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) {
36 unsigned char buf[16384];
37 unsigned char keybuf[16];
41 struct MD5Context md5c;
44 /* Slurp the whole file (minus the header) into a buffer. */
45 len = fread(buf, 1, sizeof(buf), fp);
47 if (len < 0 || len == sizeof(buf))
48 goto end; /* file too big or not read */
53 * A zero byte. (The signature includes a terminating NUL.)
55 if (len-i < 1 || buf[i] != 0)
59 /* One byte giving encryption type, and one reserved uint32. */
63 if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES)
67 goto end; /* reserved field not present */
68 if (buf[i] != 0 || buf[i+1] != 0 || buf[i+2] != 0 || buf[i+3] != 0)
69 goto end; /* reserved field nonzero, panic! */
72 /* Now the serious stuff. An ordinary SSH 1 public key. */
73 i += makekey(buf+i, key, NULL, 1);
75 goto end; /* overran */
77 /* Next, the comment field. */
80 if (len-i < j) goto end;
81 comment = smalloc(j+1);
83 memcpy(comment, buf+i, j);
88 *commentptr = comment;
90 key->comment = comment;
92 return ciphertype != 0;
96 * Decrypt remainder of buffer.
100 MD5Update(&md5c, passphrase, strlen(passphrase));
101 MD5Final(keybuf, &md5c);
102 des3_decrypt_pubkey(keybuf, buf+i, (len-i+7)&~7);
103 memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
107 * We are now in the secret part of the key. The first four
108 * bytes should be of the form a, b, a, b.
110 if (len-i < 4) goto end;
111 if (buf[i] != buf[i+2] || buf[i+1] != buf[i+3]) { ret = -1; goto end; }
115 * After that, we have one further bignum which is our
116 * decryption exponent, and then the three auxiliary values
119 i += makeprivate(buf+i, key);
120 if (len-i < 0) goto end;
121 i += ssh1_read_bignum(buf+i, &key->iqmp);
122 if (len-i < 0) goto end;
123 i += ssh1_read_bignum(buf+i, &key->q);
124 if (len-i < 0) goto end;
125 i += ssh1_read_bignum(buf+i, &key->p);
126 if (len-i < 0) goto end;
128 if (!rsa_verify(key)) {
135 memset(buf, 0, sizeof(buf)); /* burn the evidence */
139 int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) {
141 unsigned char buf[64];
143 fp = fopen(filename, "rb");
145 return 0; /* doesn't even exist */
148 * Read the first line of the file and see if it's a v1 private
151 if (fgets(buf, sizeof(buf), fp) &&
152 !strcmp(buf, rsa_signature)) {
153 return loadrsakey_main(fp, key, NULL, passphrase);
157 * Otherwise, we have nothing. Return empty-handed.
164 * See whether an RSA key is encrypted. Return its comment field as
167 int rsakey_encrypted(char *filename, char **comment) {
169 unsigned char buf[64];
171 fp = fopen(filename, "rb");
173 return 0; /* doesn't even exist */
176 * Read the first line of the file and see if it's a v1 private
179 if (fgets(buf, sizeof(buf), fp) &&
180 !strcmp(buf, rsa_signature)) {
181 return loadrsakey_main(fp, NULL, comment, NULL);
184 return 0; /* wasn't the right kind of file */
188 * Save an RSA key file. Return nonzero on success.
190 int saversakey(char *filename, struct RSAKey *key, char *passphrase) {
191 unsigned char buf[16384];
192 unsigned char keybuf[16];
193 struct MD5Context md5c;
194 unsigned char *p, *estart;
198 * Write the initial signature.
201 memcpy(p, rsa_signature, sizeof(rsa_signature));
202 p += sizeof(rsa_signature);
205 * One byte giving encryption type, and one reserved (zero)
208 *p++ = (passphrase ? SSH_CIPHER_3DES : 0);
209 PUT_32BIT(p, 0); p += 4;
212 * An ordinary SSH 1 public key consists of: a uint32
213 * containing the bit count, then two bignums containing the
214 * modulus and exponent respectively.
