* [PATCH 1/3] X.509: unpack RSA signatureValue field from BIT STRING
@ 2018-02-24 16:03 Maciej S. Szmigiero
0 siblings, 0 replies; 2+ messages in thread
From: Maciej S. Szmigiero @ 2018-02-24 16:03 UTC (permalink / raw)
To: Herbert Xu, David S. Miller
Cc: David Howells, Tom Lendacky, Gary Hook, keyrings, linux-crypto,
linux-kernel
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
---
crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index ce2df8c9c583..88c26a4538ae 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")) {
+ /* 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;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH 1/3] X.509: unpack RSA signatureValue field from BIT STRING
2018-06-26 15:59 [PATCH 0/3] KEYS: Miscellaneous fixes David Howells
@ 2018-06-26 15:59 ` David Howells
0 siblings, 0 replies; 2+ messages in thread
From: David Howells @ 2018-06-26 15:59 UTC (permalink / raw)
To: jmorris
Cc: Maciej S. Szmigiero, linux-kernel, stable, dhowells,
linux-security-module, keyrings
From: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
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: David Howells <dhowells@redhat.com>
---
crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++
1 file changed, 9 insertions(+)
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;
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-06-26 15:59 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-02-24 16:03 [PATCH 1/3] X.509: unpack RSA signatureValue field from BIT STRING Maciej S. Szmigiero
2018-06-26 15:59 [PATCH 0/3] KEYS: Miscellaneous fixes David Howells
2018-06-26 15:59 ` [PATCH 1/3] X.509: unpack RSA signatureValue field from BIT STRING David Howells
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).