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authorMaciej S. Szmigiero <mail@maciej.szmigiero.name>2018-05-19 14:23:54 +0200
committerJames Morris <james.morris@microsoft.com>2018-06-25 12:17:08 -0700
commitb65c32ec5a942ab3ada93a048089a938918aba7f (patch)
treed2925b709736bacd96191013a9309f4b875b0c0d /crypto/asymmetric_keys
parent7b4e88434c4e7982fb053c49657e1c8bbb8692d9 (diff)
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X.509: unpack RSA signatureValue field from BIT STRING
The signatureValue field of a X.509 certificate is encoded as a BIT STRING. For RSA signatures this BIT STRING is of so-called primitive subtype, which contains a u8 prefix indicating a count of unused bits in the encoding. We have to strip this prefix from signature data, just as we already do for key data in x509_extract_key_data() function. This wasn't noticed earlier because this prefix byte is zero for RSA key sizes divisible by 8. Since BIT STRING is a big-endian encoding adding zero prefixes has no bearing on its value. The signature length, however was incorrect, which is a problem for RSA implementations that need it to be exactly correct (like AMD CCP). Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Fixes: c26fd69fa009 ("X.509: Add a crypto key parser for binary (DER) X.509 certificates") Cc: stable@vger.kernel.org Signed-off-by: James Morris <james.morris@microsoft.com>
Diffstat (limited to 'crypto/asymmetric_keys')
-rw-r--r--crypto/asymmetric_keys/x509_cert_parser.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 7d81e6bb461a..b6cabac4b62b 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -249,6 +249,15 @@ int x509_note_signature(void *context, size_t hdrlen,
return -EINVAL;
}
+ if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0) {
+ /* Discard the BIT STRING metadata */
+ if (vlen < 1 || *(const u8 *)value != 0)
+ return -EBADMSG;
+
+ value++;
+ vlen--;
+ }
+
ctx->cert->raw_sig = value;
ctx->cert->raw_sig_size = vlen;
return 0;