[PATCH 3/9] PKCS#7: Handle blacklisted certificates

David Howells
2016-11-16T18:11:12Z

PKCS#7: Handle certificates that are blacklisted when verifying the chain
of trust on the signatures on a PKCS#7 message.

Signed-off-by: David Howells <dhowells@redhat.com>
---

crypto/asymmetric_keys/pkcs7_parser.h | 1 +
crypto/asymmetric_keys/pkcs7_verify.c | 32 ++++++++++++++++++++++++--------
2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/crypto/asymmetric_keys/pkcs7_parser.h b/crypto/asymmetric_keys/pkcs7_parser.h
index f4e81074f5e0..ac341e19e530 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.h
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -23,6 +23,7 @@ struct pkcs7_signed_info {
struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
unsigned index;
bool unsupported_crypto; /* T if not usable due to missing crypto */
+ bool blacklisted;

/* Message digest - the digest of the Content Data (or NULL) */
const void *msgdigest;
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 2ffd69769466..2d93d9eccb4d 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -190,6 +190,18 @@ static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
x509->subject,
x509->raw_serial_size, x509->raw_serial);
x509->seen = true;
+
+ if (x509->blacklisted) {
+ /* If this cert is blacklisted, then mark everything
+ * that depends on this as blacklisted too.
+ */
+ sinfo->blacklisted = true;
+ for (p = sinfo->signer; p != x509; p = p->signer)
+ p->blacklisted = true;
+ pr_debug("- blacklisted\n");
+ return 0;
+ }
+
if (x509->unsupported_key)
goto unsupported_crypto_in_x509;

@@ -357,17 +369,19 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
*
* (*) -EBADMSG if some part of the message was invalid, or:
*
- * (*) -ENOPKG if none of the signature chains are verifiable because suitable
- * crypto modules couldn't be found, or:
+ * (*) 0 if no signature chains were found to be blacklisted or to contain
+ * unsupported crypto, or:
*
- * (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
- * (note that a signature chain may be of zero length), or:
+ * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
+ *
+ * (*) -ENOPKG if none of the signature chains are verifiable because suitable
+ * crypto modules couldn't be found.
*/
int pkcs7_verify(struct pkcs7_message *pkcs7,
enum key_being_used_for usage)
{
struct pkcs7_signed_info *sinfo;
- int enopkg = -ENOPKG;
+ int actual_ret = -ENOPKG;
int ret;

kenter("");
@@ -412,6 +426,8 @@ int pkcs7_verify(struct pkcs7_message *pkcs7,

for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
ret = pkcs7_verify_one(pkcs7, sinfo);
+ if (sinfo->blacklisted && actual_ret == -ENOPKG)
+ actual_ret = -EKEYREJECTED;
if (ret < 0) {
if (ret == -ENOPKG) {
sinfo->unsupported_crypto = true;
@@ -420,11 +436,11 @@ int pkcs7_verify(struct pkcs7_message *pkcs7,
kleave(" = %d", ret);
return ret;
}
- enopkg = 0;
+ actual_ret = 0;
}

- kleave(" = %d", enopkg);
- return enopkg;
+ kleave(" = %d", actual_ret);
+ return actual_ret;
}
EXPORT_SYMBOL_GPL(pkcs7_verify);