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Merge pull request #4185 from endocode/djalal-sandbox-first-protection-v1

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core:sandbox: Add new ProtectKernelTunables=, ProtectControlGroups=, ProtectSystem=strict and fixes
This commit is contained in:
Evgeny Vereshchagin
2016-09-28 04:50:30 +03:00
committed by GitHub
parent b8fafaf4a1 cdfbd1fb26
commit cc238590e4
45 changed files with 1560 additions and 479 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/fs-util.c
+187
View File
@@ -597,3 +597,190 @@ int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
return r;
}
int chase_symlinks(const char *path, const char *_root, char **ret) {
_cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
_cleanup_close_ int fd = -1;
unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
char *todo;
int r;
assert(path);
/* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
* symlinks relative to a root directory, instead of the root of the host.
*
* Note that "root" matters only if we encounter an absolute symlink, it's unused otherwise. Most importantly
* this means the path parameter passed in is not prefixed by it.
*
* Algorithmically this operates on two path buffers: "done" are the components of the path we already
* processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
* process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
* each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
* slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
* at a minimum. */
r = path_make_absolute_cwd(path, &buffer);
if (r < 0)
return r;
if (_root) {
r = path_make_absolute_cwd(_root, &root);
if (r < 0)
return r;
}
fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (fd < 0)
return -errno;
todo = buffer;
for (;;) {
_cleanup_free_ char *first = NULL;
_cleanup_close_ int child = -1;
struct stat st;
size_t n, m;
/* Determine length of first component in the path */
n = strspn(todo, "/"); /* The slashes */
m = n + strcspn(todo + n, "/"); /* The entire length of the component */
/* Extract the first component. */
first = strndup(todo, m);
if (!first)
return -ENOMEM;
todo += m;
/* Just a single slash? Then we reached the end. */
if (isempty(first) || path_equal(first, "/"))
break;
/* Just a dot? Then let's eat this up. */
if (path_equal(first, "/."))
continue;
/* Two dots? Then chop off the last bit of what we already found out. */
if (path_equal(first, "/..")) {
_cleanup_free_ char *parent = NULL;
int fd_parent = -1;
if (isempty(done) || path_equal(done, "/"))
return -EINVAL;
parent = dirname_malloc(done);
if (!parent)
return -ENOMEM;
/* Don't allow this to leave the root dir */
if (root &&
path_startswith(done, root) &&
!path_startswith(parent, root))
return -EINVAL;
free(done);
done = parent;
parent = NULL;
fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (fd_parent < 0)
return -errno;
safe_close(fd);
fd = fd_parent;
continue;
}
/* Otherwise let's see what this is. */
child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (child < 0)
return -errno;
if (fstat(child, &st) < 0)
return -errno;
if (S_ISLNK(st.st_mode)) {
_cleanup_free_ char *destination = NULL;
/* This is a symlink, in this case read the destination. But let's make sure we don't follow
* symlinks without bounds. */
if (--max_follow <= 0)
return -ELOOP;
r = readlinkat_malloc(fd, first + n, &destination);
if (r < 0)
return r;
if (isempty(destination))
return -EINVAL;
if (path_is_absolute(destination)) {
/* An absolute destination. Start the loop from the beginning, but use the root
* directory as base. */
safe_close(fd);
fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
if (fd < 0)
return -errno;
free(buffer);
buffer = destination;
destination = NULL;
todo = buffer;
free(done);
/* Note that we do not revalidate the root, we take it as is. */
if (isempty(root))
done = NULL;
else {
done = strdup(root);
if (!done)
return -ENOMEM;
}
} else {
char *joined;
/* A relative destination. If so, this is what we'll prefix what's left to do with what
* we just read, and start the loop again, but remain in the current directory. */
joined = strjoin("/", destination, todo, NULL);
if (!joined)
return -ENOMEM;
free(buffer);
todo = buffer = joined;
}
continue;
}
/* If this is not a symlink, then let's just add the name we read to what we already verified. */
if (!done) {
done = first;
first = NULL;
} else {
if (!strextend(&done, first, NULL))
return -ENOMEM;
}
/* And iterate again, but go one directory further down. */
safe_close(fd);
fd = child;
child = -1;
}
if (!done) {
/* Special case, turn the empty string into "/", to indicate the root directory. */
done = strdup("/");
if (!done)
return -ENOMEM;
}
*ret = done;
done = NULL;
return 0;
}
src/basic/fs-util.h
+2
View File
@@ -77,3 +77,5 @@ union inotify_event_buffer {
};
int inotify_add_watch_fd(int fd, int what, uint32_t mask);
int chase_symlinks(const char *path, const char *_root, char **ret);
src/basic/mount-util.c
+48 -23
View File
@@ -36,6 +36,7 @@
#include "set.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strv.h"
static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
@@ -287,10 +288,12 @@ int umount_recursive(const char *prefix, int flags) {
continue;
if (umount2(p, flags) < 0) {
r = -errno;
r = log_debug_errno(errno, "Failed to umount %s: %m", p);
continue;
}
log_debug("Successfully unmounted %s", p);
again = true;
n++;
@@ -311,24 +314,21 @@ static int get_mount_flags(const char *path, unsigned long *flags) {
return 0;
}
int bind_remount_recursive(const char *prefix, bool ro) {
int bind_remount_recursive(const char *prefix, bool ro, char **blacklist) {
_cleanup_set_free_free_ Set *done = NULL;
_cleanup_free_ char *cleaned = NULL;
int r;
/* Recursively remount a directory (and all its submounts)
* read-only or read-write. If the directory is already
* mounted, we reuse the mount and simply mark it
* MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
* operation). If it isn't we first make it one. Afterwards we
* apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to all
* submounts we can access, too. When mounts are stacked on
* the same mount point we only care for each individual
* "top-level" mount on each point, as we cannot
* influence/access the underlying mounts anyway. We do not
* have any effect on future submounts that might get
* propagated, they migt be writable. This includes future
* submounts that have been triggered via autofs. */
/* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already
* mounted, we reuse the mount and simply mark it MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
* operation). If it isn't we first make it one. Afterwards we apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to
* all submounts we can access, too. When mounts are stacked on the same mount point we only care for each
* individual "top-level" mount on each point, as we cannot influence/access the underlying mounts anyway. We
* do not have any effect on future submounts that might get propagated, they migt be writable. This includes
* future submounts that have been triggered via autofs.
