| 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 GET_32BIT(cp) \ |
| 14 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
| 15 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
| 16 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
| 17 | ((unsigned long)(unsigned char)(cp)[3])) |
| 18 | |
| 19 | #define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n" |
| 20 | |
| 21 | #define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\ |
| 22 | (x)-'a'<26 ? (x)-'a'+26 :\ |
| 23 | (x)-'0'<10 ? (x)-'0'+52 :\ |
| 24 | (x)=='+' ? 62 : \ |
| 25 | (x)=='/' ? 63 : 0 ) |
| 26 | |
| 27 | static int loadrsakey_main(FILE *fp, struct RSAKey *key, |
| 28 | char **commentptr, char *passphrase) { |
| 29 | unsigned char buf[16384]; |
| 30 | unsigned char keybuf[16]; |
| 31 | int len; |
| 32 | int i, j, ciphertype; |
| 33 | int ret = 0; |
| 34 | struct MD5Context md5c; |
| 35 | char *comment; |
| 36 | |
| 37 | /* Slurp the whole file (minus the header) into a buffer. */ |
| 38 | len = fread(buf, 1, sizeof(buf), fp); |
| 39 | fclose(fp); |
| 40 | if (len < 0 || len == sizeof(buf)) |
| 41 | goto end; /* file too big or not read */ |
| 42 | |
| 43 | i = 0; |
| 44 | |
| 45 | /* |
| 46 | * A zero byte. (The signature includes a terminating NUL.) |
| 47 | */ |
| 48 | if (len-i < 1 || buf[i] != 0) |
| 49 | goto end; |
| 50 | i++; |
| 51 | |
| 52 | /* One byte giving encryption type, and one reserved uint32. */ |
| 53 | if (len-i < 1) |
| 54 | goto end; |
| 55 | ciphertype = buf[i]; |
| 56 | if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES) |
| 57 | goto end; |
| 58 | i++; |
| 59 | if (len-i < 4) |
| 60 | goto end; /* reserved field not present */ |
| 61 | if (buf[i] != 0 || buf[i+1] != 0 || buf[i+2] != 0 || buf[i+3] != 0) |
| 62 | goto end; /* reserved field nonzero, panic! */ |
| 63 | i += 4; |
| 64 | |
| 65 | /* Now the serious stuff. An ordinary SSH 1 public key. */ |
| 66 | i += makekey(buf+i, key, NULL, 1); |
| 67 | if (len-i < 0) |
| 68 | goto end; /* overran */ |
| 69 | |
| 70 | /* Next, the comment field. */ |
| 71 | j = GET_32BIT(buf+i); |
| 72 | i += 4; |
| 73 | if (len-i < j) goto end; |
| 74 | comment = malloc(j+1); |
| 75 | if (comment) { |
| 76 | memcpy(comment, buf+i, j); |
| 77 | comment[j] = '\0'; |
| 78 | } |
| 79 | i += j; |
| 80 | if (commentptr) |
| 81 | *commentptr = comment; |
| 82 | if (key) |
| 83 | key->comment = comment; |
| 84 | if (!key) { |
| 85 | return ciphertype != 0; |
| 86 | } |
| 87 | |
| 88 | /* |
| 89 | * Decrypt remainder of buffer. |
| 90 | */ |
| 91 | if (ciphertype) { |
| 92 | MD5Init(&md5c); |
| 93 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 94 | MD5Final(keybuf, &md5c); |
| 95 | des3_decrypt_pubkey(keybuf, buf+i, (len-i+7)&~7); |
| 96 | memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */ |
| 97 | } |
| 98 | |
| 99 | /* |
| 100 | * We are now in the secret part of the key. The first four |
| 101 | * bytes should be of the form a, b, a, b. |
| 102 | */ |
| 103 | if (len-i < 4) goto end; |
| 104 | if (buf[i] != buf[i+2] || buf[i+1] != buf[i+3]) { ret = -1; goto end; } |
| 105 | i += 4; |
| 106 | |
| 107 | /* |
| 108 | * After that, we have one further bignum which is our |
| 109 | * decryption modulus, and then we're done. |
| 110 | */ |
| 111 | i += makeprivate(buf+i, key); |
| 112 | if (len-i < 0) goto end; |
| 113 | |
| 114 | ret = 1; |
| 115 | end: |
| 116 | memset(buf, 0, sizeof(buf)); /* burn the evidence */ |
| 117 | return ret; |
| 118 | } |
| 119 | |
| 120 | int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) { |
| 121 | FILE *fp; |
| 122 | unsigned char buf[64]; |
| 123 | |
| 124 | fp = fopen(filename, "rb"); |
| 125 | if (!fp) |
| 126 | return 0; /* doesn't even exist */ |
| 127 | |
| 128 | /* |
| 129 | * Read the first line of the file and see if it's a v1 private |
| 130 | * key file. |
| 131 | */ |
| 132 | if (fgets(buf, sizeof(buf), fp) && |
| 133 | !strcmp(buf, rsa_signature)) { |
| 134 | return loadrsakey_main(fp, key, NULL, passphrase); |
| 135 | } |
| 136 | |
| 137 | /* |
| 138 | * Otherwise, we have nothing. Return empty-handed. |
| 139 | */ |
| 140 | fclose(fp); |
| 141 | return 0; |
| 142 | } |
| 143 | |
| 144 | /* |
| 145 | * See whether an RSA key is encrypted. Return its comment field as |
| 146 | * well. |
| 147 | */ |
| 148 | int rsakey_encrypted(char *filename, char **comment) { |
| 149 | FILE *fp; |
| 150 | unsigned char buf[64]; |
| 151 | |
| 152 | fp = fopen(filename, "rb"); |
| 153 | if (!fp) |
| 154 | return 0; /* doesn't even exist */ |
| 155 | |
| 156 | /* |
| 157 | * Read the first line of the file and see if it's a v1 private |
| 158 | * key file. |
| 159 | */ |
| 160 | if (fgets(buf, sizeof(buf), fp) && |
| 161 | !strcmp(buf, rsa_signature)) { |
| 162 | return loadrsakey_main(fp, NULL, comment, NULL); |
| 163 | } |
| 164 | return 0; /* wasn't the right kind of file */ |
| 165 | } |