216 PUT_32BIT(p, ssh1_bignum_bitcount(key->modulus)); p += 4;
217 p += ssh1_write_bignum(p, key->modulus);
218 p += ssh1_write_bignum(p, key->exponent);
221 * A string containing the comment field.
224 PUT_32BIT(p, strlen(key->comment)); p += 4;
225 memcpy(p, key->comment, strlen(key->comment));
226 p += strlen(key->comment);
228 PUT_32BIT(p, 0); p += 4;
232 * The encrypted portion starts here.
237 * Two bytes, then the same two bytes repeated.
239 *p++ = random_byte();
240 *p++ = random_byte();
241 p[0] = p[-2]; p[1] = p[-1]; p += 2;
244 * Four more bignums: the decryption exponent, then iqmp, then
247 p += ssh1_write_bignum(p, key->private_exponent);
248 p += ssh1_write_bignum(p, key->iqmp);
249 p += ssh1_write_bignum(p, key->q);
250 p += ssh1_write_bignum(p, key->p);
253 * Now write zeros until the encrypted portion is a multiple of
256 while ((p-estart) % 8)
260 * Now encrypt the encrypted portion.
264 MD5Update(&md5c, passphrase, strlen(passphrase));
265 MD5Final(keybuf, &md5c);
266 des3_encrypt_pubkey(keybuf, estart, p-estart);
267 memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
271 * Done. Write the result to the file.
273 fp = fopen(filename, "wb");
275 int ret = (fwrite(buf, 1, p-buf, fp) == (size_t)(p-buf));
276 ret = ret && (fclose(fp) == 0);
282 /* ----------------------------------------------------------------------
283 * SSH2 private key load/store functions.
287 * PuTTY's own format for SSH2 keys is as follows:
289 * The file is text. Lines are terminated by CRLF, although CR-only
290 * and LF-only are tolerated on input.
292 * The first line says "PuTTY-User-Key-File-1: " plus the name of the
293 * algorithm ("ssh-dss", "ssh-rsa" etc. Although, of course, this
294 * being PuTTY, "ssh-dss" is not supported.)
296 * The next line says "Encryption: " plus an encryption type.
297 * Currently the only supported encryption types are "aes256-cbc"
300 * The next line says "Comment: " plus the comment string.
302 * Next there is a line saying "Public-Lines: " plus a number N.
303 * The following N lines contain a base64 encoding of the public
304 * part of the key. This is encoded as the standard SSH2 public key
305 * blob (with no initial length): so for RSA, for example, it will
312 * Next, there is a line saying "Private-Lines: " plus a number N,
313 * and then N lines containing the (potentially encrypted) private
314 * part of the key. For the key type "ssh-rsa", this will be
317 * mpint private_exponent
318 * mpint p (the larger of the two primes)
319 * mpint q (the smaller prime)
320 * mpint iqmp (the inverse of q modulo p)
321 * data padding (to reach a multiple of the cipher block size)
323 * Finally, there is a line saying "Private-Hash: " plus a hex
324 * representation of a SHA-1 hash of the plaintext version of the
325 * private part, including the final padding.
327 * If the key is encrypted, the encryption key is derived from the
328 * passphrase by means of a succession of SHA-1 hashes. Each hash
331 * uint32 sequence-number
334 * where the sequence-number increases from zero. As many of these
335 * hashes are used as necessary.
337 * NOTE! It is important that all _public_ data can be verified
338 * with reference to the _private_ data. There exist attacks based
339 * on modifying the public key but leaving the private section
342 * With RSA, this is easy: verify that n = p*q, and also verify
343 * that e*d == 1 modulo (p-1)(q-1). With DSA (if we were ever to
344 * support it), we would need to store extra data in the private
345 * section other than just x.
