2 * Code for PuTTY to import and export private key files in other
3 * SSH clients' formats.
14 #define PUT_32BIT(cp, value) do { \
15 (cp)[3] = (unsigned char)(value); \
16 (cp)[2] = (unsigned char)((value) >> 8); \
17 (cp)[1] = (unsigned char)((value) >> 16); \
18 (cp)[0] = (unsigned char)((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 int openssh_encrypted(char *filename);
27 struct ssh2_userkey *openssh_read(char *filename, char *passphrase);
28 int openssh_write(char *filename, struct ssh2_userkey *key, char *passphrase);
30 int sshcom_encrypted(char *filename, char **comment);
31 struct ssh2_userkey *sshcom_read(char *filename, char *passphrase);
32 int sshcom_write(char *filename, struct ssh2_userkey *key, char *passphrase);
35 * Given a key type, determine whether we know how to import it.
37 int import_possible(int type)
39 if (type == SSH_KEYTYPE_OPENSSH)
41 if (type == SSH_KEYTYPE_SSHCOM)
47 * Given a key type, determine what native key type
48 * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
51 int import_target_type(int type)
54 * There are no known foreign SSH1 key formats.
56 return SSH_KEYTYPE_SSH2;
60 * Determine whether a foreign key is encrypted.
62 int import_encrypted(char *filename, int type, char **comment)
64 if (type == SSH_KEYTYPE_OPENSSH) {
65 *comment = dupstr(filename); /* OpenSSH doesn't do key comments */
66 return openssh_encrypted(filename);
68 if (type == SSH_KEYTYPE_SSHCOM) {
69 return sshcom_encrypted(filename, comment);
77 int import_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase)
85 struct ssh2_userkey *import_ssh2(char *filename, int type, char *passphrase)
87 if (type == SSH_KEYTYPE_OPENSSH)
88 return openssh_read(filename, passphrase);
89 if (type == SSH_KEYTYPE_SSHCOM)
90 return sshcom_read(filename, passphrase);
97 int export_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase)
103 * Export an SSH2 key.
105 int export_ssh2(char *filename, int type,
106 struct ssh2_userkey *key, char *passphrase)
108 if (type == SSH_KEYTYPE_OPENSSH)
109 return openssh_write(filename, key, passphrase);
110 if (type == SSH_KEYTYPE_SSHCOM)
111 return sshcom_write(filename, key, passphrase);
115 /* ----------------------------------------------------------------------
116 * Helper routines. (The base64 ones are defined in sshpubk.c.)
119 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
120 ((c) >= 'a' && (c) <= 'z') || \
121 ((c) >= '0' && (c) <= '9') || \
122 (c) == '+' || (c) == '/' || (c) == '=' \
125 extern int base64_decode_atom(char *atom, unsigned char *out);
126 extern int base64_lines(int datalen);
127 extern void base64_encode_atom(unsigned char *data, int n, char *out);
128 extern void base64_encode(FILE *fp, unsigned char *data, int datalen, int cpl);
131 * Read an ASN.1/BER identifier and length pair.
133 * Flags are a combination of the #defines listed below.
135 * Returns -1 if unsuccessful; otherwise returns the number of
136 * bytes used out of the source data.
139 /* ASN.1 tag classes. */
140 #define ASN1_CLASS_UNIVERSAL (0 << 6)
141 #define ASN1_CLASS_APPLICATION (1 << 6)
142 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
143 #define ASN1_CLASS_PRIVATE (3 << 6)
144 #define ASN1_CLASS_MASK (3 << 6)
146 /* Primitive versus constructed bit. */
147 #define ASN1_CONSTRUCTED (1 << 5)
149 int ber_read_id_len(void *source, int sourcelen,
150 int *id, int *length, int *flags)
152 unsigned char *p = (unsigned char *) source;
157 *flags = (*p & 0xE0);
158 if ((*p & 0x1F) == 0x1F) {
161 *id = (*id << 7) | (*p & 0x7F);
166 *id = (*id << 7) | (*p & 0x7F);
183 *length = (*length << 8) | (*p++);
190 return p - (unsigned char *) source;
194 * Write an ASN.1/BER identifier and length pair. Returns the
195 * number of bytes consumed. Assumes dest contains enough space.
196 * Will avoid writing anything if dest is NULL, but still return
197 * amount of space required.
199 int ber_write_id_len(void *dest, int id, int length, int flags)
201 unsigned char *d = (unsigned char *)dest;
206 * Identifier is one byte.
