7cca0d81 |
1 | #include <stdio.h> |
2 | #include <stdlib.h> |
65a22376 |
3 | #include <assert.h> |
7cca0d81 |
4 | |
e5574168 |
5 | #include "ssh.h" |
6 | |
7cca0d81 |
7 | #define GET_32BIT(cp) \ |
8 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
9 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
10 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
11 | ((unsigned long)(unsigned char)(cp)[3])) |
12 | |
d5859615 |
13 | #define PUT_32BIT(cp, value) { \ |
14 | (cp)[0] = (unsigned char)((value) >> 24); \ |
15 | (cp)[1] = (unsigned char)((value) >> 16); \ |
16 | (cp)[2] = (unsigned char)((value) >> 8); \ |
17 | (cp)[3] = (unsigned char)(value); } |
18 | |
9c621433 |
19 | #if 0 |
c5fbd713 |
20 | #define DEBUG_DSS |
9c621433 |
21 | #else |
22 | #define diagbn(x,y) |
23 | #endif |
24 | |
32874aea |
25 | static void getstring(char **data, int *datalen, char **p, int *length) |
26 | { |
7cca0d81 |
27 | *p = NULL; |
28 | if (*datalen < 4) |
32874aea |
29 | return; |
7cca0d81 |
30 | *length = GET_32BIT(*data); |
32874aea |
31 | *datalen -= 4; |
32 | *data += 4; |
7cca0d81 |
33 | if (*datalen < *length) |
32874aea |
34 | return; |
7cca0d81 |
35 | *p = *data; |
32874aea |
36 | *data += *length; |
37 | *datalen -= *length; |
7cca0d81 |
38 | } |
32874aea |
39 | static Bignum getmp(char **data, int *datalen) |
40 | { |
7cca0d81 |
41 | char *p; |
3709bfe9 |
42 | int length; |
7cca0d81 |
43 | Bignum b; |
44 | |
45 | getstring(data, datalen, &p, &length); |
46 | if (!p) |
32874aea |
47 | return NULL; |
7cca0d81 |
48 | if (p[0] & 0x80) |
32874aea |
49 | return NULL; /* negative mp */ |
3709bfe9 |
50 | b = bignum_from_bytes(p, length); |
7cca0d81 |
51 | return b; |
52 | } |
53 | |
32874aea |
54 | static Bignum get160(char **data, int *datalen) |
55 | { |
7cca0d81 |
56 | Bignum b; |
57 | |
3709bfe9 |
58 | b = bignum_from_bytes(*data, 20); |
32874aea |
59 | *data += 20; |
60 | *datalen -= 20; |
7cca0d81 |
61 | |
7cca0d81 |
62 | return b; |
63 | } |
64 | |
e055a386 |
65 | struct dss_key { |
66 | Bignum p, q, g, y; |
67 | }; |
7cca0d81 |
68 | |
32874aea |
69 | static void *dss_newkey(char *data, int len) |
70 | { |
7cca0d81 |
71 | char *p; |
72 | int slen; |
e055a386 |
73 | struct dss_key *dss; |
74 | |
dcbde236 |
75 | dss = smalloc(sizeof(struct dss_key)); |
32874aea |
76 | if (!dss) |
77 | return NULL; |
7cca0d81 |
78 | getstring(&data, &len, &p, &slen); |
9c621433 |
79 | |
80 | #ifdef DEBUG_DSS |
81 | { |
32874aea |
82 | int i; |
83 | printf("key:"); |
84 | for (i = 0; i < len; i++) |
85 | printf(" %02x", (unsigned char) (data[i])); |
86 | printf("\n"); |
9c621433 |
87 | } |
88 | #endif |
89 | |
7cca0d81 |
90 | if (!p || memcmp(p, "ssh-dss", 7)) { |
dcbde236 |
91 | sfree(dss); |
e055a386 |
92 | return NULL; |
7cca0d81 |
93 | } |
e055a386 |
94 | dss->p = getmp(&data, &len); |
95 | dss->q = getmp(&data, &len); |
96 | dss->g = getmp(&data, &len); |
97 | dss->y = getmp(&data, &len); |
98 | |
99 | return dss; |
7cca0d81 |
100 | } |
101 | |
32874aea |
102 | static void dss_freekey(void *key) |
103 | { |
104 | struct dss_key *dss = (struct dss_key *) key; |
e055a386 |
105 | freebn(dss->p); |
106 | freebn(dss->q); |
107 | freebn(dss->g); |
108 | freebn(dss->y); |
