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 */
617 * Space to create key blob in.
619 blobsize = 256+key->keyblob_len;
620 blob = snewn(blobsize, unsigned char);
622 if (key->type == OSSH_DSA)
623 memcpy(blob+4, "ssh-dss", 7);
624 else if (key->type == OSSH_RSA)
625 memcpy(blob+4, "ssh-rsa", 7);
629 for (i = 0; i < num_integers; i++) {
630 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
633 if (ret < 0 || id != 2 ||
634 key->keyblob+key->keyblob_len-p < len) {
635 errmsg = "ASN.1 decoding failure";
636 retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
642 * The first integer should be zero always (I think
643 * this is some sort of version indication).
645 if (len != 1 || p[0] != 0) {
646 errmsg = "version number mismatch";
649 } else if (key->type == OSSH_RSA) {
651 * Integers 1 and 2 go into the public blob but in the
652 * opposite order; integers 3, 4, 5 and 8 go into the
653 * private blob. The other two (6 and 7) are ignored.
656 /* Save the details for after we deal with number 2. */
659 } else if (i != 6 && i != 7) {
660 PUT_32BIT(blob+blobptr, len);
661 memcpy(blob+blobptr+4, p, len);
664 PUT_32BIT(blob+blobptr, modlen);
665 memcpy(blob+blobptr+4, modptr, modlen);
670 } else if (key->type == OSSH_DSA) {
672 * Integers 1-4 go into the public blob; integer 5 goes
673 * into the private blob.
675 PUT_32BIT(blob+blobptr, len);
676 memcpy(blob+blobptr+4, p, len);
682 /* Skip past the number. */
687 * Now put together the actual key. Simplest way to do this is
688 * to assemble our own key blobs and feed them to the createkey
689 * functions; this is a bit faffy but it does mean we get all
690 * the sanity checks for free.
692 assert(privptr > 0); /* should have bombed by now if not */
693 retkey = snew(struct ssh2_userkey);
694 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
695 retkey->data = retkey->alg->createkey(blob, privptr,
696 blob+privptr, blobptr-privptr);
699 errmsg = "unable to create key data structure";
703 retkey->comment = dupstr("imported-openssh-key");
704 errmsg = NULL; /* no error */
709 smemclr(blob, blobsize);
712 smemclr(key->keyblob, key->keyblob_size);
714 smemclr(key, sizeof(*key));
716 if (errmsg_p) *errmsg_p = errmsg;
720 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
723 unsigned char *pubblob, *privblob, *spareblob;
724 int publen, privlen, sparelen = 0;
725 unsigned char *outblob;
727 struct mpint_pos numbers[9];
728 int nnumbers, pos, len, seqlen, i;
729 char *header, *footer;
736 * Fetch the key blobs.
738 pubblob = key->alg->public_blob(key->data, &publen);
739 privblob = key->alg->private_blob(key->data, &privlen);
740 spareblob = outblob = NULL;
743 * Find the sequence of integers to be encoded into the OpenSSH
744 * key blob, and also decide on the header line.
746 if (key->alg == &ssh_rsa) {
748 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
749 Bignum bd, bp, bq, bdmp1, bdmq1;
752 * These blobs were generated from inside PuTTY, so we needn't
753 * treat them as untrusted.
755 pos = 4 + GET_32BIT(pubblob);
756 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
757 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
759 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
760 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
761 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
762 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
764 assert(e.start && iqmp.start); /* can't go wrong */
766 /* We also need d mod (p-1) and d mod (q-1). */
767 bd = bignum_from_bytes(d.start, d.bytes);
768 bp = bignum_from_bytes(p.start, p.bytes);
769 bq = bignum_from_bytes(q.start, q.bytes);
772 bdmp1 = bigmod(bd, bp);
773 bdmq1 = bigmod(bd, bq);
778 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
779 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
780 sparelen = dmp1.bytes + dmq1.bytes;
781 spareblob = snewn(sparelen, unsigned char);
782 dmp1.start = spareblob;
783 dmq1.start = spareblob + dmp1.bytes;
784 for (i = 0; i < dmp1.bytes; i++)
785 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
786 for (i = 0; i < dmq1.bytes; i++)
787 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
791 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
802 header = "-----BEGIN RSA PRIVATE KEY-----\n";
803 footer = "-----END RSA PRIVATE KEY-----\n";
804 } else if (key->alg == &ssh_dss) {
806 struct mpint_pos p, q, g, y, x;
809 * These blobs were generated from inside PuTTY, so we needn't
810 * treat them as untrusted.
