koan_core/
auth.rs

1//! Authentication primitives: Ed25519 JWT signing, Argon2id password hashing.
2//!
3//! Ed25519 keypair is generated once and stored in the config directory.
4//! JWTs use EdDSA (Ed25519) for signing — 128-bit security, tiny keys, fast.
5
6use std::fs;
7use std::path::PathBuf;
8use std::time::{SystemTime, UNIX_EPOCH};
9
10use jsonwebtoken::{Algorithm, DecodingKey, EncodingKey, Header, Validation};
11use ring::signature::KeyPair;
12use serde::{Deserialize, Serialize};
13use thiserror::Error;
14
15use crate::config;
16
17// ---------------------------------------------------------------------------
18// Errors
19// ---------------------------------------------------------------------------
20
21#[derive(Debug, Error)]
22pub enum AuthError {
23    #[error("jwt error: {0}")]
24    Jwt(#[from] jsonwebtoken::errors::Error),
25    #[error("argon2 hash error: {0}")]
26    Hash(String),
27    #[error("password verification failed")]
28    InvalidPassword,
29    #[error("io error: {0}")]
30    Io(#[from] std::io::Error),
31    #[error("keypair not found — run `koan auth setup` first")]
32    NoKeypair,
33    #[error("{0}")]
34    Other(String),
35}
36
37// ---------------------------------------------------------------------------
38// Roles
39// ---------------------------------------------------------------------------
40
41#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
42#[serde(rename_all = "lowercase")]
43pub enum Role {
44    Admin,
45    User,
46    Readonly,
47}
48
49impl Role {
50    pub fn as_str(&self) -> &'static str {
51        match self {
52            Role::Admin => "admin",
53            Role::User => "user",
54            Role::Readonly => "readonly",
55        }
56    }
57
58    /// Returns true if this role has at least the given permission level.
59    /// Admin > User > Readonly.
60    pub fn has_permission(&self, required: Role) -> bool {
61        match required {
62            Role::Readonly => true,
63            Role::User => matches!(self, Role::Admin | Role::User),
64            Role::Admin => matches!(self, Role::Admin),
65        }
66    }
67}
68
69impl std::str::FromStr for Role {
70    type Err = String;
71
72    fn from_str(s: &str) -> Result<Self, Self::Err> {
73        match s {
74            "admin" => Ok(Role::Admin),
75            "user" => Ok(Role::User),
76            "readonly" => Ok(Role::Readonly),
77            _ => Err(format!("invalid role: '{s}'")),
78        }
79    }
80}
81
82impl std::fmt::Display for Role {
83    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
84        f.write_str(self.as_str())
85    }
86}
87
88// ---------------------------------------------------------------------------
89// JWT Claims
90// ---------------------------------------------------------------------------
91
92#[derive(Debug, Serialize, Deserialize)]
93pub struct Claims {
94    /// Subject — user ID.
95    pub sub: i64,
96    /// Username.
97    pub username: String,
98    /// Role.
99    pub role: String,
100    /// Issued at (unix timestamp).
101    pub iat: u64,
102    /// Expiration (unix timestamp).
103    pub exp: u64,
104}
105
106// ---------------------------------------------------------------------------
107// Password hashing (Argon2id)
108// ---------------------------------------------------------------------------
109
110/// Hash a password using Argon2id with a random salt.
111pub fn hash_password(password: &str) -> Result<String, AuthError> {
112    use argon2::Argon2;
113    use argon2::password_hash::{PasswordHasher, SaltString, rand_core::OsRng};
114
115    let salt = SaltString::generate(&mut OsRng);
116    let argon2 = Argon2::default();
117    argon2
118        .hash_password(password.as_bytes(), &salt)
119        .map(|h| h.to_string())
120        .map_err(|e| AuthError::Hash(e.to_string()))
121}
122
123/// Verify a password against an Argon2id hash.
124pub fn verify_password(password: &str, hash: &str) -> Result<(), AuthError> {
125    use argon2::Argon2;
126    use argon2::password_hash::{PasswordHash, PasswordVerifier};
127
128    let parsed = PasswordHash::new(hash).map_err(|e| AuthError::Hash(e.to_string()))?;
129    Argon2::default()
130        .verify_password(password.as_bytes(), &parsed)
131        .map_err(|_| AuthError::InvalidPassword)
132}
133
134// ---------------------------------------------------------------------------
135// Random secrets
136// ---------------------------------------------------------------------------
137
138/// Generate a 256-bit random secret, hex encoded.
