Line data Source code
1 : //! Definitions for SCRAM messages.
2 :
3 : use std::fmt;
4 : use std::ops::Range;
5 :
6 : use base64::Engine as _;
7 : use base64::prelude::BASE64_STANDARD;
8 :
9 : use super::base64_decode_array;
10 : use super::key::{SCRAM_KEY_LEN, ScramKey};
11 : use super::signature::SignatureBuilder;
12 : use crate::sasl::ChannelBinding;
13 :
14 : /// Faithfully taken from PostgreSQL.
15 : pub(crate) const SCRAM_RAW_NONCE_LEN: usize = 18;
16 :
17 : /// Although we ignore all extensions, we still have to validate the message.
18 33 : fn validate_sasl_extensions<'a>(parts: impl Iterator<Item = &'a str>) -> Option<()> {
19 33 : for mut chars in parts.map(|s| s.chars()) {
20 6 : let attr = chars.next()?;
21 6 : if !attr.is_ascii_alphabetic() {
22 1 : return None;
23 5 : }
24 5 : let eq = chars.next()?;
25 4 : if eq != '=' {
26 1 : return None;
27 3 : }
28 : }
29 :
30 30 : Some(())
31 33 : }
32 :
33 : #[derive(Debug)]
34 : pub(crate) struct ClientFirstMessage<'a> {
35 : /// `client-first-message-bare`.
36 : pub(crate) bare: &'a str,
37 : /// Channel binding mode.
38 : pub(crate) cbind_flag: ChannelBinding<&'a str>,
39 : /// Client nonce.
40 : pub(crate) nonce: &'a str,
41 : }
42 :
43 : impl<'a> ClientFirstMessage<'a> {
44 : // NB: FromStr doesn't work with lifetimes
45 21 : pub(crate) fn parse(input: &'a str) -> Option<Self> {
46 21 : let mut parts = input.split(',');
47 :
48 21 : let cbind_flag = ChannelBinding::parse(parts.next()?)?;
49 :
50 : // PG doesn't support authorization identity,
51 : // so we don't bother defining GS2 header type
52 21 : let authzid = parts.next()?;
53 21 : if !authzid.is_empty() {
54 1 : return None;
55 20 : }
56 20 :
57 20 : // Unfortunately, `parts.as_str()` is unstable
58 20 : let pos = authzid.as_ptr() as usize - input.as_ptr() as usize + 1;
59 20 : let (_, bare) = input.split_at(pos);
60 :
61 : // In theory, these might be preceded by "reserved-mext" (i.e. "m=")
62 20 : let username = parts.next()?.strip_prefix("n=")?;
63 :
64 : // https://github.com/postgres/postgres/blob/f83908798f78c4cafda217ca875602c88ea2ae28/src/backend/libpq/auth-scram.c#L13-L14
65 20 : if !username.is_empty() {
66 1 : tracing::warn!(username, "scram username provided, but is not expected");
67 : // TODO(conrad):
68 : // return None;
69 19 : }
70 :
71 20 : let nonce = parts.next()?.strip_prefix("r=")?;
72 :
73 : // Validate but ignore auth extensions
74 20 : validate_sasl_extensions(parts)?;
75 :
76 17 : Some(Self {
77 17 : bare,
78 17 : cbind_flag,
79 17 : nonce,
80 17 : })
81 21 : }
82 :
83 : /// Build a response to [`ClientFirstMessage`].
84 12 : pub(crate) fn build_server_first_message(
85 12 : &self,
86 12 : nonce: &[u8; SCRAM_RAW_NONCE_LEN],
87 12 : salt_base64: &str,
88 12 : iterations: u32,
89 12 : ) -> OwnedServerFirstMessage {
90 : use std::fmt::Write;
91 :
92 12 : let mut message = String::new();
93 12 : write!(&mut message, "r={}", self.nonce).unwrap();
94 12 : BASE64_STANDARD.encode_string(nonce, &mut message);
95 12 : let combined_nonce = 2..message.len();
96 12 : write!(&mut message, ",s={salt_base64},i={iterations}").unwrap();
97 12 :
98 12 : // This design guarantees that it's impossible to create a
99 12 : // server-first-message without receiving a client-first-message
100 12 : OwnedServerFirstMessage {
101 12 : message,
102 12 : nonce: combined_nonce,
103 12 : }
104 12 : }
105 : }
106 :
107 : #[derive(Debug)]
108 : pub(crate) struct ClientFinalMessage<'a> {
109 : /// `client-final-message-without-proof`.
110 : pub(crate) without_proof: &'a str,
111 : /// Channel binding data (base64).
112 : pub(crate) channel_binding: &'a str,
113 : /// Combined client & server nonce.
114 : pub(crate) nonce: &'a str,
115 : /// Client auth proof.
116 : pub(crate) proof: [u8; SCRAM_KEY_LEN],
117 : }
118 :
119 : impl<'a> ClientFinalMessage<'a> {
120 : // NB: FromStr doesn't work with lifetimes
121 13 : pub(crate) fn parse(input: &'a str) -> Option<Self> {
122 13 : let (without_proof, proof) = input.rsplit_once(',')?;
123 :
124 13 : let mut parts = without_proof.split(',');
125 13 : let channel_binding = parts.next()?.strip_prefix("c=")?;
126 13 : let nonce = parts.next()?.strip_prefix("r=")?;
127 :
128 : // Validate but ignore auth extensions
129 13 : validate_sasl_extensions(parts)?;
130 :
131 13 : let proof = base64_decode_array(proof.strip_prefix("p=")?)?;
132 :
133 13 : Some(Self {
134 13 : without_proof,
135 13 : channel_binding,
136 13 : nonce,
137 13 : proof,
138 13 : })
139 13 : }
140 :
141 : /// Build a response to [`ClientFinalMessage`].
