errno(r, "Couldn't read credential '%s', ignoring: %m", cn);
else
*ret_is_hashed = false;
} else if (r < 0)
log_debug_errno(r, "Couldn't read credential '%s', ignoring: %m", cn);
else
*ret_is_hashed = true;
*ret_password = TAKE_PTR(creds_password);
return r;
}
static const char* const credential_boot_policy_table[_CRED_BOOT_POLICY_MAX] = {
[CRED_BOOT_STRICT] = "strict",
[CRED_BOOT_TOFU] = "tofu",
[CRED_BOOT_RELAXED] = "relaxed",
[CRED_BOOT_OFF] = "off",
};
DEFINE_STRING_TABLE_LOOKUP(credential_boot_policy, CredentialBootPolicy);
bool credential_boot_policy_accepts_null(CredentialBootPolicy policy, bool first_boot, bool have_tpm2, bool secure_boot) {
/* Decides whether a null-key encrypted credential (which offers neither confidentiality nor
* authenticity) may be accepted, given the configured policy and the current system state. */
switch (policy) {
case CRED_BOOT_STRICT:
return false;
case CRED_BOOT_TOFU:
return first_boot || !have_tpm2;
case CRED_BOOT_RELAXED:
return !secure_boot || !have_tpm2;
case CRED_BOOT_OFF:
return true;
default:
assert_not_reached();
}
}
#if HAVE_OPENSSL
#define CREDENTIAL_HOST_SECRET_SIZE 4096
static const sd_id128_t credential_app_id =
SD_ID128_MAKE(d3,ac,ec,ba,0d,ad,4c,df,b8,c9,38,15,28,93,6c,58);
struct credential_host_secret_format {
/* The hashed machine ID of the machine this belongs to. Why? We want to ensure that each machine
* gets its own secret, even if people forget to flush out this secret file. Hence we bind it to the
* machine ID, for which there's hopefully a better chance it will be flushed out. We use a hashed
* machine ID instead of the literal one, because it's trivial to, and it might be a good idea not
* being able to directly associate a secret key file with a host. */
sd_id128_t machine_id;
/* The actual secret key */
uint8_t data[CREDENTIAL_HOST_SECRET_SIZE];
} _packed_;
static void warn_not_encrypted(int fd, CredentialSecretFlags flags, const char *dirname, const char *filename) {
int r;
assert(fd >= 0);
assert(dirname);
assert(filename);
if (!FLAGS_SET(flags, CREDENTIAL_SECRET_WARN_NOT_ENCRYPTED))
return;
r = fd_is_encrypted(fd);
if (r < 0)
log_debug_errno(r, "Failed to determine if credential secret file '%s/%s' is encrypted.",
dirname, filename);
else if (r == 0)
log_warning("Credential secret file '%s/%s' is not located on encrypted media, using anyway.",
dirname, filename);
}
static int make_credential_host_secret(
int dfd,
const sd_id128_t machine_id,
CredentialSecretFlags flags,
const char *dirname,
const char *fn,
struct iovec *ret) {
_cleanup_free_ char *t = NULL;
_cleanup_close_ int fd = -EBADF;
int r;
assert(dfd >= 0);
assert(fn);
fd = open_tmpfile_linkable_at(dfd, fn, O_CLOEXEC|O_WRONLY, &t);
if (fd < 0)
return log_debug_errno(fd, "Failed to create temporary file for credential host secret: %m");
CLEANUP_TMPFILE_AT(dfd, t);
r = chattr_secret(fd, 0);
if (r < 0)
log_debug_errno(r, "Failed to set file attributes for secrets file, ignoring: %m");
struct credential_host_secret_format buf = {
.machine_id = machine_id,
};
CLEANUP_ERASE(buf);
r = crypto_random_bytes(buf.data, sizeof(buf.data));
if (r < 0)
return r;
r = loop_write(fd, &buf, sizeof(buf));
if (r < 0)
return r;
if (fchmod(fd, 0400) < 0)
return -errno;
warn_not_encrypted(fd, flags, dirname, fn);
r = link_tmpfile_at(fd, dfd, t, fn, LINK_TMPFILE_SYNC);
if (r < 0)
return log_debug_errno(r, "Failed to link host key into place: %m");
t = mfree(t); /* disarm CLEANUP_TMPFILE_AT() */
if (ret) {
void *copy;
copy = memdup(buf.data, sizeof(buf.data));
if (!copy)
return -ENOMEM;
*ret = IOVEC_MAKE(copy, sizeof(buf.data));
}
return 0;
}
int get_credential_host_secret(CredentialSecretFlags flags, struct iovec *ret) {
_cleanup_free_ char *_dirname = NULL, *_filename = NULL;
_cleanup_close_ int dfd = -EBADF;
sd_id128_t machine_id;
const char *dirname, *filename;
int r;
r = sd_id128_get_machine_app_specific(credential_app_id, &machine_id);
if (r < 0)
return r;
const char *e = secure_getenv("SYSTEMD_CREDENTIAL_SECRET");
if (e) {
if (!path_is_normalized(e))
return -EINVAL;
if (!path_is_absolute(e))
return -EINVAL;
r = path_split_prefix_filename(e, &_dirname, &_filename);
if (r < 0)
return r;
if (r == O_DIRECTORY)
return -EINVAL;
/* We validate that the path is absolute above, hence dirname must be extractable. */
dirname = _dirname;
filename = _filename;
} else {
dirname = "/var/lib/systemd";
filename = "credential.secret";
}
assert(dirname);
assert(filename);
(void) mkdir_parents(dirname, 0755);
dfd = open_mkdir(dirname, O_CLOEXEC, 0755);
if (dfd < 0)
return log_debug_errno(dfd, "Failed to create or open directory '%s': %m", dirname);
if (FLAGS_SET(flags, CREDENTIAL_SECRET_FAIL_ON_TEMPORARY_FS)) {
r = fd_is_temporary_fs(dfd);
if (r < 0)
return log_debug_errno(r, "Failed to check directory '%s': %m", dirname);
if (r > 0)
return log_debug_errno(SYNTHETIC_ERRNO(ENOMEDIUM),
"Directory '%s' is on a temporary file system, refusing.", dirname);
}
for (unsigned attempt = 0;; attempt++) {
_cleanup_(erase_and_freep) struct credential_host_secret_format *f = NULL;
_cleanup_close_ int fd = -EBADF;
size_t l = 0;
ssize_t n = 0;
struct stat st;
if (attempt >= 3) /* Somebody is playing games with us */
return log_debug_errno(SYNTHETIC_ERRNO(EIO),
"All attempts to create secret store in %s failed.", dirname);
fd = openat(dfd, filename, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW);
if (fd < 0) {
if (errno != ENOENT || !FLAGS_SET(flags, CREDENTIAL_SECRET_GENERATE))
return log_debug_errno(errno,
"Failed to open %s/%s: %m", dirname, filename);
r = make_credential_host_secret(dfd, machine_id, flags, dirname, filename, ret);
if (r == -EEXIST) {
log_debug_errno(r, "Credential secret %s/%s appeared while we were creating it, rereading.",
dirname, filename);
continue;
}
if (r < 0)
return log_debug_errno(r, "Failed to create credential secret %s/%s: %m",
dirname, filename);
return 0;
}
if (fstat(fd, &st) < 0)
return log_debug_errno(errno, "Failed to stat %s/%s: %m", dirname, filename);
r = stat_verify_regular(&st);
if (r < 0)
return log_debug_errno(r, "%s/%s is not a regular file: %m", dirname, filename);
if (st.st_nlink == 0) /* Deleted by now, try again */
continue;
if (st.st_nlink > 1)
/* Our deletion check won't work if hardlinked somewhere else */
return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
"%s/%s has too many links, refusing.",
dirname, filename);
if ((st.st_mode & 07777) != 0400)
/* Don't use file if not 0400 access mode */
return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
"%s/%s has permissive access mode, refusing.",
dirname, filename);
l = st.st_size;
if (l < offsetof(struct credential_host_secret_format, data) + 1)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"%s/%s is too small, refusing.", dirname, filename);
if (l > 16*1024*1024)
return log_debug_errno(SYNTHETIC_ERRNO(E2BIG),
"%s/%s is too big, refusing.", dirname, filename);
f = malloc(l+1);
if (!f)
return log_oom_debug();
n = read(fd, f, l+1);
if (n < 0)
return log_debug_errno(errno,
"Failed to read %s/%s: %m", dirname, filename);
if ((size_t) n != l) /* What? The size changed? */
return log_debug_errno(SYNTHETIC_ERRNO(EIO),
"Failed to read %s/%s.", dirname, filename);
if (sd_id128_equal(machine_id, f->machine_id)) {
size_t sz;
warn_not_encrypted(fd, flags, dirname, filename);
sz = l - offsetof(struct credential_host_secret_format, data);
assert(sz > 0);
if (ret) {
void *copy;
assert(sz <= sizeof(f->data)); /* Ensure we don't read past f->data bounds */
copy = memdup(f->data, sz);
if (!copy)
return log_oom_debug();
*ret = IOVEC_MAKE(copy, sz);
}
return 0;
}
/* Hmm, this secret is from somewhere else. Let's delete the file. Let's first acquire a lock
* to ensure we are the only ones accessing the file while we delete it. */
log_notice("'%s/%s' comes from a different machine ID, deleting.", dirname, filename);
if (flock(fd, LOCK_EX) < 0)
return log_debug_errno(errno,
"Failed to flock %s/%s: %m", dirname, filename);
/* Before we delete it check that the file is still linked into the file system */
if (fstat(fd, &st) < 0)
return log_debug_errno(errno, "Failed to stat %s/%s: %m", dirname, filename);
if (st.st_nlink == 0) /* Already deleted by now? */
continue;
if (st.st_nlink != 1) /* Safety check, someone is playing games with us */
return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
"%s/%s unexpectedly has too many links.",
dirname, filename);
if (unlinkat(dfd, filename, 0) < 0)
return log_debug_errno(errno, "Failed to unlink %s/%s: %m", dirname, filename);
/* And now try again */
}
}
/* Construction is like this:
*
* A symmetric encryption key is derived from:
*
* 1. Either the "host" key (a key stored in /var/lib/credential.secret)
*
* 2. A key generated by letting the TPM2 calculate an HMAC hash of some nonce we pass to it, keyed
* by a key derived from its internal seed key.