209 if (d) *d++ = id | flags;
213 * Identifier is multiple bytes: the first byte is 11111
214 * plus the flags, and subsequent bytes encode the value of
215 * the identifier, 7 bits at a time, with the top bit of
216 * each byte 1 except the last one which is 0.
219 if (d) *d++ = 0x1F | flags;
220 for (n = 1; (id >> (7*n)) > 0; n++)
221 continue; /* count the bytes */
224 if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
230 * Length is one byte.
233 if (d) *d++ = length;
237 * Length is multiple bytes. The first is 0x80 plus the
238 * number of subsequent bytes, and the subsequent bytes
239 * encode the actual length.
241 for (n = 1; (length >> (8*n)) > 0; n++)
242 continue; /* count the bytes */
244 if (d) *d++ = 0x80 | n;
247 if (d) *d++ = (length >> (8*n)) & 0xFF;
254 static int put_string(void *target, void *data, int len)
256 unsigned char *d = (unsigned char *)target;
259 memcpy(d+4, data, len);
263 static int put_mp(void *target, void *data, int len)
265 unsigned char *d = (unsigned char *)target;
266 unsigned char *i = (unsigned char *)data;
271 memcpy(d+5, data, len);
275 memcpy(d+4, data, len);
280 /* Simple structure to point to an mp-int within a blob. */
281 struct mpint_pos { void *start; int bytes; };
283 int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
286 unsigned char *d = (unsigned char *) data;
290 bytes = GET_32BIT(d);
301 return len; /* ensure further calls fail as well */
304 /* ----------------------------------------------------------------------
305 * Code to read and write OpenSSH private keys.
308 enum { OSSH_DSA, OSSH_RSA };
313 unsigned char *keyblob;
314 int keyblob_len, keyblob_size;
317 struct openssh_key *load_openssh_key(char *filename)
319 struct openssh_key *ret;
325 int base64_chars = 0;
327 ret = smalloc(sizeof(*ret));
329 ret->keyblob_len = ret->keyblob_size = 0;
331 memset(ret->iv, 0, sizeof(ret->iv));
333 fp = fopen(filename, "r");
335 errmsg = "Unable to open key file";
338 if (!fgets(buffer, sizeof(buffer), fp) ||
339 0 != strncmp(buffer, "-----BEGIN ", 11) ||
340 0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) {
341 errmsg = "File does not begin with OpenSSH key header";
344 if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n"))
345 ret->type = OSSH_RSA;
346 else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n"))
347 ret->type = OSSH_DSA;
349 errmsg = "Unrecognised key type";
355 if (!fgets(buffer, sizeof(buffer), fp)) {
356 errmsg = "Unexpected end of file";
359 if (0 == strncmp(buffer, "-----END ", 9) &&
360 0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n"))
362 if ((p = strchr(buffer, ':')) != NULL) {
364 errmsg = "Header found in body of key data";
368 while (*p && isspace((unsigned char)*p)) p++;
369 if (!strcmp(buffer, "Proc-Type")) {
370 if (p[0] != '4' || p[1] != ',') {
371 errmsg = "Proc-Type is not 4 (only 4 is supported)";
375 if (!strcmp(p, "ENCRYPTED\n"))
377 } else if (!strcmp(buffer, "DEK-Info")) {
380 if (strncmp(p, "DES-EDE3-CBC,", 13)) {
381 errmsg = "Ciphers other than DES-EDE3-CBC not supported";
385 for (i = 0; i < 8; i++) {
386 if (1 != sscanf(p, "%2x", &j))
392 errmsg = "Expected 16-digit iv in DEK-Info";
400 while (isbase64(*p)) {
401 base64_bit[base64_chars++] = *p;
402 if (base64_chars == 4) {
403 unsigned char out[3];
408 len = base64_decode_atom(base64_bit, out);
411 errmsg = "Invalid base64 encoding";
415 if (ret->keyblob_len + len > ret->keyblob_size) {
416 ret->keyblob_size = ret->keyblob_len + len + 256;
417 ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size);
420 memcpy(ret->keyblob + ret->keyblob_len, out, len);
421 ret->keyblob_len += len;
423 memset(out, 0, sizeof(out));
431 if (ret->keyblob_len == 0 || !ret->keyblob) {
432 errmsg = "Key body not present";
436 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
