The internal 'min' helper function in channel.go incorrectly cast the
input data length (int) to uint32 before comparing it with the
maximum packet size. On 64-bit systems, if the data length is a
multiple of 2^32 (approx. 4GB), this cast results in 0.
Consequently, the function returns 0, causing the WriteExtended loop
to spin indefinitely because it attempts to reserve 0 bytes while
the remaining data length is still positive.
This change renames the helper to 'minPayloadSize' to avoid confusion
with the Go 1.21 built-in 'min' and updates the logic to use int64
for comparisons, preventing truncation and the resulting infinite loop.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixesgolang/go#79567
Fixes CVE-2026-39834
Change-Id: Id5bf81d9f06c7042452acffe1c76580ff878665e
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781663
Reviewed-by: Neal Patel <nealpatel@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Previously the library did not verify the "User Presence" (UP) bit in
signatures generated by FIDO/U2F security keys
(sk-ecdsa-sha2-nistp256@openssh.com and sk-ssh-ed25519@openssh.com).
This allowed signatures without physical interaction to be accepted
if the underlying hardware produced them, deviating from the default
secure behavior expected by the FIDO standards and OpenSSH.
skECDSAPublicKey.Verify and skEd25519PublicKey.Verify now enforce
the user-presence bit (0x01, constant flagUserPresence) by default.
Signatures whose flags byte has UP clear fail with the sentinel
errSKMissingUserPresence.
The server public-key authentication path honors the OpenSSH
"no-touch-required" extension as an opt-out. noTouchAllowed reports
true when the extension is present either in the Permissions
returned by PublicKeyCallback (authorized_keys-level opt-out) or in
the certificate's own Extensions (CA-level opt-out); in that case
skKeyWithoutUP is used to derive a clone of the SK public key (and,
for certificates, a clone of the wrapping Certificate whose inner
Key is the cloned SK key) whose Verify accepts UP-clear signatures.
The originals are never mutated, so a per-session opt-out cannot
leak across authentication attempts or connections. Matching
OpenSSH, the opt-out is read only from Extensions, never from
CriticalOptions.
skKeyWithoutUP is iterative and unwraps at most one level of
*Certificate: the SSH cert format forbids Certificate.Key from being
another Certificate (parseCert rejects it) but callers can still
construct such a value directly in Go, so a recursive descent would
be driven to unbounded depth by malformed or cyclic input. Any such
pathological *Certificate is returned unchanged.
CertChecker.CheckCert applies skKeyWithoutUP unconditionally to the
certificate's CA key before verifying the CA signature, matching
OpenSSH, which calls sshkey_verify with detailsp==NULL in
sshkey.c:cert_parse and never extracts or enforces UP/UV flags on
CA signatures. The UP bit on a CA signature reflects the CA
operator's presence at cert-issuance time, which has no bearing on
whether the user being authenticated is present now, so enforcing it
here would only break interop with certificates issued by
non-interactive SK CAs without a corresponding security benefit. The
skKeyWithoutUP call is a no-op for non-SK CA keys (the common case).
This change breaks backward compatibility for clients or keys that
generate user-authentication signatures without the User Presence
flag set. Previously those signatures were accepted by the server.
They will now be rejected with "ssh: signature missing required user
presence flag" unless the "no-touch-required" extension is
explicitly granted to the session by the server callbacks, or
carried by the user certificate.
This issue was found during a security audit by NCC Group
Cryptography Services, sponsored by Teleport.
Fixesgolang/go#79566
Fixes CVE-2026-39831
Change-Id: I74b6de3bb6a2d7a0f34d7fa36bbbbf06f0b3fc6b
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781662
Reviewed-by: Neal Patel <nealpatel@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
The parseDSA function previously accepted DSA keys with arbitrary values
for the sub-prime Q and did not validate that group elements G and Y
were within the modulus P.
Malicious actors could provide a key with a massively large Q (e.g.,
millions of bits), leading to excessive CPU consumption during signature
verification.
