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measure: add 'sign' verb

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This commit is contained in:
Lennart Poettering
2022-09-08 16:27:07 +02:00
parent e8ccb5c7e1
commit cdaaa62ca1
2 changed files with 398 additions and 31 deletions
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src/boot/measure.c
+301 -10
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@@ -14,6 +14,7 @@
#include "parse-argument.h"
#include "parse-util.h"
#include "pretty-print.h"
#include "sha256.h"
#include "terminal-util.h"
#include "tpm-pcr.h"
#include "tpm2-util.h"
@@ -24,11 +25,17 @@
static char *arg_sections[_UNIFIED_SECTION_MAX] = {};
static char **arg_banks = NULL;
static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
static char *arg_tpm2_device = NULL;
static char *arg_private_key = NULL;
static char *arg_public_key = NULL;
static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_PRETTY_AUTO|JSON_FORMAT_COLOR_AUTO|JSON_FORMAT_OFF;
static PagerFlags arg_pager_flags = 0;
static bool arg_current = false;
STATIC_DESTRUCTOR_REGISTER(arg_banks, strv_freep);
STATIC_DESTRUCTOR_REGISTER(arg_tpm2_device, freep);
STATIC_DESTRUCTOR_REGISTER(arg_private_key, freep);
STATIC_DESTRUCTOR_REGISTER(arg_public_key, freep);
static inline void free_sections(char*(*sections)[_UNIFIED_SECTION_MAX]) {
for (UnifiedSection c = 0; c < _UNIFIED_SECTION_MAX; c++)
@@ -46,10 +53,11 @@ static int help(int argc, char *argv[], void *userdata) {
return log_oom();
printf("%1$s [OPTIONS...] COMMAND ...\n"
"\n%5$sPre-calculate PCR hash for kernel image.%6$s\n"
"\n%5$sPre-calculate and sign PCR hash for a unified kernel image.%6$s\n"
"\n%3$sCommands:%4$s\n"
" status Show current PCR values\n"
" calculate Calculate expected PCR values\n"
" status Show current PCR values\n"
" calculate Calculate expected PCR values\n"
" sign Calculate and sign expected PCR values\n"
"\n%3$sOptions:%4$s\n"
" -h --help Show this help\n"
" --version Print version\n"
@@ -62,6 +70,9 @@ static int help(int argc, char *argv[], void *userdata) {
" --dtb=PATH Path to Devicetree file\n"
" -c --current Use current PCR values\n"
" --bank=DIGEST Select TPM bank (SHA1, SHA256)\n"
" --tpm2-device=PATH Use specified TPM2 device\n"
" --private-key=KEY Private key (PEM) to sign with\n"
" --public-key=KEY Public key (PEM) to validate against\n"
" --json=MODE Output as JSON\n"
" -j Same as --json=pretty on tty, --json=short otherwise\n"
"\nSee the %2$s for details.\n",
@@ -88,6 +99,9 @@ static int parse_argv(int argc, char *argv[]) {
_ARG_SECTION_LAST,
ARG_DTB = _ARG_SECTION_LAST,
ARG_BANK,
ARG_PRIVATE_KEY,
ARG_PUBLIC_KEY,
ARG_TPM2_DEVICE,
ARG_JSON,
};
@@ -103,6 +117,9 @@ static int parse_argv(int argc, char *argv[]) {
{ "dtb", required_argument, NULL, ARG_DTB },
{ "current", no_argument, NULL, 'c' },
{ "bank", required_argument, NULL, ARG_BANK },
{ "tpm2-device", required_argument, NULL, ARG_TPM2_DEVICE },
{ "private-key", required_argument, NULL, ARG_PRIVATE_KEY },
{ "public-key", required_argument, NULL, ARG_PUBLIC_KEY },
{ "json", required_argument, NULL, ARG_JSON },
{}
};
@@ -155,6 +172,36 @@ static int parse_argv(int argc, char *argv[]) {
break;
}
case ARG_PRIVATE_KEY:
r = parse_path_argument(optarg, /* suppress_root= */ false, &arg_private_key);
if (r < 0)
return r;
break;
case ARG_PUBLIC_KEY:
r = parse_path_argument(optarg, /* suppress_root= */ false, &arg_public_key);
if (r < 0)
return r;
break;
case ARG_TPM2_DEVICE: {
_cleanup_free_ char *device = NULL;
if (streq(optarg, "list"))
return tpm2_list_devices();
if (!streq(optarg, "auto")) {
device = strdup(optarg);
if (!device)
return log_oom();
}
free_and_replace(arg_tpm2_device, device);
break;
}
case 'j':
arg_json_format_flags = JSON_FORMAT_PRETTY_AUTO|JSON_FORMAT_COLOR_AUTO;
break;
@@ -377,14 +424,9 @@ static int measure_pcr(PcrState *pcr_states, size_t n) {
return 0;
}
static int verb_calculate(int argc, char *argv[], void *userdata) {