139///
140/// Used for bearer-style secrets that are compared verbatim rather than hashed
141/// (introspection key, Subsonic shared secret), so the entropy has to carry the
142/// whole security argument.
143pub fn random_token() -> Result<String, AuthError> {
144    use ring::rand::SecureRandom;
145
146    let mut bytes = [0u8; 32];
147    ring::rand::SystemRandom::new()
148        .fill(&mut bytes)
149        .map_err(|_| AuthError::Hash("rng failure".into()))?;
150    Ok(bytes.iter().map(|b| format!("{:02x}", b)).collect())
151}
152
153/// SHA-256 of `input`, hex encoded. Refresh tokens are stored under this so a
154/// database read does not yield usable credentials.
155pub fn sha256_hex(input: &str) -> String {
156    ring::digest::digest(&ring::digest::SHA256, input.as_bytes())
157        .as_ref()
158        .iter()
159        .map(|b| format!("{:02x}", b))
160        .collect()
161}
162
163// ---------------------------------------------------------------------------
164// Ed25519 Keypair management
165// ---------------------------------------------------------------------------
166
167pub fn keypair_dir() -> PathBuf {
168    config::config_dir().join("auth")
169}
170
171fn private_key_path() -> PathBuf {
172    keypair_dir().join("ed25519.pem")
173}
174
175fn public_key_path() -> PathBuf {
176    keypair_dir().join("ed25519.pub.pem")
177}
178
179/// Derive a new Ed25519 keypair as PEM. Touches no filesystem state.
180/// Returns (private_pem, public_pem).
181pub fn generate_keypair_pem() -> Result<(String, String), AuthError> {
182    // jsonwebtoken's EncodingKey::from_ed_pem expects PKCS8 PEM.
183    let rng = ring::rand::SystemRandom::new();
184    let pkcs8_doc = ring::signature::Ed25519KeyPair::generate_pkcs8(&rng)
185        .map_err(|e| AuthError::Other(format!("keypair generation failed: {}", e)))?;
186
187    let private_pem = pem::encode(&pem::Pem::new("PRIVATE KEY", pkcs8_doc.as_ref()));
188
189    // Extract public key from the keypair.
190    let kp = ring::signature::Ed25519KeyPair::from_pkcs8(pkcs8_doc.as_ref())
191        .map_err(|e| AuthError::Other(format!("keypair parse failed: {}", e)))?;
192    let pub_bytes = kp.public_key().as_ref();
193
194    // Wrap public key in SubjectPublicKeyInfo DER (for Ed25519 this is a fixed prefix + 32 bytes).
195    // OID 1.3.101.112 = id-EdDSA (Ed25519).
196    let mut spki = vec![
197        0x30, 0x2a, // SEQUENCE, 42 bytes total
198        0x30, 0x05, // SEQUENCE (AlgorithmIdentifier), 5 bytes
199        0x06, 0x03, 0x2b, 0x65, 0x70, // OID 1.3.101.112
200        0x03, 0x21, 0x00, // BIT STRING, 33 bytes, 0 unused bits
201    ];
202    spki.extend_from_slice(pub_bytes);
203    let public_pem = pem::encode(&pem::Pem::new("PUBLIC KEY", spki));
204
205    Ok((private_pem, public_pem))
206}
207
208/// Generate a new Ed25519 keypair and write PEM files to the config dir.
209/// Returns (private_pem, public_pem).
210pub fn generate_keypair() -> Result<(Vec<u8>, Vec<u8>), AuthError> {
211    let (private_pem, public_pem) = generate_keypair_pem()?;
212
213    let dir = keypair_dir();
214    fs::create_dir_all(&dir)?;
215
216    // Ensure the auth directory is gitignored — keys must never be committed.
217    let gitignore = dir.join(".gitignore");
218    if !gitignore.exists() {
219        let _ = fs::write(&gitignore, "*\n");
220    }
221
222    // Write key files with restrictive permissions set BEFORE writing content
223    // to avoid a window where the file exists with default (world-readable) mode.