*
* 3. The concatenation of the above.
*
* 4. Or a fixed "empty" key. This will not provide confidentiality or authenticity, of course, but is
* useful to encode credentials for the initrd on TPM-less systems, where we simply have no better
* concept to bind things to. Note that decryption of a key set up like this will be refused on
* systems that have a TPM and have SecureBoot enabled.
*
* The above is hashed with SHA256 which is then used as encryption key for AES256-GCM. The encrypted
* credential is a short (unencrypted) header describing which of the three keys to use, the IV to use for
* AES256-GCM and some more meta information (sizes of certain objects) that is strictly speaking redundant,
* but kinda nice to have since we can have a more generic parser. If the TPM2 key is used this is followed
* by another (unencrypted) header, with information about the TPM2 policy used (specifically: the PCR mask
* to bind against, and a hash of the resulting policy — the latter being redundant, but speeding up things a
* bit, since we can more quickly refuse PCR state), followed by a sealed/exported TPM2 HMAC key. This is
* then followed by the encrypted data, which begins with a metadata header (which contains validity
* timestamps as well as the credential name), followed by the actual credential payload. The file ends in
* the AES256-GCM tag. To make things simple, the AES256-GCM AAD covers the main and the TPM2 header in
* full. This means the whole file is either protected by AAD, or is ciphertext, or is the tag. No
* unprotected data is included.
*/
struct _packed_ encrypted_credential_header {
sd_id128_t id;
le32_t key_size;
le32_t block_size;
le32_t iv_size;
le32_t tag_size;
uint8_t iv[];
/* Followed by NUL bytes until next 8 byte boundary */
};
struct _packed_ tpm2_credential_header {
le64_t pcr_mask; /* Note that the spec for PC Clients only mandates 24 PCRs, and that's what systems
* generally have. But keep the door open for more. */
le16_t pcr_bank; /* For now, either TPM2_ALG_SHA256 or TPM2_ALG_SHA1 */
le16_t primary_alg; /* Primary key algorithm (either TPM2_ALG_RSA or TPM2_ALG_ECC for now) */
le32_t blob_size;
le32_t policy_hash_size;
uint8_t policy_hash_and_blob[];
/* Followed by NUL bytes until next 8 byte boundary */
};
struct _packed_ tpm2_public_key_credential_header {
le64_t pcr_mask; /* PCRs used for the public key PCR policy (usually just PCR 11, i.e. the unified kernel) */
le32_t size; /* Size of DER public key */
uint8_t data[]; /* DER public key */
/* Followed by NUL bytes until next 8 byte boundary */
};
struct _packed_ scoped_credential_header {
le64_t flags; /* SCOPE_HASH_DATA_BASE_FLAGS for now */
};
/* This header is encrypted */
struct _packed_ metadata_credential_header {
le64_t timestamp;
le64_t not_after;
le32_t name_size;
char name[];
/* Followed by NUL bytes until next 8 byte boundary */
};
struct _packed_ scoped_hash_data {
le64_t flags; /* copy of the scoped_credential_header.flags */
le32_t uid;
sd_id128_t machine_id;
char username[]; /* followed by the username */
/* Later on we might want to extend this: with a cgroup path to allow per-app secrets, and with the user's $HOME encryption key */
};
enum {
/* Flags for scoped_hash_data.flags and scoped_credential_header.flags */
SCOPE_HASH_DATA_HAS_UID = 1 << 0,
SCOPE_HASH_DATA_HAS_MACHINE = 1 << 1,
SCOPE_HASH_DATA_HAS_USERNAME = 1 << 2,
SCOPE_HASH_DATA_BASE_FLAGS = SCOPE_HASH_DATA_HAS_UID | SCOPE_HASH_DATA_HAS_USERNAME | SCOPE_HASH_DATA_HAS_MACHINE,
};
/* Some generic limit for parts of the encrypted credential for which we don't know the right size ahead of
* time, but where we are really sure it won't be larger than this. Should be larger than any possible IV,
* padding, tag size and so on. This is purely used for early filtering out of invalid sizes. */
#define CREDENTIAL_FIELD_SIZE_MAX (16U*1024U)
static int sha256_hash_host_and_tpm2_key(
const struct iovec *host_key,
const struct iovec *tpm2_key,
uint8_t ret[static SHA256_DIGEST_LENGTH]) {
_cleanup_(EVP_MD_CTX_freep) EVP_MD_CTX *md = NULL;
unsigned l;
int r;
assert(iovec_is_valid(host_key));
assert(iovec_is_valid(tpm2_key));
assert(ret);
/* Combines the host key and the TPM2 HMAC hash into a SHA256 hash value we'll use as symmetric encryption key. */
r = dlopen_libcrypto(LOG_DEBUG);
if (r < 0)
return r;
md = sym_EVP_MD_CTX_new();
if (!md)
return log_oom();
if (sym_EVP_DigestInit_ex(md, sym_EVP_sha256(), NULL) != 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initial SHA256 context.");
if (iovec_is_set(host_key) && sym_EVP_DigestUpdate(md, host_key->iov_base, host_key->iov_len) != 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to hash host key.");
if (iovec_is_set(tpm2_key) && sym_EVP_DigestUpdate(md, tpm2_key->iov_base, tpm2_key->iov_len) != 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to hash TPM2 key.");
assert(sym_EVP_MD_CTX_get_size(md) == SHA256_DIGEST_LENGTH);
if (sym_EVP_DigestFinal_ex(md, ret, &l) != 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to finalize SHA256 hash.");
assert(l == SHA256_DIGEST_LENGTH);
return 0;
}
static int mangle_uid_into_key(
uid_t uid,
uint8_t md[static SHA256_DIGEST_LENGTH]) {
_cleanup_free_ struct passwd *pw = NULL;
sd_id128_t mid;
int r;
assert(uid_is_valid(uid));
assert(md);
/* If we shall encrypt for a specific user, we HMAC() a structure with the user's credentials
* (specifically, UID, user name, machine ID) with the key we'd otherwise use for system credentials,
* and use the resulting hash as actual encryption key. */
r = getpwuid_malloc(uid, &pw);
if (r < 0)
return log_error_errno(r, "Failed to resolve UID "UID_FMT": %m", uid);
r = sd_id128_get_machine(&mid);
if (r < 0)
return log_error_errno(r, "Failed to read machine ID: %m");
size_t sz = offsetof(struct scoped_hash_data, username) + strlen(pw->pw_name) + 1;
_cleanup_free_ struct scoped_hash_data *d = malloc0(sz);
if (!d)
return log_oom();
d->flags = htole64(SCOPE_HASH_DATA_BASE_FLAGS);
d->uid = htole32(uid);
d->machine_id = mid;
strcpy(d->username, pw->pw_name);
_cleanup_(erase_and_freep) void *buf = NULL;
size_t buf_size = 0;
r = openssl_hmac_many(
"sha256",
md, SHA256_DIGEST_LENGTH,
&IOVEC_MAKE(d, sz), 1,
&buf, &buf_size);
if (r < 0)
return r;
assert(buf_size == SHA256_DIGEST_LENGTH);
memcpy(md, buf, buf_size);
return 0;
}
int encrypt_credential_and_warn(
sd_id128_t with_key,
const char *name,
usec_t timestamp,
usec_t not_after,
const char *tpm2_device,
uint32_t tpm2_hash_pcr_mask,
const char *tpm2_pubkey_path,
uint32_t tpm2_pubkey_pcr_mask,
uid_t uid,
const struct iovec *input,
CredentialFlags flags,
struct iovec *ret) {
