Line data Source code
1 : //! Implementation of the SCRAM authentication algorithm.
2 :
3 : use std::convert::Infallible;
4 :
5 : use base64::Engine as _;
6 : use base64::prelude::BASE64_STANDARD;
7 : use hmac::{Hmac, Mac};
8 : use sha2::Sha256;
9 :
10 : use super::ScramKey;
11 : use super::messages::{
12 : ClientFinalMessage, ClientFirstMessage, OwnedServerFirstMessage, SCRAM_RAW_NONCE_LEN,
13 : };
14 : use super::pbkdf2::Pbkdf2;
15 : use super::secret::ServerSecret;
16 : use super::signature::SignatureBuilder;
17 : use super::threadpool::ThreadPool;
18 : use crate::intern::EndpointIdInt;
19 : use crate::sasl::{self, ChannelBinding, Error as SaslError};
20 :
21 : /// The only channel binding mode we currently support.
22 : #[derive(Debug)]
23 : struct TlsServerEndPoint;
24 :
25 : impl std::fmt::Display for TlsServerEndPoint {
26 6 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
27 6 : write!(f, "tls-server-end-point")
28 6 : }
29 : }
30 :
31 : impl std::str::FromStr for TlsServerEndPoint {
32 : type Err = sasl::Error;
33 :
34 6 : fn from_str(s: &str) -> Result<Self, Self::Err> {
35 6 : match s {
36 6 : "tls-server-end-point" => Ok(TlsServerEndPoint),
37 0 : _ => Err(sasl::Error::ChannelBindingBadMethod(s.into())),
38 : }
39 6 : }
40 : }
41 :
42 : struct SaslSentInner {
43 : cbind_flag: ChannelBinding<TlsServerEndPoint>,
44 : client_first_message_bare: String,
45 : server_first_message: OwnedServerFirstMessage,
46 : }
47 :
48 : struct SaslInitial {
49 : nonce: fn() -> [u8; SCRAM_RAW_NONCE_LEN],
50 : }
51 :
52 : enum ExchangeState {
53 : /// Waiting for [`ClientFirstMessage`].
54 : Initial(SaslInitial),
55 : /// Waiting for [`ClientFinalMessage`].
56 : SaltSent(SaslSentInner),
57 : }
58 :
59 : /// Server's side of SCRAM auth algorithm.
60 : pub(crate) struct Exchange<'a> {
61 : state: ExchangeState,
62 : secret: &'a ServerSecret,
63 : tls_server_end_point: crate::tls::TlsServerEndPoint,
64 : }
65 :
66 : impl<'a> Exchange<'a> {
67 13 : pub(crate) fn new(
68 13 : secret: &'a ServerSecret,
69 13 : nonce: fn() -> [u8; SCRAM_RAW_NONCE_LEN],
70 13 : tls_server_end_point: crate::tls::TlsServerEndPoint,
71 13 : ) -> Self {
72 13 : Self {
73 13 : state: ExchangeState::Initial(SaslInitial { nonce }),
74 13 : secret,
75 13 : tls_server_end_point,
76 13 : }
77 13 : }
78 : }
79 :
80 : // copied from <https://github.com/neondatabase/rust-postgres/blob/20031d7a9ee1addeae6e0968e3899ae6bf01cee2/postgres-protocol/src/authentication/sasl.rs#L236-L248>
81 4 : async fn derive_client_key(
82 4 : pool: &ThreadPool,
83 4 : endpoint: EndpointIdInt,
84 4 : password: &[u8],
85 4 : salt: &[u8],
86 4 : iterations: u32,
87 4 : ) -> ScramKey {
88 4 : let salted_password = pool
89 4 : .spawn_job(endpoint, Pbkdf2::start(password, salt, iterations))
90 4 : .await;
91 :
92 4 : let make_key = |name| {
93 4 : let key = Hmac::<Sha256>::new_from_slice(&salted_password)
94 4 : .expect("HMAC is able to accept all key sizes")
95 4 : .chain_update(name)
96 4 : .finalize();
97 :
98 4 : <[u8; 32]>::from(key.into_bytes())
99 4 : };
100 :
101 4 : make_key(b"Client Key").into()
102 4 : }
103 :
104 4 : pub(crate) async fn exchange(
105 4 : pool: &ThreadPool,
106 4 : endpoint: EndpointIdInt,
107 4 : secret: &ServerSecret,
108 4 : password: &[u8],
109 4 : ) -> sasl::Result<sasl::Outcome<super::ScramKey>> {
110 4 : let salt = BASE64_STANDARD.decode(&*secret.salt_base64)?;
111 4 : let client_key = derive_client_key(pool, endpoint, password, &salt, secret.iterations).await;
112 :
113 4 : if secret.is_password_invalid(&client_key).into() {
114 1 : Ok(sasl::Outcome::Failure("password doesn't match"))
115 : } else {
116 3 : Ok(sasl::Outcome::Success(client_key))
117 : }
118 4 : }
119 :
120 : impl SaslInitial {
121 13 : fn transition(
122 13 : &self,
123 13 : secret: &ServerSecret,
124 13 : tls_server_end_point: &crate::tls::TlsServerEndPoint,
125 13 : input: &str,
126 13 : ) -> sasl::Result<sasl::Step<SaslSentInner, Infallible>> {