224    #[cfg(unix)]
225    {
226        use std::fs::OpenOptions;
227        use std::io::Write;
228        use std::os::unix::fs::OpenOptionsExt;
229        use std::os::unix::fs::PermissionsExt;
230
231        let mut f = OpenOptions::new()
232            .write(true)
233            .create(true)
234            .truncate(true)
235            .mode(0o600)
236            .open(private_key_path())?;
237        f.write_all(private_pem.as_bytes())?;
238
239        let mut f = OpenOptions::new()
240            .write(true)
241            .create(true)
242            .truncate(true)
243            .mode(0o644)
244            .open(public_key_path())?;
245        f.write_all(public_pem.as_bytes())?;
246
247        let _ = fs::set_permissions(&dir, fs::Permissions::from_mode(0o700));
248    }
249
250    #[cfg(not(unix))]
251    {
252        fs::write(private_key_path(), &private_pem)?;
253        fs::write(public_key_path(), &public_pem)?;
254    }
255
256    Ok((private_pem.into_bytes(), public_pem.into_bytes()))
257}
258
259/// Load the Ed25519 keypair from disk. Returns (private_pem, public_pem).
260pub fn load_keypair() -> Result<(Vec<u8>, Vec<u8>), AuthError> {
261    let priv_path = private_key_path();
262    let pub_path = public_key_path();
263
264    if !priv_path.exists() || !pub_path.exists() {
265        return Err(AuthError::NoKeypair);
266    }
267
268    let private_pem = fs::read(&priv_path)?;
269    let public_pem = fs::read(&pub_path)?;
270    Ok((private_pem, public_pem))
271}
272
273/// Load or generate the keypair. Generates if missing.
274pub fn load_or_generate_keypair() -> Result<(Vec<u8>, Vec<u8>), AuthError> {
275    match load_keypair() {
276        Ok(kp) => Ok(kp),
277        Err(AuthError::NoKeypair) => generate_keypair(),
278        Err(e) => Err(e),
279    }
280}
281
282// ---------------------------------------------------------------------------
283// JWT encode / decode
284// ---------------------------------------------------------------------------
285
286/// Mint a new access token.
287pub fn mint_access_token(
288    private_pem: &[u8],
289    user_id: i64,
290    username: &str,
291    role: Role,
292    ttl_secs: u64,
293) -> Result<String, AuthError> {
294    mint_access_token_with_role_str(private_pem, user_id, username, role.as_str(), ttl_secs)
295}
296
297/// Mint an access token carrying an arbitrary `role` claim.
298///
299/// The claim is a free-text string on the wire; this is the seam that lets the
300/// consumers of a token be tested against role values they cannot parse.
301pub fn mint_access_token_with_role_str(
302    private_pem: &[u8],
303    user_id: i64,
304    username: &str,
305    role: &str,
306    ttl_secs: u64,
307) -> Result<String, AuthError> {
308    let now = SystemTime::now()
309        .duration_since(UNIX_EPOCH)
310        .unwrap()
311        .as_secs();
312
313    let claims = Claims {
314        sub: user_id,
315        username: username.to_string(),
316        role: role.to_string(),
317        iat: now,
318        exp: now + ttl_secs,
319    };
320
321    let key = EncodingKey::from_ed_pem(private_pem)?;
322    let header = Header::new(Algorithm::EdDSA);
323    let token = jsonwebtoken::encode(&header, &claims, &key)?;
324    Ok(token)
325}
326
327/// Validate an access token and return its claims.
328pub fn validate_access_token(public_pem: &[u8], token: &str) -> Result<Claims, AuthError> {
329    let key = DecodingKey::from_ed_pem(public_pem)?;
330    let mut validation = Validation::new(Algorithm::EdDSA);
331    // Only require exp (expiry). sub and iat are custom fields, not JWT spec strings.
332    validation.set_required_spec_claims(&["exp"]);
333
334    let data = jsonwebtoken::decode::<Claims>(token, &key, &validation)?;
335    Ok(data.claims)
336}
337
338// ---------------------------------------------------------------------------
339// Time helpers
340// ---------------------------------------------------------------------------
341
342pub fn now_unix() -> u64 {
343    SystemTime::now()
344        .duration_since(UNIX_EPOCH)
345        .unwrap()
346        .as_secs()
347}
348
349/// Parse a duration string like "15m", "7d", "24h", "3600s" into seconds.
