diff options
Diffstat (limited to 'oxish')
| -rw-r--r-- | oxish/src/authentication.rs | 51 |
1 files changed, 22 insertions, 29 deletions
diff --git a/oxish/src/authentication.rs b/oxish/src/authentication.rs index ebe44a3..42f4b0f 100644 --- a/oxish/src/authentication.rs +++ b/oxish/src/authentication.rs @@ -171,7 +171,7 @@ async fn inner<T: AsyncRead + AsyncWrite + Unpin>( // Signature, no authorized key => verify signature against fake key (Some(sig), None) => ( sig, - match AuthorizedKey::fake(&public_key.algorithm, provider) { + match fake_key(&public_key.algorithm, provider) { Ok(key) => key, Err(_) => { warn!(algorithm = ?public_key.algorithm, "unsupported public key algorithm"); @@ -232,6 +232,27 @@ async fn inner<T: AsyncRead + AsyncWrite + Unpin>( } } +/// Build a fake key for the given `algorithm` to mitigate timing attacks +/// +/// We want to execute a signature verification even when the user does not have a matching +/// authorized key, so we build a fake key for the requested algorithm and verify the +/// signature against it. This ensures that the response time is consistent regardless of +/// whether the user has a matching authorized key. +fn fake_key( + algorithm: &PublicKeyAlgorithm<'_>, + provider: &dyn CryptoProvider, +) -> Result<AuthorizedKey, CryptoError> { + AuthorizedKey::from_str( + match algorithm { + PublicKeyAlgorithm::EcdsaSha2Nistp256 => "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBE4MlZd759Tv7GElTKPf1D0FCmDWB9LEkkWyaP3E8T0H/fKyFnA0e0yBm/XpkG9erfxrcgMkAu1CM3e19g9bZWg=", + PublicKeyAlgorithm::Ed25519 => "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDX+GNCeikghR3A2bLB0KmlovqxdC+BUHAfYhYGcUJxA", + _ => return Err(CryptoError::UnknownAlgorithm), + }, + provider, + ) + .ok_or(CryptoError::KeyRejected) +} + /// Default [`UserStore`] implementation /// /// Uses the system database when running as root, and a single-user store otherwise. @@ -605,27 +626,6 @@ pub struct AuthorizedKey { } impl AuthorizedKey { - /// Build a fake key for the given `algorithm` to mitigate timing attacks - /// - /// We want to execute a signature verification even when the user does not have a matching - /// authorized key, so we build a fake key for the requested algorithm and verify the - /// signature against it. This ensures that the response time is consistent regardless of - /// whether the user has a matching authorized key. - fn fake( - algorithm: &PublicKeyAlgorithm<'_>, - provider: &dyn CryptoProvider, - ) -> Result<Self, CryptoError> { - Self::from_str( - match algorithm { - PublicKeyAlgorithm::EcdsaSha2Nistp256 => Self::FAKE_ECDSA_P256_KEY, - PublicKeyAlgorithm::Ed25519 => Self::FAKE_ED25519_KEY, - _ => return Err(CryptoError::UnknownAlgorithm), - }, - provider, - ) - .ok_or(CryptoError::KeyRejected) - } - /// Build an `AuthorizedKey` from a string in the format used in `authorized_keys` pub fn from_str(s: &str, provider: &dyn CryptoProvider) -> Option<Self> { let key = match s.split_once('#') { @@ -780,13 +780,6 @@ impl AuthorizedKey { .await .map_err(|_| ProtoError::InvalidPacket("signature verification task failed"))? } - - /// Random ECDSA-P256 key used to mitigate timing attacks during authentication - const FAKE_ECDSA_P256_KEY: &'static str = "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBE4MlZd759Tv7GElTKPf1D0FCmDWB9LEkkWyaP3E8T0H/fKyFnA0e0yBm/XpkG9erfxrcgMkAu1CM3e19g9bZWg="; - - /// Random Ed25519 public key used to mitigate timing attacks during authentication - const FAKE_ED25519_KEY: &'static str = - "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDX+GNCeikghR3A2bLB0KmlovqxdC+BUHAfYhYGcUJxA"; } impl fmt::Debug for AuthorizedKey { |