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).
312 * The next line says "Encryption: " plus an encryption type.
313 * Currently the only supported encryption types are "aes256-cbc"
316 * The next line says "Comment: " plus the comment string.
318 * Next there is a line saying "Public-Lines: " plus a number N.
319 * The following N lines contain a base64 encoding of the public
320 * part of the key. This is encoded as the standard SSH2 public key
321 * blob (with no initial length): so for RSA, for example, it will
328 * Next, there is a line saying "Private-Lines: " plus a number N,
329 * and then N lines containing the (potentially encrypted) private
330 * part of the key. For the key type "ssh-rsa", this will be
333 * mpint private_exponent
334 * mpint p (the larger of the two primes)
335 * mpint q (the smaller prime)
336 * mpint iqmp (the inverse of q modulo p)
337 * data padding (to reach a multiple of the cipher block size)
339 * And for "ssh-dss", it will be composed of
341 * mpint x (the private key parameter)
342 * string hash (20-byte hash of mpints p || q || g)
344 * Finally, there is a line saying _either_
346 * - "Private-Hash: " plus a hex representation of a SHA-1 hash of
347 * the plaintext version of the private part, including the
352 * - "Private-MAC: " plus a hex representation of a HMAC-SHA-1 of
353 * the plaintext version of the private part, including the
356 * The key to the MAC is itself a SHA-1 hash of:
358 * data "putty-private-key-file-mac-key"
361 * Encrypted keys should have a MAC, whereas unencrypted ones must
364 * If the key is encrypted, the encryption key is derived from the
365 * passphrase by means of a succession of SHA-1 hashes. Each hash
368 * uint32 sequence-number
371 * where the sequence-number increases from zero. As many of these
372 * hashes are used as necessary.
374 * NOTE! It is important that all _public_ data can be verified
375 * with reference to the _private_ data. There exist attacks based
376 * on modifying the public key but leaving the private section
379 * With RSA, this is easy: verify that n = p*q, and also verify
380 * that e*d == 1 modulo (p-1)(q-1). With DSA, we need to store
381 * extra data in the private section other than just x, namely a
382 * hash of p||q||g. (It's then easy to verify that y is equal to
386 static int read_header(FILE * fp, char *header)
393 if (c == '\n' || c == '\r' || c == EOF)
394 return 0; /* failure */
400 return 1; /* success! */
403 return 0; /* failure */
407 return 0; /* failure */
410 static char *read_body(FILE * fp)
418 text = smalloc(size);
424 if (c == '\r' || c == '\n') {
426 if (c != '\r' && c != '\n' && c != EOF)
434 if (len + 1 > size) {
436 text = srealloc(text, size);
443 int base64_decode_atom(char *atom, unsigned char *out)
450 for (i = 0; i < 4; i++) {
452 if (c >= 'A' && c <= 'Z')
454 else if (c >= 'a' && c <= 'z')
456 else if (c >= '0' && c <= '9')
465 return 0; /* invalid atom */
469 if (vals[0] == -1 || vals[1] == -1)
471 if (vals[2] == -1 && vals[3] != -1)
476 else if (vals[2] != -1)
481 word = ((vals[0] << 18) |
482 (vals[1] << 12) | ((vals[2] & 0x3F) << 6) | (vals[3] & 0x3F));
483 out[0] = (word >> 16) & 0xFF;
485 out[1] = (word >> 8) & 0xFF;
487 out[2] = word & 0xFF;
491 static char *read_blob(FILE * fp, int nlines, int *bloblen)
498 /* We expect at most 64 base64 characters, ie 48 real bytes, per line. */
499 blob = smalloc(48 * nlines);
501 for (i = 0; i < nlines; i++) {
502 line = read_body(fp);
507 linelen = strlen(line);
508 if (linelen % 4 != 0 || linelen > 64) {
513 for (j = 0; j < linelen; j += 4) {
514 k = base64_decode_atom(line + j, blob + len);
529 * Magic error return value for when the passphrase is wrong.
