| 1 | /* |
| 2 | * RSA implementation just sufficient for ssh client-side |
| 3 | * initialisation step |
| 4 | * |
| 5 | * Rewritten for more speed by Joris van Rantwijk, Jun 1999. |
| 6 | */ |
| 7 | |
| 8 | #include <stdio.h> |
| 9 | #include <stdlib.h> |
| 10 | #include <string.h> |
| 11 | |
| 12 | #include "ssh.h" |
| 13 | |
| 14 | |
| 15 | int makekey(unsigned char *data, struct RSAKey *result, |
| 16 | unsigned char **keystr, int order) { |
| 17 | unsigned char *p = data; |
| 18 | int i; |
| 19 | |
| 20 | if (result) { |
| 21 | result->bits = 0; |
| 22 | for (i=0; i<4; i++) |
| 23 | result->bits = (result->bits << 8) + *p++; |
| 24 | } else |
| 25 | p += 4; |
| 26 | |
| 27 | /* |
| 28 | * order=0 means exponent then modulus (the keys sent by the |
| 29 | * server). order=1 means modulus then exponent (the keys |
| 30 | * stored in a keyfile). |
| 31 | */ |
| 32 | |
| 33 | if (order == 0) |
| 34 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
| 35 | if (result) |
| 36 | result->bytes = (((p[0] << 8) + p[1]) + 7) / 8; |
| 37 | if (keystr) *keystr = p+2; |
| 38 | p += ssh1_read_bignum(p, result ? &result->modulus : NULL); |
| 39 | if (order == 1) |
| 40 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
| 41 | |
| 42 | return p - data; |
| 43 | } |
| 44 | |
| 45 | int makeprivate(unsigned char *data, struct RSAKey *result) { |
| 46 | return ssh1_read_bignum(data, &result->private_exponent); |
| 47 | } |
| 48 | |
| 49 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
| 50 | Bignum b1, b2; |
| 51 | int i; |
| 52 | unsigned char *p; |
| 53 | |
| 54 | memmove(data+key->bytes-length, data, length); |
| 55 | data[0] = 0; |
| 56 | data[1] = 2; |
| 57 | |
| 58 | for (i = 2; i < key->bytes-length-1; i++) { |
| 59 | do { |
| 60 | data[i] = random_byte(); |
| 61 | } while (data[i] == 0); |
| 62 | } |
| 63 | data[key->bytes-length-1] = 0; |
| 64 | |
| 65 | b1 = bignum_from_bytes(data, key->bytes); |
| 66 | |
| 67 | b2 = modpow(b1, key->exponent, key->modulus); |
| 68 | |
| 69 | p = data; |
| 70 | for (i=key->bytes; i-- ;) { |
| 71 | *p++ = bignum_byte(b2, i); |
| 72 | } |
| 73 | |
| 74 | freebn(b1); |
| 75 | freebn(b2); |
| 76 | } |
| 77 | |
| 78 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) { |
| 79 | Bignum ret; |
| 80 | ret = modpow(input, key->private_exponent, key->modulus); |
| 81 | return ret; |
| 82 | } |
| 83 | |
| 84 | int rsastr_len(struct RSAKey *key) { |
| 85 | Bignum md, ex; |
| 86 | int mdlen, exlen; |
| 87 | |
| 88 | md = key->modulus; |
| 89 | ex = key->exponent; |
| 90 | mdlen = (ssh1_bignum_bitcount(md)+15) / 16; |
| 91 | exlen = (ssh1_bignum_bitcount(ex)+15) / 16; |
| 92 | return 4 * (mdlen+exlen) + 20; |
| 93 | } |
| 94 | |
| 95 | void rsastr_fmt(char *str, struct RSAKey *key) { |
| 96 | Bignum md, ex; |
| 97 | int len = 0, i, nibbles; |
| 98 | static const char hex[] = "0123456789abcdef"; |
| 99 | |
| 100 | md = key->modulus; |
| 101 | ex = key->exponent; |
| 102 | |
| 103 | len += sprintf(str+len, "0x"); |
| 104 | |
| 105 | nibbles = (3 + ssh1_bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1; |
| 106 | for (i=nibbles; i-- ;) |
| 107 | str[len++] = hex[(bignum_byte(ex, i/2) >> (4*(i%2))) & 0xF]; |
| 108 | |
| 109 | len += sprintf(str+len, ",0x"); |
| 110 | |
| 111 | nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1; |
| 112 | for (i=nibbles; i-- ;) |
| 113 | str[len++] = hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF]; |
| 114 | |
| 115 | str[len] = '\0'; |
| 116 | } |
| 117 | |
| 118 | /* |
| 119 | * Generate a fingerprint string for the key. Compatible with the |
| 120 | * OpenSSH fingerprint code. |
| 121 | */ |
| 122 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) { |
| 123 | struct MD5Context md5c; |
| 124 | unsigned char digest[16]; |
| 125 | char buffer[16*3+40]; |
