async_snmp/v3/
mod.rs

1//! SNMPv3 security module.
2//!
3//! This module implements the User-based Security Model (USM) as defined
4//! in RFC 3414 and RFC 7860, including:
5//!
6//! - USM security parameters encoding/decoding
7//! - Key localization (password-to-key derivation)
8//! - Authentication (HMAC-MD5-96, HMAC-SHA-96, HMAC-SHA-224/256/384/512)
9//! - Privacy (DES-CBC, AES-128/192/256-CFB)
10//! - Engine discovery and time synchronization
11
12pub mod auth;
13mod engine;
14mod privacy;
15mod usm;
16
17pub use auth::{LocalizedKey, MasterKey, MasterKeys};
18pub use engine::{
19    DEFAULT_MSG_MAX_SIZE, EngineCache, EngineState, MAX_ENGINE_TIME, TIME_WINDOW,
20    parse_discovery_response, parse_discovery_response_with_limits,
21};
22pub use engine::{
23    is_decryption_error_report, is_not_in_time_window_report, is_unknown_engine_id_report,
24    is_unknown_user_name_report, is_unsupported_sec_level_report, is_wrong_digest_report,
25};
26pub use privacy::{PrivKey, PrivacyError, PrivacyResult, SaltCounter};
27pub use usm::UsmSecurityParams;
28
29/// Key extension strategy for privacy key derivation.
30///
31/// This is an internal type used to select the appropriate key extension
32/// algorithm when deriving privacy keys. The correct algorithm is auto-detected
33/// based on the auth/priv protocol combination.
34#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
35pub(crate) enum KeyExtension {
36    /// No key extension. Use standard RFC 3414 key derivation.
37    #[default]
38    None,
39    /// Blumenthal key extension (draft-blumenthal-aes-usm-04) for AES-192/256.
40    Blumenthal,
41    /// Reeder key extension (draft-reeder-snmpv3-usm-3desede-00) for 3DES.
42    Reeder,
43}
44
45/// Error returned when parsing a protocol name fails.
46#[derive(Debug, Clone, PartialEq, Eq)]
47pub struct ParseProtocolError {
48    input: String,
49    kind: ProtocolKind,
50}
51
52#[derive(Debug, Clone, Copy, PartialEq, Eq)]
53enum ProtocolKind {
54    Auth,
55    Priv,
56}
57
58impl std::fmt::Display for ParseProtocolError {
59    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
60        match self.kind {
61            ProtocolKind::Auth => write!(
62                f,
63                "unknown authentication protocol '{}'; expected one of: MD5, SHA, SHA-224, SHA-256, SHA-384, SHA-512",
64                self.input
65            ),
66            ProtocolKind::Priv => write!(
67                f,
68                "unknown privacy protocol '{}'; expected one of: DES, AES, AES-128, AES-192, AES-256",
69                self.input
70            ),
71        }
72    }
73}
74
75impl std::error::Error for ParseProtocolError {}
76
77/// Authentication protocol identifiers.
78#[derive(Debug, Clone, Copy, PartialEq, Eq)]
79#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
80pub enum AuthProtocol {
81    /// HMAC-MD5-96 (RFC 3414)
82    Md5,
83    /// HMAC-SHA-96 (RFC 3414)
84    Sha1,
85    /// HMAC-SHA-224 (RFC 7860)
86    Sha224,
87    /// HMAC-SHA-256 (RFC 7860)
88    Sha256,
89    /// HMAC-SHA-384 (RFC 7860)
90    Sha384,
91    /// HMAC-SHA-512 (RFC 7860)
92    Sha512,
93}
94
95impl std::fmt::Display for AuthProtocol {
96    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
97        match self {
98            Self::Md5 => write!(f, "MD5"),
99            Self::Sha1 => write!(f, "SHA"),
100            Self::Sha224 => write!(f, "SHA-224"),
101            Self::Sha256 => write!(f, "SHA-256"),
102            Self::Sha384 => write!(f, "SHA-384"),
103            Self::Sha512 => write!(f, "SHA-512"),
104        }
105    }
106}
107
108impl std::str::FromStr for AuthProtocol {
109    type Err = ParseProtocolError;
110
111    fn from_str(s: &str) -> Result<Self, Self::Err> {
112        match s.to_ascii_uppercase().as_str() {
113            "MD5" => Ok(Self::Md5),
114            "SHA" | "SHA1" | "SHA-1" => Ok(Self::Sha1),
115            "SHA224" | "SHA-224" => Ok(Self::Sha224),
116            "SHA256" | "SHA-256" => Ok(Self::Sha256),
117            "SHA384" | "SHA-384" => Ok(Self::Sha384),
118            "SHA512" | "SHA-512" => Ok(Self::Sha512),
119            _ => Err(ParseProtocolError {
120                input: s.to_string(),
121                kind: ProtocolKind::Auth,
122            }),
123        }
124    }
125}
126
127impl AuthProtocol {
128    /// Get the digest output length in bytes.