_cleanup_(iovec_done) struct iovec tpm2_blob = {}, tpm2_policy_hash = {}, iv = {}, pubkey = {};
_cleanup_(iovec_done_erase) struct iovec tpm2_key = {}, output = {}, host_key = {};
_cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
_cleanup_free_ struct metadata_credential_header *m = NULL;
#if HAVE_TPM2
uint16_t tpm2_pcr_bank = 0, tpm2_primary_alg = 0;
#endif
struct encrypted_credential_header *h;
int ksz, bsz, ivsz, tsz, added, r;
uint8_t md[SHA256_DIGEST_LENGTH];
const EVP_CIPHER *cc;
sd_id128_t id;
size_t p, ml;
assert(iovec_is_valid(input));
assert(ret);
/* Only one of these two flags may be set at the same time */
assert(!FLAGS_SET(flags, CREDENTIAL_ALLOW_NULL) || !FLAGS_SET(flags, CREDENTIAL_REFUSE_NULL));
CLEANUP_ERASE(md);
if (!CRED_KEY_IS_VALID(with_key) && !CRED_KEY_IS_AUTO(with_key))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid key type: " SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(with_key));
if (name && !credential_name_valid(name))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid credential name: %s", name);
if (not_after != USEC_INFINITY && timestamp != USEC_INFINITY && not_after < timestamp)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Credential is invalidated before it is valid (" USEC_FMT " < " USEC_FMT ").", not_after, timestamp);
if (DEBUG_LOGGING) {
char buf[FORMAT_TIMESTAMP_MAX];
if (name)
log_debug("Including credential name '%s' in encrypted credential.", name);
if (timestamp != USEC_INFINITY)
log_debug("Including timestamp '%s' in encrypted credential.", format_timestamp(buf, sizeof(buf), timestamp));
if (not_after != USEC_INFINITY)
log_debug("Including not-after timestamp '%s' in encrypted credential.", format_timestamp(buf, sizeof(buf), not_after));
}
if (CRED_KEY_IS_SCOPED(with_key)) {
if (!uid_is_valid(uid))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Scoped credential key type "SD_ID128_FORMAT_STR" selected, but no UID specified.", SD_ID128_FORMAT_VAL(with_key));
} else
uid = UID_INVALID;
if (CRED_KEY_WANTS_HOST(with_key) || CRED_KEY_REQUIRES_HOST(with_key)) {
r = get_credential_host_secret(
CREDENTIAL_SECRET_GENERATE|
CREDENTIAL_SECRET_WARN_NOT_ENCRYPTED|
(CRED_KEY_WANTS_HOST(with_key) ? CREDENTIAL_SECRET_FAIL_ON_TEMPORARY_FS : 0),
&host_key);
if (r == -ENOMEDIUM && CRED_KEY_WANTS_HOST(with_key))
log_debug_errno(r, "Credential host secret location on temporary file system, not using.");
else if (r < 0)
return log_error_errno(r, "Failed to determine local credential host secret: %m");
}
if (tpm2_hash_pcr_mask == UINT32_MAX)
tpm2_hash_pcr_mask = 0;
if (tpm2_pubkey_pcr_mask == UINT32_MAX)
tpm2_pubkey_pcr_mask = UINT32_C(1) << TPM2_PCR_KERNEL_BOOT;
#if HAVE_TPM2
bool try_tpm2;
if (CRED_KEY_WANTS_TPM2(with_key)) {
/* If automatic mode is selected lets see if a TPM2 it is present. If we are running in a
* container tpm2_support will detect this, and will return a different flag combination of
* TPM2_SUPPORT_FULL, effectively skipping the use of TPM2 when inside one. */
try_tpm2 = tpm2_is_mostly_supported();
if (!try_tpm2)
log_debug("System lacks TPM2 support or running in a container, not attempting to use TPM2.");
} else
try_tpm2 = CRED_KEY_REQUIRES_TPM2(with_key);
if (try_tpm2) {
/* If the firmware does not support TPMs, then UKI measurements are not going to work, hence
* PCR 11 public key stuff cannot work. Because of that, if PK is only wanted (but not
* required) we won't try it. */
if ((CRED_KEY_WANTS_TPM2_PK(with_key) && tpm2_is_fully_supported()) || CRED_KEY_REQUIRES_TPM2_PK(with_key)) {
/* Load public key for PCR policies, if one is specified, or explicitly requested */
r = tpm2_load_pcr_public_key(tpm2_pubkey_path, &pubkey.iov_base, &pubkey.iov_len);
if (r < 0) {
if (r != -ENOENT || tpm2_pubkey_path || CRED_KEY_REQUIRES_TPM2_PK(with_key))
return log_error_errno(r, "Failed to read TPM PCR public key: %m");
log_debug_errno(r, "Failed to read TPM2 PCR public key, proceeding without: %m");
}
}
if (!iovec_is_set(&pubkey))
tpm2_pubkey_pcr_mask = 0;
_cleanup_(tpm2_context_unrefp) Tpm2Context *tpm2_context = NULL;
r = tpm2_context_new_or_warn(tpm2_device, &tpm2_context);
if (r < 0)
return r;
r = tpm2_get_best_pcr_bank(tpm2_context, tpm2_hash_pcr_mask | tpm2_pubkey_pcr_mask, &tpm2_pcr_bank);
if (r < 0)
return log_error_errno(r, "Could not find best pcr bank: %m");
log_debug("Selected literal PCR mask: 0x%x, PK PCR mask: 0x%x", tpm2_hash_pcr_mask, tpm2_pubkey_pcr_mask);
TPML_PCR_SELECTION tpm2_hash_pcr_selection;
tpm2_tpml_pcr_selection_from_mask(tpm2_hash_pcr_mask, tpm2_pcr_bank, &tpm2_hash_pcr_selection);
_cleanup_free_ Tpm2PCRValue *tpm2_hash_pcr_values = NULL;
size_t tpm2_n_hash_pcr_values;
r = tpm2_pcr_read(tpm2_context, &tpm2_hash_pcr_selection, &tpm2_hash_pcr_values, &tpm2_n_hash_pcr_values);
if (r < 0)
return log_error_errno(r, "Could not read PCR values: %m");
TPM2B_PUBLIC public;
if (iovec_is_set(&pubkey)) {
r = tpm2_tpm2b_public_from_pem(pubkey.iov_base, pubkey.iov_len, &public);
if (r < 0)
return log_error_errno(r, "Could not convert public key to TPM2B_PUBLIC: %m");
}
TPM2B_DIGEST tpm2_policy = TPM2B_DIGEST_MAKE(NULL, TPM2_SHA256_DIGEST_SIZE);
r = tpm2_calculate_sealing_policy(
tpm2_hash_pcr_values,
tpm2_n_hash_pcr_values,
iovec_is_set(&pubkey) ? &public : NULL,
/* pubkey_policy_ref= */ NULL,
/* use_pin= */ false,
/* pcrlock_policy= */ NULL,
&tpm2_policy);
if (r < 0)
return log_error_errno(r, "Could not calculate sealing policy digest: %m");
struct iovec *blobs = NULL;
size_t n_blobs = 0;
CLEANUP_ARRAY(blobs, n_blobs, iovec_array_free);
r = tpm2_seal(tpm2_context,
/* seal_key_handle= */ 0,
&tpm2_policy,
/* n_policy= */ 1,
/* pin= */ NULL,
&tpm2_key,
&blobs,
&n_blobs,
&tpm2_primary_alg,
/* ret_srk= */ NULL);
if (r < 0) {
if (sd_id128_equal(with_key, _CRED_AUTO_INITRD))
log_warning("TPM2 present and used, but we didn't manage to talk to it. Credential will be refused if SecureBoot is enabled.");
else if (!sd_id128_in_set(with_key, _CRED_AUTO, _CRED_AUTO_SCOPED))
return log_error_errno(r, "Failed to seal to TPM2: %m");
log_notice_errno(r, "TPM2 sealing didn't work, continuing without TPM2: %m");
}
if (!iovec_memdup(&IOVEC_MAKE(tpm2_policy.buffer, tpm2_policy.size), &tpm2_policy_hash))
return log_oom();
assert(n_blobs == 1);
tpm2_blob = TAKE_STRUCT(blobs[0]);
assert(tpm2_blob.iov_len <= CREDENTIAL_FIELD_SIZE_MAX);
assert(tpm2_policy_hash.iov_len <= CREDENTIAL_FIELD_SIZE_MAX);
}
#endif
if (CRED_KEY_IS_AUTO(with_key)) {
/* Let's settle the key type in auto mode now. */
if (iovec_is_set(&host_key) && iovec_is_set(&tpm2_key))
id = iovec_is_set(&pubkey) ? (sd_id128_equal(with_key, _CRED_AUTO_SCOPED) ?
CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC_WITH_PK_SCOPED : CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC_WITH_PK)
: (sd_id128_equal(with_key, _CRED_AUTO_SCOPED) ?
CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC_SCOPED : CRED_AES256_GCM_BY_HOST_AND_TPM2_HMAC);
else if (iovec_is_set(&tpm2_key) && !sd_id128_equal(with_key, _CRED_AUTO_SCOPED))
id = iovec_is_set(&pubkey) ? CRED_AES256_GCM_BY_TPM2_HMAC_WITH_PK : CRED_AES256_GCM_BY_TPM2_HMAC;
else if (iovec_is_set(&host_key))
id = sd_id128_equal(with_key, _CRED_AUTO_SCOPED) ? CRED_AES256_GCM_BY_HOST_SCOPED : CRED_AES256_GCM_BY_HOST;
else if (sd_id128_equal(with_key, _CRED_AUTO_INITRD))
id = CRED_AES256_GCM_BY_NULL;
else
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"TPM2 not available and host key located on temporary file system, no encryption key available.");
} else
id = with_key;
if (sd_id128_equal(id, CRED_AES256_GCM_BY_NULL)) {
if (FLAGS_SET(flags, CREDENTIAL_REFUSE_NULL))
return log_error_errno(SYNTHETIC_ERRNO(EHWPOISON), "Attempted to encrypt with null key, but this is disallowed.");
if (!FLAGS_SET(flags, CREDENTIAL_ALLOW_NULL))
log_warning("Using a null key for encryption and signing. Confidentiality or authenticity will not be provided.");
}
/* Let's now take the host key and the TPM2 key and hash it together, to use as encryption key for the data */
r = sha256_hash_host_and_tpm2_key(&host_key, &tpm2_key, md);
if (r < 0)
return r;
if (uid_is_valid(uid)) {
r = mangle_uid_into_key(uid, md);
if (r < 0)
return r;
}
r = dlopen_libcrypto(LOG_DEBUG);
if (r < 0)
return r;
assert_se(cc = sym_EVP_aes_256_gcm());
ksz = sym_EVP_CIPHER_get_key_length(cc);
assert(ksz == sizeof(md));
bsz = sym_EVP_CIPHER_get_block_size(cc);
assert(bsz > 0);
assert((size_t) bsz <= CREDENTIAL_FIELD_SIZE_MAX);
ivsz = sym_EVP_CIPHER_get_iv_length(cc);
if (ivsz > 0) {
assert((size_t) ivsz <= CREDENTIAL_FIELD_SIZE_MAX);
r = crypto_random_bytes_allocate_iovec(ivsz, &iv);
if (r < 0)
return log_error_errno(r, "Failed to acquired randomized IV: %m");
}
tsz = 16; /* FIXME: On OpenSSL 3 there is EVP_CIPHER_CTX_get_tag_length(), until then let's hardcode this */
context = sym_EVP_CIPHER_CTX_new();
if (!context)
return log_openssl_errors(LOG_ERR, "Failed to allocate encryption object");
if (sym_EVP_EncryptInit_ex(context, cc, NULL, md, iv.iov_base) != 1)
return log_openssl_errors(LOG_ERR, "Failed to initialize encryption context");
/* Just an upper estimate */
output.iov_len =
ALIGN8(offsetof(struct encrypted_credential_header, iv) + ivsz) +
ALIGN8(iovec_is_set(&tpm2_key) ? offsetof(struct tpm2_credential_header, policy_hash_and_blob) + tpm2_blob.iov_len + tpm2_policy_hash.iov_len : 0) +
ALIGN8(iovec_is_set(&pubkey) ? offsetof(struct tpm2_public_key_credential_header, data) + pubkey.iov_len : 0) +
ALIGN8(uid_is_valid(uid) ? sizeof(struct scoped_credential_header) : 0) +
ALIGN8(offsetof(struct metadata_credential_header, name) + strlen_ptr(name)) +
input->iov_len + 2U * (size_t) bsz +
tsz;
/* Silence static analyzers */
assert(output.iov_len >= input->iov_len);
output.iov_base = malloc0(output.iov_len);
if (!output.iov_base)
return log_oom();
h = (struct encrypted_credential_header*) output.iov_base;
h->id = id;
h->block_size = htole32(bsz);
h->key_size = htole32(ksz);
h->tag_size = htole32(tsz);
h->iv_size = htole32(ivsz);
memcpy(h->iv, iv.iov_base, ivsz);
p = ALIGN8(offsetof(struct encrypted_credential_header, iv) + ivsz);
#if HAVE_TPM2
if (iovec_is_set(&tpm2_key)) {
struct tpm2_credential_header *t;
t = (struct tpm2_credential_header*) ((uint8_t*) output.iov_base + p);
t->pcr_mask = htole64(tpm2_hash_pcr_mask);
t->pcr_bank = htole16(tpm2_pcr_bank);
t->primary_alg = htole16(tpm2_primary_alg);
t->blob_size = htole32(tpm2_blob.iov_len);
t->policy_hash_size = htole32(tpm2_policy_hash.iov_len);
memcpy(t->policy_hash_and_blob, tpm2_blob.iov_base, tpm2_blob.iov_len);
memcpy(t->policy_hash_and_blob + tpm2_blob.iov_len, tpm2_policy_hash.iov_base, tpm2_policy_hash.iov_len);
p += ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) + tpm2_blob.iov_len + tpm2_policy_hash.iov_len);
}
#endif
if (iovec_is_set(&pubkey)) {
struct tpm2_public_key_credential_header *z;
z = (struct tpm2_public_key_credential_header*) ((uint8_t*) output.iov_base + p);
z->pcr_mask = htole64(tpm2_pubkey_pcr_mask);
z->size = htole32(pubkey.iov_len);
memcpy(z->data, pubkey.iov_base, pubkey.iov_len);
p += ALIGN8(offsetof(struct tpm2_public_key_credential_header, data) + pubkey.iov_len);
}
if (uid_is_valid(uid)) {
struct scoped_credential_header *w;
w = (struct scoped_credential_header*) ((uint8_t*) output.iov_base + p);
w->flags = htole64(SCOPE_HASH_DATA_BASE_FLAGS);
p += ALIGN8(sizeof(struct scoped_credential_header));
}
/* Pass the encrypted + TPM2 header + scoped header as AAD */
if (sym_EVP_EncryptUpdate(context, NULL, &added, output.iov_base, p) != 1)
return log_openssl_errors(LOG_ERR, "Failed to write AAD data");
/* Now construct the metadata header */
ml = strlen_ptr(name);
m = malloc0(ALIGN8(offsetof(struct metadata_credential_header, name) + ml));
if (!m)
return log_oom();
m->timestamp = htole64(timestamp);
m->not_after = htole64(not_after);
m->name_size = htole32(ml);
memcpy_safe(m->name, name, ml);
/* And encrypt the metadata header */
if (sym_EVP_EncryptUpdate(context, (uint8_t*) output.iov_base + p, &added, (const unsigned char*) m, ALIGN8(offsetof(struct metadata_credential_header, name) + ml)) != 1)
return log_openssl_errors(LOG_ERR, "Failed to encrypt metadata header");
assert(added >= 0);
assert((size_t) added <= output.iov_len - p);
p += added;
/* Then encrypt the plaintext */
if (sym_EVP_EncryptUpdate(context, (uint8_t*) output.iov_base + p, &added, input->iov_base, input->iov_len) != 1)
return log_openssl_errors(LOG_ERR, "Failed to encrypt data");
assert(added >= 0);
assert((size_t) added <= output.iov_len - p);
p += added;
/* Finalize */
if (sym_EVP_EncryptFinal_ex(context, (uint8_t*) output.iov_base + p, &added) != 1)
return log_openssl_errors(LOG_ERR, "Failed to finalize data encryption");
assert(added >= 0);
assert((size_t) added <= output.iov_len - p);
p += added;
assert(p <= output.iov_len - tsz);
/* Append tag */
if (sym_EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_GET_TAG, tsz, (uint8_t*) output.iov_base + p) != 1)
return log_openssl_errors(LOG_ERR, "Failed to get tag");
p += tsz;
assert(p <= output.iov_len);
output.iov_len = p;
if (DEBUG_LOGGING && input->iov_len > 0) {
size_t base64_size;
base64_size = DIV_ROUND_UP(output.iov_len * 4, 3); /* Include base64 size increase in debug output */
assert(base64_size >= input->iov_len);
log_debug("Input of %zu bytes grew to output of %zu bytes (+%2zu%%).", input->iov_len, base64_size, base64_size * 100 / input->iov_len - 100);
}
*ret = TAKE_STRUCT(output);
return 0;
}
static CredentialBootPolicy query_credential_boot_policy(void) {
static CredentialBootPolicy cached = _CRED_BOOT_POLICY_INVALID;
_cleanup_free_ char *value = NULL;
int r;
if (cached >= 0)
return cached;
/* default to RELAXED if invalid or unset */