348 static int read_header(FILE *fp, char *header) {
354 if (c == '\n' || c == '\r' || c == EOF)
355 return 0; /* failure */
361 return 1; /* success! */
364 return 0; /* failure */
368 return 0; /* failure */
371 static char *read_body(FILE *fp) {
378 text = smalloc(size);
384 if (c == '\r' || c == '\n') {
386 if (c != '\r' && c != '\n' && c != EOF)
394 if (len + 1 > size) {
396 text = srealloc(text, size);
403 int base64_decode_atom(char *atom, unsigned char *out) {
409 for (i = 0; i < 4; i++) {
411 if (c >= 'A' && c <= 'Z')
413 else if (c >= 'a' && c <= 'z')
415 else if (c >= '0' && c <= '9')
424 return 0; /* invalid atom */
428 if (vals[0] == -1 || vals[1] == -1)
430 if (vals[2] == -1 && vals[3] != -1)
435 else if (vals[2] != -1)
440 word = ((vals[0] << 18) |
442 ((vals[2] & 0x3F) << 6) |
444 out[0] = (word >> 16) & 0xFF;
446 out[1] = (word >> 8) & 0xFF;
448 out[2] = word & 0xFF;
452 static char *read_blob(FILE *fp, int nlines, int *bloblen) {
458 /* We expect at most 64 base64 characters, ie 48 real bytes, per line. */
459 blob = smalloc(48 * nlines);
461 for (i = 0; i < nlines; i++) {
462 line = read_body(fp);
467 linelen = strlen(line);
468 if (linelen % 4 != 0 || linelen > 64) {
473 for (j = 0; j < linelen; j += 4) {
474 k = base64_decode_atom(line+j, blob+len);
489 * Magic error return value for when the passphrase is wrong.
491 struct ssh2_userkey ssh2_wrong_passphrase = {
495 struct ssh2_userkey *ssh2_load_userkey(char *filename, char *passphrase) {
497 char header[40], *b, *comment, *hash;
498 const struct ssh_signkey *alg;
499 struct ssh2_userkey *ret;
500 int cipher, cipherblk;
501 unsigned char *public_blob, *private_blob;
502 int public_blob_len, private_blob_len;
505 ret = NULL; /* return NULL for most errors */
506 comment = hash = NULL;
507 public_blob = private_blob = NULL;
509 fp = fopen(filename, "rb");
513 /* Read the first header line which contains the key type. */
514 if (!read_header(fp, header) || 0!=strcmp(header, "PuTTY-User-Key-File-1"))
516 if ((b = read_body(fp)) == NULL)
518 /* Select key algorithm structure. Currently only ssh-rsa. */
519 if (!strcmp(b, "ssh-rsa"))
527 /* Read the Encryption header line. */
528 if (!read_header(fp, header) || 0!=strcmp(header, "Encryption"))
530 if ((b = read_body(fp)) == NULL)
532 if (!strcmp(b, "aes256-cbc")) {
533 cipher = 1; cipherblk = 16;
534 } else if (!strcmp(b, "none")) {
535 cipher = 0; cipherblk = 1;
542 /* Read the Comment header line. */
543 if (!read_header(fp, header) || 0!=strcmp(header, "Comment"))
545 if ((comment = read_body(fp)) == NULL)
548 /* Read the Public-Lines header line and the public blob. */
549 if (!read_header(fp, header) || 0!=strcmp(header, "Public-Lines"))
551 if ((b = read_body(fp)) == NULL)
555 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
558 /* Read the Private-Lines header line and the Private blob. */
559 if (!read_header(fp, header) || 0!=strcmp(header, "Private-Lines"))
561 if ((b = read_body(fp)) == NULL)
565 if ((private_blob = read_blob(fp, i, &private_blob_len)) == NULL)
568 /* Read the Private-Hash header line. */
569 if (!read_header(fp, header) || 0!=strcmp(header, "Private-Hash"))
571 if ((hash = read_body(fp)) == NULL)
578 * Decrypt the private blob.