437 errmsg = "Encrypted key blob is not a multiple of cipher block size";
441 memset(buffer, 0, sizeof(buffer));
442 memset(base64_bit, 0, sizeof(base64_bit));
446 memset(buffer, 0, sizeof(buffer));
447 memset(base64_bit, 0, sizeof(base64_bit));
450 memset(ret->keyblob, 0, ret->keyblob_size);
453 memset(&ret, 0, sizeof(ret));
459 int openssh_encrypted(char *filename)
461 struct openssh_key *key = load_openssh_key(filename);
466 ret = key->encrypted;
467 memset(key->keyblob, 0, key->keyblob_size);
469 memset(&key, 0, sizeof(key));
474 struct ssh2_userkey *openssh_read(char *filename, char *passphrase)
476 struct openssh_key *key = load_openssh_key(filename);
477 struct ssh2_userkey *retkey;
479 int ret, id, len, flags;
481 struct ssh2_userkey *retval = NULL;
484 int blobsize, blobptr, privptr;
493 if (key->encrypted) {
495 * Derive encryption key from passphrase and iv/salt:
497 * - let block A equal MD5(passphrase || iv)
498 * - let block B equal MD5(A || passphrase || iv)
499 * - block C would be MD5(B || passphrase || iv) and so on
500 * - encryption key is the first N bytes of A || B
502 struct MD5Context md5c;
503 unsigned char keybuf[32];
506 MD5Update(&md5c, passphrase, strlen(passphrase));
507 MD5Update(&md5c, key->iv, 8);
508 MD5Final(keybuf, &md5c);
511 MD5Update(&md5c, keybuf, 16);
512 MD5Update(&md5c, passphrase, strlen(passphrase));
513 MD5Update(&md5c, key->iv, 8);
514 MD5Final(keybuf+16, &md5c);
517 * Now decrypt the key blob.
519 des3_decrypt_pubkey_ossh(keybuf, key->iv,
520 key->keyblob, key->keyblob_len);
522 memset(&md5c, 0, sizeof(md5c));
523 memset(keybuf, 0, sizeof(keybuf));
527 * Now we have a decrypted key blob, which contains an ASN.1
528 * encoded private key. We must now untangle the ASN.1.
530 * We expect the whole key blob to be formatted as a SEQUENCE
531 * (0x30 followed by a length code indicating that the rest of
532 * the blob is part of the sequence). Within that SEQUENCE we
533 * expect to see a bunch of INTEGERs. What those integers mean
534 * depends on the key type:
536 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
537 * dmp1, dmq1, iqmp in that order. (The last three are d mod
538 * (p-1), d mod (q-1), inverse of q mod p respectively.)
540 * - For DSA, we expect them to be 0, p, q, g, y, x in that
546 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
547 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
549 if (ret < 0 || id != 16) {
550 errmsg = "ASN.1 decoding failure";
551 retval = SSH2_WRONG_PASSPHRASE;
555 /* Expect a load of INTEGERs. */
556 if (key->type == OSSH_RSA)
558 else if (key->type == OSSH_DSA)
562 * Space to create key blob in.
564 blobsize = 256+key->keyblob_len;
565 blob = smalloc(blobsize);
567 if (key->type == OSSH_DSA)
568 memcpy(blob+4, "ssh-dss", 7);
569 else if (key->type == OSSH_RSA)
570 memcpy(blob+4, "ssh-rsa", 7);
574 for (i = 0; i < num_integers; i++) {
575 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
578 if (ret < 0 || id != 2 ||
579 key->keyblob+key->keyblob_len-p < len) {
580 errmsg = "ASN.1 decoding failure";
586 * The first integer should be zero always (I think
587 * this is some sort of version indication).
589 if (len != 1 || p[0] != 0) {
590 errmsg = "Version number mismatch";
593 } else if (key->type == OSSH_RSA) {
595 * Integers 1 and 2 go into the public blob but in the
596 * opposite order; integers 3, 4, 5 and 8 go into the
597 * private blob. The other two (6 and 7) are ignored.
600 /* Save the details for after we deal with number 2. */
603 } else if (i != 6 && i != 7) {
604 PUT_32BIT(blob+blobptr, len);
605 memcpy(blob+blobptr+4, p, len);
608 PUT_32BIT(blob+blobptr, modlen);
609 memcpy(blob+blobptr+4, modptr, modlen);
614 } else if (key->type == OSSH_DSA) {
616 * Integers 1-4 go into the public blob; integer 5 goes
617 * into the private blob.
