{"id":2234482,"url":"http://patchwork.ozlabs.org/api/1.2/covers/2234482/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/cover/20260507-kerbmi-v3-0-397ebbb53eff@microsoft.com/","project":{"id":12,"url":"http://patchwork.ozlabs.org/api/1.2/projects/12/?format=json","name":"Linux CIFS Client","link_name":"linux-cifs-client","list_id":"linux-cifs.vger.kernel.org","list_email":"linux-cifs@vger.kernel.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260507-kerbmi-v3-0-397ebbb53eff@microsoft.com>","list_archive_url":null,"date":"2026-05-07T16:52:12","name":"[v3,0/2] smb: client: Spec-compliance fixes for Kerberos key derivation","submitter":{"id":92318,"url":"http://patchwork.ozlabs.org/api/1.2/people/92318/?format=json","name":"Piyush Sachdeva","email":"s.piyush1024@gmail.com"},"mbox":"http://patchwork.ozlabs.org/project/linux-cifs-client/cover/20260507-kerbmi-v3-0-397ebbb53eff@microsoft.com/mbox/","series":[{"id":503227,"url":"http://patchwork.ozlabs.org/api/1.2/series/503227/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/list/?series=503227","date":"2026-05-07T16:52:12","name":"smb: client: Spec-compliance fixes for Kerberos key derivation","version":3,"mbox":"http://patchwork.ozlabs.org/series/503227/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/covers/2234482/comments/","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-cifs@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=IZ8vnqbX;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c09:e001:a7::12fc:5321; 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charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","X-B4-Tracking":"v=1; b=H4sIAAAAAAAC/zWNQQ6CMBBFr0JmbU0zFQOuvIdhYYepjAZKWiQa0\n rtbUJcvef/9BSIH4QinYoHAs0TxQwazK4C663BjJW1mQI1HfcBaPTjYXlRLuioNtVg7giyPgZ2\n 8ttCl+XJ82jvTtK5Xo5M4+fDenmZcvV/U6H90RqWVtnXlGMv8Vp57oeCjd9OefA9NSukDAbn91\n LIAAAA=","X-Change-ID":"20260429-kerbmi-dc0853cd29fc","To":"Steve French , linux-cifs@vger.kernel.org,\n Shyam Prasad N ,\n Bharath SM , Paulo Alcantara ,\n Ronnie Sahlberg , Tom Talpey ","Cc":"samba-technical@lists.samba.org, linux-kernel@vger.kernel.org,\n stable@vger.kernel.org, vaibsharma@microsoft.com","X-Mailer":"b4 0.15.2","X-Developer-Signature":"v=1; a=openpgp-sha256; l=3196;\n i=psachdeva@microsoft.com; h=from:subject:message-id;\n bh=QhvtuPuYuRikxrXlvfGt1GYpisVF2O1XfkkjalC53Gw=;\n b=owGbwMvMwCV29FJ3ncRHDT/G02pJDJl/Djt29ets/C4cHbakV6Ptv5ByCLPywWLreA9z4eML9\n KJebz7dMZGFQYyLwVJMkWXDiTuyvPG7JOd9emIEM4eVCWSItEgDAxCwMPDlJuaVGukY6ZlqG+oZ\n GukY6BgzcHEKwFRrTGJkmL5nbW9+q87HpdH5Gr17C1T+v/k2eTlbEKfbJwt7td2rtzEynKn8cSI\n rwac1bWFr6Oy59+Q9pi9UZUgVfyW3hnt6NIc6IwA=","X-Developer-Key":"i=psachdeva@microsoft.com; a=openpgp;\n fpr=80350F71F916134953C3EB979E19C6F9839C3CFC"},"content":"This series fixes two MS-SMB2 section 3.2.5.3 spec violations in the\nKerberos session key handling path of fs/smb/client.\n\nPatch 1/2 (resend of v1 with a small cleanup folded in) fixes the\nAES-256 mount failure with sec=krb5: encryption and decryption key\nderivation must use Session.FullSessionKey (the full Kerberos session\nkey, typically 32 bytes for the aes256-cts-hmac-sha1-96 enctype)\ninstead of Session.SessionKey (the first 16 bytes).\n\nPatch 2/2 closes the related corner case in the same section of the\nspec: when the GSS protocol returns a session key shorter than 16\nbytes, the buffer must be right-padded with zero bytes. The current\ncode copies the GSS key verbatim, which causes generate_key() to read\npast the end of the allocated buffer and derive keys that do not match\nthe server. The trigger is deprecated short-key Kerberos enctypes\n(e.g. single-DES, 8-byte session key); modern KDCs disable these by\ndefault, so this is a latent issue rather than a reachable one, but it\nis still a kernel slab over-read and a literal spec violation.\n\nVerified against Azure Files (AES-256-GCM + Kerberos aes256-cts) which\npreviously failed to mount with EAGAIN; the dmesg \"Session Key\" trace\nunder CONFIG_CIFS_DEBUG_DUMP_KEYS now shows the full 32-byte session\nkey being used for encryption/decryption KDF input.\n\nLink: https://lore.kernel.org/linux-cifs/20260409161538.3618-1-s.piyush1024@gmail.com/\n\nChanges since v2:\n - Patch 1/2: cast ses->auth_key.len to int when used as field width\n for \"%*ph\" in the CONFIG_CIFS_DEBUG_DUMP_KEYS dump, fixing a\n -Wformat warning. Reported by Sashiko.\n\nChanges since v1:\n - Patch 1/2: initialize full_key_size at declaration to silence\n -Wmaybe-uninitialized on some toolchains, and drop the now-\n redundant else branch (self-review).\n - Patch 1/2: tighten the FullSessionKey condition to also require\n Connection.Dialect == \"3.1.1\", matching MS-SMB2 3.2.5.3.1 verbatim.\n - New patch 2/2: zero-pad short GSS session keys per MS-SMB2 3.2.5.3,\n eliminating a latent slab over-read in generate_key().\n\nSigned-off-by: Piyush Sachdeva \nSigned-off-by: Piyush Sachdeva \n---\nTo: Steve French \nTo: Paulo Alcantara \nTo: Ronnie Sahlberg \nTo: Shyam Prasad N \nTo: Tom Talpey \nTo: Bharath SM \nCc: linux-cifs@vger.kernel.org\nCc: stable@vger.kernel.org\nCc: samba-technical@lists.samba.org\nCc: linux-kernel@vger.kernel.org\nCc: vaibsharma@microsoft.com\n\n---\nPiyush Sachdeva (2):\n smb: client: Use FullSessionKey for AES-256 encryption key derivation\n smb: client: Zero-pad short GSS session keys per MS-SMB2\n\n fs/smb/client/ioctl.c | 2 +-\n fs/smb/client/smb2pdu.c | 23 ++++++++++++++++++-----\n fs/smb/client/smb2transport.c | 35 ++++++++++++++++++++++++++---------\n 3 files changed, 45 insertions(+), 15 deletions(-)\n---\nbase-commit: 0cbc300257d9b399491909806777f504ec687c1d\nchange-id: 20260429-kerbmi-dc0853cd29fc\n\nBest regards,\n-- \nPiyush Sachdeva "}