2 * Code for PuTTY to import and export private key files in other
3 * SSH clients' formats.
15 int openssh_encrypted(const Filename *filename);
16 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
17 const char **errmsg_p);
18 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
21 int sshcom_encrypted(const Filename *filename, char **comment);
22 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
23 const char **errmsg_p);
24 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
28 * Given a key type, determine whether we know how to import it.
30 int import_possible(int type)
32 if (type == SSH_KEYTYPE_OPENSSH)
34 if (type == SSH_KEYTYPE_SSHCOM)
40 * Given a key type, determine what native key type
41 * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
44 int import_target_type(int type)
47 * There are no known foreign SSH-1 key formats.
49 return SSH_KEYTYPE_SSH2;
53 * Determine whether a foreign key is encrypted.
55 int import_encrypted(const Filename *filename, int type, char **comment)
57 if (type == SSH_KEYTYPE_OPENSSH) {
58 /* OpenSSH doesn't do key comments */
59 *comment = dupstr(filename_to_str(filename));
60 return openssh_encrypted(filename);
62 if (type == SSH_KEYTYPE_SSHCOM) {
63 return sshcom_encrypted(filename, comment);
69 * Import an SSH-1 key.
71 int import_ssh1(const Filename *filename, int type,
72 struct RSAKey *key, char *passphrase, const char **errmsg_p)
78 * Import an SSH-2 key.
80 struct ssh2_userkey *import_ssh2(const Filename *filename, int type,
81 char *passphrase, const char **errmsg_p)
83 if (type == SSH_KEYTYPE_OPENSSH)
84 return openssh_read(filename, passphrase, errmsg_p);
85 if (type == SSH_KEYTYPE_SSHCOM)
86 return sshcom_read(filename, passphrase, errmsg_p);
91 * Export an SSH-1 key.
93 int export_ssh1(const Filename *filename, int type, struct RSAKey *key,
100 * Export an SSH-2 key.
102 int export_ssh2(const Filename *filename, int type,
103 struct ssh2_userkey *key, char *passphrase)
105 if (type == SSH_KEYTYPE_OPENSSH)
106 return openssh_write(filename, key, passphrase);
107 if (type == SSH_KEYTYPE_SSHCOM)
108 return sshcom_write(filename, key, passphrase);
113 * Strip trailing CRs and LFs at the end of a line of text.
115 void strip_crlf(char *str)
117 char *p = str + strlen(str);
119 while (p > str && (p[-1] == '\r' || p[-1] == '\n'))
123 /* ----------------------------------------------------------------------
124 * Helper routines. (The base64 ones are defined in sshpubk.c.)
127 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
128 ((c) >= 'a' && (c) <= 'z') || \
129 ((c) >= '0' && (c) <= '9') || \
130 (c) == '+' || (c) == '/' || (c) == '=' \
134 * Read an ASN.1/BER identifier and length pair.
136 * Flags are a combination of the #defines listed below.
138 * Returns -1 if unsuccessful; otherwise returns the number of
139 * bytes used out of the source data.
142 /* ASN.1 tag classes. */
143 #define ASN1_CLASS_UNIVERSAL (0 << 6)
144 #define ASN1_CLASS_APPLICATION (1 << 6)
145 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
146 #define ASN1_CLASS_PRIVATE (3 << 6)
147 #define ASN1_CLASS_MASK (3 << 6)
149 /* Primitive versus constructed bit. */
150 #define ASN1_CONSTRUCTED (1 << 5)
152 static int ber_read_id_len(void *source, int sourcelen,
153 int *id, int *length, int *flags)
155 unsigned char *p = (unsigned char *) source;
160 *flags = (*p & 0xE0);
161 if ((*p & 0x1F) == 0x1F) {
167 *id = (*id << 7) | (*p & 0x7F);
185 *length = (*length << 8) | (*p++);
192 return p - (unsigned char *) source;
196 * Write an ASN.1/BER identifier and length pair. Returns the
197 * number of bytes consumed. Assumes dest contains enough space.
198 * Will avoid writing anything if dest is NULL, but still return
199 * amount of space required.
201 static int ber_write_id_len(void *dest, int id, int length, int flags)
203 unsigned char *d = (unsigned char *)dest;
208 * Identifier is one byte.
211 if (d) *d++ = id | flags;
215 * Identifier is multiple bytes: the first byte is 11111
216 * plus the flags, and subsequent bytes encode the value of
217 * the identifier, 7 bits at a time, with the top bit of
218 * each byte 1 except the last one which is 0.
221 if (d) *d++ = 0x1F | flags;
222 for (n = 1; (id >> (7*n)) > 0; n++)
223 continue; /* count the bytes */
226 if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
232 * Length is one byte.
235 if (d) *d++ = length;
239 * Length is multiple bytes. The first is 0x80 plus the
240 * number of subsequent bytes, and the subsequent bytes
241 * encode the actual length.
