From nobody Sat Jul 25 03:21:16 2026 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D03EA72623; Mon, 20 Jul 2026 02:14:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784513655; cv=none; b=L1JMVOwrzC/SN0l6Sj6Ri/vxcEshxyaXfLRTCpcX7B2aNr6vnBH9Y/ypNFNL0UY6SN/lk4lsLPpWWy5i+CwVmM31UlewsV/QCQ0xtpUT7z7k4bgFKX7XoQ0GoV7FPrusn9+Ul5Yp2qR2JMOzrCVJ7jF0qNlIBxvaSxD4I9vhShY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784513655; c=relaxed/simple; bh=SrWleWXqhe9ZAaOZLDCbF/+5e+by+hmpkLG9x9qAqTs=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=eyW4xkGcdNgtRCWbj+Sz4VZoj3VQYYPczF04Xagc/AP7eH4Dir+AkPq4vG1gwejypIBhGCXVygEfur7klbmfNnAVw5arTv5EaNrAwFX4u0V8AoYgfqEu1lS9Fmxwz3Oqf5rULBnL6ccukAiMlJGI/GlIgdGRk7PsvelBCA4V+cc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: b02e5cb883e011f1aa26b74ffac11d73-20260720 X-CTIC-Tags: HR_CC_COUNT, HR_CC_DOMAIN_COUNT, HR_CC_NAME, HR_CC_NO_NAME, HR_CTE_8B HR_CTT_MISS, HR_DATE_H, HR_DATE_WKD, HR_DATE_ZONE, HR_FROM_NAME HR_SJ_DIGIT_LEN, HR_SJ_LANG, HR_SJ_LEN, HR_SJ_LETTER, HR_SJ_NOR_SYM HR_SJ_PHRASE, HR_SJ_PHRASE_LEN, HR_SJ_WS, HR_TO_COUNT, HR_TO_DOMAIN_COUNT HR_TO_NO_NAME, IP_TRUSTED, SRC_TRUSTED, DN_TRUSTED, SA_EXISTED SN_EXISTED, SPF_NOPASS, DKIM_NOPASS, DMARC_NOPASS, CIE_GOOD CIE_GOOD_SPF, GTI_FG_BS, GTI_RG_INFO, GTI_C_BU, AMN_GOOD ABX_MISS_RDNS X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.12,REQID:7fcd9d23-5882-46a9-ac6c-a8f12cda6b17,IP:15, URL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:15 X-CID-INFO: VERSION:1.3.12,REQID:7fcd9d23-5882-46a9-ac6c-a8f12cda6b17,IP:15,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION:r elease,TS:15 X-CID-META: VersionHash:e7bac3a,CLOUDID:e9db82c961f5bb119f0c487871581647,BulkI D:260720101408BWPN2JAN,BulkQuantity:0,Recheck:0,SF:10|38|66|78|102|127|850 |865|898,TC:nil,Content:0|15|50,EDM:-3,IP:-2,URL:0,File:nil,RT:nil,Bulk:ni l,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE :0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: b02e5cb883e011f1aa26b74ffac11d73-20260720 X-User: yijiangshan@kylinos.cn Received: from localhost.localdomain [(116.128.244.171)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 322931628; Mon, 20 Jul 2026 10:14:07 +0800 From: Jiangshan Yi To: lukas@wunner.de, ignat@linux.win, herbert@gondor.apana.org.au, davem@davemloft.net Cc: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, 13667453960@163.com, Jiangshan Yi Subject: [PATCH] crypto: rsassa-pkcs1 - Use constant-time digest comparison Date: Mon, 20 Jul 2026 10:13:22 +0800 Message-Id: <20260720021322.122784-1-yijiangshan@kylinos.cn> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The digest comparison in rsassa_pkcs1_verify() uses memcmp(), whose execution time depends on the position of the first mismatched byte. This creates a timing side-channel that could allow an attacker to forge RSA PKCS#1 v1.5 signatures byte by byte. Notably, the same function already uses crypto_memneq() for the hash prefix comparison (line 287), making the memcmp() at line 294 an inconsistent oversight. Replace memcmp() with crypto_memneq() to perform a constant-time comparison, consistent with the rest of the function and the crypto subsystem (gcm, ccm, chacha20poly1305, krb5enc, etc.). Signed-off-by: Jiangshan Yi --- crypto/rsassa-pkcs1.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/crypto/rsassa-pkcs1.c b/crypto/rsassa-pkcs1.c index 94fa5e9600e7..a612a9eef2dd 100644 --- a/crypto/rsassa-pkcs1.c +++ b/crypto/rsassa-pkcs1.c @@ -291,7 +291,7 @@ static int rsassa_pkcs1_verify(struct crypto_sig *tfm, /* RFC 8017 sec 8.2.2 step 4 - comparison of digest with out_buf */ if (dlen !=3D dst_len - pos) return -EKEYREJECTED; - if (memcmp(digest, out_buf + pos, dlen) !=3D 0) + if (crypto_memneq(digest, out_buf + pos, dlen)) return -EKEYREJECTED; =20 return 0; --=20 2.25.1