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).
14 #define PUT_32BIT(cp, value) do { \
16 (cp)[2] = (value) >> 8; \
17 (cp)[1] = (value) >> 16; \
18 (cp)[0] = (value) >> 24; } while (0)
20 #define GET_32BIT(cp) \
21 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
22 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
23 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
24 ((unsigned long)(unsigned char)(cp)[3]))
26 #define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n"
28 #define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\
29 (x)-'a'<26 ? (x)-'a'+26 :\
30 (x)-'0'<10 ? (x)-'0'+52 :\
34 static int loadrsakey_main(FILE * fp, struct RSAKey *key,
35 char **commentptr, char *passphrase)
37 unsigned char buf[16384];
38 unsigned char keybuf[16];
42 struct MD5Context md5c;
45 /* Slurp the whole file (minus the header) into a buffer. */
46 len = fread(buf, 1, sizeof(buf), fp);
48 if (len < 0 || len == sizeof(buf))
49 goto end; /* file too big or not read */
54 * A zero byte. (The signature includes a terminating NUL.)
56 if (len - i < 1 || buf[i] != 0)
60 /* One byte giving encryption type, and one reserved uint32. */
64 if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES)
68 goto end; /* reserved field not present */
69 if (buf[i] != 0 || buf[i + 1] != 0 || buf[i + 2] != 0
70 || buf[i + 3] != 0) goto end; /* reserved field nonzero, panic! */
73 /* Now the serious stuff. An ordinary SSH 1 public key. */
74 i += makekey(buf + i, key, NULL, 1);
76 goto end; /* overran */
78 /* Next, the comment field. */
79 j = GET_32BIT(buf + i);
83 comment = smalloc(j + 1);
85 memcpy(comment, buf + i, j);
90 *commentptr = comment;
92 key->comment = comment;
94 return ciphertype != 0;
98 * Decrypt remainder of buffer.
102 MD5Update(&md5c, passphrase, strlen(passphrase));
103 MD5Final(keybuf, &md5c);
104 des3_decrypt_pubkey(keybuf, buf + i, (len - i + 7) & ~7);
105 memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
109 * We are now in the secret part of the key. The first four
110 * bytes should be of the form a, b, a, b.
114 if (buf[i] != buf[i + 2] || buf[i + 1] != buf[i + 3]) {
121 * After that, we have one further bignum which is our
122 * decryption exponent, and then the three auxiliary values
125 i += makeprivate(buf + i, key);
128 i += ssh1_read_bignum(buf + i, &key->iqmp);
131 i += ssh1_read_bignum(buf + i, &key->q);
134 i += ssh1_read_bignum(buf + i, &key->p);
138 if (!rsa_verify(key)) {
145 memset(buf, 0, sizeof(buf)); /* burn the evidence */
149 int loadrsakey(char *filename, struct RSAKey *key, char *passphrase)
152 unsigned char buf[64];
154 fp = fopen(filename, "rb");
156 return 0; /* doesn't even exist */
159 * Read the first line of the file and see if it's a v1 private
162 if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) {
163 return loadrsakey_main(fp, key, NULL, passphrase);
167 * Otherwise, we have nothing. Return empty-handed.
174 * See whether an RSA key is encrypted. Return its comment field as
177 int rsakey_encrypted(char *filename, char **comment)
180 unsigned char buf[64];
182 fp = fopen(filename, "rb");
184 return 0; /* doesn't even exist */
187 * Read the first line of the file and see if it's a v1 private
190 if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) {
191 return loadrsakey_main(fp, NULL, comment, NULL);
194 return 0; /* wasn't the right kind of file */
198 * Save an RSA key file. Return nonzero on success.
200 int saversakey(char *filename, struct RSAKey *key, char *passphrase)
202 unsigned char buf[16384];
203 unsigned char keybuf[16];
204 struct MD5Context md5c;
205 unsigned char *p, *estart;
209 * Write the initial signature.
212 memcpy(p, rsa_signature, sizeof(rsa_signature));
213 p += sizeof(rsa_signature);
216 * One byte giving encryption type, and one reserved (zero)
219 *p++ = (passphrase ? SSH_CIPHER_3DES : 0);
224 * An ordinary SSH 1 public key consists of: a uint32
225 * containing the bit count, then two bignums containing the
226 * modulus and exponent respectively.
228 PUT_32BIT(p, bignum_bitcount(key->modulus));
230 p += ssh1_write_bignum(p, key->modulus);
231 p += ssh1_write_bignum(p, key->exponent);
234 * A string containing the comment field.
237 PUT_32BIT(p, strlen(key->comment));
239 memcpy(p, key->comment, strlen(key->comment));
240 p += strlen(key->comment);
247 * The encrypted portion starts here.