*
* If the "blacklist" parameter is specified it may contain a list of subtrees to exclude from the
* remount operation. Note that we'll ignore the blacklist for the top-level path. */
cleaned = strdup(prefix);
if (!cleaned)
@@ -385,6 +385,33 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (r < 0)
return r;
if (!path_startswith(p, cleaned))
continue;
/* Ignore this mount if it is blacklisted, but only if it isn't the top-level mount we shall
* operate on. */
if (!path_equal(cleaned, p)) {
bool blacklisted = false;
char **i;
STRV_FOREACH(i, blacklist) {
if (path_equal(*i, cleaned))
continue;
if (!path_startswith(*i, cleaned))
continue;
if (path_startswith(p, *i)) {
blacklisted = true;
log_debug("Not remounting %s, because blacklisted by %s, called for %s", p, *i, cleaned);
break;
}
}
if (blacklisted)
continue;
}
/* Let's ignore autofs mounts. If they aren't
* triggered yet, we want to avoid triggering
* them, as we don't make any guarantees for
@@ -396,12 +423,9 @@ int bind_remount_recursive(const char *prefix, bool ro) {
continue;
}
if (path_startswith(p, cleaned) &&
!set_contains(done, p)) {
if (!set_contains(done, p)) {
r = set_consume(todo, p);
p = NULL;
if (r == -EEXIST)
continue;
if (r < 0)
@@ -418,8 +442,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (!set_contains(done, cleaned) &&
!set_contains(todo, cleaned)) {
/* The prefix directory itself is not yet a
* mount, make it one. */
/* The prefix directory itself is not yet a mount, make it one. */
if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
return -errno;
@@ -430,6 +453,8 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (mount(NULL, prefix, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
return -errno;
log_debug("Made top-level directory %s a mount point.", prefix);
x = strdup(cleaned);
if (!x)
return -ENOMEM;
@@ -447,8 +472,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (r < 0)
return r;
/* Deal with mount points that are obstructed by a
* later mount */
/* Deal with mount points that are obstructed by a later mount */
r = path_is_mount_point(x, 0);
if (r == -ENOENT || r == 0)
continue;
@@ -463,6 +487,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
return -errno;
log_debug("Remounted %s read-only.", x);
}
}
}
src/basic/mount-util.h
+1 -1
View File
@@ -35,7 +35,7 @@ int path_is_mount_point(const char *path, int flags);
int repeat_unmount(const char *path, int flags);
int umount_recursive(const char *target, int flags);
int bind_remount_recursive(const char *prefix, bool ro);
int bind_remount_recursive(const char *prefix, bool ro, char **blacklist);
int mount_move_root(const char *path);
src/basic/user-util.c
+31 -1
View File
@@ -31,14 +31,15 @@
#include <unistd.h>
#include <utmp.h>
#include "missing.h"
#include "alloc-util.h"
#include "fd-util.h"
#include "formats-util.h"
#include "macro.h"
#include "missing.h"
#include "parse-util.h"
#include "path-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "utf8.h"
@@ -175,6 +176,35 @@ int get_user_creds(
return 0;
}
int get_user_creds_clean(
const char **username,
uid_t *uid, gid_t *gid,
const char **home,
const char **shell) {
int r;
/* Like get_user_creds(), but resets home/shell to NULL if they don't contain anything relevant. */
r = get_user_creds(username, uid, gid, home, shell);
if (r < 0)
return r;
if (shell &&
(isempty(*shell) || PATH_IN_SET(*shell,
"/bin/nologin",
"/sbin/nologin",
"/usr/bin/nologin",
"/usr/sbin/nologin")))
*shell = NULL;
if (home &&
(isempty(*home) || path_equal(*home, "/")))
*home = NULL;
return 0;
}
int get_group_creds(const char **groupname, gid_t *gid) {
struct group *g;
gid_t id;
src/basic/user-util.h
+1
View File
@@ -40,6 +40,7 @@ char* getlogname_malloc(void);
char* getusername_malloc(void);
int get_user_creds(const char **username, uid_t *uid, gid_t *gid, const char **home, const char **shell);
int get_user_creds_clean(const char **username, uid_t *uid, gid_t *gid, const char **home, const char **shell);
int get_group_creds(const char **groupname, gid_t *gid);
char* uid_to_name(uid_t uid);