812 pos = 4 + GET_32BIT(pubblob);
813 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
814 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
815 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
816 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
818 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
820 assert(y.start && x.start); /* can't go wrong */
822 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
830 header = "-----BEGIN DSA PRIVATE KEY-----\n";
831 footer = "-----END DSA PRIVATE KEY-----\n";
833 assert(0); /* zoinks! */
834 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
838 * Now count up the total size of the ASN.1 encoded integers,
839 * so as to determine the length of the containing SEQUENCE.
842 for (i = 0; i < nnumbers; i++) {
843 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
844 len += numbers[i].bytes;
847 /* Now add on the SEQUENCE header. */
848 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
849 /* Round up to the cipher block size, ensuring we have at least one
850 * byte of padding (see below). */
853 outlen = (outlen+8) &~ 7;
856 * Now we know how big outblob needs to be. Allocate it.
858 outblob = snewn(outlen, unsigned char);
861 * And write the data into it.
864 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
865 for (i = 0; i < nnumbers; i++) {
866 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
867 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
868 pos += numbers[i].bytes;
872 * Padding on OpenSSH keys is deterministic. The number of
873 * padding bytes is always more than zero, and always at most
874 * the cipher block length. The value of each padding byte is
875 * equal to the number of padding bytes. So a plaintext that's
876 * an exact multiple of the block size will be padded with 08
877 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
878 * plaintext one byte less than a multiple of the block size
879 * will be padded with just 01.
881 * This enables the OpenSSL key decryption function to strip
882 * off the padding algorithmically and return the unpadded
883 * plaintext to the next layer: it looks at the final byte, and
884 * then expects to find that many bytes at the end of the data
885 * with the same value. Those are all removed and the rest is
889 while (pos < outlen) {
890 outblob[pos++] = outlen - len;
896 * For the moment, we still encrypt our OpenSSH keys using
901 * Invent an iv. Then derive encryption key from passphrase
904 * - let block A equal MD5(passphrase || iv)
905 * - let block B equal MD5(A || passphrase || iv)
906 * - block C would be MD5(B || passphrase || iv) and so on
907 * - encryption key is the first N bytes of A || B
909 struct MD5Context md5c;
910 unsigned char keybuf[32];
912 for (i = 0; i < 8; i++) iv[i] = random_byte();
915 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
916 MD5Update(&md5c, iv, 8);
917 MD5Final(keybuf, &md5c);
920 MD5Update(&md5c, keybuf, 16);
921 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
922 MD5Update(&md5c, iv, 8);
923 MD5Final(keybuf+16, &md5c);
926 * Now encrypt the key blob.
928 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
930 smemclr(&md5c, sizeof(md5c));
931 smemclr(keybuf, sizeof(keybuf));
935 * And save it. We'll use Unix line endings just in case it's
936 * subsequently transferred in binary mode.
938 fp = f_open(filename, "wb", TRUE); /* ensure Unix line endings */
943 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
944 for (i = 0; i < 8; i++)
945 fprintf(fp, "%02X", iv[i]);
948 base64_encode(fp, outblob, outlen, 64);
955 smemclr(outblob, outlen);
959 smemclr(spareblob, sparelen);
963 smemclr(privblob, privlen);
967 smemclr(pubblob, publen);
973 /* ----------------------------------------------------------------------
974 * Code to read ssh.com private keys.
