eaf1e20a |
1 | /* |
2 | * Diffie-Hellman implementation for PuTTY. |
3 | */ |
4 | |
e5574168 |
5 | #include "ssh.h" |
6 | |
e5574168 |
7 | /* |
d1aaf71d |
8 | * The primes used in the group1 and group14 key exchange. |
e5574168 |
9 | */ |
d1aaf71d |
10 | static const unsigned char P1[] = { |
3709bfe9 |
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 |
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22 | }; |
d1aaf71d |
23 | static const unsigned char P14[] = { |
24 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, |
25 | 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, |
26 | 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, |
27 | 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, |
28 | 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, |
29 | 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, |
30 | 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, |
31 | 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, |
32 | 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, |
33 | 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D, |
34 | 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36, |
35 | 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F, |
36 | 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56, |
37 | 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, |
38 | 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08, |
39 | 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B, |
40 | 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, |
41 | 0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9, |
42 | 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C, |
43 | 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10, |
44 | 0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF, |
45 | 0xFF, 0xFF, 0xFF, 0xFF |
46 | }; |
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47 | |
48 | /* |
d1aaf71d |
49 | * The generator g = 2 (used for both group1 and group14). |
e5574168 |
50 | */ |
27cd7fc2 |
51 | static const unsigned char G[] = { 2 }; |
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52 | |
34557659 |
53 | static const struct ssh_kex ssh_diffiehellman_group1_sha1 = { |
d1aaf71d |
54 | "diffie-hellman-group1-sha1", "group1", |
b672f405 |
55 | P1, G, lenof(P1), lenof(G), &ssh_sha1 |
d1aaf71d |
56 | }; |
57 | |
34557659 |
58 | static const struct ssh_kex *const group1_list[] = { |
59 | &ssh_diffiehellman_group1_sha1 |
60 | }; |
61 | |
62 | const struct ssh_kexes ssh_diffiehellman_group1 = { |
63 | sizeof(group1_list) / sizeof(*group1_list), |
64 | group1_list |
65 | }; |
66 | |
67 | static const struct ssh_kex ssh_diffiehellman_group14_sha1 = { |
d1aaf71d |
68 | "diffie-hellman-group14-sha1", "group14", |
b672f405 |
69 | P14, G, lenof(P14), lenof(G), &ssh_sha1 |
d1aaf71d |
70 | }; |
71 | |
34557659 |
72 | static const struct ssh_kex *const group14_list[] = { |
73 | &ssh_diffiehellman_group14_sha1 |
74 | }; |
75 | |
76 | const struct ssh_kexes ssh_diffiehellman_group14 = { |
77 | sizeof(group14_list) / sizeof(*group14_list), |
78 | group14_list |
79 | }; |
80 | |
2ccb2fc8 |
81 | static const struct ssh_kex ssh_diffiehellman_gex_sha256 = { |
82 | "diffie-hellman-group-exchange-sha256", NULL, |
83 | NULL, NULL, 0, 0, &ssh_sha256 |
84 | }; |
85 | |
34557659 |
86 | static const struct ssh_kex ssh_diffiehellman_gex_sha1 = { |
d1aaf71d |
87 | "diffie-hellman-group-exchange-sha1", NULL, |
b672f405 |
88 | NULL, NULL, 0, 0, &ssh_sha1 |
d1aaf71d |
89 | }; |
90 | |
34557659 |
91 | static const struct ssh_kex *const gex_list[] = { |
2ccb2fc8 |
92 | &ssh_diffiehellman_gex_sha256, |
34557659 |
93 | &ssh_diffiehellman_gex_sha1 |
94 | }; |
95 | |
96 | const struct ssh_kexes ssh_diffiehellman_gex = { |
97 | sizeof(gex_list) / sizeof(*gex_list), |
98 | gex_list |
99 | }; |
100 | |
e5574168 |
101 | /* |
3709bfe9 |
102 | * Variables. |
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103 | */ |
27cd7fc2 |
104 | struct dh_ctx { |
105 | Bignum x, e, p, q, qmask, g; |
106 | }; |
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107 | |
108 | /* |
3709bfe9 |
109 | * Common DH initialisation. |
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110 | */ |
27cd7fc2 |
111 | static void dh_init(struct dh_ctx *ctx) |
32874aea |
112 | { |
27cd7fc2 |
113 | ctx->q = bignum_rshift(ctx->p, 1); |
114 | ctx->qmask = bignum_bitmask(ctx->q); |
115 | ctx->x = ctx->e = NULL; |
3709bfe9 |
116 | } |
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117 | |
118 | /* |
d1aaf71d |
119 | * Initialise DH for a standard group. |