619 PUT_32BIT(blob+blobptr, len);
620 memcpy(blob+blobptr+4, p, len);
626 /* Skip past the number. */
631 * Now put together the actual key. Simplest way to do this is
632 * to assemble our own key blobs and feed them to the createkey
633 * functions; this is a bit faffy but it does mean we get all
634 * the sanity checks for free.
636 assert(privptr > 0); /* should have bombed by now if not */
637 retkey = smalloc(sizeof(struct ssh2_userkey));
638 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
639 retkey->data = retkey->alg->createkey(blob, privptr,
640 blob+privptr, blobptr-privptr);
643 errmsg = "unable to create key data structure";
647 retkey->comment = dupstr("imported-openssh-key");
648 errmsg = NULL; /* no error */
653 memset(blob, 0, blobsize);
656 memset(key->keyblob, 0, key->keyblob_size);
658 memset(&key, 0, sizeof(key));
663 int openssh_write(char *filename, struct ssh2_userkey *key, char *passphrase)
665 unsigned char *pubblob, *privblob, *spareblob;
666 int publen, privlen, sparelen;
667 unsigned char *outblob;
669 struct mpint_pos numbers[9];
670 int nnumbers, pos, len, seqlen, i;
671 char *header, *footer;
678 * Fetch the key blobs.
680 pubblob = key->alg->public_blob(key->data, &publen);
681 privblob = key->alg->private_blob(key->data, &privlen);
682 spareblob = outblob = NULL;
685 * Find the sequence of integers to be encoded into the OpenSSH
686 * key blob, and also decide on the header line.
688 if (key->alg == &ssh_rsa) {
690 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
691 Bignum bd, bp, bq, bdmp1, bdmq1;
693 pos = 4 + GET_32BIT(pubblob);
694 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
695 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
697 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
698 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
699 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
700 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
702 assert(e.start && iqmp.start); /* can't go wrong */
704 /* We also need d mod (p-1) and d mod (q-1). */
705 bd = bignum_from_bytes(d.start, d.bytes);
706 bp = bignum_from_bytes(p.start, p.bytes);
707 bq = bignum_from_bytes(q.start, q.bytes);
710 bdmp1 = bigmod(bd, bp);
711 bdmq1 = bigmod(bd, bq);
716 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
717 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
718 sparelen = dmp1.bytes + dmq1.bytes;
719 spareblob = smalloc(sparelen);
720 dmp1.start = spareblob;
721 dmq1.start = spareblob + dmp1.bytes;
722 for (i = 0; i < dmp1.bytes; i++)
723 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
724 for (i = 0; i < dmq1.bytes; i++)
725 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
729 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
740 header = "-----BEGIN RSA PRIVATE KEY-----\n";
741 footer = "-----END RSA PRIVATE KEY-----\n";
742 } else if (key->alg == &ssh_dss) {
744 struct mpint_pos p, q, g, y, x;
746 pos = 4 + GET_32BIT(pubblob);
747 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
748 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
749 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
750 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
752 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
754 assert(y.start && x.start); /* can't go wrong */
756 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
764 header = "-----BEGIN DSA PRIVATE KEY-----\n";
765 footer = "-----END DSA PRIVATE KEY-----\n";
767 assert(0); /* zoinks! */
771 * Now count up the total size of the ASN.1 encoded integers,
772 * so as to determine the length of the containing SEQUENCE.
775 for (i = 0; i < nnumbers; i++) {
776 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
777 len += numbers[i].bytes;
780 /* Now add on the SEQUENCE header. */
781 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
782 /* Round up to the cipher block size, ensuring we have at least one
783 * byte of padding (see below). */
786 outlen = (outlen+8) &~ 7;
789 * Now we know how big outblob needs to be. Allocate it.
791 outblob = smalloc(outlen);
794 * And write the data into it.
797 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
798 for (i = 0; i < nnumbers; i++) {
799 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
800 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
801 pos += numbers[i].bytes;
805 * Padding on OpenSSH keys is deterministic. The number of
806 * padding bytes is always more than zero, and always at most
807 * the cipher block length. The value of each padding byte is
808 * equal to the number of padding bytes. So a plaintext that's
809 * an exact multiple of the block size will be padded with 08
810 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
811 * plaintext one byte less than a multiple of the block size
812 * will be padded with just 01.
