Longwei Wang

A flaw exists where the source-address critical option in the Permissions returned by certain authentication callbacks is not validated against the client's remote address. This results in source-address restrictions being silently ignored when using the `PasswordCallback`, `KeyboardInteractiveCallback`, `NoClientAuthCallback`, and `GSSAPIWithMICConfig.AllowLogin` callbacks. The restriction was previously only enforced for `PublicKeyCallback` and `VerifiedPublicKeyCallback` paths.

The `ToASCII()` and `ToUnicode()` functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For instance, `ToUnicode("xn--example-.com")` returns "example.com" instead of an error. This behavior can lead to privilege escalation in programs using the idna package; a program performing privilege checks on an ASCII hostname might reject "example.com" but permit "xn--example-.com", and subsequently granting access to "example.com" after converting the hostname to Unicode.