dcbde236 |
109 | sfree(dss); |
e055a386 |
110 | } |
111 | |
32874aea |
112 | static char *dss_fmtkey(void *key) |
113 | { |
114 | struct dss_key *dss = (struct dss_key *) key; |
7cca0d81 |
115 | char *p; |
d5859615 |
116 | int len, i, pos, nibbles; |
117 | static const char hex[] = "0123456789abcdef"; |
e055a386 |
118 | if (!dss->p) |
32874aea |
119 | return NULL; |
120 | len = 8 + 4 + 1; /* 4 x "0x", punctuation, \0 */ |
121 | len += 4 * (bignum_bitcount(dss->p) + 15) / 16; |
122 | len += 4 * (bignum_bitcount(dss->q) + 15) / 16; |
123 | len += 4 * (bignum_bitcount(dss->g) + 15) / 16; |
124 | len += 4 * (bignum_bitcount(dss->y) + 15) / 16; |
dcbde236 |
125 | p = smalloc(len); |
32874aea |
126 | if (!p) |
127 | return NULL; |
d5859615 |
128 | |
129 | pos = 0; |
32874aea |
130 | pos += sprintf(p + pos, "0x"); |
131 | nibbles = (3 + bignum_bitcount(dss->p)) / 4; |
132 | if (nibbles < 1) |
133 | nibbles = 1; |
134 | for (i = nibbles; i--;) |
135 | p[pos++] = |
136 | hex[(bignum_byte(dss->p, i / 2) >> (4 * (i % 2))) & 0xF]; |
137 | pos += sprintf(p + pos, ",0x"); |
138 | nibbles = (3 + bignum_bitcount(dss->q)) / 4; |
139 | if (nibbles < 1) |
140 | nibbles = 1; |
141 | for (i = nibbles; i--;) |
142 | p[pos++] = |
143 | hex[(bignum_byte(dss->q, i / 2) >> (4 * (i % 2))) & 0xF]; |
144 | pos += sprintf(p + pos, ",0x"); |
145 | nibbles = (3 + bignum_bitcount(dss->g)) / 4; |
146 | if (nibbles < 1) |
147 | nibbles = 1; |
148 | for (i = nibbles; i--;) |
149 | p[pos++] = |
150 | hex[(bignum_byte(dss->g, i / 2) >> (4 * (i % 2))) & 0xF]; |
151 | pos += sprintf(p + pos, ",0x"); |
152 | nibbles = (3 + bignum_bitcount(dss->y)) / 4; |
153 | if (nibbles < 1) |
154 | nibbles = 1; |
155 | for (i = nibbles; i--;) |
156 | p[pos++] = |
157 | hex[(bignum_byte(dss->y, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
158 | p[pos] = '\0'; |
7cca0d81 |
159 | return p; |
160 | } |
161 | |
32874aea |
162 | static char *dss_fingerprint(void *key) |
163 | { |
164 | struct dss_key *dss = (struct dss_key *) key; |
d5859615 |
165 | struct MD5Context md5c; |
166 | unsigned char digest[16], lenbuf[4]; |
32874aea |
167 | char buffer[16 * 3 + 40]; |
d5859615 |
168 | char *ret; |
169 | int numlen, i; |
170 | |
171 | MD5Init(&md5c); |
172 | MD5Update(&md5c, "\0\0\0\7ssh-dss", 11); |
173 | |
174 | #define ADD_BIGNUM(bignum) \ |
ddecd643 |
175 | numlen = (bignum_bitcount(bignum)+8)/8; \ |
d5859615 |
176 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
177 | for (i = numlen; i-- ;) { \ |
178 | unsigned char c = bignum_byte(bignum, i); \ |
179 | MD5Update(&md5c, &c, 1); \ |
180 | } |
e055a386 |
181 | ADD_BIGNUM(dss->p); |
182 | ADD_BIGNUM(dss->q); |
183 | ADD_BIGNUM(dss->g); |
184 | ADD_BIGNUM(dss->y); |
d5859615 |
185 | #undef ADD_BIGNUM |
186 | |
187 | MD5Final(digest, &md5c); |
188 | |
ddecd643 |
189 | sprintf(buffer, "ssh-dss %d ", bignum_bitcount(dss->p)); |
d5859615 |
190 | for (i = 0; i < 16; i++) |
32874aea |
191 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
192 | digest[i]); |
193 | ret = smalloc(strlen(buffer) + 1); |
d5859615 |
194 | if (ret) |
32874aea |
195 | strcpy(ret, buffer); |
d5859615 |
196 | return ret; |
197 | } |
198 | |
e055a386 |
