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1 | #include "ssh.h" |
2 | |
3 | struct ssh_kex ssh_diffiehellman = { |
4 | "diffie-hellman-group1-sha1" |
5 | }; |
6 | |
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7 | struct ssh_kex ssh_diffiehellman_gex = { |
8 | "diffie-hellman-group-exchange-sha1" |
9 | }; |
10 | |
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11 | /* |
12 | * The prime p used in the key exchange. |
13 | */ |
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14 | static unsigned char P[] = { |
15 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, |
16 | 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, |
17 | 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, |
18 | 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, |
19 | 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, |
20 | 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, |
21 | 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, |
22 | 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, |
23 | 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, |
24 | 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, |
25 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF |
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26 | }; |
27 | |
28 | /* |
3709bfe9 |
29 | * The generator g = 2. |
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30 | */ |
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31 | static unsigned char G[] = { 2 }; |
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32 | |
33 | /* |
3709bfe9 |
34 | * Variables. |
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35 | */ |
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36 | static Bignum x, e, p, q, qmask, g; |
37 | static int need_to_free_pg; |
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38 | |
39 | /* |
3709bfe9 |
40 | * Common DH initialisation. |
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41 | */ |
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42 | static void dh_init(void) { |
43 | q = bignum_rshift(p, 1); |
44 | qmask = bignum_bitmask(q); |
45 | } |
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46 | |
47 | /* |
3709bfe9 |
48 | * Initialise DH for the standard group1. |
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49 | */ |
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50 | void dh_setup_group1(void) { |
51 | p = bignum_from_bytes(P, sizeof(P)); |
52 | g = bignum_from_bytes(G, sizeof(G)); |
53 | dh_init(); |
54 | } |
55 | |
56 | /* |
a92dd380 |
57 | * Initialise DH for an alternative group. |
58 | */ |
59 | void dh_setup_group(Bignum pval, Bignum gval) { |
60 | p = copybn(pval); |
61 | g = copybn(gval); |
62 | dh_init(); |
63 | } |
64 | |
65 | /* |
3709bfe9 |
66 | * Clean up. |
67 | */ |
68 | void dh_cleanup(void) { |
69 | freebn(p); |
70 | freebn(g); |
71 | freebn(q); |
72 | freebn(qmask); |
73 | } |
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74 | |
75 | /* |
76 | * DH stage 1: invent a number x between 1 and q, and compute e = |
77 | * g^x mod p. Return e. |
78 | */ |
79 | Bignum dh_create_e(void) { |
80 | int i; |
81 | |
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82 | int nbytes; |
83 | unsigned char *buf; |
84 | |
85 | nbytes = ssh1_bignum_length(qmask); |
86 | buf = smalloc(nbytes); |
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87 | |
a71540b9 |
88 | do { |
89 | /* |
90 | * Create a potential x, by ANDing a string of random bytes |
3709bfe9 |
91 | * with qmask. |
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92 | */ |
3709bfe9 |
93 | if (x) freebn(x); |
94 | ssh1_write_bignum(buf, qmask); |
95 | for (i = 2; i < nbytes; i++) |
96 | buf[i] &= random_byte(); |
97 | ssh1_read_bignum(buf, &x); |
98 | } while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, q) >= 0); |
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99 | |
100 | /* |
101 | * Done. Now compute e = g^x mod p. |
102 | */ |
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103 | e = modpow(g, x, p); |
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104 | |
105 | return e; |
106 | } |
107 | |
108 | /* |
109 | * DH stage 2: given a number f, compute K = f^x mod p. |
110 | */ |
111 | Bignum dh_find_K(Bignum f) { |
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112 | return modpow(f, x, p); |
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113 | } |