243 for (n = 1; (length >> (8*n)) > 0; n++)
244 continue; /* count the bytes */
246 if (d) *d++ = 0x80 | n;
249 if (d) *d++ = (length >> (8*n)) & 0xFF;
256 static int put_string(void *target, void *data, int len)
258 unsigned char *d = (unsigned char *)target;
261 memcpy(d+4, data, len);
265 static int put_mp(void *target, void *data, int len)
267 unsigned char *d = (unsigned char *)target;
268 unsigned char *i = (unsigned char *)data;
273 memcpy(d+5, data, len);
277 memcpy(d+4, data, len);
282 /* Simple structure to point to an mp-int within a blob. */
283 struct mpint_pos { void *start; int bytes; };
285 static int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
288 unsigned char *d = (unsigned char *) data;
292 bytes = toint(GET_32BIT(d));
293 if (bytes < 0 || len-4 < bytes)
303 return len; /* ensure further calls fail as well */
306 /* ----------------------------------------------------------------------
307 * Code to read and write OpenSSH private keys.
310 enum { OSSH_DSA, OSSH_RSA };
311 enum { OSSH_ENC_3DES, OSSH_ENC_AES };
314 int encrypted, encryption;
316 unsigned char *keyblob;
317 int keyblob_len, keyblob_size;
320 static struct openssh_key *load_openssh_key(const Filename *filename,
321 const char **errmsg_p)
323 struct openssh_key *ret;
329 int base64_chars = 0;
331 ret = snew(struct openssh_key);
333 ret->keyblob_len = ret->keyblob_size = 0;
335 memset(ret->iv, 0, sizeof(ret->iv));
337 fp = f_open(filename, "r", FALSE);
339 errmsg = "unable to open key file";
343 if (!(line = fgetline(fp))) {
344 errmsg = "unexpected end of file";
348 if (0 != strncmp(line, "-----BEGIN ", 11) ||
349 0 != strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) {
350 errmsg = "file does not begin with OpenSSH key header";
353 if (!strcmp(line, "-----BEGIN RSA PRIVATE KEY-----"))
354 ret->type = OSSH_RSA;
355 else if (!strcmp(line, "-----BEGIN DSA PRIVATE KEY-----"))
356 ret->type = OSSH_DSA;
358 errmsg = "unrecognised key type";
361 smemclr(line, strlen(line));
367 if (!(line = fgetline(fp))) {
368 errmsg = "unexpected end of file";
372 if (0 == strncmp(line, "-----END ", 9) &&
373 0 == strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) {
378 if ((p = strchr(line, ':')) != NULL) {
380 errmsg = "header found in body of key data";
384 while (*p && isspace((unsigned char)*p)) p++;
385 if (!strcmp(line, "Proc-Type")) {
386 if (p[0] != '4' || p[1] != ',') {
387 errmsg = "Proc-Type is not 4 (only 4 is supported)";
391 if (!strcmp(p, "ENCRYPTED"))
393 } else if (!strcmp(line, "DEK-Info")) {
396 if (!strncmp(p, "DES-EDE3-CBC,", 13)) {
397 ret->encryption = OSSH_ENC_3DES;
399 } else if (!strncmp(p, "AES-128-CBC,", 12)) {
400 ret->encryption = OSSH_ENC_AES;
403 errmsg = "unsupported cipher";
406 p = strchr(p, ',') + 1;/* always non-NULL, by above checks */
407 for (i = 0; i < ivlen; i++) {
408 if (1 != sscanf(p, "%2x", &j)) {
409 errmsg = "expected more iv data in DEK-Info";
416 errmsg = "more iv data than expected in DEK-Info";
424 while (isbase64(*p)) {
425 base64_bit[base64_chars++] = *p;
426 if (base64_chars == 4) {
427 unsigned char out[3];
432 len = base64_decode_atom(base64_bit, out);
435 errmsg = "invalid base64 encoding";
439 if (ret->keyblob_len + len > ret->keyblob_size) {
440 ret->keyblob_size = ret->keyblob_len + len + 256;
441 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
445 memcpy(ret->keyblob + ret->keyblob_len, out, len);
446 ret->keyblob_len += len;
448 smemclr(out, sizeof(out));
454 smemclr(line, strlen(line));
462 if (ret->keyblob_len == 0 || !ret->keyblob) {
463 errmsg = "key body not present";
467 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
468 errmsg = "encrypted key blob is not a multiple of cipher block size";
472 smemclr(base64_bit, sizeof(base64_bit));
473 if (errmsg_p) *errmsg_p = NULL;
478 smemclr(line, strlen(line));
482 smemclr(base64_bit, sizeof(base64_bit));
485 smemclr(ret->keyblob, ret->keyblob_size);
488 smemclr(ret, sizeof(*ret));
491 if (errmsg_p) *errmsg_p = errmsg;
496 int openssh_encrypted(const Filename *filename)
498 struct openssh_key *key = load_openssh_key(filename, NULL);
503 ret = key->encrypted;
504 smemclr(key->keyblob, key->keyblob_size);
506 smemclr(key, sizeof(*key));
511 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
512 const char **errmsg_p)
514 struct openssh_key *key = load_openssh_key(filename, errmsg_p);
515 struct ssh2_userkey *retkey;
517 int ret, id, len, flags;
519 struct ssh2_userkey *retval = NULL;
522 int blobsize = 0, blobptr, privptr;
531 if (key->encrypted) {
533 * Derive encryption key from passphrase and iv/salt:
535 * - let block A equal MD5(passphrase || iv)
536 * - let block B equal MD5(A || passphrase || iv)
537 * - block C would be MD5(B || passphrase || iv) and so on
538 * - encryption key is the first N bytes of A || B
540 * (Note that only 8 bytes of the iv are used for key
541 * derivation, even when the key is encrypted with AES and
542 * hence there are 16 bytes available.)