252 * Two bytes, then the same two bytes repeated.
254 *p++ = random_byte();
255 *p++ = random_byte();
261 * Four more bignums: the decryption exponent, then iqmp, then
264 p += ssh1_write_bignum(p, key->private_exponent);
265 p += ssh1_write_bignum(p, key->iqmp);
266 p += ssh1_write_bignum(p, key->q);
267 p += ssh1_write_bignum(p, key->p);
270 * Now write zeros until the encrypted portion is a multiple of
273 while ((p - estart) % 8)
277 * Now encrypt the encrypted portion.
281 MD5Update(&md5c, passphrase, strlen(passphrase));
282 MD5Final(keybuf, &md5c);
283 des3_encrypt_pubkey(keybuf, estart, p - estart);
284 memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
288 * Done. Write the result to the file.
290 fp = fopen(filename, "wb");
292 int ret = (fwrite(buf, 1, p - buf, fp) == (size_t) (p - buf));
293 ret = ret && (fclose(fp) == 0);
299 /* ----------------------------------------------------------------------
300 * SSH2 private key load/store functions.
304 * PuTTY's own format for SSH2 keys is as follows:
306 * The file is text. Lines are terminated by CRLF, although CR-only
307 * and LF-only are tolerated on input.
309 * The first line says "PuTTY-User-Key-File-1: " plus the name of the
310 * algorithm ("ssh-dss", "ssh-rsa" etc. Although, of course, this
311 * being PuTTY, "ssh-dss" is not supported.)
313 * The next line says "Encryption: " plus an encryption type.
314 * Currently the only supported encryption types are "aes256-cbc"
317 * The next line says "Comment: " plus the comment string.
319 * Next there is a line saying "Public-Lines: " plus a number N.
320 * The following N lines contain a base64 encoding of the public
321 * part of the key. This is encoded as the standard SSH2 public key
322 * blob (with no initial length): so for RSA, for example, it will
329 * Next, there is a line saying "Private-Lines: " plus a number N,
330 * and then N lines containing the (potentially encrypted) private
331 * part of the key. For the key type "ssh-rsa", this will be
334 * mpint private_exponent
335 * mpint p (the larger of the two primes)
336 * mpint q (the smaller prime)
337 * mpint iqmp (the inverse of q modulo p)
338 * data padding (to reach a multiple of the cipher block size)
340 * Finally, there is a line saying "Private-Hash: " plus a hex
341 * representation of a SHA-1 hash of the plaintext version of the
342 * private part, including the final padding.
344 * If the key is encrypted, the encryption key is derived from the
345 * passphrase by means of a succession of SHA-1 hashes. Each hash
348 * uint32 sequence-number
351 * where the sequence-number increases from zero. As many of these
352 * hashes are used as necessary.
354 * NOTE! It is important that all _public_ data can be verified
355 * with reference to the _private_ data. There exist attacks based
356 * on modifying the public key but leaving the private section
359 * With RSA, this is easy: verify that n = p*q, and also verify
360 * that e*d == 1 modulo (p-1)(q-1). With DSA (if we were ever to
361 * support it), we would need to store extra data in the private
362 * section other than just x.
365 static int read_header(FILE * fp, char *header)
372 if (c == '\n' || c == '\r' || c == EOF)
373 return 0; /* failure */
379 return 1; /* success! */
382 return 0; /* failure */
386 return 0; /* failure */
389 static char *read_body(FILE * fp)
397 text = smalloc(size);
403 if (c == '\r' || c == '\n') {
405 if (c != '\r' && c != '\n' && c != EOF)
413 if (len + 1 > size) {
415 text = srealloc(text, size);
422 int base64_decode_atom(char *atom, unsigned char *out)
429 for (i = 0; i < 4; i++) {
431 if (c >= 'A' && c <= 'Z')
433 else if (c >= 'a' && c <= 'z')
435 else if (c >= '0' && c <= '9')
444 return 0; /* invalid atom */
448 if (vals[0] == -1 || vals[1] == -1)
450 if (vals[2] == -1 && vals[3] != -1)
455 else if (vals[2] != -1)
460 word = ((vals[0] << 18) |
461 (vals[1] << 12) | ((vals[2] & 0x3F) << 6) | (vals[3] & 0x3F));
462 out[0] = (word >> 16) & 0xFF;
464 out[1] = (word >> 8) & 0xFF;
466 out[2] = word & 0xFF;
470 static char *read_blob(FILE * fp, int nlines, int *bloblen)
477 /* We expect at most 64 base64 characters, ie 48 real bytes, per line. */
478 blob = smalloc(48 * nlines);
480 for (i = 0; i < nlines; i++) {
481 line = read_body(fp);
486 linelen = strlen(line);
487 if (linelen % 4 != 0 || linelen > 64) {
492 for (j = 0; j < linelen; j += 4) {
493 k = base64_decode_atom(line + j, blob + len);
508 * Magic error return value for when the passphrase is wrong.
