| 1 | /* |
| 2 | * Generic SSH public-key handling operations. In particular, |
| 3 | * reading of SSH public-key files, and also the generic `sign' |
| 4 | * operation for ssh2 (which checks the type of the key and |
| 5 | * dispatches to the appropriate key-type specific function). |
| 6 | */ |
| 7 | |
| 8 | #include <stdio.h> |
| 9 | #include <stdlib.h> |
| 10 | |
| 11 | #include "ssh.h" |
| 12 | |
| 13 | #define PUT_32BIT(cp, value) do { \ |
| 14 | (cp)[3] = (value); \ |
| 15 | (cp)[2] = (value) >> 8; \ |
| 16 | (cp)[1] = (value) >> 16; \ |
| 17 | (cp)[0] = (value) >> 24; } while (0) |
| 18 | |
| 19 | #define GET_32BIT(cp) \ |
| 20 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
| 21 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
| 22 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
| 23 | ((unsigned long)(unsigned char)(cp)[3])) |
| 24 | |
| 25 | #define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n" |
| 26 | |
| 27 | #define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\ |
| 28 | (x)-'a'<26 ? (x)-'a'+26 :\ |
| 29 | (x)-'0'<10 ? (x)-'0'+52 :\ |
| 30 | (x)=='+' ? 62 : \ |
| 31 | (x)=='/' ? 63 : 0 ) |
| 32 | |
| 33 | static int loadrsakey_main(FILE *fp, struct RSAKey *key, struct RSAAux *aux, |
| 34 | char **commentptr, char *passphrase) { |
| 35 | unsigned char buf[16384]; |
| 36 | unsigned char keybuf[16]; |
| 37 | int len; |
| 38 | int i, j, ciphertype; |
| 39 | int ret = 0; |
| 40 | struct MD5Context md5c; |
| 41 | char *comment; |
| 42 | |
| 43 | /* Slurp the whole file (minus the header) into a buffer. */ |
| 44 | len = fread(buf, 1, sizeof(buf), fp); |
| 45 | fclose(fp); |
| 46 | if (len < 0 || len == sizeof(buf)) |
| 47 | goto end; /* file too big or not read */ |
| 48 | |
| 49 | i = 0; |
| 50 | |
| 51 | /* |
| 52 | * A zero byte. (The signature includes a terminating NUL.) |
| 53 | */ |
| 54 | if (len-i < 1 || buf[i] != 0) |
| 55 | goto end; |
| 56 | i++; |
| 57 | |
| 58 | /* One byte giving encryption type, and one reserved uint32. */ |
| 59 | if (len-i < 1) |
| 60 | goto end; |
| 61 | ciphertype = buf[i]; |
| 62 | if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES) |
| 63 | goto end; |
| 64 | i++; |
| 65 | if (len-i < 4) |
| 66 | goto end; /* reserved field not present */ |
| 67 | if (buf[i] != 0 || buf[i+1] != 0 || buf[i+2] != 0 || buf[i+3] != 0) |
| 68 | goto end; /* reserved field nonzero, panic! */ |
| 69 | i += 4; |
| 70 | |
| 71 | /* Now the serious stuff. An ordinary SSH 1 public key. */ |
| 72 | i += makekey(buf+i, key, NULL, 1); |
| 73 | if (len-i < 0) |
| 74 | goto end; /* overran */ |
| 75 | |
| 76 | /* Next, the comment field. */ |
| 77 | j = GET_32BIT(buf+i); |
| 78 | i += 4; |
| 79 | if (len-i < j) goto end; |
| 80 | comment = smalloc(j+1); |
| 81 | if (comment) { |
| 82 | memcpy(comment, buf+i, j); |
| 83 | comment[j] = '\0'; |
| 84 | } |
| 85 | i += j; |
| 86 | if (commentptr) |
| 87 | *commentptr = comment; |
| 88 | if (key) |