544 struct MD5Context md5c;
545 unsigned char keybuf[32];
548 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
549 MD5Update(&md5c, (unsigned char *)key->iv, 8);
550 MD5Final(keybuf, &md5c);
553 MD5Update(&md5c, keybuf, 16);
554 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
555 MD5Update(&md5c, (unsigned char *)key->iv, 8);
556 MD5Final(keybuf+16, &md5c);
559 * Now decrypt the key blob.
561 if (key->encryption == OSSH_ENC_3DES)
562 des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv,
563 key->keyblob, key->keyblob_len);
566 assert(key->encryption == OSSH_ENC_AES);
567 ctx = aes_make_context();
568 aes128_key(ctx, keybuf);
569 aes_iv(ctx, (unsigned char *)key->iv);
570 aes_ssh2_decrypt_blk(ctx, key->keyblob, key->keyblob_len);
571 aes_free_context(ctx);
574 smemclr(&md5c, sizeof(md5c));
575 smemclr(keybuf, sizeof(keybuf));
579 * Now we have a decrypted key blob, which contains an ASN.1
580 * encoded private key. We must now untangle the ASN.1.
582 * We expect the whole key blob to be formatted as a SEQUENCE
583 * (0x30 followed by a length code indicating that the rest of
584 * the blob is part of the sequence). Within that SEQUENCE we
585 * expect to see a bunch of INTEGERs. What those integers mean
586 * depends on the key type:
588 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
589 * dmp1, dmq1, iqmp in that order. (The last three are d mod
590 * (p-1), d mod (q-1), inverse of q mod p respectively.)
592 * - For DSA, we expect them to be 0, p, q, g, y, x in that
598 /* Expect the SEQUENCE header. Take its absence as a failure to
599 * decrypt, if the key was encrypted. */
600 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
602 if (ret < 0 || id != 16) {
603 errmsg = "ASN.1 decoding failure";
604 retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
608 /* Expect a load of INTEGERs. */
609 if (key->type == OSSH_RSA)
611 else if (key->type == OSSH_DSA)
614 num_integers = 0; /* placate compiler warnings */
616 if (key->type == OSSH_RSA || key->type == OSSH_DSA) {
618 * Space to create key blob in.
620 blobsize = 256+key->keyblob_len;
621 blob = snewn(blobsize, unsigned char);
623 if (key->type == OSSH_DSA)
624 memcpy(blob+4, "ssh-dss", 7);
625 else if (key->type == OSSH_RSA)
626 memcpy(blob+4, "ssh-rsa", 7);
630 for (i = 0; i < num_integers; i++) {
631 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
634 if (ret < 0 || id != 2 ||
635 key->keyblob+key->keyblob_len-p < len) {
636 errmsg = "ASN.1 decoding failure";
637 retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
643 * The first integer should be zero always (I think
644 * this is some sort of version indication).
646 if (len != 1 || p[0] != 0) {
647 errmsg = "version number mismatch";
650 } else if (key->type == OSSH_RSA) {
652 * Integers 1 and 2 go into the public blob but in the
653 * opposite order; integers 3, 4, 5 and 8 go into the
654 * private blob. The other two (6 and 7) are ignored.
657 /* Save the details for after we deal with number 2. */
660 } else if (i != 6 && i != 7) {
661 PUT_32BIT(blob+blobptr, len);
662 memcpy(blob+blobptr+4, p, len);
665 PUT_32BIT(blob+blobptr, modlen);
666 memcpy(blob+blobptr+4, modptr, modlen);
671 } else if (key->type == OSSH_DSA) {
673 * Integers 1-4 go into the public blob; integer 5 goes
674 * into the private blob.
