| 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 | } |