581 unsigned char key[40];
587 if (private_blob_len % cipherblk)
590 passlen = strlen(passphrase);
593 SHA_Bytes(&s, "\0\0\0\0", 4);
594 SHA_Bytes(&s, passphrase, passlen);
595 SHA_Final(&s, key+0);
597 SHA_Bytes(&s, "\0\0\0\1", 4);
598 SHA_Bytes(&s, passphrase, passlen);
599 SHA_Final(&s, key+20);
600 aes256_decrypt_pubkey(key, private_blob, private_blob_len);
604 * Verify the private hash.
608 unsigned char binary[20];
610 SHA_Simple(private_blob, private_blob_len, binary);
611 for (i = 0; i < 20; i++)
612 sprintf(realhash+2*i, "%02x", binary[i]);
614 if (strcmp(hash, realhash)) {
615 /* An incorrect hash is an unconditional Error if the key is
616 * unencrypted. Otherwise, it means Wrong Passphrase. */
617 ret = cipher ? SSH2_WRONG_PASSPHRASE : NULL;
624 * Create and return the key.
626 ret = smalloc(sizeof(struct ssh2_userkey));
628 ret->comment = comment;
629 ret->data = alg->createkey(public_blob, public_blob_len,
630 private_blob, private_blob_len);
645 if (comment) sfree(comment);
646 if (hash) sfree(hash);
647 if (public_blob) sfree(public_blob);
648 if (private_blob) sfree(private_blob);
652 char *ssh2_userkey_loadpub(char *filename, char **algorithm, int *pub_blob_len) {
655 const struct ssh_signkey *alg;
656 unsigned char *public_blob;
662 fp = fopen(filename, "rb");
666 /* Read the first header line which contains the key type. */
667 if (!read_header(fp, header) || 0!=strcmp(header, "PuTTY-User-Key-File-1"))
669 if ((b = read_body(fp)) == NULL)
671 /* Select key algorithm structure. Currently only ssh-rsa. */
672 if (!strcmp(b, "ssh-rsa"))
680 /* Read the Encryption header line. */
681 if (!read_header(fp, header) || 0!=strcmp(header, "Encryption"))
683 if ((b = read_body(fp)) == NULL)
685 sfree(b); /* we don't care */
687 /* Read the Comment header line. */
688 if (!read_header(fp, header) || 0!=strcmp(header, "Comment"))
690 if ((b = read_body(fp)) == NULL)
692 sfree(b); /* we don't care */
694 /* Read the Public-Lines header line and the public blob. */
695 if (!read_header(fp, header) || 0!=strcmp(header, "Public-Lines"))
697 if ((b = read_body(fp)) == NULL)
701 if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
705 *pub_blob_len = public_blob_len;
706 *algorithm = alg->name;
714 if (public_blob) sfree(public_blob);
718 int ssh2_userkey_encrypted(char *filename, char **commentptr) {
720 char header[40], *b, *comment;
723 if (commentptr) *commentptr = NULL;
725 fp = fopen(filename, "rb");
728 if (!read_header(fp, header) || 0!=strcmp(header, "PuTTY-User-Key-File-1")) {
729 fclose(fp); return 0;
731 if ((b = read_body(fp)) == NULL) {
732 fclose(fp); return 0;
734 sfree(b); /* we don't care about key type here */
735 /* Read the Encryption header line. */
736 if (!read_header(fp, header) || 0!=strcmp(header, "Encryption")) {
737 fclose(fp); return 0;
739 if ((b = read_body(fp)) == NULL) {
740 fclose(fp); return 0;
743 /* Read the Comment header line. */
744 if (!read_header(fp, header) || 0!=strcmp(header, "Comment")) {
745 fclose(fp); sfree(b); return 1;
747 if ((comment = read_body(fp)) == NULL) {
748 fclose(fp); sfree(b); return 1;
751 if (commentptr) *commentptr = comment;
754 if (!strcmp(b, "aes256-cbc"))
762 int base64_lines(int datalen) {
763 /* When encoding, we use 64 chars/line, which equals 48 real chars. */
764 return (datalen+47) / 48;
767 void base64_encode_atom(unsigned char *data, int n, char *out) {
768 static const char base64_chars[] =
769 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
773 word = data[0] << 16;
775 word |= data[1] << 8;
778 out[0] = base64_chars[(word >> 18) & 0x3F];
779 out[1] = base64_chars[(word >> 12) & 0x3F];
781 out[2] = base64_chars[(word >> 6) & 0x3F];
785 out[3] = base64_chars[word & 0x3F];
790 void base64_encode(FILE *fp, unsigned char *data, int datalen) {
795 while (datalen > 0) {
800 n = (datalen < 3 ? datalen : 3);
801 base64_encode_atom(data, n, out);
804 fwrite(out, 1, 4, fp);
810 int ssh2_save_userkey(char *filename, struct ssh2_userkey *key, char *passphrase) {
812 unsigned char *pub_blob, *priv_blob, *priv_blob_encrypted;
813 int pub_blob_len, priv_blob_len, priv_encrypted_len;
818 unsigned char priv_hash[20];
821 * Fetch the key component blobs.
