Multiple users of mod_check_sig check for the marker, then call
mod_check_sig, extract signature length, and remove the signature.
Put this code in one place together with mod_check_sig.
This changes the error from ENOENT to ENODATA for ima_read_modsig in the
case the signature marker is missing.
This also changes the buffer length in ima_read_modsig from size_t to
unsigned long. This reduces the possible value range on 32bit but the
length refers to kernel in-memory buffer which cannot be longer than
ULONG_MAX.
Also change mod_check_sig to unsigned long while at it.
Signed-off-by: Michal Suchanek
---
v3: - Philipp Rudo : Update the commit with note about
change of raturn value
- Preserve the EBADMSG error code while moving code araound
v4: - remove unused variable ms in module_signing.c
- note about buffer length
v5: - also change the functions in module_signature.c to unsigned long
---
include/linux/module_signature.h| 4 +-
kernel/module_signature.c | 58 -
kernel/module_signing.c | 27 ++
security/integrity/ima/ima_modsig.c | 22 ++-
4 files changed, 66 insertions(+), 45 deletions(-)
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 7eb4b00381ac..e5fb157c085c 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -40,7 +40,9 @@ struct module_signature {
__be32 sig_len;/* Length of signature data */
};
-int mod_check_sig(const struct module_signature *ms, size_t file_len,
+int mod_check_sig(const struct module_signature *ms, unsigned long file_len,
+ const char *name);
+int mod_parse_sig(const void *data, unsigned long *len, unsigned long *sig_len,
const char *name);
#endif /* _LINUX_MODULE_SIGNATURE_H */
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
index 00132d12487c..4a36405ecd08 100644
--- a/kernel/module_signature.c
+++ b/kernel/module_signature.c
@@ -8,17 +8,39 @@
#include
#include
+#include
#include
#include
+/**
+ * mod_check_sig_marker - check that the given data has signature marker at
the end
+ *
+ * @data: Data with appended signature
+ * @len: Length of data. Signature marker length is subtracted on
success.
+ */
+static inline int mod_check_sig_marker(const void *data, unsigned long *len)
+{
+ const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+
+ if (markerlen > *len)
+ return -ENODATA;
+
+ if (memcmp(data + *len - markerlen, MODULE_SIG_STRING,
+ markerlen))
+ return -ENODATA;
+
+ *len -= markerlen;
+ return 0;
+}
+
/**
* mod_check_sig - check that the given signature is sane
*
* @ms:Signature to check.
- * @file_len: Size of the file to which @ms is appended.
+ * @file_len: Size of the file to which @ms is appended (without the marker).
* @name: What is being checked. Used for error messages.
*/
-int mod_check_sig(const struct module_signature *ms, size_t file_len,
+int mod_check_sig(const struct module_signature *ms, unsigned long file_len,
const char *name)
{
if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
@@ -44,3 +66,35 @@ int mod_check_sig(const struct module_signature *ms, size_t
file_len,
return 0;
}
+
+/**
+ * mod_parse_sig - check that the given signature is sane and determine
signature length
+ *
+ * @data: Data with appended signature.
+ * @len: Length of data. Signature and marker length is subtracted on
success.
+ * @sig_len: Length of signature. Filled on success.
+ * @name: What is being checked. Used for error messages.
+ */
+int mod_parse_sig(const void *data, unsigned long *len, unsigned long
*sig_len, const char *name)
+{
+ const struct module_signature *sig;
+ int rc;
+
+ rc = mod_check_sig_marker(data, len);
+ if (rc)
+ return rc;
+
+ if (*len < sizeof(*sig))
+ return -EBADMSG;
+
+ sig = data + (*len - sizeof(*sig));
+
+ rc = mod_check_sig(sig, *len, name);
+ if (rc)
+ return rc;
+
+ *sig_len = be32_to_cpu(sig->sig_len);
+ *len -= *sig_len + sizeof(*sig);
+
+ return 0;
+}
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 20857d2a15ca..1d4cb03cce21 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -25,35 +25,16 @@ int verify_appended_signature(const void *data, unsigned
long *len,
struct key *trusted_keys,
enum key_being_used_for purpose)
{
- const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
- struct module_signature *ms;
- unsigned long sig_len, modlen = *len;
+ unsigned long sig_len;
int ret;
- pr_devel("==>%s %s(,%lu)\n", __func__,