676 PUT_32BIT(blob+blobptr, len);
677 memcpy(blob+blobptr+4, p, len);
683 /* Skip past the number. */
688 * Now put together the actual key. Simplest way to do this is
689 * to assemble our own key blobs and feed them to the createkey
690 * functions; this is a bit faffy but it does mean we get all
691 * the sanity checks for free.
693 assert(privptr > 0); /* should have bombed by now if not */
694 retkey = snew(struct ssh2_userkey);
695 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
696 retkey->data = retkey->alg->createkey(blob, privptr,
697 blob+privptr, blobptr-privptr);
700 errmsg = "unable to create key data structure";
705 assert(0 && "Bad key type from load_openssh_key");
708 retkey->comment = dupstr("imported-openssh-key");
709 errmsg = NULL; /* no error */
714 smemclr(blob, blobsize);
717 smemclr(key->keyblob, key->keyblob_size);
719 smemclr(key, sizeof(*key));
721 if (errmsg_p) *errmsg_p = errmsg;
725 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
728 unsigned char *pubblob, *privblob, *spareblob;
729 int publen, privlen, sparelen = 0;
730 unsigned char *outblob;
732 struct mpint_pos numbers[9];
733 int nnumbers, pos, len, seqlen, i;
734 char *header, *footer;
741 * Fetch the key blobs.
743 pubblob = key->alg->public_blob(key->data, &publen);
744 privblob = key->alg->private_blob(key->data, &privlen);
745 spareblob = outblob = NULL;
751 * Encode the OpenSSH key blob, and also decide on the header
754 if (key->alg == &ssh_rsa || key->alg == &ssh_dss) {
756 * The RSA and DSS handlers share some code because the two
757 * key types have very similar ASN.1 representations, as a
758 * plain SEQUENCE of big integers. So we set up a list of
759 * bignums per key type and then construct the actual blob in
760 * common code after that.
762 if (key->alg == &ssh_rsa) {
764 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
765 Bignum bd, bp, bq, bdmp1, bdmq1;
768 * These blobs were generated from inside PuTTY, so we needn't
769 * treat them as untrusted.
771 pos = 4 + GET_32BIT(pubblob);
772 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
773 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
775 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
776 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
777 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
778 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
780 assert(e.start && iqmp.start); /* can't go wrong */
782 /* We also need d mod (p-1) and d mod (q-1). */
783 bd = bignum_from_bytes(d.start, d.bytes);
784 bp = bignum_from_bytes(p.start, p.bytes);
785 bq = bignum_from_bytes(q.start, q.bytes);
788 bdmp1 = bigmod(bd, bp);
789 bdmq1 = bigmod(bd, bq);
794 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
795 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
796 sparelen = dmp1.bytes + dmq1.bytes;
797 spareblob = snewn(sparelen, unsigned char);
798 dmp1.start = spareblob;
799 dmq1.start = spareblob + dmp1.bytes;
800 for (i = 0; i < dmp1.bytes; i++)
801 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
802 for (i = 0; i < dmq1.bytes; i++)
803 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
807 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
818 header = "-----BEGIN RSA PRIVATE KEY-----\n";
819 footer = "-----END RSA PRIVATE KEY-----\n";
820 } else { /* ssh-dss */
822 struct mpint_pos p, q, g, y, x;
825 * These blobs were generated from inside PuTTY, so we needn't
826 * treat them as untrusted.
828 pos = 4 + GET_32BIT(pubblob);
829 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
830 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
831 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
832 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
834 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
836 assert(y.start && x.start); /* can't go wrong */
838 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
846 header = "-----BEGIN DSA PRIVATE KEY-----\n";
847 footer = "-----END DSA PRIVATE KEY-----\n";
851 * Now count up the total size of the ASN.1 encoded integers,
852 * so as to determine the length of the containing SEQUENCE.
855 for (i = 0; i < nnumbers; i++) {
856 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
857 len += numbers[i].bytes;
860 /* Now add on the SEQUENCE header. */
861 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
864 * Now we know how big outblob needs to be. Allocate it.
866 outblob = snewn(len, unsigned char);
869 * And write the data into it.
872 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
873 for (i = 0; i < nnumbers; i++) {
874 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
875 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
876 pos += numbers[i].bytes;
879 assert(0); /* zoinks! */
880 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
886 * For the moment, we still encrypt our OpenSSH keys using
890 struct MD5Context md5c;
891 unsigned char keybuf[32];
894 * Round up to the cipher block size, ensuring we have at
895 * least one byte of padding (see below).
897 outlen = (len+8) &~ 7;
899 unsigned char *tmp = snewn(outlen, unsigned char);
900 memcpy(tmp, outblob, len);
901 smemclr(outblob, len);
907 * Padding on OpenSSH keys is deterministic. The number of
908 * padding bytes is always more than zero, and always at most
909 * the cipher block length. The value of each padding byte is
910 * equal to the number of padding bytes. So a plaintext that's
911 * an exact multiple of the block size will be padded with 08
912 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
913 * plaintext one byte less than a multiple of the block size
914 * will be padded with just 01.