814 * This enables the OpenSSL key decryption function to strip
815 * off the padding algorithmically and return the unpadded
816 * plaintext to the next layer: it looks at the final byte, and
817 * then expects to find that many bytes at the end of the data
818 * with the same value. Those are all removed and the rest is
822 while (pos < outlen) {
823 outblob[pos++] = outlen - len;
831 * Invent an iv. Then derive encryption key from passphrase
834 * - let block A equal MD5(passphrase || iv)
835 * - let block B equal MD5(A || passphrase || iv)
836 * - block C would be MD5(B || passphrase || iv) and so on
837 * - encryption key is the first N bytes of A || B
839 struct MD5Context md5c;
840 unsigned char keybuf[32];
842 for (i = 0; i < 8; i++) iv[i] = random_byte();
845 MD5Update(&md5c, passphrase, strlen(passphrase));
846 MD5Update(&md5c, iv, 8);
847 MD5Final(keybuf, &md5c);
850 MD5Update(&md5c, keybuf, 16);
851 MD5Update(&md5c, passphrase, strlen(passphrase));
852 MD5Update(&md5c, iv, 8);
853 MD5Final(keybuf+16, &md5c);
856 * Now encrypt the key blob.
858 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
860 memset(&md5c, 0, sizeof(md5c));
861 memset(keybuf, 0, sizeof(keybuf));
865 * And save it. We'll use Unix line endings just in case it's
866 * subsequently transferred in binary mode.
868 fp = fopen(filename, "wb"); /* ensure Unix line endings */
873 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
874 for (i = 0; i < 8; i++)
875 fprintf(fp, "%02X", iv[i]);
878 base64_encode(fp, outblob, outlen, 64);
885 memset(outblob, 0, outlen);
889 memset(spareblob, 0, sparelen);
893 memset(privblob, 0, privlen);
897 memset(pubblob, 0, publen);
903 /* ----------------------------------------------------------------------
904 * Code to read ssh.com private keys.
908 * The format of the base64 blob is largely ssh2-packet-formatted,
909 * except that mpints are a bit different: they're more like the
910 * old ssh1 mpint. You have a 32-bit bit count N, followed by
911 * (N+7)/8 bytes of data.
913 * So. The blob contains:
915 * - uint32 0x3f6ff9eb (magic number)
916 * - uint32 size (total blob size)
917 * - string key-type (see below)
918 * - string cipher-type (tells you if key is encrypted)
919 * - string encrypted-blob
921 * (The first size field includes the size field itself and the
922 * magic number before it. All other size fields are ordinary ssh2
923 * strings, so the size field indicates how much data is to
926 * The encrypted blob, once decrypted, contains a single string
927 * which in turn contains the payload. (This allows padding to be
928 * added after that string while still making it clear where the
929 * real payload ends. Also it probably makes for a reasonable
932 * The payload blob, for an RSA key, contains:
935 * - mpint n (yes, the public and private stuff is intermixed)
936 * - mpint u (presumably inverse of p mod q)
937 * - mpint p (p is the smaller prime)
938 * - mpint q (q is the larger)
940 * For a DSA key, the payload blob contains:
948 * Alternatively, if the parameters are `predefined', that
949 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
950 * containing some predefined parameter specification. *shudder*,
951 * but I doubt we'll encounter this in real life.
953 * The key type strings are ghastly. The RSA key I looked at had a
956 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
958 * and the DSA key wasn't much better:
960 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
962 * It isn't clear that these will always be the same. I think it
963 * might be wise just to look at the `if-modn{sign{rsa' and
964 * `dl-modp{sign{dsa' prefixes.
