3.16.61-rc1 review patch. If anyone has any objections, please let me know.
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From: "Maciej S. Szmigiero" mail@maciej.szmigiero.name
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") Signed-off-by: James Morris james.morris@microsoft.com [bwh: Backported to 3.16: - x509_certificate::sig is a structure, not a pointer - public_key_signature::pkey_algo is an enumeration type, not a string] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- crypto/asymmetric_keys/x509_cert_parser.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/crypto/asymmetric_keys/x509_cert_parser.c +++ b/crypto/asymmetric_keys/x509_cert_parser.c @@ -205,6 +205,15 @@ int x509_note_signature(void *context, s return -EINVAL; }
+ if (ctx->cert->sig.pkey_algo == 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;