cached = CRED_BOOT_RELAXED;
r = proc_cmdline_get_key("systemd.credentials_boot_policy", PROC_CMDLINE_STRIP_RD_PREFIX, &value);
if (r < 0)
log_debug_errno(r, "Failed to read systemd.credentials_boot_policy= from kernel command line, ignoring: %m");
else if (r > 0) {
CredentialBootPolicy p = credential_boot_policy_from_string(value);
if (p < 0)
log_warning("Invalid systemd.credentials_boot_policy= value '%s', ignoring.", value);
else
cached = p;
}
return cached;
}
static int check_null_key_policy(CredentialFlags flags) {
if (FLAGS_SET(flags, CREDENTIAL_REFUSE_NULL))
return log_error_errno(SYNTHETIC_ERRNO(EHWPOISON),
"Credential uses null key, but that's not allowed, refusing.");
if (FLAGS_SET(flags, CREDENTIAL_ALLOW_NULL))
return 0;
/* So this is a credential encrypted with a zero length key. We support this to cover for the
* case where neither a host key not a TPM2 are available (specifically: initrd environments
* where the host key is not yet accessible and no TPM2 chip exists at all), to minimize
* different codeflow for TPM2 and non-TPM2 codepaths. Of course, credentials encoded this
* way offer no confidentiality nor authenticity. Because of that it's important we refuse to
* use them on systems that actually *do* have a TPM2 chip – if we are in SecureBoot
* mode. Otherwise an attacker could hand us credentials like this and we'd use them thinking
* they are trusted, even though they are not.
*
* Which conditions actually lead us to accept a null-key credential is configurable via
* systemd.credentials_boot_policy=, which also covers the first boot case (before any key
* exists yet); the decision itself is made in credential_boot_policy_accepts_null(). */
CredentialBootPolicy policy = query_credential_boot_policy();
bool have_tpm2 = efi_has_tpm2(), secure_boot = is_efi_secure_boot();
/* in_first_boot() can return <0 on error: use the safe default in this case (not-first-boot). */
bool first_boot = in_first_boot() > 0;
if (!credential_boot_policy_accepts_null(policy, first_boot, have_tpm2, secure_boot))
return log_error_errno(SYNTHETIC_ERRNO(EHWPOISON),
"Credential uses null key, but systemd.credentials_boot_policy=%s refuses it here (TPM2=%s, SecureBoot=%s, first boot=%s).",
credential_boot_policy_to_string(policy),
yes_no(have_tpm2), yes_no(secure_boot), yes_no(first_boot));
/* Accepting a null-key credential on a tpm2 host is undesired so keep it auditable */
if (have_tpm2 && !first_boot)
log_warning("Credential uses null key intended for use when TPM2 is absent, but TPM2 is present! "
"Accepting anyway, under systemd.credentials_boot_policy=%s.",
credential_boot_policy_to_string(policy));
else
log_debug("Credential uses null key, accepted under systemd.credentials_boot_policy=%s.",
credential_boot_policy_to_string(policy));
return 0;
}
int decrypt_credential_and_warn(
const char *validate_name,
usec_t validate_timestamp,
const char *tpm2_device,
const char *tpm2_signature_path,
uid_t uid,
const struct iovec *input,
CredentialFlags flags,
struct iovec *ret) {
_cleanup_(iovec_done_erase) struct iovec host_key = {}, plaintext = {}, tpm2_key = {};
_cleanup_(sd_json_variant_unrefp) sd_json_variant *signature_json = NULL;
_cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
struct encrypted_credential_header *h;
struct metadata_credential_header *m;
uint8_t md[SHA256_DIGEST_LENGTH];
const EVP_CIPHER *cc;
size_t p, hs;
int r, added;
assert(iovec_is_valid(input));
assert(ret);
/* Only one of these two flags may be set at the same time */
assert(!FLAGS_SET(flags, CREDENTIAL_ALLOW_NULL) || !FLAGS_SET(flags, CREDENTIAL_REFUSE_NULL));
CLEANUP_ERASE(md);
/* Relevant error codes:
*
* -EBADMSG → Corrupted file
* -EOPNOTSUPP → Unsupported file type (could be: requires TPM but we have no TPM)
* -EHOSTDOWN → Need PCR signature file, but couldn't find it
* -EHWPOISON → Attempt to unlock with NULL key and either CREDENTIAL_ALLOW_REFUSE is on, or CREDENTIAL_ALLOW_NULL is off, but the system has a TPM and SecureBoot is on
* -EMEDIUMTYPE → File has unexpected scope, i.e. user-scoped credential is attempted to be unlocked in system scope, or vice versa
* -EDESTADDRREQ → Credential is incorrectly named (i.e. the authenticated name does not match the actual name)
* -ESTALE → Credential's validity has passed
* -ESRCH → User specified for scope does not exist on this system
*
* (plus the various error codes tpm2_unseal() returns) */
h = (struct encrypted_credential_header*) input->iov_base;
/* The ID must fit in, for the current and all future formats */
if (input->iov_len < sizeof(h->id))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
if (!CRED_KEY_IS_VALID(h->id))
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Unknown encryption format, or corrupted data.");
if (CRED_KEY_REQUIRES_TPM2_PK(h->id)) {
r = tpm2_load_pcr_signature(tpm2_signature_path, &signature_json);
if (r == -ENOENT)
return log_error_errno(SYNTHETIC_ERRNO(EHOSTDOWN), "Couldn't find PCR signature file: %m");
if (r < 0)
return log_error_errno(r, "Failed to load PCR signature: %m");
}
if (sd_id128_equal(h->id, CRED_AES256_GCM_BY_NULL)) {
r = check_null_key_policy(flags);
if (r < 0)
return r;
}
if (CRED_KEY_IS_SCOPED(h->id)) {
if (!uid_is_valid(uid))
return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "Encrypted file is scoped to a user, but no user selected.");
} else {
/* Refuse to unlock system credentials if user scope is requested. */
if (uid_is_valid(uid) && !FLAGS_SET(flags, CREDENTIAL_ANY_SCOPE))
return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "Encrypted file is scoped to the system, but user scope selected.");
uid = UID_INVALID;
}
/* Now we know the minimum header size */
if (input->iov_len < offsetof(struct encrypted_credential_header, iv))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
/* Verify some basic header values */
if (le32toh(h->key_size) != sizeof(md))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected key size in header.");
if (le32toh(h->block_size) <= 0 || le32toh(h->block_size) > CREDENTIAL_FIELD_SIZE_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected block size in header.");
if (le32toh(h->iv_size) > CREDENTIAL_FIELD_SIZE_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "IV size too large.");
if (le32toh(h->tag_size) != 16) /* FIXME: On OpenSSL 3, let's verify via EVP_CIPHER_CTX_get_tag_length() */
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected tag size in header.");
/* Ensure we have space for the full header now (we don't know the size of the name hence this is a
* lower limit only) */
if (input->iov_len <
ALIGN8(offsetof(struct encrypted_credential_header, iv) + le32toh(h->iv_size)) +
ALIGN8(CRED_KEY_REQUIRES_TPM2(h->id) ? offsetof(struct tpm2_credential_header, policy_hash_and_blob) : 0) +
ALIGN8(CRED_KEY_REQUIRES_TPM2_PK(h->id) ? offsetof(struct tpm2_public_key_credential_header, data) : 0) +
ALIGN8(CRED_KEY_IS_SCOPED(h->id) ? sizeof(struct scoped_credential_header) : 0) +
ALIGN8(offsetof(struct metadata_credential_header, name)) +