static int pcr_states_allocate(PcrState **ret) {
_cleanup_(pcr_state_free_all) PcrState *pcr_states = NULL;
_cleanup_(json_variant_unrefp) JsonVariant *w = NULL;
size_t n = 0;
int r;
if (!arg_sections[UNIFIED_SECTION_LINUX] && !arg_current)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Either --linux= or --current must be specified, refusing.");
pcr_states = new0(PcrState, strv_length(arg_banks) + 1);
if (!pcr_states)
@@ -419,6 +461,25 @@ static int verb_calculate(int argc, char *argv[], void *userdata) {
};
}
*ret = TAKE_PTR(pcr_states);
return (int) n;
}
static int verb_calculate(int argc, char *argv[], void *userdata) {
_cleanup_(json_variant_unrefp) JsonVariant *w = NULL;
_cleanup_(pcr_state_free_all) PcrState *pcr_states = NULL;
size_t n;
int r;
if (!arg_sections[UNIFIED_SECTION_LINUX] && !arg_current)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Either --linux= or --current must be specified, refusing.");
r = pcr_states_allocate(&pcr_states);
if (r < 0)
return r;
n = (size_t) r;
r = measure_pcr(pcr_states, n);
if (r < 0)
return r;
@@ -464,6 +525,235 @@ static int verb_calculate(int argc, char *argv[], void *userdata) {
return 0;
}
static TPM2_ALG_ID convert_evp_md_name_to_tpm2_alg(const EVP_MD *md) {
const char *mdname;
mdname = EVP_MD_name(md);
if (strcaseeq(mdname, "sha1"))
return TPM2_ALG_SHA1;
if (strcaseeq(mdname, "sha256"))
return TPM2_ALG_SHA256;
if (strcaseeq(mdname, "sha384"))
return TPM2_ALG_SHA384;
if (strcaseeq(mdname, "sha512"))
return TPM2_ALG_SHA512;
return TPM2_ALG_ERROR;
}
static int verb_sign(int argc, char *argv[], void *userdata) {
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
_cleanup_(pcr_state_free_all) PcrState *pcr_states = NULL;
_cleanup_(EVP_PKEY_freep) EVP_PKEY *privkey = NULL, *pubkey = NULL;
_cleanup_(tpm2_context_destroy) struct tpm2_context c = {};
_cleanup_fclose_ FILE *privkeyf = NULL , *pubkeyf = NULL;
ESYS_TR session_handle = ESYS_TR_NONE;
TSS2_RC rc;
size_t n;
int r;
if (!arg_sections[UNIFIED_SECTION_LINUX] && !arg_current)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Either --linux= or --current must be specified, refusing.");
if (!arg_private_key)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No private key specified, use --private-key=.");
if (!arg_public_key)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No public key specified, use --public-key=.");
/* When signing we only support JSON output */
arg_json_format_flags &= ~JSON_FORMAT_OFF;
privkeyf = fopen(arg_private_key, "re");
if (!privkeyf)
return log_error_errno(errno, "Failed to open private key file '%s': %m", arg_private_key);
pubkeyf = fopen(arg_public_key, "re");
if (!pubkeyf)
return log_error_errno(errno, "Failed to open public key file '%s': %m", arg_public_key);
privkey = PEM_read_PrivateKey(privkeyf, NULL, NULL, NULL);
if (!privkey)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to parse private key '%s'.", arg_private_key);
pubkey = PEM_read_PUBKEY(pubkeyf, NULL, NULL, NULL);
if (!pubkey)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to parse public key '%s'.", arg_public_key);
r = pcr_states_allocate(&pcr_states);
if (r < 0)
return r;
n = (size_t) r;
r = measure_pcr(pcr_states, n);
if (r < 0)
return r;
r = dlopen_tpm2();
if (r < 0)
return r;
r = tpm2_context_init(arg_tpm2_device, &c);
if (r < 0)
return r;
for (size_t i = 0; i < n; i++) {
static const TPMT_SYM_DEF symmetric = {
.algorithm = TPM2_ALG_AES,
.keyBits.aes = 128,
.mode.aes = TPM2_ALG_CFB,
};
PcrState *p = pcr_states + i;
rc = sym_Esys_StartAuthSession(
c.esys_context,
ESYS_TR_NONE,
ESYS_TR_NONE,
ESYS_TR_NONE,
ESYS_TR_NONE,
ESYS_TR_NONE,
NULL,
TPM2_SE_TRIAL,
&symmetric,
TPM2_ALG_SHA256,
&session_handle);
if (rc != TSS2_RC_SUCCESS) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to open session in TPM: %s", sym_Tss2_RC_Decode(rc));
goto finish;
}
/* Generate a single hash value from the PCRs included in our policy. Given that that's