This change restricts the sub-prime Q to exactly 160 bits, as required
by FIPS 186-2, and ensures that G and Y are strictly less than P.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixesgolang/go#79565
Fixes CVE-2026-39829
Change-Id: I526118d94684076088d0625178844f64c1303ec8
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781661
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Neal Patel <nealpatel@google.com>
Previously, the RSA key parser accepted keys with arbitrary modulus
sizes. Processing keys with extremely large moduli (e.g., > 8192 bits)
can consume excessive CPU resources during verification, potentially
leading to a Denial of Service (DoS).
This change introduces a limit of 8192 bits for the RSA modulus in
parseRSA, rejecting keys that exceed this size in line with the limit
enforced by crypto/tls.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixesgolang/go#79565
Fixes CVE-2026-39829
Change-Id: Ibdddad1859a4d9db5c9f052d06c82f29bfc2e5e5
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781641
Reviewed-by: Neal Patel <nealpatel@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Previously, the mux implementation handled global request responses by
blocking until the response could be sent to the globalResponses channel.
Since this channel has a buffer size of 1, unsolicited responses from a
server (or responses arriving after a timeout) would fill the buffer.
Subsequent unsolicited responses would block handleGlobalPacket, stalling
the entire connection's read loop and causing a denial of service.
This change modifies handleGlobalPacket to use a non-blocking send. If
no goroutine is waiting for a response (or the buffer is full), the
message is dropped. This aligns with OpenSSH behavior, which ignores
unexpected global responses.
Additionally, SendRequest now drains the globalResponses channel after
acquiring the mutex but before sending the request. This ensures that
any stale responses or "spam" buffered just before the lock was acquired
are discarded, preventing race conditions where a legitimate request
might otherwise consume an unrelated response.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixesgolang/go#79564
Fixes CVE-2026-39830
Change-Id: Ia0c46355203d557eadcd432c10b87c8a044e1089
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781640
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Neal Patel <nealpatel@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
In serverAuthenticate, the permissions variable is reset to nil at the
beginning of the authentication loop. If an authentication callback
returns a PartialSuccessError along with non-nil Permissions, those
permissions are currently silently discarded before the next
authentication step.
This change returns an error if a callback returns both a PartialSuccessError
and non-nil Permissions, preventing API misuse where the user might
erroneously expect those permissions to be preserved or merged into the
final session permissions.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixesgolang/go#79562
Fixes CVE-2026-39828
Change-Id: I632c9e46e2b5e8804ef88081063a3612a2462f9f
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781621
Reviewed-by: Neal Patel <nealpatel@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
When a server rejects an incoming channel request via
NewChannel.Reject, the channel is left in the multiplexer's
channel list. Because the channel is never explicitly removed or
closed, its internal buffers and sync primitives remain allocated
for the lifetime of the SSH connection.
A malicious client could exploit this behavior by repeatedly
requesting to open channels that are destined to be rejected,
causing unbounded memory growth and potentially leading to a
Denial of Service (DoS) via resource exhaustion.
This change fixes the leak by calling ch.mux.chanList.remove
within the Reject method, removing the channel from the list and allowing the
garbage collector to reclaim the associated memory immediately.
Fixesgolang/go#35127
Fixes CVE-2026-3982
Change-Id: Iaa177f5dfd151812dd404e528a4a1c77527a0e29
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/781320
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Nicholas Husin <nsh@golang.org>
Reviewed-by: Nicholas Husin <husin@google.com>
The in-memory keyring supports the "lifetime" constraint but does not
implement the "confirm" constraint. Previously, keyring.Add silently
ignored ConfirmBeforeUse: the key was stored, advertised through List,
and used for signing without any interactive confirmation, potentially
misleading callers into believing this security measure was enforced.
Return an error when ConfirmBeforeUse is set instead of silently
downgrading the caller's security expectations. Implementing real
confirm-before-use in an in-memory library keyring is infeasible (there
is no UI or confirmation callback), so failing closed is the correct
behavior; adding actual confirm support would require an API addition
and is out of scope.
