[RFC PATCH 03/20] X.509: Allow X.509 certs to be blacklisted [ver #2]

[David Howells]

Allow X.509 certs to be blacklisted based on their TBS hash.  This is
convenient since we have to determine this anyway to be able to check the
signature on an X.509 certificate.

If a certificate built into the kernel is blacklisted, something like the
following might then be seen during boot:

	X.509: Cert 123412341234c55c1dcc601ab8e172917706aa32fb5eaf826813547fdf02dd46 is blacklisted
	Problem loading in-kernel X.509 certificate (-129)

where the hex string shown is the blacklisted hash.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 crypto/asymmetric_keys/x509_parser.h     |    1 +
 crypto/asymmetric_keys/x509_public_key.c |   19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
index dbeed6018e63..be7cf2eae3bd 100644
--- a/crypto/asymmetric_keys/x509_parser.h
+++ b/crypto/asymmetric_keys/x509_parser.h
@@ -43,6 +43,7 @@ struct x509_certificate {
 	bool		verified;
 	bool		trusted;
 	bool		unsupported_crypto;	/* T if can't be verified due to missing crypto */
+	bool		blacklisted;
 };
 
 /*
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 9e9e5a6a9ed6..c4f3c40a4ab9 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -92,7 +92,7 @@ struct key *x509_request_asymmetric_key(struct key *keyring,
 		lookup = skid->data;
 		len = skid->len;
 	}
-	
+
 	/* Construct an identifier "id:<keyid>". */
 	p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
 	if (!req)
@@ -141,7 +141,7 @@ struct key *x509_request_asymmetric_key(struct key *keyring,
 			goto reject;
 		}
 	}
-	
+
 	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
 	return key;
 
@@ -211,6 +211,16 @@ int x509_get_sig_params(struct x509_certificate *cert)
 		goto error;
 	might_sleep();
 	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
+	if (ret < 0)
+		goto error;
+
+	ret = is_bin_hash_blacklisted(digest, digest_size);
+	if (ret == -EKEYREJECTED) {
+		pr_err("Cert %*phN is blacklisted\n", (int)digest_size, digest);
+		cert->blacklisted = true;
+		ret = 0;
+	}
+
 error:
 	crypto_free_shash(tfm);
 	pr_devel("<==%s() = %d\n", __func__, ret);
@@ -327,6 +337,11 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 			prep->trusted = 1;
 	}
 
+	/* Don't permit addition of blacklisted keys */
+	ret = -EKEYREJECTED;
+	if (cert->blacklisted)
+		goto error_free_cert;
+
 	/* Propose a description */
 	sulen = strlen(cert->subject);
 	if (cert->raw_skid) {