916 * This enables the OpenSSL key decryption function to strip
917 * off the padding algorithmically and return the unpadded
918 * plaintext to the next layer: it looks at the final byte, and
919 * then expects to find that many bytes at the end of the data
920 * with the same value. Those are all removed and the rest is
924 while (pos < outlen) {
925 outblob[pos++] = outlen - len;
929 * Invent an iv. Then derive encryption key from passphrase
932 * - let block A equal MD5(passphrase || iv)
933 * - let block B equal MD5(A || passphrase || iv)
934 * - block C would be MD5(B || passphrase || iv) and so on
935 * - encryption key is the first N bytes of A || B
937 for (i = 0; i < 8; i++) iv[i] = random_byte();
940 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
941 MD5Update(&md5c, iv, 8);
942 MD5Final(keybuf, &md5c);
945 MD5Update(&md5c, keybuf, 16);
946 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
947 MD5Update(&md5c, iv, 8);
948 MD5Final(keybuf+16, &md5c);
951 * Now encrypt the key blob.
953 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
955 smemclr(&md5c, sizeof(md5c));
956 smemclr(keybuf, sizeof(keybuf));
959 * If no encryption, the blob has exactly its original
966 * And save it. We'll use Unix line endings just in case it's
967 * subsequently transferred in binary mode.
969 fp = f_open(filename, "wb", TRUE); /* ensure Unix line endings */
974 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
975 for (i = 0; i < 8; i++)
976 fprintf(fp, "%02X", iv[i]);
979 base64_encode(fp, outblob, outlen, 64);
986 smemclr(outblob, outlen);
990 smemclr(spareblob, sparelen);
994 smemclr(privblob, privlen);
998 smemclr(pubblob, publen);
1004 /* ----------------------------------------------------------------------
1005 * Code to read ssh.com private keys.
1009 * The format of the base64 blob is largely SSH-2-packet-formatted,
1010 * except that mpints are a bit different: they're more like the
1011 * old SSH-1 mpint. You have a 32-bit bit count N, followed by
1012 * (N+7)/8 bytes of data.
1014 * So. The blob contains:
1016 * - uint32 0x3f6ff9eb (magic number)
1017 * - uint32 size (total blob size)
1018 * - string key-type (see below)
1019 * - string cipher-type (tells you if key is encrypted)
1020 * - string encrypted-blob
1022 * (The first size field includes the size field itself and the
1023 * magic number before it. All other size fields are ordinary SSH-2
1024 * strings, so the size field indicates how much data is to
1027 * The encrypted blob, once decrypted, contains a single string
1028 * which in turn contains the payload. (This allows padding to be
1029 * added after that string while still making it clear where the
1030 * real payload ends. Also it probably makes for a reasonable
1031 * decryption check.)
1033 * The payload blob, for an RSA key, contains:
1036 * - mpint n (yes, the public and private stuff is intermixed)
1037 * - mpint u (presumably inverse of p mod q)
1038 * - mpint p (p is the smaller prime)
1039 * - mpint q (q is the larger)
1041 * For a DSA key, the payload blob contains:
1049 * Alternatively, if the parameters are `predefined', that
1050 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
1051 * containing some predefined parameter specification. *shudder*,
1052 * but I doubt we'll encounter this in real life.
1054 * The key type strings are ghastly. The RSA key I looked at had a
1057 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
1059 * and the DSA key wasn't much better:
1061 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
1063 * It isn't clear that these will always be the same. I think it
1064 * might be wise just to look at the `if-modn{sign{rsa' and
1065 * `dl-modp{sign{dsa' prefixes.