966 * Finally, the encryption. The cipher-type string appears to be
967 * either `none' or `3des-cbc'. Looks as if this is SSH2-style
968 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
969 * from the passphrase by means of yet another hashing faff:
971 * - first 16 bytes are MD5(passphrase)
972 * - next 16 bytes are MD5(passphrase || first 16 bytes)
973 * - if there were more, they'd be MD5(passphrase || first 32),
977 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
980 char comment[256]; /* allowing any length is overkill */
981 unsigned char *keyblob;
982 int keyblob_len, keyblob_size;
985 struct sshcom_key *load_sshcom_key(char *filename)
987 struct sshcom_key *ret;
994 int base64_chars = 0;
996 ret = smalloc(sizeof(*ret));
997 ret->comment[0] = '\0';
999 ret->keyblob_len = ret->keyblob_size = 0;
1001 fp = fopen(filename, "r");
1003 errmsg = "Unable to open key file";
1006 if (!fgets(buffer, sizeof(buffer), fp) ||
1007 0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1008 errmsg = "File does not begin with ssh.com key header";
1014 if (!fgets(buffer, sizeof(buffer), fp)) {
1015 errmsg = "Unexpected end of file";
1018 if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1020 if ((p = strchr(buffer, ':')) != NULL) {
1022 errmsg = "Header found in body of key data";
1026 while (*p && isspace((unsigned char)*p)) p++;
1028 * Header lines can end in a trailing backslash for
1031 while ((len = strlen(p)) > (int)(sizeof(buffer) - (p-buffer) -1) ||
1032 p[len-1] != '\n' || p[len-2] == '\\') {
1033 if (len > (int)((p-buffer) + sizeof(buffer)-2)) {
1034 errmsg = "Header line too long to deal with";
1037 if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) {
1038 errmsg = "Unexpected end of file";
1042 p[strcspn(p, "\n")] = '\0';
1043 if (!strcmp(buffer, "Comment")) {
1044 /* Strip quotes in comment if present. */
1045 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1047 p[strlen(p)-1] = '\0';
1049 strncpy(ret->comment, p, sizeof(ret->comment));
1050 ret->comment[sizeof(ret->comment)-1] = '\0';
1056 while (isbase64(*p)) {
1057 base64_bit[base64_chars++] = *p;
1058 if (base64_chars == 4) {
1059 unsigned char out[3];
1063 len = base64_decode_atom(base64_bit, out);
1066 errmsg = "Invalid base64 encoding";
1070 if (ret->keyblob_len + len > ret->keyblob_size) {
1071 ret->keyblob_size = ret->keyblob_len + len + 256;
1072 ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size);
1075 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1076 ret->keyblob_len += len;
1084 if (ret->keyblob_len == 0 || !ret->keyblob) {
1085 errmsg = "Key body not present";
1094 memset(ret->keyblob, 0, ret->keyblob_size);
1095 sfree(ret->keyblob);
1097 memset(&ret, 0, sizeof(ret));
1103 int sshcom_encrypted(char *filename, char **comment)
1105 struct sshcom_key *key = load_sshcom_key(filename);
1106 int pos, len, answer;
1113 * Check magic number.
1115 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
1116 return 0; /* key is invalid */
1119 * Find the cipher-type string.
1123 if (key->keyblob_len < pos+4)
1124 goto done; /* key is far too short */
1125 pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */
1126 if (key->keyblob_len < pos+4)
1127 goto done; /* key is far too short */
1128 len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */
1129 if (key->keyblob_len < pos+4+len)
1130 goto done; /* cipher type string is incomplete */
1131 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1135 *comment = dupstr(key->comment);
1136 memset(key->keyblob, 0, key->keyblob_size);
1137 sfree(key->keyblob);
1138 memset(&key, 0, sizeof(key));
1143 int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1147 unsigned char *d = (unsigned char *) data;
1151 bits = GET_32BIT(d);
1153 bytes = (bits + 7) / 8;
1164 return len; /* ensure further calls fail as well */
1167 static int sshcom_put_mpint(void *target, void *data, int len)
1169 unsigned char *d = (unsigned char *)target;
1170 unsigned char *i = (unsigned char *)data;
1171 int bits = len * 8 - 1;
1174 if (*i & (1 << (bits & 7)))
1180 PUT_32BIT(d, bits+1);
1181 memcpy(d+4, i, len);
1185 struct ssh2_userkey *sshcom_read(char *filename, char *passphrase)
1187 struct sshcom_key *key = load_sshcom_key(filename);
1190 const char prefix_rsa[] = "if-modn{sign{rsa";
1191 const char prefix_dsa[] = "dl-modp{sign{dsa";
1192 enum { RSA, DSA } type;
1196 struct ssh2_userkey *ret = NULL, *retkey;
1197 const struct ssh_signkey *alg;
1198 unsigned char *blob = NULL;
1199 int blobsize, publen, privlen;
1205 * Check magic number.
1207 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1208 errmsg = "Key does not begin with magic number";
1213 * Determine the key type.
1216 if (key->keyblob_len < pos+4 ||
1217 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1218 errmsg = "Key blob does not contain a key type string";
1221 if (len > sizeof(prefix_rsa) - 1 &&
1222 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1224 } else if (len > sizeof(prefix_dsa) - 1 &&
1225 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1228 errmsg = "Key is of unknown type";
1234 * Determine the cipher type.
1236 if (key->keyblob_len < pos+4 ||
1237 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1238 errmsg = "Key blob does not contain a cipher type string";
1241 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1243 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1246 errmsg = "Key encryption is of unknown type";
1252 * Get hold of the encrypted part of the key.