823 pub_blob = key->alg->public_blob(key->data, &pub_blob_len);
824 priv_blob = key->alg->private_blob(key->data, &priv_blob_len);
825 if (!pub_blob || !priv_blob) {
832 * Determine encryption details, and encrypt the private blob.
835 cipherstr = "aes256-cbc";
841 priv_encrypted_len = priv_blob_len + cipherblk - 1;
842 priv_encrypted_len -= priv_encrypted_len % cipherblk;
843 priv_blob_encrypted = smalloc(priv_encrypted_len);
844 memset(priv_blob_encrypted, 0, priv_encrypted_len);
845 memcpy(priv_blob_encrypted, priv_blob, priv_blob_len);
846 /* Create padding based on the SHA hash of the unpadded blob. This prevents
847 * too easy a known-plaintext attack on the last block. */
848 SHA_Simple(priv_blob, priv_blob_len, priv_hash);
849 assert(priv_encrypted_len - priv_blob_len < 20);
850 memcpy(priv_blob_encrypted + priv_blob_len, priv_hash,
851 priv_encrypted_len - priv_blob_len);
853 /* Now create the _real_ private hash. */
854 SHA_Simple(priv_blob_encrypted, priv_encrypted_len, priv_hash);
860 passlen = strlen(passphrase);
863 SHA_Bytes(&s, "\0\0\0\0", 4);
864 SHA_Bytes(&s, passphrase, passlen);
865 SHA_Final(&s, key+0);
867 SHA_Bytes(&s, "\0\0\0\1", 4);
868 SHA_Bytes(&s, passphrase, passlen);
869 SHA_Final(&s, key+20);
870 aes256_encrypt_pubkey(key, priv_blob_encrypted, priv_encrypted_len);
873 fp = fopen(filename, "w");
876 fprintf(fp, "PuTTY-User-Key-File-1: %s\n", key->alg->name);
877 fprintf(fp, "Encryption: %s\n", cipherstr);
878 fprintf(fp, "Comment: %s\n", key->comment);
879 fprintf(fp, "Public-Lines: %d\n", base64_lines(pub_blob_len));
880 base64_encode(fp, pub_blob, pub_blob_len);
881 fprintf(fp, "Private-Lines: %d\n", base64_lines(priv_encrypted_len));
882 base64_encode(fp, priv_blob_encrypted, priv_encrypted_len);
883 fprintf(fp, "Private-Hash: ");
884 for (i = 0; i < 20; i++)
885 fprintf(fp, "%02x", priv_hash[i]);
891 /* ----------------------------------------------------------------------
892 * A function to determine which version of SSH to try on a private
893 * key file. Returns 0 on failure, 1 or 2 on success.
895 int keyfile_version(char *filename) {
899 fp = fopen(filename, "r");
905 return 1; /* "SSH PRIVATE KEY FORMAT" etc */
906 if (i == 'P') /* "PuTTY-User-Key-File" etc */
908 return 0; /* unrecognised or EOF */