| 89 | key->comment = comment; |
| 90 | if (!key) { |
| 91 | return ciphertype != 0; |
| 92 | } |
| 93 | |
| 94 | /* |
| 95 | * Decrypt remainder of buffer. |
| 96 | */ |
| 97 | if (ciphertype) { |
| 98 | MD5Init(&md5c); |
| 99 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 100 | MD5Final(keybuf, &md5c); |
| 101 | des3_decrypt_pubkey(keybuf, buf+i, (len-i+7)&~7); |
| 102 | memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */ |
| 103 | } |
| 104 | |
| 105 | /* |
| 106 | * We are now in the secret part of the key. The first four |
| 107 | * bytes should be of the form a, b, a, b. |
| 108 | */ |
| 109 | if (len-i < 4) goto end; |
| 110 | if (buf[i] != buf[i+2] || buf[i+1] != buf[i+3]) { ret = -1; goto end; } |
| 111 | i += 4; |
| 112 | |
| 113 | /* |
| 114 | * After that, we have one further bignum which is our |
| 115 | * decryption exponent, and then the three auxiliary values |
| 116 | * (iqmp, q, p). |
| 117 | */ |
| 118 | i += makeprivate(buf+i, key); |
| 119 | if (len-i < 0) goto end; |
| 120 | if (aux) { |
| 121 | i += ssh1_read_bignum(buf+i, &aux->iqmp); |
| 122 | if (len-i < 0) goto end; |
| 123 | i += ssh1_read_bignum(buf+i, &aux->q); |
| 124 | if (len-i < 0) goto end; |
| 125 | i += ssh1_read_bignum(buf+i, &aux->p); |
| 126 | if (len-i < 0) goto end; |
| 127 | } |
| 128 | |
| 129 | ret = 1; |
| 130 | end: |
| 131 | memset(buf, 0, sizeof(buf)); /* burn the evidence */ |
| 132 | return ret; |
| 133 | } |
| 134 | |
| 135 | int loadrsakey(char *filename, struct RSAKey *key, struct RSAAux *aux, |
| 136 | char *passphrase) { |
| 137 | FILE *fp; |
| 138 | unsigned char buf[64]; |
| 139 | |
| 140 | fp = fopen(filename, "rb"); |
| 141 | if (!fp) |
| 142 | return 0; /* doesn't even exist */ |
| 143 | |
| 144 | /* |
| 145 | * Read the first line of the file and see if it's a v1 private |
| 146 | * key file. |
| 147 | */ |
| 148 | if (fgets(buf, sizeof(buf), fp) && |
| 149 | !strcmp(buf, rsa_signature)) { |
| 150 | return loadrsakey_main(fp, key, aux, NULL, passphrase); |
| 151 | } |
| 152 | |
| 153 | /* |
| 154 | * Otherwise, we have nothing. Return empty-handed. |
| 155 | */ |
| 156 | fclose(fp); |
| 157 | return 0; |
| 158 | } |
| 159 | |
| 160 | /* |
| 161 | * See whether an RSA key is encrypted. Return its comment field as |
| 162 | * well. |
| 163 | */ |
| 164 | int rsakey_encrypted(char *filename, char **comment) { |
| 165 | FILE *fp; |
| 166 | unsigned char buf[64]; |
| 167 | |
| 168 | fp = fopen(filename, "rb"); |
| 169 | if (!fp) |
| 170 | return 0; /* doesn't even exist */ |
| 171 | |
| 172 | /* |
| 173 | * Read the first line of the file and see if it's a v1 private |
| 174 | * key file. |
| 175 | */ |
| 176 | if (fgets(buf, sizeof(buf), fp) && |
| 177 | !strcmp(buf, rsa_signature)) { |
| 178 | return loadrsakey_main(fp, NULL, NULL, comment, NULL); |
| 179 | } |
| 180 | fclose(fp); |
| 181 | return 0; /* wasn't the right kind of file */ |
| 182 | } |
| 183 | |
| 184 | /* |