1067 * Finally, the encryption. The cipher-type string appears to be
1068 * either `none' or `3des-cbc'. Looks as if this is SSH-2-style
1069 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
1070 * from the passphrase by means of yet another hashing faff:
1072 * - first 16 bytes are MD5(passphrase)
1073 * - next 16 bytes are MD5(passphrase || first 16 bytes)
1074 * - if there were more, they'd be MD5(passphrase || first 32),
1078 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
1081 char comment[256]; /* allowing any length is overkill */
1082 unsigned char *keyblob;
1083 int keyblob_len, keyblob_size;
1086 static struct sshcom_key *load_sshcom_key(const Filename *filename,
1087 const char **errmsg_p)
1089 struct sshcom_key *ret;
1096 int base64_chars = 0;
1098 ret = snew(struct sshcom_key);
1099 ret->comment[0] = '\0';
1100 ret->keyblob = NULL;
1101 ret->keyblob_len = ret->keyblob_size = 0;
1103 fp = f_open(filename, "r", FALSE);
1105 errmsg = "unable to open key file";
1108 if (!(line = fgetline(fp))) {
1109 errmsg = "unexpected end of file";
1113 if (0 != strcmp(line, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")) {
1114 errmsg = "file does not begin with ssh.com key header";
1117 smemclr(line, strlen(line));
1123 if (!(line = fgetline(fp))) {
1124 errmsg = "unexpected end of file";
1128 if (!strcmp(line, "---- END SSH2 ENCRYPTED PRIVATE KEY ----")) {
1133 if ((p = strchr(line, ':')) != NULL) {
1135 errmsg = "header found in body of key data";
1139 while (*p && isspace((unsigned char)*p)) p++;
1140 hdrstart = p - line;
1143 * Header lines can end in a trailing backslash for
1146 len = hdrstart + strlen(line+hdrstart);
1148 while (line[len-1] == '\\') {
1152 line2 = fgetline(fp);
1154 errmsg = "unexpected end of file";
1159 line2len = strlen(line2);
1160 line = sresize(line, len + line2len + 1, char);
1161 strcpy(line + len - 1, line2);
1162 len += line2len - 1;
1165 smemclr(line2, strlen(line2));
1169 p = line + hdrstart;
1171 if (!strcmp(line, "Comment")) {
1172 /* Strip quotes in comment if present. */
1173 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1175 p[strlen(p)-1] = '\0';
1177 strncpy(ret->comment, p, sizeof(ret->comment));
1178 ret->comment[sizeof(ret->comment)-1] = '\0';
1184 while (isbase64(*p)) {
1185 base64_bit[base64_chars++] = *p;
1186 if (base64_chars == 4) {
1187 unsigned char out[3];
1191 len = base64_decode_atom(base64_bit, out);
1194 errmsg = "invalid base64 encoding";
1198 if (ret->keyblob_len + len > ret->keyblob_size) {
1199 ret->keyblob_size = ret->keyblob_len + len + 256;
1200 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
1204 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1205 ret->keyblob_len += len;
1211 smemclr(line, strlen(line));
1216 if (ret->keyblob_len == 0 || !ret->keyblob) {
1217 errmsg = "key body not present";
1222 if (errmsg_p) *errmsg_p = NULL;
1230 smemclr(line, strlen(line));
1236 smemclr(ret->keyblob, ret->keyblob_size);
1237 sfree(ret->keyblob);
1239 smemclr(ret, sizeof(*ret));
1242 if (errmsg_p) *errmsg_p = errmsg;
1246 int sshcom_encrypted(const Filename *filename, char **comment)
1248 struct sshcom_key *key = load_sshcom_key(filename, NULL);
1249 int pos, len, answer;
1258 * Check magic number.
1260 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) {
1261 goto done; /* key is invalid */
1265 * Find the cipher-type string.
1268 if (key->keyblob_len < pos+4)
1269 goto done; /* key is far too short */
1270 len = toint(GET_32BIT(key->keyblob + pos));
1271 if (len < 0 || len > key->keyblob_len - pos - 4)
1272 goto done; /* key is far too short */
1273 pos += 4 + len; /* skip key type */
1274 len = toint(GET_32BIT(key->keyblob + pos)); /* find cipher-type length */
1275 if (len < 0 || len > key->keyblob_len - pos - 4)
1276 goto done; /* cipher type string is incomplete */
1277 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1282 *comment = dupstr(key->comment);
1283 smemclr(key->keyblob, key->keyblob_size);
1284 sfree(key->keyblob);
1285 smemclr(key, sizeof(*key));
1288 *comment = dupstr("");
1293 static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1295 unsigned bits, bytes;
1296 unsigned char *d = (unsigned char *) data;
1300 bits = GET_32BIT(d);
1302 bytes = (bits + 7) / 8;
1313 return len; /* ensure further calls fail as well */
1316 static int sshcom_put_mpint(void *target, void *data, int len)
1318 unsigned char *d = (unsigned char *)target;
1319 unsigned char *i = (unsigned char *)data;
1320 int bits = len * 8 - 1;
1323 if (*i & (1 << (bits & 7)))
1329 PUT_32BIT(d, bits+1);
1330 memcpy(d+4, i, len);
1334 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
1335 const char **errmsg_p)
1337 struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
1340 const char prefix_rsa[] = "if-modn{sign{rsa";
1341 const char prefix_dsa[] = "dl-modp{sign{dsa";
1342 enum { RSA, DSA } type;
1346 struct ssh2_userkey *ret = NULL, *retkey;
1347 const struct ssh_signkey *alg;
1348 unsigned char *blob = NULL;
1349 int blobsize = 0, publen, privlen;
1355 * Check magic number.
1357 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1358 errmsg = "key does not begin with magic number";
1363 * Determine the key type.
