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[62.108.10.193]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c15dfda815dsm326168966b.36.2026.07.10.10.30.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 10:30:52 -0700 (PDT) Date: Fri, 10 Jul 2026 19:30:50 +0200 From: "David C.C.M. Gall" To: David Howells , Lukas Wunner , Ignat Korchagin , Herbert Xu , "David S. Miller" , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Cc: gregkh@linuxfoundation.org Subject: [PATCH] crypto: pkcs7_verify: use constant-time comparison for digest and signature verification Message-ID: Precedence: bulk X-Mailing-List: keyrings@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Replace memcmp() with crypto_memneq() for cryptographic digest and signature comparisons to prevent timing side-channel attacks. crypto/asymmetric_keys/pkcs7_verify.c: PKCS#7 message digest comparison during signature verification passes argument pkcs7 and attached signatures to pkcs7_digest via pkcs7_verify_one. pkcs7_digest utilized memcmp which could leak valid prefix length for attached signatures via timing side-channel. Assisted-by: gregkh_clanker_t1000 Signed-off-by: David C.C.M. Gall --- crypto/asymmetric_keys/pkcs7_verify.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c index 474e2c1ae21b..28953e53177b 100644 --- a/crypto/asymmetric_keys/pkcs7_verify.c +++ b/crypto/asymmetric_keys/pkcs7_verify.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include "pkcs7_parser.h" @@ -93,8 +94,8 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7, goto error; } - if (memcmp(sig->m, sinfo->msgdigest, - sinfo->msgdigest_len) != 0) { + if (crypto_memneq(sig->m, sinfo->msgdigest, + sinfo->msgdigest_len)) { pr_warn("Sig %u: Message digest doesn't match\n", sinfo->index); ret = -EKEYREJECTED; -- 2.43.0