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Fri, 13 Nov 2026 15:59:30 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id yAHVN+Ez92rsVgAAD6G6ig (envelope-from ); Fri, 13 Nov 2026 15:59:30 +0000 Date: Fri, 13 Nov 2026 12:59:28 -0300 From: Enzo Matsumiya To: Wong Steve Cc: pc@manguebit.org, linkinjeon@kernel.org, linux-cifs@vger.kernel.org, sprasad@microsoft.com, smfrench@gmail.com, ronniesahlberg@gmail.com, bharathsm@microsoft.com, linux-kernel@vger.kernel.org, daniel.birtwhistle@gehealthcare.com, samba-technical@lists.samba.org, tom@talpey.com Subject: Re: [PATCH] smb: client: fail SMB2 responses with a bad signature Message-ID: References: <20261113-smb2-sign-v1-1-937ee7c20f08@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 06CFF21F07 X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-13.51 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; URIBL_BLOCKED(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:email]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_TO(0.00)[gmail.com]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_TWELVE(0.00)[12]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[manguebit.org,kernel.org,vger.kernel.org,microsoft.com,gmail.com,gehealthcare.com,lists.samba.org,talpey.com]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; MISSING_XM_UA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:email] X-Spam-Score: -13.51 On 11/13, Wong Steve wrote: >On 11/13, Enzo Matsumiya wrote: >> However, I still think the error should only be returned if signing is >> required (*) AND rc == -EACCES. >> >> Any other error should always be returned unconditionally. >> >> (*) Note that "signing required" at that point means that either/both >> client and server required signing, and the other side agreed -- it >> doesn't really matter who asked for it. > >Thanks for looking at it. > >I think the existing server->sign check already covers that. >cifs_enable_signing() only sets server->sign when the server requires >signing and the client allows it, or when the client requires it (mount >option or SecurityFlags) and the server supports it. Both sides merely >supporting signing doesn't turn it on. > >smb2_verify_signature() is only called under that check, so the new >return passes on -EACCES for a mismatch, and any other error from it >(e.g. from smb3_calc_signature()) as well. > >Is there a case I'm missing where server->sign is set but signing isn't >required in your sense? Not really, you're 100% correct, sorry. I just remembered that there's a very specific exception to that, and it's currently not handled; SMB 3.1.1 tcon requests (!anonymous && !guest) are signed unconditionally, but the responses are never verified because they're gated by server->sign. While your patch fix this indirectly, I couldn't find in the spec whether such tcon responses should also fail if signing isn't required. Anyway, I think this can be discussed later in a follow up patch. @Paulo, @Namjae: Reviewed-by: Enzo Matsumiya Cheers, Enzo