postgres_protocol/password/
mod.rs

1//! Functions to encrypt a password in the client.
2//!
3//! This is intended to be used by client applications that wish to
4//! send commands like `ALTER USER joe PASSWORD 'pwd'`. The password
5//! need not be sent in cleartext if it is encrypted on the client
6//! side. This is good because it ensures the cleartext password won't
7//! end up in logs pg_stat displays, etc.
8
9use crate::authentication::sasl;
10use base64::display::Base64Display;
11use base64::engine::general_purpose::STANDARD;
12use hmac::{Hmac, Mac};
13use md5::Md5;
14use rand::RngCore;
15use sha2::digest::FixedOutput;
16use sha2::{Digest, Sha256};
17
18#[cfg(test)]
19mod test;
20
21const SCRAM_DEFAULT_ITERATIONS: u32 = 4096;
22const SCRAM_DEFAULT_SALT_LEN: usize = 16;
23
24/// Hash password using SCRAM-SHA-256 with a randomly-generated
25/// salt.
26///
27/// The client may assume the returned string doesn't contain any
28/// special characters that would require escaping in an SQL command.
29pub fn scram_sha_256(password: &[u8]) -> String {
30    let mut salt: [u8; SCRAM_DEFAULT_SALT_LEN] = [0; SCRAM_DEFAULT_SALT_LEN];
31    let mut rng = rand::rng();
32    rng.fill_bytes(&mut salt);
33    scram_sha_256_salt(password, salt)
34}
35
36// Internal implementation of scram_sha_256 with a caller-provided
37// salt. This is useful for testing.
38pub(crate) fn scram_sha_256_salt(password: &[u8], salt: [u8; SCRAM_DEFAULT_SALT_LEN]) -> String {
39    // Prepare the password, per [RFC
40    // 4013](https://tools.ietf.org/html/rfc4013), if possible.
41    //
42    // Postgres treats passwords as byte strings (without embedded NUL
43    // bytes), but SASL expects passwords to be valid UTF-8.
44    //
45    // Follow the behavior of libpq's PQencryptPasswordConn(), and
46    // also the backend. If the password is not valid UTF-8, or if it
47    // contains prohibited characters (such as non-ASCII whitespace),
48    // just skip the SASLprep step and use the original byte
49    // sequence.
50    let prepared: Vec<u8> = match std::str::from_utf8(password) {
51        Ok(password_str) => {
52            match stringprep::saslprep(password_str) {
53                Ok(p) => p.into_owned().into_bytes(),
54                // contains invalid characters; skip saslprep
55                Err(_) => Vec::from(password),
56            }
57        }
58        // not valid UTF-8; skip saslprep
59        Err(_) => Vec::from(password),
60    };
61
62    // salt password
63    let salted_password = sasl::hi(&prepared, &salt, SCRAM_DEFAULT_ITERATIONS);
64
65    // client key
66    let mut hmac = Hmac::<Sha256>::new_from_slice(&salted_password)
67        .expect("HMAC is able to accept all key sizes");
68    hmac.update(b"Client Key");
69    let client_key = hmac.finalize().into_bytes();
70
71    // stored key
72    let mut hash = Sha256::default();
73    hash.update(client_key.as_slice());
74    let stored_key = hash.finalize_fixed();
75
76    // server key
77    let mut hmac = Hmac::<Sha256>::new_from_slice(&salted_password)
78        .expect("HMAC is able to accept all key sizes");
79    hmac.update(b"Server Key");
80    let server_key = hmac.finalize().into_bytes();
81
82    format!(
83        "SCRAM-SHA-256${}:{}${}:{}",
84        SCRAM_DEFAULT_ITERATIONS,
85        Base64Display::new(&salt, &STANDARD),
86        Base64Display::new(&stored_key, &STANDARD),
87        Base64Display::new(&server_key, &STANDARD)
88    )
89}
90
91/// **Not recommended, as MD5 is not considered to be secure.**
92///
93/// Hash password using MD5 with the username as the salt.
94///
95/// The client may assume the returned string doesn't contain any
96/// special characters that would require escaping.
97pub fn md5(password: &[u8], username: &str) -> String {
98    // salt password with username
99    let mut salted_password = Vec::from(password);
100    salted_password.extend_from_slice(username.as_bytes());
101
102    let mut hash = Md5::new();
103    hash.update(&salted_password);
104    let digest = hash.finalize();
105    format!("md5{:x}", digest)
106}
postgres_protocol/password/mod.rs

postgres_protocol/password/
mod.rs
