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tka: guard against key-length panics when verifying signatures

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In late 2022 a subtle but crucial part of documentation was added to ed25519.Verify: It
will panic if len(publicKey) is not [PublicKeySize].

02ed0e5e67

This change catches that error so it won't lead to a panic.

Signed-off-by: Tom DNetto <tom@tailscale.com>
Updates https://github.com/tailscale/corp/issues/8568
This commit is contained in:
Tom DNetto 2023-07-19 12:43:15 -07:00 committed by Tom
parent 486ab427b4
commit bec9815f02
2 changed files with 9 additions and 0 deletions
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3
tka/key.go
View File

@ -145,6 +145,9 @@ func signatureVerify(s *tkatype.Signature, aumDigest tkatype.AUMSigHash, key Key
// so we should use the public contained in the state machine. // so we should use the public contained in the state machine.
switch key.Kind { switch key.Kind {
case Key25519: case Key25519:
if len(key.Public) != ed25519.PublicKeySize {
return fmt.Errorf("ed25519 key has wrong length: %d", len(key.Public))
}
if ed25519consensus.Verify(ed25519.PublicKey(key.Public), aumDigest[:], s.Signature) { if ed25519consensus.Verify(ed25519.PublicKey(key.Public), aumDigest[:], s.Signature) {
return nil return nil
} }

6
tka/sig.go
View File

@ -225,6 +225,9 @@ func (s *NodeKeySignature) verifySignature(nodeKey key.NodePublic, verificationK
if !ok { if !ok {
return errors.New("missing rotation key") return errors.New("missing rotation key")
} }
if len(verifyPub) != ed25519.PublicKeySize {
return fmt.Errorf("bad rotation key length: %d", len(verifyPub))
}
if !ed25519.Verify(ed25519.PublicKey(verifyPub[:]), sigHash[:], s.Signature) { if !ed25519.Verify(ed25519.PublicKey(verifyPub[:]), sigHash[:], s.Signature) {
return errors.New("invalid signature") return errors.New("invalid signature")
} }
@ -249,6 +252,9 @@ func (s *NodeKeySignature) verifySignature(nodeKey key.NodePublic, verificationK
} }
switch verificationKey.Kind { switch verificationKey.Kind {
case Key25519: case Key25519:
if len(verificationKey.Public) != ed25519.PublicKeySize {
return fmt.Errorf("ed25519 key has wrong length: %d", len(verificationKey.Public))
}
if ed25519consensus.Verify(ed25519.PublicKey(verificationKey.Public), sigHash[:], s.Signature) { if ed25519consensus.Verify(ed25519.PublicKey(verificationKey.Public), sigHash[:], s.Signature) {
return nil return nil
} }