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{ "id": 2231471, "url": "http://patchwork.ozlabs.org/api/covers/2231471/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-cifs-client/cover/20260430-kerbmi-v2-0-0b98fe250425@microsoft.com/", "project": { "id": 12, "url": "http://patchwork.ozlabs.org/api/projects/12/?format=api", "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": "<20260430-kerbmi-v2-0-0b98fe250425@microsoft.com>", "list_archive_url": null, "date": "2026-04-30T17:48:22", "name": "[v2,0/2] smb: client: Spec-compliance fixes for Kerberos key derivation", "submitter": { "id": 92318, "url": "http://patchwork.ozlabs.org/api/people/92318/?format=api", "name": "Piyush Sachdeva", "email": "s.piyush1024@gmail.com" }, "mbox": "http://patchwork.ozlabs.org/project/linux-cifs-client/cover/20260430-kerbmi-v2-0-0b98fe250425@microsoft.com/mbox/", "series": [ { "id": 502352, "url": "http://patchwork.ozlabs.org/api/series/502352/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-cifs-client/list/?series=502352", "date": "2026-04-30T17:48:22", "name": "smb: client: Spec-compliance fixes for Kerberos key derivation", "version": 2, "mbox": "http://patchwork.ozlabs.org/series/502352/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/covers/2231471/comments/", "headers": { "Return-Path": "\n <linux-cifs+bounces-11311-incoming=patchwork.ozlabs.org@vger.kernel.org>", "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=Cww5Qex/;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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charset=\"utf-8\"", "Content-Transfer-Encoding": "7bit", "X-B4-Tracking": "v=1; b=H4sIAAAAAAAC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyjHQUlJIzE\n vPSU3UzU4B8JSMDIzMDEyNL3ezUoqTcTN2UZAMLU+PkFCPLtGQloOKCotS0zAqwQdGxEH5xaVJ\n WanIJSLdSbS0Azr6/WGoAAAA=", "X-Change-ID": "20260429-kerbmi-dc0853cd29fc", "To": "Steve French <sfrench@samba.org>, linux-cifs@vger.kernel.org,\n Shyam Prasad N <sprasad@microsoft.com>,\n Bharath SM <bharathsm@microsoft.com>", "Cc": "samba-technical@lists.samba.org, linux-kernel@vger.kernel.org,\n vaibsharma@microsoft.com", "X-Mailer": "b4 0.15.2", "X-Developer-Signature": "v=1; a=openpgp-sha256; l=2612;\n i=psachdeva@microsoft.com; h=from:subject:message-id;\n bh=GqJ6tP9cEJF8yaCQdar1w41VrPtzXU/fP0c4/Bu1opo=;\n b=owGbwMvMwCV29FJ3ncRHDT/G02pJDJmfp75fI3ksbQJDR6flvRvW/uWzlwdXPLni2u05deqe1\n xdWFeu4dUxkYRDjYrAUU2TZcOKOLG/8Lsl5n54YwcxhZQIZIi3SwAAELAx8uYl5pUY6Rnqm2oZ6\n hkY6BjrGDFycAjDV6skM/0M0j8b9mKXgPrs3eEnfzukhm3RfmM/a+iZUJSqyTyPRUJ2RYdeKqt7\n Hp1um8P45es+Bydw9zWmaue2bCXvmJyy76nvgBzsA", "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 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 <psachdeva@microsoft.com>\nSigned-off-by: Piyush Sachdeva <s.piyush1024@gmail.com>\nBcc: vaibsharma@microsoft.com\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 <s.piyush1024@gmail.com>" }