350pub fn parse_duration_secs(s: &str) -> Option<u64> {
351    let s = s.trim();
352    if s.is_empty() {
353        return None;
354    }
355
356    let (num_str, multiplier) = if let Some(n) = s.strip_suffix('d') {
357        (n, 86400)
358    } else if let Some(n) = s.strip_suffix('h') {
359        (n, 3600)
360    } else if let Some(n) = s.strip_suffix('m') {
361        (n, 60)
362    } else if let Some(n) = s.strip_suffix('s') {
363        (n, 1)
364    } else {
365        (s, 1)
366    };
367
368    let num: u64 = num_str.parse().ok()?;
369    Some(num * multiplier)
370}
371
372// ---------------------------------------------------------------------------
373// Tests
374// ---------------------------------------------------------------------------
375
376#[cfg(test)]
377mod tests {
378    use super::*;
379
380    #[test]
381    fn password_hash_and_verify() {
382        let password = "hunter2";
383        let hash = hash_password(password).unwrap();
384        assert!(hash.starts_with("$argon2"));
385        verify_password(password, &hash).unwrap();
386    }
387
388    #[test]
389    fn password_verify_wrong() {
390        let hash = hash_password("correct").unwrap();
391        let result = verify_password("wrong", &hash);
392        assert!(matches!(result, Err(AuthError::InvalidPassword)));
393    }
394
395    #[test]
396    fn keypair_generate_and_jwt_roundtrip() {
397        let (priv_pem, pub_pem) = generate_keypair_pem().unwrap();
398
399        let token =
400            mint_access_token(priv_pem.as_bytes(), 42, "testuser", Role::Admin, 3600).unwrap();
401        let claims = validate_access_token(pub_pem.as_bytes(), &token).unwrap();
402
403        assert_eq!(claims.sub, 42);
404        assert_eq!(claims.username, "testuser");
405        assert_eq!(claims.role, "admin");
406    }
407
408    #[test]
409    fn expired_token_rejected() {
410        let (priv_pem, pub_pem) = generate_keypair_pem().unwrap();
411        // Manually create a token that expired 10 minutes ago.
412        let now = std::time::SystemTime::now()
413            .duration_since(std::time::UNIX_EPOCH)
414            .unwrap()
415            .as_secs();
416        let claims = Claims {
417            sub: 1,
418            username: "user".into(),
419            role: "user".into(),
420            iat: now - 1200,
421            exp: now - 600, // expired 10 min ago
422        };
423        let key = jsonwebtoken::EncodingKey::from_ed_pem(priv_pem.as_bytes()).unwrap();
424        let header = jsonwebtoken::Header::new(jsonwebtoken::Algorithm::EdDSA);
425        let token = jsonwebtoken::encode(&header, &claims, &key).unwrap();
426        let result = validate_access_token(pub_pem.as_bytes(), &token);
427        assert!(result.is_err());
428    }
429
430    #[test]
431    fn role_permissions() {
432        assert!(Role::Admin.has_permission(Role::Admin));
433        assert!(Role::Admin.has_permission(Role::User));
434        assert!(Role::Admin.has_permission(Role::Readonly));
435
436        assert!(!Role::User.has_permission(Role::Admin));
437        assert!(Role::User.has_permission(Role::User));
438        assert!(Role::User.has_permission(Role::Readonly));
439
440        assert!(!Role::Readonly.has_permission(Role::Admin));
441        assert!(!Role::Readonly.has_permission(Role::User));
442        assert!(Role::Readonly.has_permission(Role::Readonly));
443    }
444
445    #[test]
446    fn parse_duration() {
447        assert_eq!(parse_duration_secs("15m"), Some(900));
448        assert_eq!(parse_duration_secs("7d"), Some(604800));
449        assert_eq!(parse_duration_secs("24h"), Some(86400));
450        assert_eq!(parse_duration_secs("3600s"), Some(3600));
451        assert_eq!(parse_duration_secs("3600"), Some(3600));
452        assert_eq!(parse_duration_secs(""), None);
453    }
454}
koan_core/auth.rs

koan_core/
auth.rs