| 185 | * Save an RSA key file. Return nonzero on success. |
| 186 | */ |
| 187 | int saversakey(char *filename, struct RSAKey *key, struct RSAAux *aux, |
| 188 | char *passphrase) { |
| 189 | unsigned char buf[16384]; |
| 190 | unsigned char keybuf[16]; |
| 191 | struct MD5Context md5c; |
| 192 | unsigned char *p, *estart; |
| 193 | FILE *fp; |
| 194 | |
| 195 | /* |
| 196 | * Write the initial signature. |
| 197 | */ |
| 198 | p = buf; |
| 199 | memcpy(p, rsa_signature, sizeof(rsa_signature)); |
| 200 | p += sizeof(rsa_signature); |
| 201 | |
| 202 | /* |
| 203 | * One byte giving encryption type, and one reserved (zero) |
| 204 | * uint32. |
| 205 | */ |
| 206 | *p++ = (passphrase ? SSH_CIPHER_3DES : 0); |
| 207 | PUT_32BIT(p, 0); p += 4; |
| 208 | |
| 209 | /* |
| 210 | * An ordinary SSH 1 public key consists of: a uint32 |
| 211 | * containing the bit count, then two bignums containing the |
| 212 | * modulus and exponent respectively. |
| 213 | */ |
| 214 | PUT_32BIT(p, ssh1_bignum_bitcount(key->modulus)); p += 4; |
| 215 | p += ssh1_write_bignum(p, key->modulus); |
| 216 | p += ssh1_write_bignum(p, key->exponent); |
| 217 | |
| 218 | /* |
| 219 | * A string containing the comment field. |
| 220 | */ |
| 221 | if (key->comment) { |
| 222 | PUT_32BIT(p, strlen(key->comment)); p += 4; |
| 223 | memcpy(p, key->comment, strlen(key->comment)); |
| 224 | p += strlen(key->comment); |
| 225 | } else { |
| 226 | PUT_32BIT(p, 0); p += 4; |
| 227 | } |
| 228 | |
| 229 | /* |
| 230 | * The encrypted portion starts here. |
| 231 | */ |
| 232 | estart = p; |
| 233 | |
| 234 | /* |
| 235 | * Two bytes, then the same two bytes repeated. |
| 236 | */ |
| 237 | *p++ = random_byte(); |
| 238 | *p++ = random_byte(); |
| 239 | p[0] = p[-2]; p[1] = p[-1]; p += 2; |
| 240 | |
| 241 | /* |
| 242 | * Four more bignums: the decryption exponent, then iqmp, then |
| 243 | * q, then p. |
| 244 | */ |
| 245 | p += ssh1_write_bignum(p, key->private_exponent); |
| 246 | p += ssh1_write_bignum(p, aux->iqmp); |
| 247 | p += ssh1_write_bignum(p, aux->q); |
| 248 | p += ssh1_write_bignum(p, aux->p); |
| 249 | |
| 250 | /* |
| 251 | * Now write zeros until the encrypted portion is a multiple of |
| 252 | * 8 bytes. |
| 253 | */ |
| 254 | while ((p-estart) % 8) |
| 255 | *p++ = '\0'; |
| 256 | |
| 257 | /* |
| 258 | * Now encrypt the encrypted portion. |
| 259 | */ |
| 260 | if (passphrase) { |
| 261 | MD5Init(&md5c); |
| 262 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 263 | MD5Final(keybuf, &md5c); |
| 264 | des3_encrypt_pubkey(keybuf, estart, p-estart); |
| 265 | memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */ |
| 266 | } |
| 267 | |
| 268 | /* |
| 269 | * Done. Write the result to the file. |
| 270 | */ |
| 271 | fp = fopen(filename, "wb"); |
| 272 | if (fp) { |
| 273 | int ret = (fwrite(buf, 1, p-buf, fp) == (size_t)(p-buf)); |
| 274 | ret = ret && (fclose(fp) == 0); |
| 275 | return ret; |
| 276 | } else |
| 277 | return 0; |
| 278 | } |