1366 if (key->keyblob_len < pos+4 ||
1367 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1368 len > key->keyblob_len - pos - 4) {
1369 errmsg = "key blob does not contain a key type string";
1372 if (len > sizeof(prefix_rsa) - 1 &&
1373 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1375 } else if (len > sizeof(prefix_dsa) - 1 &&
1376 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1379 errmsg = "key is of unknown type";
1385 * Determine the cipher type.
1387 if (key->keyblob_len < pos+4 ||
1388 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1389 len > key->keyblob_len - pos - 4) {
1390 errmsg = "key blob does not contain a cipher type string";
1393 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1395 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1398 errmsg = "key encryption is of unknown type";
1404 * Get hold of the encrypted part of the key.
1406 if (key->keyblob_len < pos+4 ||
1407 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1408 len > key->keyblob_len - pos - 4) {
1409 errmsg = "key blob does not contain actual key data";
1412 ciphertext = (char *)key->keyblob + pos + 4;
1414 if (cipherlen == 0) {
1415 errmsg = "length of key data is zero";
1420 * Decrypt it if necessary.
1424 * Derive encryption key from passphrase and iv/salt:
1426 * - let block A equal MD5(passphrase)
1427 * - let block B equal MD5(passphrase || A)
1428 * - block C would be MD5(passphrase || A || B) and so on
1429 * - encryption key is the first N bytes of A || B
1431 struct MD5Context md5c;
1432 unsigned char keybuf[32], iv[8];
1434 if (cipherlen % 8 != 0) {
1435 errmsg = "encrypted part of key is not a multiple of cipher block"
1441 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1442 MD5Final(keybuf, &md5c);
1445 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1446 MD5Update(&md5c, keybuf, 16);
1447 MD5Final(keybuf+16, &md5c);
1450 * Now decrypt the key blob.
1452 memset(iv, 0, sizeof(iv));
1453 des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1456 smemclr(&md5c, sizeof(md5c));
1457 smemclr(keybuf, sizeof(keybuf));
1460 * Hereafter we return WRONG_PASSPHRASE for any parsing
1461 * error. (But only if we've just tried to decrypt it!
1462 * Returning WRONG_PASSPHRASE for an unencrypted key is
1466 ret = SSH2_WRONG_PASSPHRASE;
1470 * Strip away the containing string to get to the real meat.
1472 len = toint(GET_32BIT(ciphertext));
1473 if (len < 0 || len > cipherlen-4) {
1474 errmsg = "containing string was ill-formed";
1481 * Now we break down into RSA versus DSA. In either case we'll
1482 * construct public and private blobs in our own format, and
1483 * end up feeding them to alg->createkey().
1485 blobsize = cipherlen + 256;
1486 blob = snewn(blobsize, unsigned char);
1489 struct mpint_pos n, e, d, u, p, q;
1491 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1492 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1493 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1494 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1495 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1496 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1498 errmsg = "key data did not contain six integers";
1504 pos += put_string(blob+pos, "ssh-rsa", 7);
1505 pos += put_mp(blob+pos, e.start, e.bytes);
1506 pos += put_mp(blob+pos, n.start, n.bytes);
1508 pos += put_string(blob+pos, d.start, d.bytes);
1509 pos += put_mp(blob+pos, q.start, q.bytes);
1510 pos += put_mp(blob+pos, p.start, p.bytes);
1511 pos += put_mp(blob+pos, u.start, u.bytes);
1512 privlen = pos - publen;
1514 struct mpint_pos p, q, g, x, y;
1517 assert(type == DSA); /* the only other option from the if above */
1519 if (GET_32BIT(ciphertext) != 0) {
1520 errmsg = "predefined DSA parameters not supported";
1523 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1524 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1525 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1526 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1527 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1529 errmsg = "key data did not contain five integers";
1535 pos += put_string(blob+pos, "ssh-dss", 7);
1536 pos += put_mp(blob+pos, p.start, p.bytes);
1537 pos += put_mp(blob+pos, q.start, q.bytes);
1538 pos += put_mp(blob+pos, g.start, g.bytes);
1539 pos += put_mp(blob+pos, y.start, y.bytes);
1541 pos += put_mp(blob+pos, x.start, x.bytes);
1542 privlen = pos - publen;
1545 assert(privlen > 0); /* should have bombed by now if not */
1547 retkey = snew(struct ssh2_userkey);
1549 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1550 if (!retkey->data) {
1552 errmsg = "unable to create key data structure";
1555 retkey->comment = dupstr(key->comment);
1557 errmsg = NULL; /* no error */
1562 smemclr(blob, blobsize);
1565 smemclr(key->keyblob, key->keyblob_size);
1566 sfree(key->keyblob);
1567 smemclr(key, sizeof(*key));
1569 if (errmsg_p) *errmsg_p = errmsg;
1573 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
1576 unsigned char *pubblob, *privblob;
1577 int publen, privlen;
1578 unsigned char *outblob;
1580 struct mpint_pos numbers[6];
1581 int nnumbers, initial_zero, pos, lenpos, i;
1589 * Fetch the key blobs.