This is a deliberate behavior change: keyring.Add previously accepted
and ignored ConfirmBeforeUse and now returns an error. This change also
updates the keyring doc comments to document the supported constraints.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Fixes CVE-2026-39833
Updates golang/go#47533Fixesgolang/go#79436
Change-Id: I1b3a286f0c1e4a4e08ac37109f7e491692ca90ae
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/778642
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Neal Patel <nealpatel@google.com>
Reviewed-by: Neal Patel <neal@golang.org>
Auto-Submit: Neal Patel <nealpatel@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
The client Add method only serialized the lifetime and confirm
constraints and silently dropped AddedKey.ConstraintExtensions before
sending the SSH_AGENTC_ADD_IDENTITY request. As a result the remote
agent always received the key with no extension constraints, regardless
of what the caller requested.
Applications that add a key believing custom constraint extensions
(such as restrict-destination-v00@openssh.com) would be enforced
instead loaded a completely unrestricted key into the agent. For
example, an administrator forwarding their agent into an untrusted jump
host and trying to limit the forwarded key with restrict-destination
never had that restriction reach the agent: any user or compromised
process on that host could make the agent sign arbitrary challenges.
Serialize each entry in key.ConstraintExtensions as an
agentConstrainExtension constraint so the constraints reach the agent,
and add a round-trip regression test that verifies the extensions
survive client serialization and server parsing.
This issue was found during a security audit by NCC Group Cryptography
Services, sponsored by Teleport.
Updates CVE-2026-39832
Updates golang/go#79435
Change-Id: I14c5583b106cbf0d282d2ba01e000e0f586f08c7
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/778640
Reviewed-by: Neal Patel <neal@golang.org>
Reviewed-by: Neal Patel <nealpatel@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
In Go 1.27 we've updated crypto/x509/pkix to avoid hex-encoding
attribute values that are string-typed. However, in TestBundle() we
assert the parsed certificate subject CN matches expected and now the
parsed value differs based on Go version.
This commit introduces some small helpers that on Go 1.25/1.26 replicate
the Go 1.27 behavior, decoding hex-encoded attribute values before
making the comparison.
In this way the test continues to pass without losing any coverage, or
introducing duplicated per-version bundles. In the future when only Go
1.27+ are supported we can revert this extra machinery.
Change-Id: I66bf6439e421169c0f9c750f88116b73ec5188fe
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/775760
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Daniel McCarney <daniel@binaryparadox.net>
Previously, pickSignatureAlgorithm constructed the list of candidate
algorithms by iterating over the static list returned by
algorithmsForKeyFormat. This caused the Signer's preference order
to be ignored in favor of the library's default internal order.
This change inverts the filtering logic to iterate over the signer's
supported algorithms first. This ensures that if a MultiAlgorithmSigner
explicitly prefers a specific algorithm (e.g., rsa-sha2-512 over
rsa-sha2-256), that preference is preserved and respected during the
handshake negotiation.
Fixesgolang/go#78248
Change-Id: I48a0aac720be7f973963342b82047ce32fc96699
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/746020
Reviewed-by: Lonny Wong <lonnywang.cn@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Providing 0 as argument for r or p results in a panic:
panic: runtime error: integer divide by zero
Providing negative values for r or p returns a misleading error:
scrypt: parameters are too large
This change avoids the panic and introduces a new error
that is returned when r or p are <= 0:
scrypt: parameters must be > 0
Change-Id: I68987b27d1eedd66644d2ec9436cba364fc1d46d
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/731780
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Auto-Submit: Roland Shoemaker <roland@golang.org>
Previously, an attacker could specify an integer up to 0xFFFFFFFF
that would directly allocate memory despite the observability of
the rest of the payload. This change places a hard cap on the
amount of mechanisms that can be specified and encoded in the
payload. Additionally, it performs a small sanity check to deny
payloads whose stated size is contradictory to the observed payload.
Thank you to Jakub Ciolek for reporting this issue.
Fixes CVE-2025-58181
Fixesgolang/go#76363
Change-Id: I0307ab3e906a3f2ae763b5f9f0310f7073f84485
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/721961
Auto-Submit: Roland Shoemaker <roland@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Neal Patel
Nicola Murino
Neal Patel
Roland Shoemaker
Dmitri Shuralyov
Gopher Robot
Daniel McCarney
repon
Filippo Valsorda
Rob Picard
Sean Liao
Juergen Graf
Michael Stapelberg
Santhanam
cuishuang