le32toh(h->tag_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
p = ALIGN8(offsetof(struct encrypted_credential_header, iv) + le32toh(h->iv_size));
if (CRED_KEY_REQUIRES_TPM2(h->id)) {
#if HAVE_TPM2
struct tpm2_credential_header* t = (struct tpm2_credential_header*) ((uint8_t*) input->iov_base + p);
struct tpm2_public_key_credential_header *z = NULL;
if (!TPM2_PCR_MASK_VALID(t->pcr_mask))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 PCR mask out of range.");
if (!tpm2_hash_alg_to_string(le16toh(t->pcr_bank)))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 PCR bank invalid or not supported");
if (!tpm2_asym_alg_to_string(le16toh(t->primary_alg)))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 primary key algorithm invalid or not supported.");
if (le32toh(t->blob_size) > CREDENTIAL_FIELD_SIZE_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected TPM2 blob size.");
if (le32toh(t->policy_hash_size) > CREDENTIAL_FIELD_SIZE_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected TPM2 policy hash size.");
/* Ensure we have space for the full TPM2 header now (still don't know the name, and its size
* though, hence still just a lower limit test only) */
if (input->iov_len <
p +
ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) + le32toh(t->blob_size) + le32toh(t->policy_hash_size)) +
ALIGN8(CRED_KEY_REQUIRES_TPM2_PK(h->id) ? offsetof(struct tpm2_public_key_credential_header, data) : 0) +
ALIGN8(CRED_KEY_IS_SCOPED(h->id) ? sizeof(struct scoped_credential_header) : 0) +
ALIGN8(offsetof(struct metadata_credential_header, name)) +
le32toh(h->tag_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
p += ALIGN8(offsetof(struct tpm2_credential_header, policy_hash_and_blob) +
le32toh(t->blob_size) +
le32toh(t->policy_hash_size));
if (CRED_KEY_REQUIRES_TPM2_PK(h->id)) {
z = (struct tpm2_public_key_credential_header*) ((uint8_t*) input->iov_base + p);
if (!TPM2_PCR_MASK_VALID(le64toh(z->pcr_mask)) || le64toh(z->pcr_mask) == 0)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "TPM2 PCR mask out of range.");
if (le32toh(z->size) > PUBLIC_KEY_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected public key size.");
if (input->iov_len <
p +
ALIGN8(offsetof(struct tpm2_public_key_credential_header, data) + le32toh(z->size)) +
ALIGN8(CRED_KEY_IS_SCOPED(h->id) ? sizeof(struct scoped_credential_header) : 0) +
ALIGN8(offsetof(struct metadata_credential_header, name)) +
le32toh(h->tag_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
p += ALIGN8(offsetof(struct tpm2_public_key_credential_header, data) +
le32toh(z->size));
}
_cleanup_(tpm2_context_unrefp) Tpm2Context *tpm2_context = NULL;
r = tpm2_context_new(tpm2_device, &tpm2_context);
if (r < 0)
return r;
// TODO: Add the SRK data to the credential structure so it can be plumbed
// through and used to verify the TPM session.
r = tpm2_unseal(tpm2_context,
le64toh(t->pcr_mask),
le16toh(t->pcr_bank),
z ? &IOVEC_MAKE(z->data, le32toh(z->size)) : NULL,
/* pubkey_policy_ref= */ NULL,
z ? le64toh(z->pcr_mask) : 0,
signature_json,
/* pin= */ NULL,
/* pcrlock_policy= */ NULL,
le16toh(t->primary_alg),
&IOVEC_MAKE(t->policy_hash_and_blob, le32toh(t->blob_size)),
/* n_blobs= */ 1,
&IOVEC_MAKE(t->policy_hash_and_blob + le32toh(t->blob_size), le32toh(t->policy_hash_size)),
/* n_known_policy_hash= */ 1,
/* srk= */ NULL,
&tpm2_key);
if (r == -EREMOTE)
return log_error_errno(r, "TPM key integrity check failed. Key most likely does not belong to this TPM.");
if (r == -EADDRNOTAVAIL)
return log_error_errno(r, "NV index referenced by key is missing, unwritten, or unusable, it could be for another system.");
if (ERRNO_IS_NEG_TPM2_UNSEAL_BAD_PCR(r))
return log_error_errno(r, "TPM policy does not match current system state. Either system has been tempered with or policy out-of-date: %m");
if (r < 0)
return log_error_errno(r, "Failed to unseal secret using TPM2: %m");
#else
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Credential requires TPM2 support, but TPM2 support not available.");
#endif
}
if (CRED_KEY_IS_SCOPED(h->id)) {
struct scoped_credential_header* sh = (struct scoped_credential_header*) ((uint8_t*) input->iov_base + p);
if (le64toh(sh->flags) != SCOPE_HASH_DATA_BASE_FLAGS)
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Scoped credential with unsupported flags.");
if (input->iov_len <
p +
sizeof(struct scoped_credential_header) +
ALIGN8(offsetof(struct metadata_credential_header, name)) +
le32toh(h->tag_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Encrypted file too short.");
p += sizeof(struct scoped_credential_header);
}
if (CRED_KEY_REQUIRES_HOST(h->id)) {
r = get_credential_host_secret(/* flags= */ 0, &host_key);
if (r < 0)
return log_error_errno(r, "Failed to determine local credential key: %m");
}
if (sd_id128_equal(h->id, CRED_AES256_GCM_BY_NULL) && !FLAGS_SET(flags, CREDENTIAL_ALLOW_NULL))
log_warning("Warning: using a null key for decryption and authentication. Confidentiality or authenticity are not provided.");
sha256_hash_host_and_tpm2_key(&host_key, &tpm2_key, md);
if (CRED_KEY_IS_SCOPED(h->id)) {
r = mangle_uid_into_key(uid, md);
if (r < 0)
return r;
}
r = dlopen_libcrypto(LOG_DEBUG);
if (r < 0)
return r;
assert_se(cc = sym_EVP_aes_256_gcm());
/* Make sure cipher expectations match the header */
if (sym_EVP_CIPHER_get_key_length(cc) != (int) le32toh(h->key_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected key size in header.");
if (sym_EVP_CIPHER_get_block_size(cc) != (int) le32toh(h->block_size))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Unexpected block size in header.");
context = sym_EVP_CIPHER_CTX_new();
if (!context)
return log_openssl_errors(LOG_ERR, "Failed to allocate decryption object");
if (sym_EVP_DecryptInit_ex(context, cc, NULL, NULL, NULL) != 1)
return log_openssl_errors(LOG_ERR, "Failed to initialize decryption context");
if (sym_EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_SET_IVLEN, le32toh(h->iv_size), NULL) != 1)
return log_openssl_errors(LOG_ERR, "Failed to set IV size on decryption context");
if (sym_EVP_DecryptInit_ex(context, NULL, NULL, md, h->iv) != 1)
return log_openssl_errors(LOG_ERR, "Failed to set IV and key");
if (sym_EVP_DecryptUpdate(context, NULL, &added, input->iov_base, p) != 1)
return log_openssl_errors(LOG_ERR, "Failed to write AAD data");
plaintext.iov_base = malloc(input->iov_len - p - le32toh(h->tag_size));
if (!plaintext.iov_base)
return -ENOMEM;
if (sym_EVP_DecryptUpdate(
context,
plaintext.iov_base,
&added,
(uint8_t*) input->iov_base + p,
input->iov_len - p - le32toh(h->tag_size)) != 1)
return log_openssl_errors(LOG_ERR, "Failed to decrypt data");
assert(added >= 0);
assert((size_t) added <= input->iov_len - p - le32toh(h->tag_size));
plaintext.iov_len = added;
if (sym_EVP_CIPHER_CTX_ctrl(context, EVP_CTRL_GCM_SET_TAG, le32toh(h->tag_size), (uint8_t*) input->iov_base + input->iov_len - le32toh(h->tag_size)) != 1)
return log_openssl_errors(LOG_ERR, "Failed to set tag");
if (sym_EVP_DecryptFinal_ex(context, (uint8_t*) plaintext.iov_base + plaintext.iov_len, &added) != 1) {