531 struct ssh2_userkey ssh2_wrong_passphrase = {
535 struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase)
538 char header[40], *b, *comment, *mac;
539 const struct ssh_signkey *alg;
540 struct ssh2_userkey *ret;
541 int cipher, cipherblk;
542 unsigned char *public_blob, *private_blob;
543 int public_blob_len, private_blob_len;
545 int passlen = passphrase ? strlen(passphrase) : 0;
547 ret = NULL; /* return NULL for most errors */
548 comment = mac = NULL;
549 public_blob = private_blob = NULL;
551 fp = fopen(filename, "rb");
555 /* Read the first header line which contains the key type. */
556 if (!read_header(fp, header)
557 || 0 != strcmp(header, "PuTTY-User-Key-File-1"))
559 if ((b = read_body(fp)) == NULL)
561 /* Select key algorithm structure. */
562 if (!strcmp(b, "ssh-rsa"))
564 else if (!strcmp(b, "ssh-dss"))
572 /* Read the Encryption header line. */
573 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
575 if ((b = read_body(fp)) == NULL)
577 if (!strcmp(b, "aes256-cbc")) {
580 } else if (!strcmp(b, "none")) {
589 /* Read the Comment header line. */
590 if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
592 if ((comment = read_body(fp)) == NULL)
595 /* Read the Public-Lines header line and the public blob. */
596 if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
598 if ((b = read_body(fp)) == NULL)
602 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
605 /* Read the Private-Lines header line and the Private blob. */
606 if (!read_header(fp, header) || 0 != strcmp(header, "Private-Lines"))
608 if ((b = read_body(fp)) == NULL)
612 if ((private_blob = read_blob(fp, i, &private_blob_len)) == NULL)
615 /* Read the Private-MAC or Private-Hash header line. */
616 if (!read_header(fp, header))
618 if (0 == strcmp(header, "Private-MAC")) {
619 if ((mac = read_body(fp)) == NULL)
622 } else if (0 == strcmp(header, "Private-Hash")) {
623 if ((mac = read_body(fp)) == NULL)
633 * Decrypt the private blob.
636 unsigned char key[40];
641 if (private_blob_len % cipherblk)
645 SHA_Bytes(&s, "\0\0\0\0", 4);
646 SHA_Bytes(&s, passphrase, passlen);
647 SHA_Final(&s, key + 0);
649 SHA_Bytes(&s, "\0\0\0\1", 4);
650 SHA_Bytes(&s, passphrase, passlen);
651 SHA_Final(&s, key + 20);
652 aes256_decrypt_pubkey(key, private_blob, private_blob_len);
656 * Verify the private hash.
660 unsigned char binary[20];
664 unsigned char mackey[20];
665 char header[] = "putty-private-key-file-mac-key";
667 if (!passphrase) /* can't have MAC in unencrypted key */
671 SHA_Bytes(&s, header, sizeof(header)-1);
672 SHA_Bytes(&s, passphrase, passlen);
673 SHA_Final(&s, mackey);
675 hmac_sha1_simple(mackey, 20, private_blob, private_blob_len,
678 memset(mackey, 0, sizeof(mackey));
679 memset(&s, 0, sizeof(s));
681 SHA_Simple(private_blob, private_blob_len, binary);
683 for (i = 0; i < 20; i++)
684 sprintf(realmac + 2 * i, "%02x", binary[i]);
686 if (strcmp(mac, realmac)) {
687 /* An incorrect MAC is an unconditional Error if the key is
688 * unencrypted. Otherwise, it means Wrong Passphrase. */
689 ret = cipher ? SSH2_WRONG_PASSPHRASE : NULL;
696 * Create and return the key.
698 ret = smalloc(sizeof(struct ssh2_userkey));
700 ret->comment = comment;
701 ret->data = alg->createkey(public_blob, public_blob_len,
702 private_blob, private_blob_len);
729 char *ssh2_userkey_loadpub(char *filename, char **algorithm,
734 const struct ssh_signkey *alg;
735 unsigned char *public_blob;
741 fp = fopen(filename, "rb");
745 /* Read the first header line which contains the key type. */
746 if (!read_header(fp, header)
747 || 0 != strcmp(header, "PuTTY-User-Key-File-1"))
749 if ((b = read_body(fp)) == NULL)
751 /* Select key algorithm structure. Currently only ssh-rsa. */
752 if (!strcmp(b, "ssh-rsa"))
754 else if (!strcmp(b, "ssh-dss"))
762 /* Read the Encryption header line. */
763 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
765 if ((b = read_body(fp)) == NULL)
767 sfree(b); /* we don't care */
769 /* Read the Comment header line. */
770 if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
772 if ((b = read_body(fp)) == NULL)
774 sfree(b); /* we don't care */
776 /* Read the Public-Lines header line and the public blob. */
777 if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
779 if ((b = read_body(fp)) == NULL)
783 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
787 *pub_blob_len = public_blob_len;
788 *algorithm = alg->name;
802 int ssh2_userkey_encrypted(char *filename, char **commentptr)
805 char header[40], *b, *comment;
811 fp = fopen(filename, "rb");
814 if (!read_header(fp, header)
815 || 0 != strcmp(header, "PuTTY-User-Key-File-1")) {
819 if ((b = read_body(fp)) == NULL) {
823 sfree(b); /* we don't care about key type here */
824 /* Read the Encryption header line. */
825 if (!read_header(fp, header) || 0 != strcmp(header, "Encryption")) {
829 if ((b = read_body(fp)) == NULL) {
834 /* Read the Comment header line. */
835 if (!read_header(fp, header) || 0 != strcmp(header, "Comment")) {
840 if ((comment = read_body(fp)) == NULL) {
847 *commentptr = comment;
850 if (!strcmp(b, "aes256-cbc"))
858 int base64_lines(int datalen)
860 /* When encoding, we use 64 chars/line, which equals 48 real chars. */
861 return (datalen + 47) / 48;
864 void base64_encode_atom(unsigned char *data, int n, char *out)
866 static const char base64_chars[] =
867 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
871 word = data[0] << 16;
873 word |= data[1] << 8;
876 out[0] = base64_chars[(word >> 18) & 0x3F];
877 out[1] = base64_chars[(word >> 12) & 0x3F];
879 out[2] = base64_chars[(word >> 6) & 0x3F];
883 out[3] = base64_chars[word & 0x3F];
888 void base64_encode(FILE * fp, unsigned char *data, int datalen)
894 while (datalen > 0) {
899 n = (datalen < 3 ? datalen : 3);
900 base64_encode_atom(data, n, out);
903 fwrite(out, 1, 4, fp);
909 int ssh2_save_userkey(char *filename, struct ssh2_userkey *key,
913 unsigned char *pub_blob, *priv_blob, *priv_blob_encrypted;
914 int pub_blob_len, priv_blob_len, priv_encrypted_len;
919 unsigned char priv_mac[20];
922 * Fetch the key component blobs.