510 struct ssh2_userkey ssh2_wrong_passphrase = {
514 struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase)
517 char header[40], *b, *comment, *hash;
518 const struct ssh_signkey *alg;
519 struct ssh2_userkey *ret;
520 int cipher, cipherblk;
521 unsigned char *public_blob, *private_blob;
522 int public_blob_len, private_blob_len;
525 ret = NULL; /* return NULL for most errors */
526 comment = hash = NULL;
527 public_blob = private_blob = NULL;
529 fp = fopen(filename, "rb");
533 /* Read the first header line which contains the key type. */
534 if (!read_header(fp, header)
535 || 0 != strcmp(header, "PuTTY-User-Key-File-1"))
537 if ((b = read_body(fp)) == NULL)
539 /* Select key algorithm structure. Currently only ssh-rsa. */
540 if (!strcmp(b, "ssh-rsa"))
548 /* Read the Encryption header line. */
549 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
551 if ((b = read_body(fp)) == NULL)
553 if (!strcmp(b, "aes256-cbc")) {
556 } else if (!strcmp(b, "none")) {
565 /* Read the Comment header line. */
566 if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
568 if ((comment = read_body(fp)) == NULL)
571 /* Read the Public-Lines header line and the public blob. */
572 if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
574 if ((b = read_body(fp)) == NULL)
578 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
581 /* Read the Private-Lines header line and the Private blob. */
582 if (!read_header(fp, header) || 0 != strcmp(header, "Private-Lines"))
584 if ((b = read_body(fp)) == NULL)
588 if ((private_blob = read_blob(fp, i, &private_blob_len)) == NULL)
591 /* Read the Private-Hash header line. */
592 if (!read_header(fp, header) || 0 != strcmp(header, "Private-Hash"))
594 if ((hash = read_body(fp)) == NULL)
601 * Decrypt the private blob.
604 unsigned char key[40];
610 if (private_blob_len % cipherblk)
613 passlen = strlen(passphrase);
616 SHA_Bytes(&s, "\0\0\0\0", 4);
617 SHA_Bytes(&s, passphrase, passlen);
618 SHA_Final(&s, key + 0);
620 SHA_Bytes(&s, "\0\0\0\1", 4);
621 SHA_Bytes(&s, passphrase, passlen);
622 SHA_Final(&s, key + 20);
623 aes256_decrypt_pubkey(key, private_blob, private_blob_len);
627 * Verify the private hash.
631 unsigned char binary[20];
633 SHA_Simple(private_blob, private_blob_len, binary);
634 for (i = 0; i < 20; i++)
635 sprintf(realhash + 2 * i, "%02x", binary[i]);
637 if (strcmp(hash, realhash)) {
638 /* An incorrect hash is an unconditional Error if the key is
639 * unencrypted. Otherwise, it means Wrong Passphrase. */
640 ret = cipher ? SSH2_WRONG_PASSPHRASE : NULL;
647 * Create and return the key.
649 ret = smalloc(sizeof(struct ssh2_userkey));
651 ret->comment = comment;
652 ret->data = alg->createkey(public_blob, public_blob_len,
653 private_blob, private_blob_len);
680 char *ssh2_userkey_loadpub(char *filename, char **algorithm,
685 const struct ssh_signkey *alg;
686 unsigned char *public_blob;
692 fp = fopen(filename, "rb");
696 /* Read the first header line which contains the key type. */
697 if (!read_header(fp, header)
698 || 0 != strcmp(header, "PuTTY-User-Key-File-1"))
700 if ((b = read_body(fp)) == NULL)
702 /* Select key algorithm structure. Currently only ssh-rsa. */
703 if (!strcmp(b, "ssh-rsa"))
711 /* Read the Encryption header line. */
712 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
714 if ((b = read_body(fp)) == NULL)
716 sfree(b); /* we don't care */
718 /* Read the Comment header line. */
719 if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
721 if ((b = read_body(fp)) == NULL)
723 sfree(b); /* we don't care */
725 /* Read the Public-Lines header line and the public blob. */
726 if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
728 if ((b = read_body(fp)) == NULL)
732 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
736 *pub_blob_len = public_blob_len;
737 *algorithm = alg->name;
751 int ssh2_userkey_encrypted(char *filename, char **commentptr)
