6 #define GET_32BIT(cp) \
7 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
8 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
9 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
10 ((unsigned long)(unsigned char)(cp)[3]))
12 #define PUT_32BIT(cp, value) { \
13 (cp)[0] = (unsigned char)((value) >> 24); \
14 (cp)[1] = (unsigned char)((value) >> 16); \
15 (cp)[2] = (unsigned char)((value) >> 8); \
16 (cp)[3] = (unsigned char)(value); }
20 * Condition this section in for debugging of DSS.
22 static void diagbn(char *prefix, Bignum md) {
23 int i, nibbles, morenibbles;
24 static const char hex[] = "0123456789ABCDEF";
26 printf("%s0x", prefix ? prefix : "");
28 nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1;
29 morenibbles = 4*md[0] - nibbles;
30 for (i=0; i<morenibbles; i++) putchar('-');
31 for (i=nibbles; i-- ;)
32 putchar(hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF]);
34 if (prefix) putchar('\n');
41 static void getstring(char **data, int *datalen, char **p, int *length) {
45 *length = GET_32BIT(*data);
46 *datalen -= 4; *data += 4;
47 if (*datalen < *length)
50 *data += *length; *datalen -= *length;
52 static Bignum getmp(char **data, int *datalen) {
57 getstring(data, datalen, &p, &length);
61 return NULL; /* negative mp */
62 b = newbn((length+1)/2);
63 for (i = 0; i < length; i++) {
66 b[j/2+1] |= ((unsigned char)p[i]) << 8;
68 b[j/2+1] |= ((unsigned char)p[i]);
70 while (b[0] > 1 && b[b[0]] == 0) b[0]--;
74 static Bignum get160(char **data, int *datalen) {
80 *data += 20; *datalen -= 20;
83 while (length > 0 && !p[0])
85 b = newbn((length+1)/2);
86 for (i = 0; i < length; i++) {
89 b[j/2+1] |= ((unsigned char)p[i]) << 8;
91 b[j/2+1] |= ((unsigned char)p[i]);
96 static Bignum dss_p, dss_q, dss_g, dss_y;
98 static void dss_setkey(char *data, int len) {
101 getstring(&data, &len, &p, &slen);
108 printf(" %02x", (unsigned char)(data[i]));
113 if (!p || memcmp(p, "ssh-dss", 7)) {
117 dss_p = getmp(&data, &len);
118 dss_q = getmp(&data, &len);
119 dss_g = getmp(&data, &len);
120 dss_y = getmp(&data, &len);
123 static char *dss_fmtkey(void) {
125 int len, i, pos, nibbles;
126 static const char hex[] = "0123456789abcdef";
129 len = 8 + 4 + 1; /* 4 x "0x", punctuation, \0 */
130 len += 4 * (dss_p[0] + dss_q[0] + dss_g[0] + dss_y[0]); /* digits */
135 pos += sprintf(p+pos, "0x");
136 nibbles = (3 + ssh1_bignum_bitcount(dss_p))/4; if (nibbles<1) nibbles=1;
137 for (i=nibbles; i-- ;)
138 p[pos++] = hex[(bignum_byte(dss_p, i/2) >> (4*(i%2))) & 0xF];
139 pos += sprintf(p+pos, ",0x");
140 nibbles = (3 + ssh1_bignum_bitcount(dss_q))/4; if (nibbles<1) nibbles=1;
141 for (i=nibbles; i-- ;)
142 p[pos++] = hex[(bignum_byte(dss_q, i/2) >> (4*(i%2))) & 0xF];
143 pos += sprintf(p+pos, ",0x");
144 nibbles = (3 + ssh1_bignum_bitcount(dss_g))/4; if (nibbles<1) nibbles=1;
145 for (i=nibbles; i-- ;)
146 p[pos++] = hex[(bignum_byte(dss_g, i/2) >> (4*(i%2))) & 0xF];
147 pos += sprintf(p+pos, ",0x");
148 nibbles = (3 + ssh1_bignum_bitcount(dss_y))/4; if (nibbles<1) nibbles=1;
149 for (i=nibbles; i-- ;)
150 p[pos++] = hex[(bignum_byte(dss_y, i/2) >> (4*(i%2))) & 0xF];
155 static char *dss_fingerprint(void) {
156 struct MD5Context md5c;
157 unsigned char digest[16], lenbuf[4];
158 char buffer[16*3+40];
163 MD5Update(&md5c, "\0\0\0\7ssh-dss", 11);
165 #define ADD_BIGNUM(bignum) \
166 numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \
167 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
168 for (i = numlen; i-- ;) { \
169 unsigned char c = bignum_byte(bignum, i); \
170 MD5Update(&md5c, &c, 1); \
178 MD5Final(digest, &md5c);
180 sprintf(buffer, "%d ", ssh1_bignum_bitcount(dss_p));
181 for (i = 0; i < 16; i++)
182 sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
183 ret = malloc(strlen(buffer)+1);
189 static int dss_verifysig(char *sig, int siglen, char *data, int datalen) {
193 Bignum r, s, w, gu1p, yu2p, gu1yu2p, u1, u2, sha, v;
203 for (i=0;i<siglen;i++)
204 printf(" %02xf", (unsigned char)(sig[i]));
209 * Commercial SSH (2.0.13) and OpenSSH disagree over the format
210 * of a DSA signature. OpenSSH is in line with the IETF drafts:
211 * it uses a string "ssh-dss", followed by a 40-byte string
212 * containing two 160-bit integers end-to-end. Commercial SSH
213 * can't be bothered with the header bit, and considers a DSA
214 * signature blob to be _just_ the 40-byte string containing
215 * the two 160-bit integers. We tell them apart by measuring
216 * the length: length 40 means the commercial-SSH bug, anything
217 * else is assumed to be IETF-compliant.
219 if (siglen != 40) { /* bug not present; read admin fields */
220 getstring(&sig, &siglen, &p, &slen);
221 if (!p || memcmp(p, "ssh-dss", 7)) {
224 sig += 4, siglen -= 4; /* skip yet another length field */
230 r = get160(&sig, &siglen);
232 s = get160(&sig, &siglen);
238 * Step 1. w <- s^-1 mod q.
240 w = modinv(s, dss_q);
244 * Step 2. u1 <- SHA(message) * w mod q.
246 SHA_Simple(data, datalen, hash);
247 p = hash; slen = 20; sha = get160(&p, &slen);
249 u1 = modmul(sha, w, dss_q);
253 * Step 3. u2 <- r * w mod q.
255 u2 = modmul(r, w, dss_q);
259 * Step 4. v <- (g^u1 * y^u2 mod p) mod q.
261 gu1p = modpow(dss_g, u1, dss_p);
262 diagbn("gu1p=", gu1p);
263 yu2p = modpow(dss_y, u2, dss_p);
264 diagbn("yu2p=", yu2p);
265 gu1yu2p = modmul(gu1p, yu2p, dss_p);
266 diagbn("gu1yu2p=", gu1yu2p);
267 v = modmul(gu1yu2p, One, dss_q);
268 diagbn("gu1yu2q=v=", v);
272 * Step 5. v should now be equal to r.
275 ret = !bignum_cmp(v, r);
289 struct ssh_hostkey ssh_dss = {