1254 if (key->keyblob_len < pos+4 ||
1255 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1256 errmsg = "Key blob does not contain actual key data";
1259 ciphertext = key->keyblob + pos + 4;
1261 if (cipherlen == 0) {
1262 errmsg = "Length of key data is zero";
1267 * Decrypt it if necessary.
1271 * Derive encryption key from passphrase and iv/salt:
1273 * - let block A equal MD5(passphrase)
1274 * - let block B equal MD5(passphrase || A)
1275 * - block C would be MD5(passphrase || A || B) and so on
1276 * - encryption key is the first N bytes of A || B
1278 struct MD5Context md5c;
1279 unsigned char keybuf[32], iv[8];
1281 if (cipherlen % 8 != 0) {
1282 errmsg = "Encrypted part of key is not a multiple of cipher block"
1288 MD5Update(&md5c, passphrase, strlen(passphrase));
1289 MD5Final(keybuf, &md5c);
1292 MD5Update(&md5c, passphrase, strlen(passphrase));
1293 MD5Update(&md5c, keybuf, 16);
1294 MD5Final(keybuf+16, &md5c);
1297 * Now decrypt the key blob.
1299 memset(iv, 0, sizeof(iv));
1300 des3_decrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen);
1302 memset(&md5c, 0, sizeof(md5c));
1303 memset(keybuf, 0, sizeof(keybuf));
1306 * Hereafter we return WRONG_PASSPHRASE for any parsing
1307 * error. (But only if we've just tried to decrypt it!
1308 * Returning WRONG_PASSPHRASE for an unencrypted key is
1312 ret = SSH2_WRONG_PASSPHRASE;
1316 * Strip away the containing string to get to the real meat.
1318 len = GET_32BIT(ciphertext);
1319 if (len > cipherlen-4) {
1320 errmsg = "containing string was ill-formed";
1327 * Now we break down into RSA versus DSA. In either case we'll
1328 * construct public and private blobs in our own format, and
1329 * end up feeding them to alg->createkey().
1331 blobsize = cipherlen + 256;
1332 blob = smalloc(blobsize);
1335 struct mpint_pos n, e, d, u, p, q;
1337 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1338 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1339 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1340 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1341 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1342 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1344 errmsg = "key data did not contain six integers";
1350 pos += put_string(blob+pos, "ssh-rsa", 7);
1351 pos += put_mp(blob+pos, e.start, e.bytes);
1352 pos += put_mp(blob+pos, n.start, n.bytes);
1354 pos += put_string(blob+pos, d.start, d.bytes);
1355 pos += put_mp(blob+pos, q.start, q.bytes);
1356 pos += put_mp(blob+pos, p.start, p.bytes);
1357 pos += put_mp(blob+pos, u.start, u.bytes);
1358 privlen = pos - publen;
1359 } else if (type == DSA) {
1360 struct mpint_pos p, q, g, x, y;
1362 if (GET_32BIT(ciphertext) != 0) {
1363 errmsg = "predefined DSA parameters not supported";
1366 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1367 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1368 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1369 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1370 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1372 errmsg = "key data did not contain five integers";
1378 pos += put_string(blob+pos, "ssh-dss", 7);
1379 pos += put_mp(blob+pos, p.start, p.bytes);
1380 pos += put_mp(blob+pos, q.start, q.bytes);
1381 pos += put_mp(blob+pos, g.start, g.bytes);
1382 pos += put_mp(blob+pos, y.start, y.bytes);
1384 pos += put_mp(blob+pos, x.start, x.bytes);
1385 privlen = pos - publen;
1388 assert(privlen > 0); /* should have bombed by now if not */
1390 retkey = smalloc(sizeof(struct ssh2_userkey));
1392 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1393 if (!retkey->data) {
1395 errmsg = "unable to create key data structure";
1398 retkey->comment = dupstr(key->comment);
1400 errmsg = NULL; /* no error */
1405 memset(blob, 0, blobsize);
1408 memset(key->keyblob, 0, key->keyblob_size);
1409 sfree(key->keyblob);
1410 memset(&key, 0, sizeof(key));
1415 int sshcom_write(char *filename, struct ssh2_userkey *key, char *passphrase)
1417 unsigned char *pubblob, *privblob;
1418 int publen, privlen;
1419 unsigned char *outblob;
1421 struct mpint_pos numbers[6];
1422 int nnumbers, initial_zero, pos, lenpos, i;
1430 * Fetch the key blobs.