1591 pubblob = key->alg->public_blob(key->data, &publen);
1592 privblob = key->alg->private_blob(key->data, &privlen);
1596 * Find the sequence of integers to be encoded into the OpenSSH
1597 * key blob, and also decide on the header line.
1599 if (key->alg == &ssh_rsa) {
1601 struct mpint_pos n, e, d, p, q, iqmp;
1604 * These blobs were generated from inside PuTTY, so we needn't
1605 * treat them as untrusted.
1607 pos = 4 + GET_32BIT(pubblob);
1608 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1609 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1611 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1612 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1613 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1614 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1616 assert(e.start && iqmp.start); /* can't go wrong */
1627 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1628 } else if (key->alg == &ssh_dss) {
1630 struct mpint_pos p, q, g, y, x;
1633 * These blobs were generated from inside PuTTY, so we needn't
1634 * treat them as untrusted.
1636 pos = 4 + GET_32BIT(pubblob);
1637 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1638 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1639 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1640 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1642 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1644 assert(y.start && x.start); /* can't go wrong */
1654 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1656 assert(0); /* zoinks! */
1657 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
1661 * Total size of key blob will be somewhere under 512 plus
1662 * combined length of integers. We'll calculate the more
1663 * precise size as we construct the blob.
1666 for (i = 0; i < nnumbers; i++)
1667 outlen += 4 + numbers[i].bytes;
1668 outblob = snewn(outlen, unsigned char);
1671 * Create the unencrypted key blob.
1674 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1675 pos += 4; /* length field, fill in later */
1676 pos += put_string(outblob+pos, type, strlen(type));
1678 char *ciphertype = passphrase ? "3des-cbc" : "none";
1679 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1681 lenpos = pos; /* remember this position */
1682 pos += 4; /* encrypted-blob size */
1683 pos += 4; /* encrypted-payload size */
1685 PUT_32BIT(outblob+pos, 0);
1688 for (i = 0; i < nnumbers; i++)
1689 pos += sshcom_put_mpint(outblob+pos,
1690 numbers[i].start, numbers[i].bytes);
1691 /* Now wrap up the encrypted payload. */
1692 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1693 /* Pad encrypted blob to a multiple of cipher block size. */
1695 int padding = -(pos - (lenpos+4)) & 7;
1697 outblob[pos++] = random_byte();
1699 ciphertext = (char *)outblob+lenpos+4;
1700 cipherlen = pos - (lenpos+4);
1701 assert(!passphrase || cipherlen % 8 == 0);
1702 /* Wrap up the encrypted blob string. */
1703 PUT_32BIT(outblob+lenpos, cipherlen);
1704 /* And finally fill in the total length field. */
1705 PUT_32BIT(outblob+4, pos);
1707 assert(pos < outlen);
1714 * Derive encryption key from passphrase and iv/salt:
1716 * - let block A equal MD5(passphrase)
1717 * - let block B equal MD5(passphrase || A)
1718 * - block C would be MD5(passphrase || A || B) and so on
1719 * - encryption key is the first N bytes of A || B
1721 struct MD5Context md5c;
1722 unsigned char keybuf[32], iv[8];
1725 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1726 MD5Final(keybuf, &md5c);
1729 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1730 MD5Update(&md5c, keybuf, 16);
1731 MD5Final(keybuf+16, &md5c);
1734 * Now decrypt the key blob.
1736 memset(iv, 0, sizeof(iv));
1737 des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1740 smemclr(&md5c, sizeof(md5c));
1741 smemclr(keybuf, sizeof(keybuf));
1745 * And save it. We'll use Unix line endings just in case it's
1746 * subsequently transferred in binary mode.
1748 fp = f_open(filename, "wb", TRUE); /* ensure Unix line endings */
1751 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1752 fprintf(fp, "Comment: \"");
1754 * Comment header is broken with backslash-newline if it goes
1755 * over 70 chars. Although it's surrounded by quotes, it
1756 * _doesn't_ escape backslashes or quotes within the string.
1757 * Don't ask me, I didn't design it.
1760 int slen = 60; /* starts at 60 due to "Comment: " */
1761 char *c = key->comment;
1762 while ((int)strlen(c) > slen) {
1763 fprintf(fp, "%.*s\\\n", slen, c);
1765 slen = 70; /* allow 70 chars on subsequent lines */
1767 fprintf(fp, "%s\"\n", c);
1769 base64_encode(fp, outblob, pos, 70);
1770 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1776 smemclr(outblob, outlen);
1780 smemclr(privblob, privlen);
1784 smemclr(pubblob, publen);