199 | static int dss_verifysig(void *key, char *sig, int siglen, |
32874aea |
200 | char *data, int datalen) |
201 | { |
202 | struct dss_key *dss = (struct dss_key *) key; |
7cca0d81 |
203 | char *p; |
c5fbd713 |
204 | int slen; |
7cca0d81 |
205 | char hash[20]; |
59600f67 |
206 | Bignum r, s, w, gu1p, yu2p, gu1yu2p, u1, u2, sha, v; |
7cca0d81 |
207 | int ret; |
208 | |
e055a386 |
209 | if (!dss->p) |
32874aea |
210 | return 0; |
7cca0d81 |
211 | |
9c621433 |
212 | #ifdef DEBUG_DSS |
213 | { |
32874aea |
214 | int i; |
215 | printf("sig:"); |
216 | for (i = 0; i < siglen; i++) |
217 | printf(" %02x", (unsigned char) (sig[i])); |
218 | printf("\n"); |
9c621433 |
219 | } |
220 | #endif |
7f7837c8 |
221 | /* |
222 | * Commercial SSH (2.0.13) and OpenSSH disagree over the format |
223 | * of a DSA signature. OpenSSH is in line with the IETF drafts: |
224 | * it uses a string "ssh-dss", followed by a 40-byte string |
225 | * containing two 160-bit integers end-to-end. Commercial SSH |
226 | * can't be bothered with the header bit, and considers a DSA |
227 | * signature blob to be _just_ the 40-byte string containing |
228 | * the two 160-bit integers. We tell them apart by measuring |
229 | * the length: length 40 means the commercial-SSH bug, anything |
230 | * else is assumed to be IETF-compliant. |
231 | */ |
32874aea |
232 | if (siglen != 40) { /* bug not present; read admin fields */ |
233 | getstring(&sig, &siglen, &p, &slen); |
234 | if (!p || slen != 7 || memcmp(p, "ssh-dss", 7)) { |
235 | return 0; |
236 | } |
237 | sig += 4, siglen -= 4; /* skip yet another length field */ |
7cca0d81 |
238 | } |
e055a386 |
239 | diagbn("p=", dss->p); |
240 | diagbn("q=", dss->q); |
241 | diagbn("g=", dss->g); |
242 | diagbn("y=", dss->y); |
7cca0d81 |
243 | r = get160(&sig, &siglen); |
9c621433 |
244 | diagbn("r=", r); |
7cca0d81 |
245 | s = get160(&sig, &siglen); |
9c621433 |
246 | diagbn("s=", s); |
7cca0d81 |
247 | if (!r || !s) |
32874aea |
248 | return 0; |
7cca0d81 |
249 | |
250 | /* |
251 | * Step 1. w <- s^-1 mod q. |
252 | */ |
e055a386 |
253 | w = modinv(s, dss->q); |
9c621433 |
254 | diagbn("w=", w); |
7cca0d81 |
255 | |
256 | /* |
257 | * Step 2. u1 <- SHA(message) * w mod q. |
258 | */ |
7cca0d81 |
259 | SHA_Simple(data, datalen, hash); |
32874aea |
260 | p = hash; |
261 | slen = 20; |
262 | sha = get160(&p, &slen); |
9c621433 |
263 | diagbn("sha=", sha); |
e055a386 |
264 | u1 = modmul(sha, w, dss->q); |
9c621433 |
265 | diagbn("u1=", u1); |
7cca0d81 |
266 | |
267 | /* |
268 | * Step 3. u2 <- r * w mod q. |
269 | */ |
e055a386 |
270 | u2 = modmul(r, w, dss->q); |
9c621433 |
271 | diagbn("u2=", u2); |
7cca0d81 |
272 | |
273 | /* |
274 | * Step 4. v <- (g^u1 * y^u2 mod p) mod q. |
275 | */ |
e055a386 |
276 | gu1p = modpow(dss->g, u1, dss->p); |
59600f67 |
277 | diagbn("gu1p=", gu1p); |
e055a386 |
278 | yu2p = modpow(dss->y, u2, dss->p); |
59600f67 |
279 | diagbn("yu2p=", yu2p); |
e055a386 |
280 | gu1yu2p = modmul(gu1p, yu2p, dss->p); |
59600f67 |
281 | diagbn("gu1yu2p=", gu1yu2p); |
e055a386 |
282 | v = modmul(gu1yu2p, One, dss->q); |
9c621433 |
283 | diagbn("gu1yu2q=v=", v); |
284 | diagbn("r=", r); |
7cca0d81 |
285 | |
286 | /* |
287 | * Step 5. v should now be equal to r. |