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120 | */ |
d1aaf71d |
121 | void *dh_setup_group(const struct ssh_kex *kex) |
32874aea |
122 | { |
3d88e64d |
123 | struct dh_ctx *ctx = snew(struct dh_ctx); |
d1aaf71d |
124 | ctx->p = bignum_from_bytes(kex->pdata, kex->plen); |
125 | ctx->g = bignum_from_bytes(kex->gdata, kex->glen); |
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126 | dh_init(ctx); |
127 | return ctx; |
3709bfe9 |
128 | } |
129 | |
130 | /* |
d1aaf71d |
131 | * Initialise DH for a server-supplied group. |
a92dd380 |
132 | */ |
d1aaf71d |
133 | void *dh_setup_gex(Bignum pval, Bignum gval) |
32874aea |
134 | { |
3d88e64d |
135 | struct dh_ctx *ctx = snew(struct dh_ctx); |
27cd7fc2 |
136 | ctx->p = copybn(pval); |
137 | ctx->g = copybn(gval); |
138 | dh_init(ctx); |
139 | return ctx; |
a92dd380 |
140 | } |
141 | |
142 | /* |
27cd7fc2 |
143 | * Clean up and free a context. |
3709bfe9 |
144 | */ |
27cd7fc2 |
145 | void dh_cleanup(void *handle) |
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146 | { |
27cd7fc2 |
147 | struct dh_ctx *ctx = (struct dh_ctx *)handle; |
148 | freebn(ctx->x); |
149 | freebn(ctx->e); |
150 | freebn(ctx->p); |
151 | freebn(ctx->g); |
152 | freebn(ctx->q); |
153 | freebn(ctx->qmask); |
154 | sfree(ctx); |
3709bfe9 |
155 | } |
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156 | |
157 | /* |
158 | * DH stage 1: invent a number x between 1 and q, and compute e = |
159 | * g^x mod p. Return e. |
7bd5a860 |
160 | * |
161 | * If `nbits' is greater than zero, it is used as an upper limit |
162 | * for the number of bits in x. This is safe provided that (a) you |
163 | * use twice as many bits in x as the number of bits you expect to |
164 | * use in your session key, and (b) the DH group is a safe prime |
165 | * (which SSH demands that it must be). |
166 | * |
167 | * P. C. van Oorschot, M. J. Wiener |
168 | * "On Diffie-Hellman Key Agreement with Short Exponents". |
169 | * Advances in Cryptology: Proceedings of Eurocrypt '96 |
170 | * Springer-Verlag, May 1996. |
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171 | */ |
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172 | Bignum dh_create_e(void *handle, int nbits) |
32874aea |
173 | { |
27cd7fc2 |
174 | struct dh_ctx *ctx = (struct dh_ctx *)handle; |
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175 | int i; |
176 | |
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177 | int nbytes; |
178 | unsigned char *buf; |
179 | |
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180 | nbytes = ssh1_bignum_length(ctx->qmask); |
3d88e64d |
181 | buf = snewn(nbytes, unsigned char); |
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182 | |
a71540b9 |
183 | do { |
184 | /* |
185 | * Create a potential x, by ANDing a string of random bytes |
3709bfe9 |
186 | * with qmask. |
a71540b9 |
187 | */ |
27cd7fc2 |
188 | if (ctx->x) |
189 | freebn(ctx->x); |
190 | if (nbits == 0 || nbits > bignum_bitcount(ctx->qmask)) { |
191 | ssh1_write_bignum(buf, ctx->qmask); |
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192 | for (i = 2; i < nbytes; i++) |
193 | buf[i] &= random_byte(); |
0016d70b |
194 | ssh1_read_bignum(buf, nbytes, &ctx->x); /* can't fail */ |
7bd5a860 |
195 | } else { |
196 | int b, nb; |
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197 | ctx->x = bn_power_2(nbits); |
2d466ffd |
198 | b = nb = 0; |
7bd5a860 |
199 | for (i = 0; i < nbits; i++) { |
200 | if (nb == 0) { |
201 | nb = 8; |
202 | b = random_byte(); |
203 | } |
27cd7fc2 |
204 | bignum_set_bit(ctx->x, i, b & 1); |
7bd5a860 |
205 | b >>= 1; |
206 | nb--; |
207 | } |
208 | } |
27cd7fc2 |
209 | } while (bignum_cmp(ctx->x, One) <= 0 || bignum_cmp(ctx->x, ctx->q) >= 0); |
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210 | |
170c1e6e |
211 | sfree(buf); |
212 | |
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213 | /* |
214 | * Done. Now compute e = g^x mod p. |
215 | */ |
27cd7fc2 |
216 | ctx->e = modpow(ctx->g, ctx->x, ctx->p); |
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217 | |
27cd7fc2 |
218 | return ctx->e; |
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219 | } |
220 | |
221 | /* |
222 | * DH stage 2: given a number f, compute K = f^x mod p. |
223 | */ |
27cd7fc2 |
224 | Bignum dh_find_K(void *handle, Bignum f) |
32874aea |
225 | { |
27cd7fc2 |
226 | struct dh_ctx *ctx = (struct dh_ctx *)handle; |
7bd5a860 |
227 | Bignum ret; |
27cd7fc2 |
228 | ret = modpow(f, ctx->x, ctx->p); |
7bd5a860 |
229 | return ret; |
e5574168 |
230 | } |