924 pub_blob = key->alg->public_blob(key->data, &pub_blob_len);
925 priv_blob = key->alg->private_blob(key->data, &priv_blob_len);
926 if (!pub_blob || !priv_blob) {
933 * Determine encryption details, and encrypt the private blob.
936 cipherstr = "aes256-cbc";
942 priv_encrypted_len = priv_blob_len + cipherblk - 1;
943 priv_encrypted_len -= priv_encrypted_len % cipherblk;
944 priv_blob_encrypted = smalloc(priv_encrypted_len);
945 memset(priv_blob_encrypted, 0, priv_encrypted_len);
946 memcpy(priv_blob_encrypted, priv_blob, priv_blob_len);
947 /* Create padding based on the SHA hash of the unpadded blob. This prevents
948 * too easy a known-plaintext attack on the last block. */
949 SHA_Simple(priv_blob, priv_blob_len, priv_mac);
950 assert(priv_encrypted_len - priv_blob_len < 20);
951 memcpy(priv_blob_encrypted + priv_blob_len, priv_mac,
952 priv_encrypted_len - priv_blob_len);
954 /* Now create the private MAC. */
957 unsigned char mackey[20];
958 char header[] = "putty-private-key-file-mac-key";
960 passlen = strlen(passphrase);
963 SHA_Bytes(&s, header, sizeof(header)-1);
964 SHA_Bytes(&s, passphrase, passlen);
965 SHA_Final(&s, mackey);
967 hmac_sha1_simple(mackey, 20,
968 priv_blob_encrypted, priv_encrypted_len,
972 memset(mackey, 0, sizeof(mackey));
973 memset(&s, 0, sizeof(s));
975 SHA_Simple(priv_blob_encrypted, priv_encrypted_len, priv_mac);
983 passlen = strlen(passphrase);
986 SHA_Bytes(&s, "\0\0\0\0", 4);
987 SHA_Bytes(&s, passphrase, passlen);
988 SHA_Final(&s, key + 0);
990 SHA_Bytes(&s, "\0\0\0\1", 4);
991 SHA_Bytes(&s, passphrase, passlen);
992 SHA_Final(&s, key + 20);
993 aes256_encrypt_pubkey(key, priv_blob_encrypted,
996 memset(key, 0, sizeof(key));
997 memset(&s, 0, sizeof(s));
1000 fp = fopen(filename, "w");
1003 fprintf(fp, "PuTTY-User-Key-File-1: %s\n", key->alg->name);
1004 fprintf(fp, "Encryption: %s\n", cipherstr);
1005 fprintf(fp, "Comment: %s\n", key->comment);
1006 fprintf(fp, "Public-Lines: %d\n", base64_lines(pub_blob_len));
1007 base64_encode(fp, pub_blob, pub_blob_len);
1008 fprintf(fp, "Private-Lines: %d\n", base64_lines(priv_encrypted_len));
1009 base64_encode(fp, priv_blob_encrypted, priv_encrypted_len);
1011 fprintf(fp, "Private-MAC: ");
1013 fprintf(fp, "Private-Hash: ");
1014 for (i = 0; i < 20; i++)
1015 fprintf(fp, "%02x", priv_mac[i]);
1021 /* ----------------------------------------------------------------------
1022 * A function to determine which version of SSH to try on a private
1023 * key file. Returns 0 on failure, 1 or 2 on success.
1025 int keyfile_version(char *filename)
1030 fp = fopen(filename, "r");
1036 return 1; /* "SSH PRIVATE KEY FORMAT" etc */
1037 if (i == 'P') /* "PuTTY-User-Key-File" etc */
1039 return 0; /* unrecognised or EOF */