978 * The format of the base64 blob is largely SSH-2-packet-formatted,
979 * except that mpints are a bit different: they're more like the
980 * old SSH-1 mpint. You have a 32-bit bit count N, followed by
981 * (N+7)/8 bytes of data.
983 * So. The blob contains:
985 * - uint32 0x3f6ff9eb (magic number)
986 * - uint32 size (total blob size)
987 * - string key-type (see below)
988 * - string cipher-type (tells you if key is encrypted)
989 * - string encrypted-blob
991 * (The first size field includes the size field itself and the
992 * magic number before it. All other size fields are ordinary SSH-2
993 * strings, so the size field indicates how much data is to
996 * The encrypted blob, once decrypted, contains a single string
997 * which in turn contains the payload. (This allows padding to be
998 * added after that string while still making it clear where the
999 * real payload ends. Also it probably makes for a reasonable
1000 * decryption check.)
1002 * The payload blob, for an RSA key, contains:
1005 * - mpint n (yes, the public and private stuff is intermixed)
1006 * - mpint u (presumably inverse of p mod q)
1007 * - mpint p (p is the smaller prime)
1008 * - mpint q (q is the larger)
1010 * For a DSA key, the payload blob contains:
1018 * Alternatively, if the parameters are `predefined', that
1019 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
1020 * containing some predefined parameter specification. *shudder*,
1021 * but I doubt we'll encounter this in real life.
1023 * The key type strings are ghastly. The RSA key I looked at had a
1026 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
1028 * and the DSA key wasn't much better:
1030 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
1032 * It isn't clear that these will always be the same. I think it
1033 * might be wise just to look at the `if-modn{sign{rsa' and
1034 * `dl-modp{sign{dsa' prefixes.
1036 * Finally, the encryption. The cipher-type string appears to be
1037 * either `none' or `3des-cbc'. Looks as if this is SSH-2-style
1038 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
1039 * from the passphrase by means of yet another hashing faff:
1041 * - first 16 bytes are MD5(passphrase)
1042 * - next 16 bytes are MD5(passphrase || first 16 bytes)
1043 * - if there were more, they'd be MD5(passphrase || first 32),
1047 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
1050 char comment[256]; /* allowing any length is overkill */
1051 unsigned char *keyblob;
1052 int keyblob_len, keyblob_size;
1055 static struct sshcom_key *load_sshcom_key(const Filename *filename,
1056 const char **errmsg_p)
1058 struct sshcom_key *ret;
1065 int base64_chars = 0;
1067 ret = snew(struct sshcom_key);
1068 ret->comment[0] = '\0';
1069 ret->keyblob = NULL;
1070 ret->keyblob_len = ret->keyblob_size = 0;
1072 fp = f_open(filename, "r", FALSE);
1074 errmsg = "unable to open key file";
1077 if (!(line = fgetline(fp))) {
1078 errmsg = "unexpected end of file";
1082 if (0 != strcmp(line, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")) {
1083 errmsg = "file does not begin with ssh.com key header";
1086 smemclr(line, strlen(line));
1092 if (!(line = fgetline(fp))) {
1093 errmsg = "unexpected end of file";
1097 if (!strcmp(line, "---- END SSH2 ENCRYPTED PRIVATE KEY ----")) {
1102 if ((p = strchr(line, ':')) != NULL) {
1104 errmsg = "header found in body of key data";
1108 while (*p && isspace((unsigned char)*p)) p++;
1109 hdrstart = p - line;
1112 * Header lines can end in a trailing backslash for
1115 len = hdrstart + strlen(line+hdrstart);
1117 while (line[len-1] == '\\') {
1121 line2 = fgetline(fp);
1123 errmsg = "unexpected end of file";
1128 line2len = strlen(line2);
1129 line = sresize(line, len + line2len + 1, char);
1130 strcpy(line + len - 1, line2);
1131 len += line2len - 1;
1134 smemclr(line2, strlen(line2));
1138 p = line + hdrstart;
1140 if (!strcmp(line, "Comment")) {
1141 /* Strip quotes in comment if present. */