| 126 | int numlen, slen, i; |
| 127 | |
| 128 | MD5Init(&md5c); |
| 129 | numlen = ssh1_bignum_length(key->modulus) - 2; |
| 130 | for (i = numlen; i-- ;) { |
| 131 | unsigned char c = bignum_byte(key->modulus, i); |
| 132 | MD5Update(&md5c, &c, 1); |
| 133 | } |
| 134 | numlen = ssh1_bignum_length(key->exponent) - 2; |
| 135 | for (i = numlen; i-- ;) { |
| 136 | unsigned char c = bignum_byte(key->exponent, i); |
| 137 | MD5Update(&md5c, &c, 1); |
| 138 | } |
| 139 | MD5Final(digest, &md5c); |
| 140 | |
| 141 | sprintf(buffer, "%d ", ssh1_bignum_bitcount(key->modulus)); |
| 142 | for (i = 0; i < 16; i++) |
| 143 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
| 144 | strncpy(str, buffer, len); str[len-1] = '\0'; |
| 145 | slen = strlen(str); |
| 146 | if (key->comment && slen < len-1) { |
| 147 | str[slen] = ' '; |
| 148 | strncpy(str+slen+1, key->comment, len-slen-1); |
| 149 | str[len-1] = '\0'; |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | void freersakey(struct RSAKey *key) { |
| 154 | if (key->modulus) freebn(key->modulus); |
| 155 | if (key->exponent) freebn(key->exponent); |
| 156 | if (key->private_exponent) freebn(key->private_exponent); |
| 157 | if (key->comment) sfree(key->comment); |
| 158 | } |
| 159 | |
| 160 | /* ---------------------------------------------------------------------- |
| 161 | * Implementation of the ssh-rsa signing key type. |
| 162 | */ |
| 163 | |
| 164 | #define GET_32BIT(cp) \ |
| 165 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
| 166 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
| 167 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
| 168 | ((unsigned long)(unsigned char)(cp)[3])) |
| 169 | |
| 170 | #define PUT_32BIT(cp, value) { \ |
| 171 | (cp)[0] = (unsigned char)((value) >> 24); \ |
| 172 | (cp)[1] = (unsigned char)((value) >> 16); \ |
| 173 | (cp)[2] = (unsigned char)((value) >> 8); \ |
| 174 | (cp)[3] = (unsigned char)(value); } |
| 175 | |
| 176 | static void getstring(char **data, int *datalen, char **p, int *length) { |
| 177 | *p = NULL; |
| 178 | if (*datalen < 4) |
| 179 | return; |
| 180 | *length = GET_32BIT(*data); |
| 181 | *datalen -= 4; *data += 4; |
| 182 | if (*datalen < *length) |
| 183 | return; |
| 184 | *p = *data; |
| 185 | *data += *length; *datalen -= *length; |
| 186 | } |
| 187 | static Bignum getmp(char **data, int *datalen) { |
| 188 | char *p; |
| 189 | int length; |
| 190 | Bignum b; |
| 191 | |
| 192 | getstring(data, datalen, &p, &length); |
| 193 | if (!p) |
| 194 | return NULL; |
| 195 | b = bignum_from_bytes(p, length); |
| 196 | return b; |
| 197 | } |
| 198 | |
| 199 | static void *rsa2_newkey(char *data, int len) { |
| 200 | char *p; |
| 201 | int slen; |
| 202 | struct RSAKey *rsa; |
| 203 | |
| 204 | rsa = smalloc(sizeof(struct RSAKey)); |
| 205 | if (!rsa) return NULL; |
| 206 | getstring(&data, &len, &p, &slen); |
| 207 | |
| 208 | if (!p || memcmp(p, "ssh-rsa", 7)) { |
| 209 | sfree(rsa); |
| 210 | return NULL; |
| 211 | } |
| 212 | rsa->exponent = getmp(&data, &len); |
| 213 | rsa->modulus = getmp(&data, &len); |
| 214 | rsa->private_exponent = NULL; |
| 215 | rsa->comment = NULL; |
| 216 | |
| 217 | return rsa; |
| 218 | } |
| 219 | |
| 220 | static void rsa2_freekey(void *key) { |
| 221 | struct RSAKey *rsa = (struct RSAKey *)key; |
| 222 | freersakey(rsa); |
| 223 | sfree(rsa); |
| 224 | } |
| 225 | |
| 226 | static char *rsa2_fmtkey(void *key) { |
| 227 | struct RSAKey *rsa = (struct RSAKey *)key; |
| 228 | char *p; |
| 229 | int len; |
| 230 | |
| 231 | len = rsastr_len(rsa); |
| 232 | p = smalloc(len); |
| 233 | rsastr_fmt(p, rsa); |
| 234 | return p; |
| 235 | } |
| 236 | |
| 237 | static char *rsa2_fingerprint(void *key) { |
| 238 | struct RSAKey *rsa = (struct RSAKey *)key; |
| 239 | struct MD5Context md5c; |