1432 pubblob = key->alg->public_blob(key->data, &publen);
1433 privblob = key->alg->private_blob(key->data, &privlen);
1437 * Find the sequence of integers to be encoded into the OpenSSH
1438 * key blob, and also decide on the header line.
1440 if (key->alg == &ssh_rsa) {
1442 struct mpint_pos n, e, d, p, q, iqmp;
1444 pos = 4 + GET_32BIT(pubblob);
1445 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1446 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1448 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1449 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1450 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1451 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1453 assert(e.start && iqmp.start); /* can't go wrong */
1464 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1465 } else if (key->alg == &ssh_dss) {
1467 struct mpint_pos p, q, g, y, x;
1469 pos = 4 + GET_32BIT(pubblob);
1470 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1471 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1472 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1473 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1475 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1477 assert(y.start && x.start); /* can't go wrong */
1487 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1489 assert(0); /* zoinks! */
1493 * Total size of key blob will be somewhere under 512 plus
1494 * combined length of integers. We'll calculate the more
1495 * precise size as we construct the blob.
1498 for (i = 0; i < nnumbers; i++)
1499 outlen += 4 + numbers[i].bytes;
1500 outblob = smalloc(outlen);
1503 * Create the unencrypted key blob.
1506 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1507 pos += 4; /* length field, fill in later */
1508 pos += put_string(outblob+pos, type, strlen(type));
1510 char *ciphertype = passphrase ? "3des-cbc" : "none";
1511 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1513 lenpos = pos; /* remember this position */
1514 pos += 4; /* encrypted-blob size */
1515 pos += 4; /* encrypted-payload size */
1517 PUT_32BIT(outblob+pos, 0);
1520 for (i = 0; i < nnumbers; i++)
1521 pos += sshcom_put_mpint(outblob+pos,
1522 numbers[i].start, numbers[i].bytes);
1523 /* Now wrap up the encrypted payload. */
1524 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1525 /* Pad encrypted blob to a multiple of cipher block size. */
1527 int padding = -(pos - (lenpos+4)) & 7;
1529 outblob[pos++] = random_byte();
1531 ciphertext = outblob+lenpos+4;
1532 cipherlen = pos - (lenpos+4);
1533 assert(!passphrase || cipherlen % 8 == 0);
1534 /* Wrap up the encrypted blob string. */
1535 PUT_32BIT(outblob+lenpos, cipherlen);
1536 /* And finally fill in the total length field. */
1537 PUT_32BIT(outblob+4, pos);
1539 assert(pos < outlen);
1546 * Derive encryption key from passphrase and iv/salt:
1548 * - let block A equal MD5(passphrase)
1549 * - let block B equal MD5(passphrase || A)
1550 * - block C would be MD5(passphrase || A || B) and so on
1551 * - encryption key is the first N bytes of A || B
1553 struct MD5Context md5c;
1554 unsigned char keybuf[32], iv[8];
1557 MD5Update(&md5c, passphrase, strlen(passphrase));
1558 MD5Final(keybuf, &md5c);
1561 MD5Update(&md5c, passphrase, strlen(passphrase));
1562 MD5Update(&md5c, keybuf, 16);
1563 MD5Final(keybuf+16, &md5c);
1566 * Now decrypt the key blob.
1568 memset(iv, 0, sizeof(iv));
1569 des3_encrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen);
1571 memset(&md5c, 0, sizeof(md5c));
1572 memset(keybuf, 0, sizeof(keybuf));
1576 * And save it. We'll use Unix line endings just in case it's
1577 * subsequently transferred in binary mode.
1579 fp = fopen(filename, "wb"); /* ensure Unix line endings */
1582 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1583 fprintf(fp, "Comment: \"");
1585 * Comment header is broken with backslash-newline if it goes
1586 * over 70 chars. Although it's surrounded by quotes, it
1587 * _doesn't_ escape backslashes or quotes within the string.
1588 * Don't ask me, I didn't design it.
1591 int slen = 60; /* starts at 60 due to "Comment: " */
1592 char *c = key->comment;
1593 while ((int)strlen(c) > slen) {
1594 fprintf(fp, "%.*s\\\n", slen, c);
1596 slen = 70; /* allow 70 chars on subsequent lines */
1598 fprintf(fp, "%s\"\n", c);
1600 base64_encode(fp, outblob, pos, 70);
1601 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1607 memset(outblob, 0, outlen);
1611 memset(privblob, 0, privlen);
1615 memset(pubblob, 0, publen);