142 7 : pub(crate) fn build_server_final_message(
143 7 : &self,
144 7 : signature_builder: SignatureBuilder<'_>,
145 7 : server_key: &ScramKey,
146 7 : ) -> String {
147 7 : let mut buf = String::from("v=");
148 7 : BASE64_STANDARD.encode_string(signature_builder.build(server_key), &mut buf);
149 7 :
150 7 : buf
151 7 : }
152 : }
153 :
154 : /// We need to keep a convenient representation of this
155 : /// message for the next authentication step.
156 : pub(crate) struct OwnedServerFirstMessage {
157 : /// Owned `server-first-message`.
158 : message: String,
159 : /// Slice into `message`.
160 : nonce: Range<usize>,
161 : }
162 :
163 : impl OwnedServerFirstMessage {
164 : /// Extract combined nonce from the message.
165 : #[inline(always)]
166 8 : pub(crate) fn nonce(&self) -> &str {
167 8 : &self.message[self.nonce.clone()]
168 8 : }
169 :
170 : /// Get reference to a text representation of the message.
171 : #[inline(always)]
172 20 : pub(crate) fn as_str(&self) -> &str {
173 20 : &self.message
174 20 : }
175 : }
176 :
177 : impl fmt::Debug for OwnedServerFirstMessage {
178 0 : fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
179 0 : f.debug_struct("ServerFirstMessage")
180 0 : .field("message", &self.as_str())
181 0 : .field("nonce", &self.nonce())
182 0 : .finish()
183 0 : }
184 : }
185 :
186 : #[cfg(test)]
187 : mod tests {
188 : use super::*;
189 :
190 : #[test]
191 1 : fn parse_client_first_message() {
192 : use ChannelBinding::*;
193 :
194 : // (Almost) real strings captured during debug sessions
195 1 : let cases = [
196 1 : (NotSupportedClient, "n,,n=,r=t8JwklwKecDLwSsA72rHmVju"),
197 1 : (NotSupportedServer, "y,,n=,r=t8JwklwKecDLwSsA72rHmVju"),
198 1 : (
199 1 : Required("tls-server-end-point"),
200 1 : "p=tls-server-end-point,,n=,r=t8JwklwKecDLwSsA72rHmVju",
201 1 : ),
202 1 : ];
203 :
204 4 : for (cb, input) in cases {
205 3 : let msg = ClientFirstMessage::parse(input).unwrap();
206 3 :
207 3 : assert_eq!(msg.bare, "n=,r=t8JwklwKecDLwSsA72rHmVju");
208 3 : assert_eq!(msg.nonce, "t8JwklwKecDLwSsA72rHmVju");
209 3 : assert_eq!(msg.cbind_flag, cb);
210 : }
211 1 : }
212 :
213 : #[test]
214 1 : fn parse_client_first_message_with_invalid_gs2_authz() {
215 1 : assert!(ClientFirstMessage::parse("n,authzid,n=,r=nonce").is_none());
216 1 : }
217 :
218 : #[test]
219 1 : fn parse_client_first_message_with_extra_params() {
220 1 : let msg = ClientFirstMessage::parse("n,,n=,r=nonce,a=foo,b=bar,c=baz").unwrap();
221 1 : assert_eq!(msg.bare, "n=,r=nonce,a=foo,b=bar,c=baz");
222 1 : assert_eq!(msg.nonce, "nonce");
223 1 : assert_eq!(msg.cbind_flag, ChannelBinding::NotSupportedClient);
224 1 : }
225 :
226 : #[test]
227 1 : fn parse_client_first_message_with_extra_params_invalid() {
228 1 : // must be of the form `<ascii letter>=<...>`
229 1 : assert!(ClientFirstMessage::parse("n,,n=,r=nonce,abc=foo").is_none());
230 1 : assert!(ClientFirstMessage::parse("n,,n=,r=nonce,1=foo").is_none());
231 1 : assert!(ClientFirstMessage::parse("n,,n=,r=nonce,a").is_none());
232 1 : }
233 :
234 : #[test]
235 1 : fn parse_client_final_message() {
236 1 : let input = [
237 1 : "c=eSws",
238 1 : "r=iiYEfS3rOgn8S3rtpSdrOsHtPLWvIkdgmHxA0hf3JNOAG4dU",
239 1 : "p=SRpfsIVS4Gk11w1LqQ4QvCUBZYQmqXNSDEcHqbQ3CHI=",
240 1 : ]
241 1 : .join(",");
242 1 :
243 1 : let msg = ClientFinalMessage::parse(&input).unwrap();
244 1 : assert_eq!(
245 1 : msg.without_proof,
246 1 : "c=eSws,r=iiYEfS3rOgn8S3rtpSdrOsHtPLWvIkdgmHxA0hf3JNOAG4dU"
247 1 : );
248 1 : assert_eq!(
249 1 : msg.nonce,
250 1 : "iiYEfS3rOgn8S3rtpSdrOsHtPLWvIkdgmHxA0hf3JNOAG4dU"
251 1 : );
252 1 : assert_eq!(
253 1 : BASE64_STANDARD.encode(msg.proof),
254 1 : "SRpfsIVS4Gk11w1LqQ4QvCUBZYQmqXNSDEcHqbQ3CHI="
255 1 : );
256 1 : }
257 : }
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