1142 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1144 p[strlen(p)-1] = '\0';
1146 strncpy(ret->comment, p, sizeof(ret->comment));
1147 ret->comment[sizeof(ret->comment)-1] = '\0';
1153 while (isbase64(*p)) {
1154 base64_bit[base64_chars++] = *p;
1155 if (base64_chars == 4) {
1156 unsigned char out[3];
1160 len = base64_decode_atom(base64_bit, out);
1163 errmsg = "invalid base64 encoding";
1167 if (ret->keyblob_len + len > ret->keyblob_size) {
1168 ret->keyblob_size = ret->keyblob_len + len + 256;
1169 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
1173 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1174 ret->keyblob_len += len;
1180 smemclr(line, strlen(line));
1185 if (ret->keyblob_len == 0 || !ret->keyblob) {
1186 errmsg = "key body not present";
1191 if (errmsg_p) *errmsg_p = NULL;
1199 smemclr(line, strlen(line));
1205 smemclr(ret->keyblob, ret->keyblob_size);
1206 sfree(ret->keyblob);
1208 smemclr(ret, sizeof(*ret));
1211 if (errmsg_p) *errmsg_p = errmsg;
1215 int sshcom_encrypted(const Filename *filename, char **comment)
1217 struct sshcom_key *key = load_sshcom_key(filename, NULL);
1218 int pos, len, answer;
1227 * Check magic number.
1229 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) {
1230 goto done; /* key is invalid */
1234 * Find the cipher-type string.
1237 if (key->keyblob_len < pos+4)
1238 goto done; /* key is far too short */
1239 len = toint(GET_32BIT(key->keyblob + pos));
1240 if (len < 0 || len > key->keyblob_len - pos - 4)
1241 goto done; /* key is far too short */
1242 pos += 4 + len; /* skip key type */
1243 len = toint(GET_32BIT(key->keyblob + pos)); /* find cipher-type length */
1244 if (len < 0 || len > key->keyblob_len - pos - 4)
1245 goto done; /* cipher type string is incomplete */
1246 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1251 *comment = dupstr(key->comment);
1252 smemclr(key->keyblob, key->keyblob_size);
1253 sfree(key->keyblob);
1254 smemclr(key, sizeof(*key));
1257 *comment = dupstr("");
1262 static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1264 unsigned bits, bytes;
1265 unsigned char *d = (unsigned char *) data;
1269 bits = GET_32BIT(d);
1271 bytes = (bits + 7) / 8;
1282 return len; /* ensure further calls fail as well */
1285 static int sshcom_put_mpint(void *target, void *data, int len)
1287 unsigned char *d = (unsigned char *)target;
1288 unsigned char *i = (unsigned char *)data;
1289 int bits = len * 8 - 1;
1292 if (*i & (1 << (bits & 7)))
1298 PUT_32BIT(d, bits+1);
1299 memcpy(d+4, i, len);
1303 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
1304 const char **errmsg_p)
1306 struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
1309 const char prefix_rsa[] = "if-modn{sign{rsa";
1310 const char prefix_dsa[] = "dl-modp{sign{dsa";
1311 enum { RSA, DSA } type;
1315 struct ssh2_userkey *ret = NULL, *retkey;
1316 const struct ssh_signkey *alg;
1317 unsigned char *blob = NULL;
1318 int blobsize = 0, publen, privlen;
1324 * Check magic number.
1326 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1327 errmsg = "key does not begin with magic number";
1332 * Determine the key type.
1335 if (key->keyblob_len < pos+4 ||
1336 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1337 len > key->keyblob_len - pos - 4) {
1338 errmsg = "key blob does not contain a key type string";
1341 if (len > sizeof(prefix_rsa) - 1 &&
1342 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1344 } else if (len > sizeof(prefix_dsa) - 1 &&
1345 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1348 errmsg = "key is of unknown type";
1354 * Determine the cipher type.
1356 if (key->keyblob_len < pos+4 ||
1357 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1358 len > key->keyblob_len - pos - 4) {
1359 errmsg = "key blob does not contain a cipher type string";
1362 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1364 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1367 errmsg = "key encryption is of unknown type";
1373 * Get hold of the encrypted part of the key.
