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); }
18 static void getstring(char **data, int *datalen, char **p, int *length) {
22 *length = GET_32BIT(*data);
23 *datalen -= 4; *data += 4;
24 if (*datalen < *length)
27 *data += *length; *datalen -= *length;
29 static Bignum getmp(char **data, int *datalen) {
34 getstring(data, datalen, &p, &length);
38 return NULL; /* negative mp */
39 b = newbn((length+1)/2);
40 for (i = 0; i < length; i++) {
43 b[j/2+1] |= ((unsigned char)p[i]) << 8;
45 b[j/2+1] |= ((unsigned char)p[i]);
50 static Bignum get160(char **data, int *datalen) {
56 *data += 20; *datalen -= 20;
59 while (length > 0 && !p[0])
61 b = newbn((length+1)/2);
62 for (i = 0; i < length; i++) {
65 b[j/2+1] |= ((unsigned char)p[i]) << 8;
67 b[j/2+1] |= ((unsigned char)p[i]);
72 static Bignum dss_p, dss_q, dss_g, dss_y;
74 static void dss_setkey(char *data, int len) {
77 getstring(&data, &len, &p, &slen);
78 if (!p || memcmp(p, "ssh-dss", 7)) {
82 dss_p = getmp(&data, &len);
83 dss_q = getmp(&data, &len);
84 dss_g = getmp(&data, &len);
85 dss_y = getmp(&data, &len);
88 static char *dss_fmtkey(void) {
90 int len, i, pos, nibbles;
91 static const char hex[] = "0123456789abcdef";
94 len = 8 + 4 + 1; /* 4 x "0x", punctuation, \0 */
95 len += 4 * (dss_p[0] + dss_q[0] + dss_g[0] + dss_y[0]); /* digits */
100 pos += sprintf(p+pos, "0x");
101 nibbles = (3 + ssh1_bignum_bitcount(dss_p))/4; if (nibbles<1) nibbles=1;
102 for (i=nibbles; i-- ;)
103 p[pos++] = hex[(bignum_byte(dss_p, i/2) >> (4*(i%2))) & 0xF];
104 pos += sprintf(p+pos, ",0x");
105 nibbles = (3 + ssh1_bignum_bitcount(dss_q))/4; if (nibbles<1) nibbles=1;
106 for (i=nibbles; i-- ;)
107 p[pos++] = hex[(bignum_byte(dss_q, i/2) >> (4*(i%2))) & 0xF];
108 pos += sprintf(p+pos, ",0x");
109 nibbles = (3 + ssh1_bignum_bitcount(dss_g))/4; if (nibbles<1) nibbles=1;
110 for (i=nibbles; i-- ;)
111 p[pos++] = hex[(bignum_byte(dss_g, i/2) >> (4*(i%2))) & 0xF];
112 pos += sprintf(p+pos, ",0x");
113 nibbles = (3 + ssh1_bignum_bitcount(dss_y))/4; if (nibbles<1) nibbles=1;
114 for (i=nibbles; i-- ;)
115 p[pos++] = hex[(bignum_byte(dss_y, i/2) >> (4*(i%2))) & 0xF];
120 static char *dss_fingerprint(void) {
121 struct MD5Context md5c;
122 unsigned char digest[16], lenbuf[4];
123 char buffer[16*3+40];
128 MD5Update(&md5c, "\0\0\0\7ssh-dss", 11);
130 #define ADD_BIGNUM(bignum) \
131 numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \
132 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
133 for (i = numlen; i-- ;) { \
134 unsigned char c = bignum_byte(bignum, i); \
135 MD5Update(&md5c, &c, 1); \
143 MD5Final(digest, &md5c);
145 sprintf(buffer, "%d ", ssh1_bignum_bitcount(dss_p));
146 for (i = 0; i < 16; i++)
147 sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
148 ret = malloc(strlen(buffer)+1);
154 static int dss_verifysig(char *sig, int siglen, char *data, int datalen) {
158 Bignum qm2, r, s, w, i1, i2, i3, u1, u2, sha, v;
165 * Commercial SSH (2.0.13) and OpenSSH disagree over the format
166 * of a DSA signature. OpenSSH is in line with the IETF drafts:
167 * it uses a string "ssh-dss", followed by a 40-byte string
168 * containing two 160-bit integers end-to-end. Commercial SSH
169 * can't be bothered with the header bit, and considers a DSA
170 * signature blob to be _just_ the 40-byte string containing
171 * the two 160-bit integers. We tell them apart by measuring
172 * the length: length 40 means the commercial-SSH bug, anything
173 * else is assumed to be IETF-compliant.
175 if (siglen != 40) { /* bug not present; read admin fields */
176 getstring(&sig, &siglen, &p, &slen);
177 if (!p || memcmp(p, "ssh-dss", 7)) {
180 sig += 4, siglen -= 4; /* skip yet another length field */
182 r = get160(&sig, &siglen);
183 s = get160(&sig, &siglen);
188 * Step 1. w <- s^-1 mod q.
192 decbn(qm2); decbn(qm2);
193 /* Now qm2 is q-2, and by Fermat's Little Theorem, s^qm2 == s^-1 (mod q).
194 * This is a silly way to do it; may fix it later. */
195 modpow(s, qm2, dss_q, w);
198 * Step 2. u1 <- SHA(message) * w mod q.
200 u1 = newbn(dss_q[0]);
201 SHA_Simple(data, datalen, hash);
202 p = hash; slen = 20; sha = get160(&p, &slen);
203 modmul(sha, w, dss_q, u1);
206 * Step 3. u2 <- r * w mod q.
208 u2 = newbn(dss_q[0]);
209 modmul(r, w, dss_q, u2);
212 * Step 4. v <- (g^u1 * y^u2 mod p) mod q.
214 i1 = newbn(dss_p[0]);
215 i2 = newbn(dss_p[0]);
216 i3 = newbn(dss_p[0]);
218 modpow(dss_g, u1, dss_p, i1);
219 modpow(dss_y, u2, dss_p, i2);
220 modmul(i1, i2, dss_p, i3);
221 modmul(i3, One, dss_q, v);
224 * Step 5. v should now be equal to r.
228 for (i = 1; i <= v[0] || i <= r[0]; i++) {
229 if ((i > v[0] && r[i] != 0) ||
230 (i > r[0] && v[i] != 0) ||
231 (i <= v[0] && i <= r[0] && r[i] != v[i]))
248 struct ssh_hostkey ssh_dss = {