| 240 | unsigned char digest[16], lenbuf[4]; |
| 241 | char buffer[16*3+40]; |
| 242 | char *ret; |
| 243 | int numlen, i; |
| 244 | |
| 245 | MD5Init(&md5c); |
| 246 | MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11); |
| 247 | |
| 248 | #define ADD_BIGNUM(bignum) \ |
| 249 | numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \ |
| 250 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
| 251 | for (i = numlen; i-- ;) { \ |
| 252 | unsigned char c = bignum_byte(bignum, i); \ |
| 253 | MD5Update(&md5c, &c, 1); \ |
| 254 | } |
| 255 | ADD_BIGNUM(rsa->exponent); |
| 256 | ADD_BIGNUM(rsa->modulus); |
| 257 | #undef ADD_BIGNUM |
| 258 | |
| 259 | MD5Final(digest, &md5c); |
| 260 | |
| 261 | sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus)); |
| 262 | for (i = 0; i < 16; i++) |
| 263 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
| 264 | ret = smalloc(strlen(buffer)+1); |
| 265 | if (ret) |
| 266 | strcpy(ret, buffer); |
| 267 | return ret; |
| 268 | } |
| 269 | |
| 270 | /* |
| 271 | * This is the magic ASN.1/DER prefix that goes in the decoded |
| 272 | * signature, between the string of FFs and the actual SHA hash |
| 273 | * value. As closely as I can tell, the meaning of it is: |
| 274 | * |
| 275 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
| 276 | * |
| 277 | * 30 21 -- a constructed SEQUENCE of length 0x21 |
| 278 | * 30 09 -- a constructed sub-SEQUENCE of length 9 |
| 279 | * 06 05 -- an object identifier, length 5 |
| 280 | * 2B 0E 03 02 1A -- |
| 281 | * 05 00 -- NULL |
| 282 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
| 283 | * [0x14 bytes of hash data follows] |
| 284 | */ |
| 285 | static unsigned char asn1_weird_stuff[] = { |
| 286 | 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B, |
| 287 | 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14, |
| 288 | }; |
| 289 | |
| 290 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
| 291 | char *data, int datalen) { |
| 292 | struct RSAKey *rsa = (struct RSAKey *)key; |
| 293 | Bignum in, out; |
| 294 | char *p; |
| 295 | int slen; |
| 296 | int bytes, i, j, ret; |
| 297 | unsigned char hash[20]; |
| 298 | |
| 299 | getstring(&sig, &siglen, &p, &slen); |
| 300 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
| 301 | return 0; |
| 302 | } |
| 303 | in = getmp(&sig, &siglen); |
| 304 | out = modpow(in, rsa->exponent, rsa->modulus); |
| 305 | freebn(in); |
| 306 | |
| 307 | ret = 1; |
| 308 | |
| 309 | bytes = ssh1_bignum_bitcount(rsa->modulus) / 8; |
| 310 | /* Top (partial) byte should be zero. */ |
| 311 | if (bignum_byte(out, bytes-1) != 0) |
| 312 | ret = 0; |
| 313 | /* First whole byte should be 1. */ |
| 314 | if (bignum_byte(out, bytes-2) != 1) |
| 315 | ret = 0; |
| 316 | /* Most of the rest should be FF. */ |
| 317 | for (i = bytes-3; i >= 20 + sizeof(asn1_weird_stuff); i--) { |
| 318 | if (bignum_byte(out, i) != 0xFF) |
| 319 | ret = 0; |
| 320 | } |
| 321 | /* Then we expect to see the asn1_weird_stuff. */ |
| 322 | for (i = 20 + sizeof(asn1_weird_stuff) - 1, j=0; i >= 20; i--,j++) { |
| 323 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
| 324 | ret = 0; |
| 325 | } |
| 326 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
| 327 | SHA_Simple(data, datalen, hash); |
| 328 | for (i = 19, j=0; i >= 0; i--,j++) { |
| 329 | if (bignum_byte(out, i) != hash[j]) |
| 330 | ret = 0; |
| 331 | } |
| 332 | |
| 333 | return ret; |
| 334 | } |
| 335 | |
| 336 | int rsa2_sign(void *key, char *sig, int siglen, |
| 337 | char *data, int datalen) { |
| 338 | return 0; /* FIXME */ |
| 339 | } |
| 340 | |
| 341 | struct ssh_signkey ssh_rsa = { |
| 342 | rsa2_newkey, |
| 343 | rsa2_freekey, |
| 344 | rsa2_fmtkey, |
| 345 | rsa2_fingerprint, |
| 346 | rsa2_verifysig, |
| 347 | rsa2_sign, |
| 348 | "ssh-rsa", |
| 349 | "rsa2" |
| 350 | }; |