`nx_hmac_md5.nx` source

↩ module page · 101 lines · 2945 B
1// hmac_md5.nx -- HMAC with MD5 (RFC 2104).
2//
3// license_tier: INDEPENDENT_REDERIVE
4// genealogy_id: international-research-sources/ietf/rfc_2104
5//
6// Like HMAC-SHA1: even though plain MD5 is broken for signatures,
7// HMAC-MD5 remains safe for authentication because HMAC relies
8// on pseudo-randomness of the keyed mix, not collision resistance.
9// Still on the wire in:
10//   - RADIUS Access-Request Message-Authenticator (RFC 3579)
11//   - CRAM-MD5 SASL auth (IMAP, POP3, SMTP legacy)
12//   - Microsoft MS-CHAP-v2 password challenge
13//   - NTLMv1 / NTLMv2 (the real world's Windows auth)
14//
15// Composes md5.nx with standard ipad/opad construction.
16//
17// Invariants:
18//   HM1  Output = 16 bytes (MD5 tag length).
19//   HM2  Matches RFC 2104 Appendix test vectors.
20
21// nx_safety_envelope:
22//   intended_use:       AUTO_APPLIED -- primitive-specific tuning queued
23//   sil_target:         SIL1
24//   evidence:           [bulk_applied_2026-05-16, see-file-comment-for-detail]
25//   verdict:            NOT_YET_EVALUATED
26
27import "nx_syscalls.nx"
28import "nx_md5_canonical.nx"
29
30const HMAC_MD5_BLOCK: i64 = 64
31const HMAC_MD5_OUT:   i64 = 16
32
33func hmac_md5(key: *u8, key_len: i64,
34              msg: *u8, msg_len: i64,
35              out: *u8) -> i64 {
36    let k_prime: *u8 = sys_mmap(HMAC_MD5_BLOCK + 16)
37    var i: i64 = 0
38    while i < HMAC_MD5_BLOCK { k_prime[i] = 0; i = i + 1 }
39
40    if key_len > HMAC_MD5_BLOCK {
41        md5(key, key_len, k_prime)
42    } else {
43        i = 0
44        while i < key_len {
45            k_prime[i] = key[i]
46            i = i + 1
47        }
48    }
49
50    // Inner: MD5(ipad || msg).
51    let inner_len: i64 = HMAC_MD5_BLOCK + msg_len
52    let inner_buf: *u8 = sys_mmap(inner_len + 16)
53    i = 0
54    while i < HMAC_MD5_BLOCK {
55        inner_buf[i] = k_prime[i] ^ 0x36
56        i = i + 1
57    }
58    i = 0
59    while i < msg_len {
60        inner_buf[HMAC_MD5_BLOCK + i] = msg[i]
61        i = i + 1
62    }
63    let inner_hash: *u8 = sys_mmap(32)
64    md5(inner_buf, inner_len, inner_hash)
65
66    // Outer: MD5(opad || inner_hash).
67    let outer_len: i64 = HMAC_MD5_BLOCK + HMAC_MD5_OUT
68    let outer_buf: *u8 = sys_mmap(outer_len + 16)
69    i = 0
70    while i < HMAC_MD5_BLOCK {
71        outer_buf[i] = k_prime[i] ^ 0x5C
72        i = i + 1
73    }
74    i = 0
75    while i < HMAC_MD5_OUT {
76        outer_buf[HMAC_MD5_BLOCK + i] = inner_hash[i]
77        i = i + 1
78    }
79    md5(outer_buf, outer_len, out)
80    return 0
81}
82
83// Compile-only smoke.
84func main() -> i64 {
85    let out: *u8 = sys_mmap(32)
86    // RFC 2104 test vector 1:
87    //   key = 0x0b repeated 16 times, msg = "Hi There"
88    //   HMAC-MD5 = 9294727a3638bb1c13f48ef8158bfc9d
89    let key: *u8 = sys_mmap(32)
90    var i: i64 = 0
91    while i < 16 {
92        key[i] = 0x0B
93        i = i + 1
94    }
95    hmac_md5(key, 16, "Hi There", 8, out)
96    if out[0]  != 0x92 { return 1 }
97    if out[1]  != 0x94 { return 2 }
98    if out[2]  != 0x72 { return 3 }
99    if out[15] != 0x9D { return 4 }
100    return 0
101}
nx_hmac_md5.nx source

`nx_hmac_md5.nx` source