129    ///
130    /// This is also the key length produced by the key localization algorithm,
131    /// which is used for privacy key derivation.
132    pub fn digest_len(self) -> usize {
133        match self {
134            Self::Md5 => 16,
135            Self::Sha1 => 20,
136            Self::Sha224 => 28,
137            Self::Sha256 => 32,
138            Self::Sha384 => 48,
139            Self::Sha512 => 64,
140        }
141    }
142
143    /// Get the truncated MAC length for authentication parameters.
144    pub fn mac_len(self) -> usize {
145        match self {
146            Self::Md5 | Self::Sha1 => 12, // HMAC-96
147            Self::Sha224 => 16,           // RFC 7860
148            Self::Sha256 => 24,           // RFC 7860
149            Self::Sha384 => 32,           // RFC 7860
150            Self::Sha512 => 48,           // RFC 7860
151        }
152    }
153}
154
155/// Privacy protocol identifiers.
156#[derive(Debug, Clone, Copy, PartialEq, Eq)]
157#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
158pub enum PrivProtocol {
159    /// DES-CBC (RFC 3414).
160    ///
161    /// Insecure: 56-bit keys are brute-forceable. Also slower than AES, which
162    /// benefits from hardware acceleration.
163    Des,
164    /// 3DES-EDE in "Outside" CBC mode (draft-reeder-snmpv3-usm-3desede-00).
165    ///
166    /// Uses three 56-bit keys for 168-bit effective security (112-bit against
167    /// meet-in-the-middle). Slower than AES and lacks hardware acceleration.
168    Des3,
169    /// AES-128-CFB (RFC 3826)
170    Aes128,
171    /// AES-192-CFB (RFC 3826)
172    Aes192,
173    /// AES-256-CFB (RFC 3826)
174    Aes256,
175}
176
177impl std::fmt::Display for PrivProtocol {
178    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
179        match self {
180            Self::Des => write!(f, "DES"),
181            Self::Des3 => write!(f, "3DES"),
182            Self::Aes128 => write!(f, "AES"),
183            Self::Aes192 => write!(f, "AES-192"),
184            Self::Aes256 => write!(f, "AES-256"),
185        }
186    }
187}
188
189impl std::str::FromStr for PrivProtocol {
190    type Err = ParseProtocolError;
191
192    fn from_str(s: &str) -> Result<Self, Self::Err> {
193        match s.to_ascii_uppercase().as_str() {
194            "DES" => Ok(Self::Des),
195            "3DES" | "3DES-EDE" | "DES3" | "TDES" => Ok(Self::Des3),
196            "AES" | "AES128" | "AES-128" => Ok(Self::Aes128),
197            "AES192" | "AES-192" => Ok(Self::Aes192),
198            "AES256" | "AES-256" => Ok(Self::Aes256),
199            _ => Err(ParseProtocolError {
200                input: s.to_string(),
201                kind: ProtocolKind::Priv,
202            }),
203        }
204    }
205}
206
207impl PrivProtocol {
208    /// Get the key length in bytes.
209    pub fn key_len(self) -> usize {
210        match self {
211            Self::Des => 16,  // 8 key + 8 pre-IV
212            Self::Des3 => 32, // 24 key + 8 pre-IV
213            Self::Aes128 => 16,
214            Self::Aes192 => 24,
215            Self::Aes256 => 32,
216        }
217    }
218
219    /// Get the IV/salt length in bytes.
220    pub fn salt_len(self) -> usize {
221        8 // All protocols use 8-byte salt
222    }
223
224    /// Returns the key extension algorithm to use for this privacy protocol
225    /// given the authentication protocol.