log_openssl_errors(LOG_ERR, "Decryption failed (incorrect key?)");
/* A GCM tag/authentication mismatch (wrong key or corrupted blob) is the common case here
* and typically leaves the OpenSSL error queue empty, so we can't rely on the translated
* errno. Return -EBADMSG unconditionally: it's this function's documented "corrupted file"
* code, and credentials_varlink_error_table[] maps it to io.systemd.Credentials.BadFormat. */
return -EBADMSG;
}
plaintext.iov_len += added;
if (plaintext.iov_len < ALIGN8(offsetof(struct metadata_credential_header, name)))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Metadata header incomplete.");
m = plaintext.iov_base;
if (le64toh(m->timestamp) != USEC_INFINITY &&
le64toh(m->not_after) != USEC_INFINITY &&
le64toh(m->timestamp) >= le64toh(m->not_after))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Timestamps of credential are not in order, refusing.");
if (le32toh(m->name_size) > CREDENTIAL_NAME_MAX)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Embedded credential name too long, refusing.");
hs = ALIGN8(offsetof(struct metadata_credential_header, name) + le32toh(m->name_size));
if (plaintext.iov_len < hs)
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Metadata header incomplete.");
if (le32toh(m->name_size) > 0) {
_cleanup_free_ char *embedded_name = NULL;
r = make_cstring(m->name, le32toh(m->name_size), MAKE_CSTRING_REFUSE_TRAILING_NUL, &embedded_name);
if (r < 0)
return log_error_errno(r, "Unable to convert embedded credential name to C string: %m");
if (!credential_name_valid(embedded_name))
return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Embedded credential name is not valid, refusing.");
if (validate_name && !streq(embedded_name, validate_name)) {
r = secure_getenv_bool("SYSTEMD_CREDENTIAL_VALIDATE_NAME");
if (r < 0 && r != -ENXIO)
log_debug_errno(r, "Failed to parse $SYSTEMD_CREDENTIAL_VALIDATE_NAME: %m");
if (r != 0)
return log_error_errno(SYNTHETIC_ERRNO(EDESTADDRREQ), "Embedded credential name '%s' does not match filename '%s', refusing.", embedded_name, validate_name);
log_debug("Embedded credential name '%s' does not match expected name '%s', but configured to use credential anyway.", embedded_name, validate_name);
}
}
if (validate_timestamp != USEC_INFINITY) {
if (le64toh(m->timestamp) != USEC_INFINITY && le64toh(m->timestamp) > validate_timestamp)
log_debug("Credential timestamp is from the future, assuming clock skew.");
if (le64toh(m->not_after) != USEC_INFINITY && le64toh(m->not_after) < validate_timestamp) {
r = secure_getenv_bool("SYSTEMD_CREDENTIAL_VALIDATE_NOT_AFTER");
if (r < 0 && r != -ENXIO)
log_debug_errno(r, "Failed to parse $SYSTEMD_CREDENTIAL_VALIDATE_NOT_AFTER: %m");
if (r != 0)
return log_error_errno(SYNTHETIC_ERRNO(ESTALE), "Credential's time passed, refusing to use.");
log_debug("Credential not-after timestamp has passed, but configured to use credential anyway.");
}
}
if (ret) {
_cleanup_(iovec_done_erase) struct iovec without_metadata = {};
without_metadata.iov_len = plaintext.iov_len - hs;
without_metadata.iov_base = memdup_suffix0((uint8_t*) plaintext.iov_base + hs, without_metadata.iov_len);
if (!without_metadata.iov_base)
return log_oom();
*ret = TAKE_STRUCT(without_metadata);
}
return 0;
}
#else
int get_credential_host_secret(CredentialSecretFlags flags, struct iovec *ret) {
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
}
int encrypt_credential_and_warn(sd_id128_t with_key, const char *name, usec_t timestamp, usec_t not_after, const char *tpm2_device, uint32_t tpm2_hash_pcr_mask, const char *tpm2_pubkey_path, uint32_t tpm2_pubkey_pcr_mask, uid_t uid, const struct iovec *input, CredentialFlags flags, struct iovec *ret) {
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
}
int decrypt_credential_and_warn(const char *validate_name, usec_t validate_timestamp, const char *tpm2_device, const char *tpm2_signature_path, uid_t uid, const struct iovec *input, CredentialFlags flags, struct iovec *ret) {
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Support for encrypted credentials not available.");
}
#endif
int ipc_encrypt_credential(const char *name, usec_t timestamp, usec_t not_after, uid_t uid, const struct iovec *input, CredentialFlags flags, struct iovec *ret) {
_cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL;
int r;
assert(input && iovec_is_valid(input));
assert(ret);
r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Credentials");
if (r < 0)
return log_error_errno(r, "Failed to connect to io.systemd.Credentials: %m");
/* Mark anything we get from the service as sensitive, given that it might use a NULL cypher, at least in theory */
r = sd_varlink_set_input_sensitive(vl);
if (r < 0)
return log_error_errno(r, "Failed to enable sensitive Varlink input: %m");
/* Create the input data blob object separately, so that we can mark it as sensitive */
_cleanup_(sd_json_variant_unrefp) sd_json_variant *jinput = NULL;
r = sd_json_build(&jinput, JSON_BUILD_IOVEC_BASE64(input));
if (r < 0)
return log_error_errno(r, "Failed to create input object: %m");
sd_json_variant_sensitive(jinput);
sd_json_variant *reply = NULL;
const char *error_id = NULL;
r = sd_varlink_callbo(
vl,
"io.systemd.Credentials.Encrypt",
&reply,
&error_id,
SD_JSON_BUILD_PAIR_CONDITION(!!name, "name", SD_JSON_BUILD_STRING(name)),
SD_JSON_BUILD_PAIR_VARIANT("data", jinput),
SD_JSON_BUILD_PAIR_CONDITION(timestamp != USEC_INFINITY, "timestamp", SD_JSON_BUILD_UNSIGNED(timestamp)),
SD_JSON_BUILD_PAIR_CONDITION(not_after != USEC_INFINITY, "notAfter", SD_JSON_BUILD_UNSIGNED(not_after)),
SD_JSON_BUILD_PAIR_CONDITION(!FLAGS_SET(flags, CREDENTIAL_ANY_SCOPE), "scope", SD_JSON_BUILD_STRING(uid_is_valid(uid) ? "user" : "system")),
SD_JSON_BUILD_PAIR_CONDITION(uid_is_valid(uid), "uid", SD_JSON_BUILD_UNSIGNED(uid)),
SD_JSON_BUILD_PAIR_CONDITION((flags & (CREDENTIAL_ALLOW_NULL|CREDENTIAL_REFUSE_NULL)) != 0, "allowNull", SD_JSON_BUILD_BOOLEAN(flags & CREDENTIAL_ALLOW_NULL)),
SD_JSON_BUILD_PAIR_BOOLEAN("allowInteractiveAuthentication", FLAGS_SET(flags, CREDENTIAL_IPC_ALLOW_INTERACTIVE)));
if (r < 0)
return log_error_errno(r, "Failed to call Encrypt() varlink call.");
if (!isempty(error_id)) {
if (streq(error_id, "io.systemd.Credentials.NoSuchUser"))
return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "No such user.");
return log_error_errno(sd_varlink_error_to_errno(error_id, reply), "Failed to encrypt: %s", error_id);
}
static const sd_json_dispatch_field dispatch_table[] = {
{ "blob", SD_JSON_VARIANT_STRING, json_dispatch_unbase64_iovec, 0, SD_JSON_MANDATORY },
{},
};
r = sd_json_dispatch(reply, dispatch_table, SD_JSON_LOG|SD_JSON_ALLOW_EXTENSIONS, ret);
if (r < 0)
return r;
return 0;
}
int ipc_decrypt_credential(const char *validate_name, usec_t validate_timestamp, uid_t uid, const struct iovec *input, CredentialFlags flags, struct iovec *ret) {
_cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL;
int r;
assert(input && iovec_is_valid(input));
assert(ret);
r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Credentials");
