e5574168 |
1 | #include "ssh.h" |
2 | |
3 | struct ssh_kex ssh_diffiehellman = { |
4 | "diffie-hellman-group1-sha1" |
5 | }; |
6 | |
7 | /* |
8 | * The prime p used in the key exchange. |
9 | */ |
3709bfe9 |
10 | static unsigned char P[] = { |
11 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, |
12 | 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, |
13 | 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, |
14 | 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, |
15 | 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, |
16 | 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, |
17 | 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, |
18 | 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, |
19 | 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, |
20 | 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, |
21 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF |
e5574168 |
22 | }; |
23 | |
24 | /* |
3709bfe9 |
25 | * The generator g = 2. |
e5574168 |
26 | */ |
3709bfe9 |
27 | static unsigned char G[] = { 2 }; |
e5574168 |
28 | |
29 | /* |
3709bfe9 |
30 | * Variables. |
e5574168 |
31 | */ |
3709bfe9 |
32 | static Bignum x, e, p, q, qmask, g; |
33 | static int need_to_free_pg; |
e5574168 |
34 | |
35 | /* |
3709bfe9 |
36 | * Common DH initialisation. |
e5574168 |
37 | */ |
3709bfe9 |
38 | static void dh_init(void) { |
39 | q = bignum_rshift(p, 1); |
40 | qmask = bignum_bitmask(q); |
41 | } |
e5574168 |
42 | |
43 | /* |
3709bfe9 |
44 | * Initialise DH for the standard group1. |
e5574168 |
45 | */ |
3709bfe9 |
46 | void dh_setup_group1(void) { |
47 | p = bignum_from_bytes(P, sizeof(P)); |
48 | g = bignum_from_bytes(G, sizeof(G)); |
49 | dh_init(); |
50 | } |
51 | |
52 | /* |
53 | * Clean up. |
54 | */ |
55 | void dh_cleanup(void) { |
56 | freebn(p); |
57 | freebn(g); |
58 | freebn(q); |
59 | freebn(qmask); |
60 | } |
e5574168 |
61 | |
62 | /* |
63 | * DH stage 1: invent a number x between 1 and q, and compute e = |
64 | * g^x mod p. Return e. |
65 | */ |
66 | Bignum dh_create_e(void) { |
67 | int i; |
68 | |
3709bfe9 |
69 | int nbytes; |
70 | unsigned char *buf; |
71 | |
72 | nbytes = ssh1_bignum_length(qmask); |
73 | buf = smalloc(nbytes); |
e5574168 |
74 | |
a71540b9 |
75 | do { |
76 | /* |
77 | * Create a potential x, by ANDing a string of random bytes |
3709bfe9 |
78 | * with qmask. |
a71540b9 |
79 | */ |
3709bfe9 |
80 | if (x) freebn(x); |
81 | ssh1_write_bignum(buf, qmask); |
82 | for (i = 2; i < nbytes; i++) |
83 | buf[i] &= random_byte(); |
84 | ssh1_read_bignum(buf, &x); |
85 | } while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, q) >= 0); |
e5574168 |
86 | |
87 | /* |
88 | * Done. Now compute e = g^x mod p. |
89 | */ |
3709bfe9 |
90 | e = modpow(g, x, p); |
e5574168 |
91 | |
92 | return e; |
93 | } |
94 | |
95 | /* |
96 | * DH stage 2: given a number f, compute K = f^x mod p. |
97 | */ |
98 | Bignum dh_find_K(Bignum f) { |
3709bfe9 |
99 | return modpow(f, x, p); |
e5574168 |
100 | } |