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authorMaciej S. Szmigiero <mail@maciej.szmigiero.name>2018-05-19 15:23:54 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-07-03 12:24:57 +0300
commitaf20e4eccc2d5a6d8985c4ff671cabd2c1ef2016 (patch)
treea03a01655a241c689e20a36e9961c9f5d605024a /crypto/asymmetric_keys
parent7dfc81992a3e0da45e45eab2f113658f3628f743 (diff)
downloadlinux-af20e4eccc2d5a6d8985c4ff671cabd2c1ef2016.tar.xz
X.509: unpack RSA signatureValue field from BIT STRING
commit b65c32ec5a942ab3ada93a048089a938918aba7f upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 ce2df8c9c583..7e6a43ffdcbe 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;