4.17-stable 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") Cc: stable@vger.kernel.org Signed-off-by: James Morris james.morris@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -249,6 +249,15 @@ int x509_note_signature(void *context, s 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;