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ssh: add VerifiedPublicKeyCallback

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Fixes golang/go#70795

Change-Id: I9b7c91f35f89495d1e9b5f6ec0c036c02a61d774
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/636335
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jorge Hernández <jorgehcrda39@gmail.com>
This commit is contained in:
Nicola Murino
2025-09-27 12:43:41 -07:00
parent 66c3d8ce71
commit 2beaa59a3c
2 changed files with 401 additions and 0 deletions
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ssh/server.go
+27
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@@ -44,6 +44,9 @@ type Permissions struct {
// pass data from the authentication callbacks to the server
// application layer.
Extensions map[string]string
// ExtraData allows to store user defined data.
ExtraData map[any]any
}
type GSSAPIWithMICConfig struct {
@@ -127,6 +130,21 @@ type ServerConfig struct {
// Permissions.Extensions entry.
PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error)
// VerifiedPublicKeyCallback, if non-nil, is called after a client
// successfully confirms having control over a key that was previously
// approved by PublicKeyCallback. The permissions object passed to the
// callback is the one returned by PublicKeyCallback for the given public
// key and its ownership is transferred to the callback. The returned
// Permissions object can be the same object, optionally modified, or a
// completely new object. If VerifiedPublicKeyCallback is non-nil,
// PublicKeyCallback is not allowed to return a PartialSuccessError, which
// can instead be returned by VerifiedPublicKeyCallback.
//
// VerifiedPublicKeyCallback does not affect which authentication methods
// are included in the list of methods that can be attempted by the client.
VerifiedPublicKeyCallback func(conn ConnMetadata, key PublicKey, permissions *Permissions,
signatureAlgorithm string) (*Permissions, error)
// KeyboardInteractiveCallback, if non-nil, is called when
// keyboard-interactive authentication is selected (RFC
// 4256). The client object's Challenge function should be
@@ -653,6 +671,9 @@ userAuthLoop:
candidate.pubKeyData = pubKeyData
candidate.perms, candidate.result = authConfig.PublicKeyCallback(s, pubKey)
_, isPartialSuccessError := candidate.result.(*PartialSuccessError)
if isPartialSuccessError && config.VerifiedPublicKeyCallback != nil {
return nil, errors.New("ssh: invalid library usage: PublicKeyCallback must not return partial success when VerifiedPublicKeyCallback is defined")
}
if (candidate.result == nil || isPartialSuccessError) &&
candidate.perms != nil &&
@@ -723,6 +744,12 @@ userAuthLoop:
authErr = candidate.result
perms = candidate.perms
if authErr == nil && config.VerifiedPublicKeyCallback != nil {
// Only call VerifiedPublicKeyCallback after the key has been accepted
// and successfully verified. If authErr is non-nil, the key is not
// considered verified and the callback must not run.
perms, authErr = config.VerifiedPublicKeyCallback(s, pubKey, perms, algo)
}
}
case "gssapi-with-mic":
if authConfig.GSSAPIWithMICConfig == nil {