diff options
| author | Matthias Kaehlcke <mka@chromium.org> | 2022-09-07 03:18:12 +0200 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2022-09-08 01:37:27 +0200 |
| commit | 6e42aec7c75947e0d6b38400628f171364eb8231 (patch) | |
| tree | 447a9e122ce9d58599900258a3e31ba1850d932d | |
| parent | dm: verity-loadpin: Only trust verity targets with enforcement (diff) | |
| download | linux-6e42aec7c75947e0d6b38400628f171364eb8231.tar.xz linux-6e42aec7c75947e0d6b38400628f171364eb8231.zip | |
LoadPin: Require file with verity root digests to have a header
LoadPin expects the file with trusted verity root digests to be
an ASCII file with one digest (hex value) per line. A pinned
root could contain files that meet these format requirements,
even though the hex values don't represent trusted root
digests.
Add a new requirement to the file format which consists in
the first line containing a fixed string. This prevents
attackers from feeding files with an otherwise valid format
to LoadPin.
Suggested-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220906181725.1.I3f51d1bb0014e5a5951be4ad3c5ad7c7ca1dfc32@changeid
| -rw-r--r-- | security/loadpin/Kconfig | 7 | ||||
| -rw-r--r-- | security/loadpin/loadpin.c | 16 |
2 files changed, 21 insertions, 2 deletions
diff --git a/security/loadpin/Kconfig b/security/loadpin/Kconfig index 994c1d9376e6..6724eaba3d36 100644 --- a/security/loadpin/Kconfig +++ b/security/loadpin/Kconfig @@ -33,4 +33,9 @@ config SECURITY_LOADPIN_VERITY on the LoadPin securityfs entry 'dm-verity'. The ioctl expects a file descriptor of a file with verity digests as parameter. The file must be located on the pinned root and - contain one digest per line. + start with the line: + + # LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS + + This is followed by the verity digests, with one digest per + line. diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c index 44521582dcba..de41621f4998 100644 --- a/security/loadpin/loadpin.c +++ b/security/loadpin/loadpin.c @@ -21,6 +21,8 @@ #include <linux/dm-verity-loadpin.h> #include <uapi/linux/loadpin.h> +#define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS" + static void report_load(const char *origin, struct file *file, char *operation) { char *cmdline, *pathname; @@ -292,9 +294,21 @@ static int read_trusted_verity_root_digests(unsigned int fd) p = strim(data); while ((d = strsep(&p, "\n")) != NULL) { - int len = strlen(d); + int len; struct dm_verity_loadpin_trusted_root_digest *trd; + if (d == data) { + /* first line, validate header */ + if (strcmp(d, VERITY_DIGEST_FILE_HEADER)) { + rc = -EPROTO; + goto err; + } + + continue; + } + + len = strlen(d); + if (len % 2) { rc = -EPROTO; goto err; |