754 char header[40], *b, *comment;
760 fp = fopen(filename, "rb");
763 if (!read_header(fp, header)
764 || 0 != strcmp(header, "PuTTY-User-Key-File-1")) {
768 if ((b = read_body(fp)) == NULL) {
772 sfree(b); /* we don't care about key type here */
773 /* Read the Encryption header line. */
774 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption")) {
778 if ((b = read_body(fp)) == NULL) {
783 /* Read the Comment header line. */
784 if (!read_header(fp, header) || 0 != strcmp(header, "Comment")) {
789 if ((comment = read_body(fp)) == NULL) {
796 *commentptr = comment;
799 if (!strcmp(b, "aes256-cbc"))
807 int base64_lines(int datalen)
809 /* When encoding, we use 64 chars/line, which equals 48 real chars. */
810 return (datalen + 47) / 48;
813 void base64_encode_atom(unsigned char *data, int n, char *out)
815 static const char base64_chars[] =
816 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
820 word = data[0] << 16;
822 word |= data[1] << 8;
825 out[0] = base64_chars[(word >> 18) & 0x3F];
826 out[1] = base64_chars[(word >> 12) & 0x3F];
828 out[2] = base64_chars[(word >> 6) & 0x3F];
832 out[3] = base64_chars[word & 0x3F];
837 void base64_encode(FILE * fp, unsigned char *data, int datalen)
843 while (datalen > 0) {
848 n = (datalen < 3 ? datalen : 3);
849 base64_encode_atom(data, n, out);
852 fwrite(out, 1, 4, fp);
858 int ssh2_save_userkey(char *filename, struct ssh2_userkey *key,
862 unsigned char *pub_blob, *priv_blob, *priv_blob_encrypted;
863 int pub_blob_len, priv_blob_len, priv_encrypted_len;
868 unsigned char priv_hash[20];
871 * Fetch the key component blobs.
873 pub_blob = key->alg->public_blob(key->data, &pub_blob_len);
874 priv_blob = key->alg->private_blob(key->data, &priv_blob_len);
875 if (!pub_blob || !priv_blob) {
882 * Determine encryption details, and encrypt the private blob.
885 cipherstr = "aes256-cbc";
891 priv_encrypted_len = priv_blob_len + cipherblk - 1;
892 priv_encrypted_len -= priv_encrypted_len % cipherblk;
893 priv_blob_encrypted = smalloc(priv_encrypted_len);
894 memset(priv_blob_encrypted, 0, priv_encrypted_len);
895 memcpy(priv_blob_encrypted, priv_blob, priv_blob_len);
896 /* Create padding based on the SHA hash of the unpadded blob. This prevents
897 * too easy a known-plaintext attack on the last block. */
898 SHA_Simple(priv_blob, priv_blob_len, priv_hash);
899 assert(priv_encrypted_len - priv_blob_len < 20);
900 memcpy(priv_blob_encrypted + priv_blob_len, priv_hash,
901 priv_encrypted_len - priv_blob_len);
903 /* Now create the _real_ private hash. */
904 SHA_Simple(priv_blob_encrypted, priv_encrypted_len, priv_hash);
910 passlen = strlen(passphrase);
913 SHA_Bytes(&s, "\0\0\0\0", 4);
914 SHA_Bytes(&s, passphrase, passlen);
915 SHA_Final(&s, key + 0);
917 SHA_Bytes(&s, "\0\0\0\1", 4);
918 SHA_Bytes(&s, passphrase, passlen);
919 SHA_Final(&s, key + 20);
920 aes256_encrypt_pubkey(key, priv_blob_encrypted,
924 fp = fopen(filename, "w");
927 fprintf(fp, "PuTTY-User-Key-File-1: %s\n", key->alg->name);
928 fprintf(fp, "Encryption: %s\n", cipherstr);
929 fprintf(fp, "Comment: %s\n", key->comment);
930 fprintf(fp, "Public-Lines: %d\n", base64_lines(pub_blob_len));
931 base64_encode(fp, pub_blob, pub_blob_len);
932 fprintf(fp, "Private-Lines: %d\n", base64_lines(priv_encrypted_len));
933 base64_encode(fp, priv_blob_encrypted, priv_encrypted_len);
934 fprintf(fp, "Private-Hash: ");
935 for (i = 0; i < 20; i++)
936 fprintf(fp, "%02x", priv_hash[i]);
942 /* ----------------------------------------------------------------------
943 * A function to determine which version of SSH to try on a private
944 * key file. Returns 0 on failure, 1 or 2 on success.
946 int keyfile_version(char *filename)
951 fp = fopen(filename, "r");
957 return 1; /* "SSH PRIVATE KEY FORMAT" etc */
958 if (i == 'P') /* "PuTTY-User-Key-File" etc */
960 return 0; /* unrecognised or EOF */