288 | */ |
289 | |
c5fbd713 |
290 | ret = !bignum_cmp(v, r); |
7cca0d81 |
291 | |
292 | freebn(w); |
7cca0d81 |
293 | freebn(sha); |
59600f67 |
294 | freebn(gu1p); |
295 | freebn(yu2p); |
296 | freebn(gu1yu2p); |
7cca0d81 |
297 | freebn(v); |
298 | freebn(r); |
299 | freebn(s); |
300 | |
301 | return ret; |
302 | } |
303 | |
32874aea |
304 | static unsigned char *dss_public_blob(void *key, int *len) |
305 | { |
306 | struct dss_key *dss = (struct dss_key *) key; |
65a22376 |
307 | int plen, qlen, glen, ylen, bloblen; |
308 | int i; |
309 | unsigned char *blob, *p; |
310 | |
32874aea |
311 | plen = (bignum_bitcount(dss->p) + 8) / 8; |
312 | qlen = (bignum_bitcount(dss->q) + 8) / 8; |
313 | glen = (bignum_bitcount(dss->g) + 8) / 8; |
314 | ylen = (bignum_bitcount(dss->y) + 8) / 8; |
65a22376 |
315 | |
316 | /* |
317 | * string "ssh-dss", mpint p, mpint q, mpint g, mpint y. Total |
318 | * 27 + sum of lengths. (five length fields, 20+7=27). |
319 | */ |
32874aea |
320 | bloblen = 27 + plen + qlen + glen + ylen; |
65a22376 |
321 | blob = smalloc(bloblen); |
322 | p = blob; |
32874aea |
323 | PUT_32BIT(p, 7); |
324 | p += 4; |
325 | memcpy(p, "ssh-dss", 7); |
326 | p += 7; |
327 | PUT_32BIT(p, plen); |
328 | p += 4; |
329 | for (i = plen; i--;) |
330 | *p++ = bignum_byte(dss->p, i); |
331 | PUT_32BIT(p, qlen); |
332 | p += 4; |
333 | for (i = qlen; i--;) |
334 | *p++ = bignum_byte(dss->q, i); |
335 | PUT_32BIT(p, glen); |
336 | p += 4; |
337 | for (i = glen; i--;) |
338 | *p++ = bignum_byte(dss->g, i); |
339 | PUT_32BIT(p, ylen); |
340 | p += 4; |
341 | for (i = ylen; i--;) |
342 | *p++ = bignum_byte(dss->y, i); |
65a22376 |
343 | assert(p == blob + bloblen); |
344 | *len = bloblen; |
345 | return blob; |
346 | } |
347 | |
32874aea |
348 | static unsigned char *dss_private_blob(void *key, int *len) |
349 | { |
65a22376 |
350 | return NULL; /* can't handle DSS private keys */ |
351 | } |
352 | |
353 | static void *dss_createkey(unsigned char *pub_blob, int pub_len, |
32874aea |
354 | unsigned char *priv_blob, int priv_len) |
355 | { |
65a22376 |
356 | return NULL; /* can't handle DSS private keys */ |
357 | } |
358 | |
32874aea |
359 | static void *dss_openssh_createkey(unsigned char **blob, int *len) |
360 | { |
45cebe79 |
361 | return NULL; /* can't handle DSS private keys */ |
362 | } |
363 | |
32874aea |
364 | static int dss_openssh_fmtkey(void *key, unsigned char *blob, int len) |
365 | { |
ddecd643 |
366 | return -1; /* can't handle DSS private keys */ |
367 | } |
368 | |
32874aea |
369 | unsigned char *dss_sign(void *key, char *data, int datalen, int *siglen) |
370 | { |
65a22376 |
371 | return NULL; /* can't handle DSS private keys */ |
e055a386 |
372 | } |
373 | |
65a22376 |
374 | const struct ssh_signkey ssh_dss = { |
e055a386 |
375 | dss_newkey, |
376 | dss_freekey, |
7cca0d81 |
377 | dss_fmtkey, |
65a22376 |
378 | dss_public_blob, |
379 | dss_private_blob, |
380 | dss_createkey, |
45cebe79 |
381 | dss_openssh_createkey, |
ddecd643 |
382 | dss_openssh_fmtkey, |
d5859615 |
383 | dss_fingerprint, |
7cca0d81 |
384 | dss_verifysig, |
e055a386 |
385 | dss_sign, |
d5859615 |
386 | "ssh-dss", |
387 | "dss" |
e5574168 |
388 | }; |