From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51998 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728613AbeKLF4H (ORCPT ); Mon, 12 Nov 2018 00:56:07 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "James Morris" , "Maciej S. Szmigiero" Date: Sun, 11 Nov 2018 19:49:05 +0000 Message-ID: Subject: [PATCH 3.16 197/366] X.509: unpack RSA signatureValue field from BIT STRING In-Reply-To: Sender: stable-owner@vger.kernel.org List-ID: 3.16.61-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "Maciej S. Szmigiero" 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 Fixes: c26fd69fa009 ("X.509: Add a crypto key parser for binary (DER) X.509 certificates") Signed-off-by: James Morris [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 --- 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;