* exactly one, the calculation is trivial. */
TPM2B_DIGEST intermediate_digest = {
.size = SHA256_DIGEST_SIZE,
};
assert(sizeof(intermediate_digest.buffer) >= SHA256_DIGEST_SIZE);
sha256_direct(p->value, p->value_size, intermediate_digest.buffer);
TPM2_ALG_ID tpmalg = convert_evp_md_name_to_tpm2_alg(p->md);
if (tpmalg == TPM2_ALG_ERROR) {
r = log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Unsupported PCR bank");
goto finish;
}
TPML_PCR_SELECTION pcr_selection;
tpm2_pcr_mask_to_selection(1 << TPM_PCR_INDEX_KERNEL_IMAGE, tpmalg, &pcr_selection);
rc = sym_Esys_PolicyPCR(
c.esys_context,
session_handle,
ESYS_TR_NONE,
ESYS_TR_NONE,
ESYS_TR_NONE,
&intermediate_digest,
&pcr_selection);
if (rc != TSS2_RC_SUCCESS) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to push PCR policy into TPM: %s", sym_Tss2_RC_Decode(rc));
goto finish;
}
_cleanup_(Esys_Freep) TPM2B_DIGEST *pcr_policy_digest = NULL;
rc = sym_Esys_PolicyGetDigest(
c.esys_context,
session_handle,
ESYS_TR_NONE,
ESYS_TR_NONE,
ESYS_TR_NONE,
&pcr_policy_digest);
if (rc != TSS2_RC_SUCCESS) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to get policy digest from TPM: %s", sym_Tss2_RC_Decode(rc));
goto finish;
}
session_handle = tpm2_flush_context_verbose(c.esys_context, session_handle);
_cleanup_(EVP_MD_CTX_freep) EVP_MD_CTX* mdctx = NULL;
mdctx = EVP_MD_CTX_new();
if (!mdctx) {
r = log_oom();
goto finish;
}
if (EVP_DigestSignInit(mdctx, NULL, p->md, NULL, privkey) != 1) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to initialize signature context.");
goto finish;
}
if (EVP_DigestSignUpdate(mdctx, pcr_policy_digest->buffer, pcr_policy_digest->size) != 1) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to sign data.");
goto finish;
}
size_t ss;
if (EVP_DigestSignFinal(mdctx, NULL, &ss) != 1) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to finalize signature");
goto finish;
}
_cleanup_free_ void *sig = malloc(ss);
if (!ss) {
r = log_oom();
goto finish;
}
if (EVP_DigestSignFinal(mdctx, sig, &ss) != 1) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
"Failed to acquire signature data");
goto finish;
}
_cleanup_free_ void *pubkey_fp = NULL;
size_t pubkey_fp_size = 0;
r = pubkey_fingerprint(pubkey, EVP_sha256(), &pubkey_fp, &pubkey_fp_size);
if (r < 0)
goto finish;
_cleanup_(json_variant_unrefp) JsonVariant *bv = NULL, *a = NULL;
r = tpm2_make_pcr_json_array(UINT64_C(1) << TPM_PCR_INDEX_KERNEL_IMAGE, &a);
if (r < 0) {
log_error_errno(r, "Failed to build JSON PCR mask array: %m");
goto finish;
}
r = json_build(&bv, JSON_BUILD_ARRAY(
JSON_BUILD_OBJECT(
JSON_BUILD_PAIR("pcrs", JSON_BUILD_VARIANT(a)), /* PCR mask */
JSON_BUILD_PAIR("pkfp", JSON_BUILD_HEX(pubkey_fp, pubkey_fp_size)), /* SHA256 fingerprint of public key (DER) used for the signature */
JSON_BUILD_PAIR("pol", JSON_BUILD_HEX(pcr_policy_digest->buffer, pcr_policy_digest->size)), /* TPM2 policy hash that is signed */
JSON_BUILD_PAIR("sig", JSON_BUILD_BASE64(sig, ss))))); /* signature data */
if (r < 0) {
log_error_errno(r, "Failed to build JSON object: %m");
goto finish;
}
r = json_variant_set_field(&v, p->bank, bv);
if (r < 0) {
log_error_errno(r, "Failed to add JSON field: %m");
goto finish;
}
}
if (!v)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unable to find a single working PCR bank.");
if (arg_json_format_flags & (JSON_FORMAT_PRETTY|JSON_FORMAT_PRETTY_AUTO))
pager_open(arg_pager_flags);
json_variant_dump(v, arg_json_format_flags, stdout, NULL);
r = 0;
finish:
session_handle = tpm2_flush_context_verbose(c.esys_context, session_handle);
return r;
}
static int compare_reported_pcr_nr(uint32_t pcr, const char *varname, const char *description) {
_cleanup_free_ char *s = NULL;
uint32_t v;
@@ -641,6 +931,7 @@ static int measure_main(int argc, char *argv[]) {
{ "help", VERB_ANY, VERB_ANY, 0, help },
{ "status", VERB_ANY, 1, VERB_DEFAULT, verb_status },
{ "calculate", VERB_ANY, 1, 0, verb_calculate },
{ "sign", VERB_ANY, 1, 0, verb_sign },
{}
};