git.distorted.org.uk Git - u/mdw/putty/blob - sshpubk.c

   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 <stdarg.h> /* FIXME */
  12 #include <windows.h> /* FIXME */
  13
  14 #include "putty.h"
  15 #include "ssh.h"
  16
  17 #define GET_32BIT(cp) \
  18     (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  19     ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  20     ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  21     ((unsigned long)(unsigned char)(cp)[3]))
  22
  23 #define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n"
  24 #define dss_signature "-----BEGIN DSA PRIVATE KEY-----\n"
  25
  26 #define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\
  27                           (x)-'a'<26 ? (x)-'a'+26 :\
  28                           (x)-'0'<10 ? (x)-'0'+52 :\
  29                           (x)=='+' ? 62 : \
  30                           (x)=='/' ? 63 : 0 )
  31
  32 static int loadrsakey_main(FILE *fp, struct RSAKey *key,
  33                            char **commentptr, char *passphrase) {
  34     unsigned char buf[16384];
  35     unsigned char keybuf[16];
  36     int len;
  37     int i, j, ciphertype;
  38     int ret = 0;
  39     struct MD5Context md5c;
  40     char *comment;
  41
  42     /* Slurp the whole file (minus the header) into a buffer. */
  43     len = fread(buf, 1, sizeof(buf), fp);
  44     fclose(fp);
  45     if (len < 0 || len == sizeof(buf))
  46         goto end;                      /* file too big or not read */
  47
  48     i = 0;
  49
  50     /*
  51      * A zero byte. (The signature includes a terminating NUL.)
  52      */
  53     if (len-i < 1 || buf[i] != 0)
  54         goto end;
  55     i++;
  56
  57     /* One byte giving encryption type, and one reserved uint32. */
  58     if (len-i < 1)
  59         goto end;
  60     ciphertype = buf[i];
  61     if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES)
  62         goto end;
  63     i++;
  64     if (len-i < 4)
  65         goto end;                      /* reserved field not present */
  66     if (buf[i] != 0 || buf[i+1] != 0 || buf[i+2] != 0 || buf[i+3] != 0)
  67         goto end;                      /* reserved field nonzero, panic! */
  68     i += 4;
  69
  70     /* Now the serious stuff. An ordinary SSH 1 public key. */
  71     i += makekey(buf+i, key, NULL, 1);
  72     if (len-i < 0)
  73         goto end;                      /* overran */
  74
  75     /* Next, the comment field. */
  76     j = GET_32BIT(buf+i);
  77     i += 4;
  78     if (len-i < j) goto end;
  79     comment = malloc(j+1);
  80     if (comment) {
  81         memcpy(comment, buf+i, j);
  82         comment[j] = '\0';
  83     }
  84     i += j;
  85     if (commentptr)
  86         *commentptr = comment;
  87     if (key)
  88         key->comment = comment;
  89     if (!key) {
  90         return ciphertype != 0;
  91     }
  92
  93     /*
  94      * Decrypt remainder of buffer.
  95      */
  96     if (ciphertype) {
  97         MD5Init(&md5c);
  98         MD5Update(&md5c, passphrase, strlen(passphrase));
  99         MD5Final(keybuf, &md5c);
 100         des3_decrypt_pubkey(keybuf, buf+i, (len-i+7)&~7);
 101         memset(keybuf, 0, sizeof(keybuf));    /* burn the evidence */
 102     }
 103
 104     /*
 105      * We are now in the secret part of the key. The first four
 106      * bytes should be of the form a, b, a, b.
 107      */
 108     if (len-i < 4) goto end;
 109     if (buf[i] != buf[i+2] || buf[i+1] != buf[i+3]) { ret = -1; goto end; }
 110     i += 4;
 111
 112     /*
 113      * After that, we have one further bignum which is our
 114      * decryption modulus, and then we're done.
 115      */
 116     i += makeprivate(buf+i, key);
 117     if (len-i < 0) goto end;
 118
 119     ret = 1;
 120     end:
 121     memset(buf, 0, sizeof(buf));       /* burn the evidence */
 122     return ret;
 123 }
 124
 125 int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) {
 126     FILE *fp;
 127     unsigned char buf[64];
 128
 129     fp = fopen(filename, "rb");
 130     if (!fp)
 131         return 0;                      /* doesn't even exist */
 132
 133     /*
 134      * Read the first line of the file and see if it's a v1 private
 135      * key file.
 136      */
 137     if (fgets(buf, sizeof(buf), fp) &&
 138         !strcmp(buf, rsa_signature)) {
 139         return loadrsakey_main(fp, key, NULL, passphrase);
 140     }
 141
 142     /*
 143      * Otherwise, we have nothing. Return empty-handed.
 144      */
 145     fclose(fp);
 146     return 0;
 147 }
 148
 149 /*
 150  * See whether an RSA key is encrypted. Return its comment field as
 151  * well.
 152  */
 153 int rsakey_encrypted(char *filename, char **comment) {
 154     FILE *fp;
 155     unsigned char buf[64];
 156
 157     fp = fopen(filename, "rb");
 158     if (!fp)
 159         return 0;                      /* doesn't even exist */
 160
 161     /*
 162      * Read the first line of the file and see if it's a v1 private
 163      * key file.
 164      */
 165     if (fgets(buf, sizeof(buf), fp) &&
 166         !strcmp(buf, rsa_signature)) {
 167         return loadrsakey_main(fp, NULL, comment, NULL);
 168     }
 169     return 0;                          /* wasn't the right kind of file */
 170 }