[PATCH 0/2] ksmbd: AES-GMAC signing support

[Michail Andreas Michalopoulos]

SMB 3.1.1 clients choose the signing algorithm in the
SMB2_SIGNING_CAPABILITIES negotiate context. ksmbd parses the client's
list, but init_smb3_11_server() then overwrites the choice with
AES-CMAC, so a client that does not offer AES-CMAC cannot connect.
Patch 1 fixes that and keeps each signing key paired with the
algorithm it was created for. Patch 2 adds AES-GMAC, which Windows and
macOS offer first, using the lib/crypto AES-GCM API.

Discussion:
https://lore.kernel.org/linux-cifs/D0F05F9A-5097-4A2D-9235-AE395961F456@xxxxxxxxx/

Testing:
- smbtorture 4.19 with each algorithm forced
  (clientsmb3signingalgorithms): without the series an HMAC-SHA256
  only client fails smb2.connect with NT_STATUS_INVALID_NETWORK_RESPONSE
  and an AES-GMAC only client cannot negotiate. With it, all three
  connect and sign with the forced algorithm; smb2.connect then stops
  at its tree disconnect check (STATUS_ACCESS_DENIED instead of
  STATUS_NETWORK_NAME_DELETED), as it does for AES-CMAC without the
  series.
- smb2.session (smbtorture 4.19, multichannel off): 21 tests pass
  instead of 12. signing-hmac-sha-256, signing-aes-128-cmac,
  signing-aes-128-gmac, encryption-aes-{128,256}-{ccm,gcm} and
  bind_negative_smb3signGtoH2X{d,s} need signing negotiation and now
  run and pass instead of being skipped. 26 other
  bind_negative_smb3sign*/smb3sne* tests now run too and fail with
  STATUS_USER_SESSION_DELETED, because binding needs multichannel;
  see the next item for them with multichannel enabled. No test that
  passed before fails.
- smb2.bench.echo and smb2.bench.read with each algorithm forced,
  smbtorture 4.19 (x86) and 4.23 (arm64).
- smb2.session.bind_negative* with multichannel enabled (smbtorture
  4.19): all tests involving AES-GMAC pass. Without the series most
  smb3sign* tests were skipped, as ksmbd could not negotiate anything
  but AES-CMAC. The four AES-CMAC <-> HMAC-SHA256 tests now run and
  fail on existing binding behaviour that this series does not touch:
  the *d variants because ksmbd rejects binding from a different
  ClientGUID (Windows accepts it), the *s variants because a session
  setup without the binding flag on an already bound connection
  succeeds instead of failing with STATUS_ACCESS_DENIED.
- Windows Server 2025: offered AES-GMAC, AES-CMAC, HMAC-SHA256 and
  ksmbd answered AES-GMAC (checked in a packet capture). A 1 GiB copy
  to and from the share came back identical (SHA256), with signing
  required and encryption off.
- macOS 26: negotiated AES-GMAC, 256 MiB copy identical.
- No "bad smb2 signature" messages in any of these runs.

End to end, smbtorture smb2.bench.read with 1 MiB reads, MB/s:

                               HMAC-SHA256   AES-CMAC   AES-GMAC
  arm64, Apple M4 VM, loopback        1354        924        797
  x86, AMD EPYC VMs, 3.56 Gbit/s       449        341        469

On arm64 AES-GMAC is currently the slowest because the arm64 GHASH
library code does not use PMULL for bulk data; I'll send a separate
lib/crypto series for that, as discussed in the thread above.

Not tested: multichannel with Windows or macOS clients (binding was
only tested with smbtorture), and SMB over RDMA.

An AI assistant was used to draft the patches and as an independent
reviewer. I ran the Windows, macOS and benchmark tests; the smbtorture
runs were done by the assistant under UML.

Michail Andreas Michalopoulos (2):
  ksmbd: sign with the negotiated SMB 3.1.1 signing algorithm
  ksmbd: add AES-GMAC signing support

 Documentation/filesystems/smb/ksmbd.rst |  2 +-
 fs/smb/server/Kconfig                   |  1 +
 fs/smb/server/auth.c                    | 60 ++++++++++++++++++++++++-
 fs/smb/server/auth.h                    |  4 +-
 fs/smb/server/mgmt/user_session.c       |  1 +
 fs/smb/server/mgmt/user_session.h       |  2 +
 fs/smb/server/smb2ops.c                 |  4 +-
 fs/smb/server/smb2pdu.c                 | 53 +++++++++++++++++++---
 8 files changed, 116 insertions(+), 11 deletions(-)


base-commit: af8c72f6550744fe948ef2dbc7ab8739c149aab2
-- 
2.43.0