if (r < 0)
return log_error_errno(r, "Failed to connect to io.systemd.Credentials: %m");
r = sd_varlink_set_input_sensitive(vl);
if (r < 0)
return log_error_errno(r, "Failed to enable sensitive Varlink input: %m");
/* Create the input data blob object separately, so that we can mark it as sensitive (it's supposed
* to be encrypted, but who knows maybe it uses the NULL cypher). */
_cleanup_(sd_json_variant_unrefp) sd_json_variant *jinput = NULL;
r = sd_json_build(&jinput, JSON_BUILD_IOVEC_BASE64(input));
if (r < 0)
return log_error_errno(r, "Failed to create input object: %m");
sd_json_variant_sensitive(jinput);
sd_json_variant *reply = NULL;
const char *error_id = NULL;
r = sd_varlink_callbo(
vl,
"io.systemd.Credentials.Decrypt",
&reply,
&error_id,
SD_JSON_BUILD_PAIR_CONDITION(!!validate_name, "name", SD_JSON_BUILD_STRING(validate_name)),
SD_JSON_BUILD_PAIR_VARIANT("blob", jinput),
SD_JSON_BUILD_PAIR_CONDITION(validate_timestamp != USEC_INFINITY, "timestamp", SD_JSON_BUILD_UNSIGNED(validate_timestamp)),
SD_JSON_BUILD_PAIR_CONDITION(!FLAGS_SET(flags, CREDENTIAL_ANY_SCOPE), "scope", SD_JSON_BUILD_STRING(uid_is_valid(uid) ? "user" : "system")),
SD_JSON_BUILD_PAIR_CONDITION(uid_is_valid(uid), "uid", SD_JSON_BUILD_UNSIGNED(uid)),
SD_JSON_BUILD_PAIR_BOOLEAN("allowInteractiveAuthentication", FLAGS_SET(flags, CREDENTIAL_IPC_ALLOW_INTERACTIVE)));
if (r < 0)
return log_error_errno(r, "Failed to call Decrypt() varlink call.");
if (!isempty(error_id)) {
const CredentialsVarlinkError *e = credentials_varlink_error_by_id(error_id);
if (e)
return log_error_errno(SYNTHETIC_ERRNO(e->errnum), "%s", e->msg);
return log_error_errno(sd_varlink_error_to_errno(error_id, reply), "Failed to decrypt: %s", error_id);
}
static const sd_json_dispatch_field dispatch_table[] = {
{ "data", SD_JSON_VARIANT_STRING, json_dispatch_unbase64_iovec, 0, SD_JSON_MANDATORY },
{},
};
r = sd_json_dispatch(reply, dispatch_table, SD_JSON_LOG|SD_JSON_ALLOW_EXTENSIONS, ret);
if (r < 0)
return r;
return 0;
}
int get_global_boot_credentials_path(char **ret) {
_cleanup_free_ char *path = NULL;
int r;
assert(ret);
/* Determines where to put global boot credentials in. Returns the path to the "/loader/credentials/"
* directory below the XBOOTLDR or ESP partition. Any credentials placed in this directory can be
* picked up later in the initrd. */
r = find_xbootldr_and_warn(
/* root= */ NULL,
/* path= */ NULL,
/* unprivileged_mode= */ false,
&path,
/* ret_fd= */ NULL);
if (r < 0) {
if (r != -ENOKEY)
return log_error_errno(r, "Failed to find XBOOTLDR partition: %m");
r = find_esp_and_warn(
/* root= */ NULL,
/* path= */ NULL,
/* unprivileged_mode= */ false,
&path,
/* ret_fd= */ NULL);
if (r < 0) {
if (r != -ENOKEY)
return log_error_errno(r, "Failed to find ESP partition: %m");
*ret = NULL;
return 0; /* not found! */
}
}
_cleanup_free_ char *joined = path_join(path, "loader/credentials");
if (!joined)
return log_oom();
log_debug("Determined global boot credentials path as: %s", joined);
*ret = TAKE_PTR(joined);
return 1; /* found! */
}
static int pick_up_credential_one(
int credential_dir_fd,
const char *credential_name,
const PickUpCredential *table_entry) {
_cleanup_free_ char *fn = NULL, *target_path = NULL;
const char *e;
int r;
assert(credential_dir_fd >= 0);
assert(credential_name);
assert(table_entry);
e = startswith(credential_name, table_entry->credential_prefix);
if (!e)
return 0; /* unmatched */
fn = strjoin(e, table_entry->filename_suffix);
if (!fn)
return log_oom();
if (!filename_is_valid(fn))
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL),
"Passed credential '%s' would result in invalid filename '%s'.",
credential_name, fn);
r = mkdir_p_label(table_entry->target_dir, 0755);
if (r < 0)
return log_warning_errno(r, "Failed to create '%s': %m", table_entry->target_dir);
target_path = path_join(table_entry->target_dir, fn);
if (!target_path)
return log_oom();
r = copy_file_at(
credential_dir_fd, credential_name,
AT_FDCWD, target_path,
/* open_flags= */ 0,
0644,
/* copy_flags= */ 0);
if (r < 0)
return log_warning_errno(r, "Failed to copy credential %s → file %s: %m",
credential_name, target_path);
log_info("Installed %s from credential.", target_path);
return 1; /* done */
}
int pick_up_credentials(const PickUpCredential *table, size_t n_table_entry) {
_cleanup_close_ int credential_dir_fd = -EBADF;
int r, ret = 0;
assert(table);
assert(n_table_entry > 0);
credential_dir_fd = open_credentials_dir();
if (IN_SET(credential_dir_fd, -ENXIO, -ENOENT)) {
/* Credential env var not set, or dir doesn't exist. */
log_debug("No credentials found.");
return 0;
}
if (credential_dir_fd < 0)
return log_error_errno(credential_dir_fd, "Failed to open credentials directory: %m");
_cleanup_free_ DirectoryEntries *des = NULL;
r = readdir_all(credential_dir_fd, RECURSE_DIR_SORT|RECURSE_DIR_IGNORE_DOT|RECURSE_DIR_MUST_BE_REGULAR, &des);
if (r < 0)
return log_error_errno(r, "Failed to enumerate credentials: %m");
FOREACH_ARRAY(i, des->entries, des->n_entries) {
struct dirent *de = *i;
FOREACH_ARRAY(t, table, n_table_entry) {
r = pick_up_credential_one(credential_dir_fd, de->d_name, t);
if (r != 0) {
RET_GATHER(ret, r);
break; /* Done, or failed. Let's move to the next credential. */
}
}
}
return ret;
}
static const CredentialsVarlinkError credentials_varlink_error_table[] = {
{ "io.systemd.Credentials.BadFormat", EBADMSG, "Bad credential format." },
{ "io.systemd.Credentials.NameMismatch", EDESTADDRREQ, "Name in credential doesn't match expectations." },
{ "io.systemd.Credentials.TimeMismatch", ESTALE, "Outside of credential validity time window." },
{ "io.systemd.Credentials.NoSuchUser", ESRCH, "No such user." },
{ "io.systemd.Credentials.BadScope", EMEDIUMTYPE, "Scope mismatch." },
{ "io.systemd.Credentials.CantFindPCRSignature", EHOSTDOWN, "PCR signature required for decryption, but could not be found." },
{ "io.systemd.Credentials.NullKeyNotAllowed", EHWPOISON, "The key was encrypted with a null key, but that's now allowed during decryption." },
{ "io.systemd.Credentials.KeyBelongsToOtherTPM", EREMOTE, "The TPM integrity check for this key failed, key probably belongs to another TPM, or was corrupted." },
{ "io.systemd.Credentials.TPMInDictionaryLockout", ENOLCK, "The TPM is in dictionary lockout mode, cannot operate." },
{ "io.systemd.Credentials.UnexpectedPCRState" , EUCLEAN, "Unexpected TPM PCR state of the system." },
{ "io.systemd.Credentials.NVIndexUnusable", EADDRNOTAVAIL, "The NV index referenced by the key is missing, unwritten, or unusable, it could be for another system." },
};
const CredentialsVarlinkError* credentials_varlink_error_by_id(const char *id) {
assert(id);
FOREACH_ELEMENT(i, credentials_varlink_error_table)
if (streq(id, i->id))
return i;
return NULL;
}
const CredentialsVarlinkError* credentials_varlink_error_by_errno(int errnum) {
assert(errnum != 0);
errnum = ABS(errnum);
FOREACH_ELEMENT(i, credentials_varlink_error_table)
if (errnum == i->errnum)
return i;
return NULL;
}
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