226    ///
227    /// Key extension is needed when the auth protocol's digest is shorter than
228    /// the privacy protocol's key requirement. The algorithm is determined by
229    /// the privacy protocol:
230    /// - AES-192/256: Blumenthal (draft-blumenthal-aes-usm-04)
231    /// - 3DES: Reeder (draft-reeder-snmpv3-usm-3desede-00)
232    pub(crate) fn key_extension_for(self, auth_protocol: AuthProtocol) -> KeyExtension {
233        let auth_len = auth_protocol.digest_len();
234        let priv_len = self.key_len();
235
236        if auth_len >= priv_len {
237            return KeyExtension::None;
238        }
239
240        match self {
241            Self::Des3 => KeyExtension::Reeder,
242            Self::Aes192 | Self::Aes256 => KeyExtension::Blumenthal,
243            Self::Des | Self::Aes128 => KeyExtension::None, // Never need extension
244        }
245    }
246}
247
248#[cfg(test)]
249mod tests {
250    use super::*;
251
252    #[test]
253    fn test_auth_protocol_display() {
254        assert_eq!(format!("{}", AuthProtocol::Md5), "MD5");
255        assert_eq!(format!("{}", AuthProtocol::Sha1), "SHA");
256        assert_eq!(format!("{}", AuthProtocol::Sha224), "SHA-224");
257        assert_eq!(format!("{}", AuthProtocol::Sha256), "SHA-256");
258        assert_eq!(format!("{}", AuthProtocol::Sha384), "SHA-384");
259        assert_eq!(format!("{}", AuthProtocol::Sha512), "SHA-512");
260    }
261
262    #[test]
263    fn test_auth_protocol_from_str() {
264        assert_eq!("MD5".parse::<AuthProtocol>().unwrap(), AuthProtocol::Md5);
265        assert_eq!("md5".parse::<AuthProtocol>().unwrap(), AuthProtocol::Md5);
266        assert_eq!("SHA".parse::<AuthProtocol>().unwrap(), AuthProtocol::Sha1);
267        assert_eq!("sha1".parse::<AuthProtocol>().unwrap(), AuthProtocol::Sha1);
268        assert_eq!("SHA-1".parse::<AuthProtocol>().unwrap(), AuthProtocol::Sha1);
269        assert_eq!(
270            "sha-224".parse::<AuthProtocol>().unwrap(),
271            AuthProtocol::Sha224
272        );
273        assert_eq!(
274            "SHA256".parse::<AuthProtocol>().unwrap(),
275            AuthProtocol::Sha256
276        );
277        assert_eq!(
278            "SHA-256".parse::<AuthProtocol>().unwrap(),
279            AuthProtocol::Sha256
280        );
281        assert_eq!(
282            "sha384".parse::<AuthProtocol>().unwrap(),
283            AuthProtocol::Sha384
284        );
285        assert_eq!(
286            "SHA-512".parse::<AuthProtocol>().unwrap(),
287            AuthProtocol::Sha512
288        );
289
290        assert!("invalid".parse::<AuthProtocol>().is_err());
291    }
292
293    #[test]
294    fn test_priv_protocol_display() {
295        assert_eq!(format!("{}", PrivProtocol::Des), "DES");
296        assert_eq!(format!("{}", PrivProtocol::Des3), "3DES");
297        assert_eq!(format!("{}", PrivProtocol::Aes128), "AES");
298        assert_eq!(format!("{}", PrivProtocol::Aes192), "AES-192");
299        assert_eq!(format!("{}", PrivProtocol::Aes256), "AES-256");
300    }
301
302    #[test]
303    fn test_priv_protocol_from_str() {
304        assert_eq!("DES".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des);
305        assert_eq!("des".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des);
306        assert_eq!("3DES".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des3);
307        assert_eq!("3des".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des3);
308        assert_eq!(
309            "3DES-EDE".parse::<PrivProtocol>().unwrap(),
310            PrivProtocol::Des3
311        );
312        assert_eq!("DES3".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des3);
313        assert_eq!("TDES".parse::<PrivProtocol>().unwrap(), PrivProtocol::Des3);
314        assert_eq!("AES".parse::<PrivProtocol>().unwrap(), PrivProtocol::Aes128);
315        assert_eq!("aes".parse::<PrivProtocol>().unwrap(), PrivProtocol::Aes128);
316        assert_eq!(
317            "AES128".parse::<PrivProtocol>().unwrap(),
318            PrivProtocol::Aes128
319        );
320        assert_eq!(
321            "AES-128".parse::<PrivProtocol>().unwrap(),
322            PrivProtocol::Aes128
323        );
324        assert_eq!(
325            "aes192".parse::<PrivProtocol>().unwrap(),
326            PrivProtocol::Aes192
327        );
328        assert_eq!(
329            "AES-192".parse::<PrivProtocol>().unwrap(),
330            PrivProtocol::Aes192
331        );
332        assert_eq!(
333            "aes256".parse::<PrivProtocol>().unwrap(),
334            PrivProtocol::Aes256
335        );
336        assert_eq!(
337            "AES-256".parse::<PrivProtocol>().unwrap(),
338            PrivProtocol::Aes256
339        );
340
341        assert!("invalid".parse::<PrivProtocol>().is_err());
342    }
343
344    #[test]
345    fn test_parse_protocol_error_display() {
346        let err = "bogus".parse::<AuthProtocol>().unwrap_err();
347        assert!(err.to_string().contains("bogus"));
348        assert!(err.to_string().contains("authentication protocol"));
349
350        let err = "bogus".parse::<PrivProtocol>().unwrap_err();
351        assert!(err.to_string().contains("bogus"));
352        assert!(err.to_string().contains("privacy protocol"));
353    }
354}
async_snmp/v3/mod.rs

async_snmp/v3/
mod.rs