127 13 : let client_first_message = ClientFirstMessage::parse(input)
128 13 : .ok_or(SaslError::BadClientMessage("invalid client-first-message"))?;
129 :
130 : // If the flag is set to "y" and the server supports channel
131 : // binding, the server MUST fail authentication
132 13 : if client_first_message.cbind_flag == ChannelBinding::NotSupportedServer
133 1 : && tls_server_end_point.supported()
134 : {
135 1 : return Err(SaslError::ChannelBindingFailed("SCRAM-PLUS not used"));
136 12 : }
137 :
138 12 : let server_first_message = client_first_message.build_server_first_message(
139 12 : &(self.nonce)(),
140 12 : &secret.salt_base64,
141 12 : secret.iterations,
142 : );
143 12 : let msg = server_first_message.as_str().to_owned();
144 :
145 12 : let next = SaslSentInner {
146 12 : cbind_flag: client_first_message.cbind_flag.and_then(str::parse)?,
147 12 : client_first_message_bare: client_first_message.bare.to_owned(),
148 12 : server_first_message,
149 : };
150 :
151 12 : Ok(sasl::Step::Continue(next, msg))
152 13 : }
153 : }
154 :
155 : impl SaslSentInner {
156 12 : fn transition(
157 12 : &self,
158 12 : secret: &ServerSecret,
159 12 : tls_server_end_point: &crate::tls::TlsServerEndPoint,
160 12 : input: &str,
161 12 : ) -> sasl::Result<sasl::Step<Infallible, super::ScramKey>> {
162 : let Self {
163 12 : cbind_flag,
164 12 : client_first_message_bare,
165 12 : server_first_message,
166 12 : } = self;
167 :
168 12 : let client_final_message = ClientFinalMessage::parse(input)
169 12 : .ok_or(SaslError::BadClientMessage("invalid client-final-message"))?;
170 :
171 12 : let channel_binding = cbind_flag.encode(|_| match tls_server_end_point {
172 6 : crate::tls::TlsServerEndPoint::Sha256(x) => Ok(x),
173 0 : crate::tls::TlsServerEndPoint::Undefined => Err(SaslError::MissingBinding),
174 6 : })?;
175 :
176 : // This might've been caused by a MITM attack
177 12 : if client_final_message.channel_binding != channel_binding {
178 4 : return Err(SaslError::ChannelBindingFailed(
179 4 : "insecure connection: secure channel data mismatch",
180 4 : ));
181 8 : }
182 :
183 8 : if client_final_message.nonce != server_first_message.nonce() {
184 0 : return Err(SaslError::BadClientMessage("combined nonce doesn't match"));
185 8 : }
186 :
187 8 : let signature_builder = SignatureBuilder {
188 8 : client_first_message_bare,
189 8 : server_first_message: server_first_message.as_str(),
190 8 : client_final_message_without_proof: client_final_message.without_proof,
191 8 : };
192 :
193 8 : let client_key = signature_builder
194 8 : .build(&secret.stored_key)
195 8 : .derive_client_key(&client_final_message.proof);
196 :
197 : // Auth fails either if keys don't match or it's pre-determined to fail.
198 8 : if secret.is_password_invalid(&client_key).into() {
199 1 : return Ok(sasl::Step::Failure("password doesn't match"));
200 7 : }
201 :
202 7 : let msg =
203 7 : client_final_message.build_server_final_message(signature_builder, &secret.server_key);
204 :
205 7 : Ok(sasl::Step::Success(client_key, msg))
206 12 : }
207 : }
208 :
209 : impl sasl::Mechanism for Exchange<'_> {
210 : type Output = super::ScramKey;
211 :
212 25 : fn exchange(mut self, input: &str) -> sasl::Result<sasl::Step<Self, Self::Output>> {
213 : use ExchangeState;
214 : use sasl::Step;
215 25 : match &self.state {
216 13 : ExchangeState::Initial(init) => {
217 13 : match init.transition(self.secret, &self.tls_server_end_point, input)? {
218 12 : Step::Continue(sent, msg) => {
219 12 : self.state = ExchangeState::SaltSent(sent);
220 12 : Ok(Step::Continue(self, msg))
221 : }
222 0 : Step::Failure(msg) => Ok(Step::Failure(msg)),
223 : }
224 : }
225 12 : ExchangeState::SaltSent(sent) => {
226 12 : match sent.transition(self.secret, &self.tls_server_end_point, input)? {
227 7 : Step::Success(keys, msg) => Ok(Step::Success(keys, msg)),
228 1 : Step::Failure(msg) => Ok(Step::Failure(msg)),
229 : }
230 : }
231 : }
232 25 : }
233 : }
|