1375 if (key->keyblob_len < pos+4 ||
1376 (len = toint(GET_32BIT(key->keyblob + pos))) < 0 ||
1377 len > key->keyblob_len - pos - 4) {
1378 errmsg = "key blob does not contain actual key data";
1381 ciphertext = (char *)key->keyblob + pos + 4;
1383 if (cipherlen == 0) {
1384 errmsg = "length of key data is zero";
1389 * Decrypt it if necessary.
1393 * Derive encryption key from passphrase and iv/salt:
1395 * - let block A equal MD5(passphrase)
1396 * - let block B equal MD5(passphrase || A)
1397 * - block C would be MD5(passphrase || A || B) and so on
1398 * - encryption key is the first N bytes of A || B
1400 struct MD5Context md5c;
1401 unsigned char keybuf[32], iv[8];
1403 if (cipherlen % 8 != 0) {
1404 errmsg = "encrypted part of key is not a multiple of cipher block"
1410 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1411 MD5Final(keybuf, &md5c);
1414 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1415 MD5Update(&md5c, keybuf, 16);
1416 MD5Final(keybuf+16, &md5c);
1419 * Now decrypt the key blob.
1421 memset(iv, 0, sizeof(iv));
1422 des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1425 smemclr(&md5c, sizeof(md5c));
1426 smemclr(keybuf, sizeof(keybuf));
1429 * Hereafter we return WRONG_PASSPHRASE for any parsing
1430 * error. (But only if we've just tried to decrypt it!
1431 * Returning WRONG_PASSPHRASE for an unencrypted key is
1435 ret = SSH2_WRONG_PASSPHRASE;
1439 * Strip away the containing string to get to the real meat.
1441 len = toint(GET_32BIT(ciphertext));
1442 if (len < 0 || len > cipherlen-4) {
1443 errmsg = "containing string was ill-formed";
1450 * Now we break down into RSA versus DSA. In either case we'll
1451 * construct public and private blobs in our own format, and
1452 * end up feeding them to alg->createkey().
1454 blobsize = cipherlen + 256;
1455 blob = snewn(blobsize, unsigned char);
1458 struct mpint_pos n, e, d, u, p, q;
1460 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1461 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1462 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1463 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1464 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1465 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1467 errmsg = "key data did not contain six integers";
1473 pos += put_string(blob+pos, "ssh-rsa", 7);
1474 pos += put_mp(blob+pos, e.start, e.bytes);
1475 pos += put_mp(blob+pos, n.start, n.bytes);
1477 pos += put_string(blob+pos, d.start, d.bytes);
1478 pos += put_mp(blob+pos, q.start, q.bytes);
1479 pos += put_mp(blob+pos, p.start, p.bytes);
1480 pos += put_mp(blob+pos, u.start, u.bytes);
1481 privlen = pos - publen;
1483 struct mpint_pos p, q, g, x, y;
1486 assert(type == DSA); /* the only other option from the if above */
1488 if (GET_32BIT(ciphertext) != 0) {
1489 errmsg = "predefined DSA parameters not supported";
1492 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1493 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1494 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1495 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1496 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1498 errmsg = "key data did not contain five integers";
1504 pos += put_string(blob+pos, "ssh-dss", 7);
1505 pos += put_mp(blob+pos, p.start, p.bytes);
1506 pos += put_mp(blob+pos, q.start, q.bytes);
1507 pos += put_mp(blob+pos, g.start, g.bytes);
1508 pos += put_mp(blob+pos, y.start, y.bytes);
1510 pos += put_mp(blob+pos, x.start, x.bytes);
1511 privlen = pos - publen;
1514 assert(privlen > 0); /* should have bombed by now if not */
1516 retkey = snew(struct ssh2_userkey);
1518 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1519 if (!retkey->data) {
1521 errmsg = "unable to create key data structure";
1524 retkey->comment = dupstr(key->comment);
1526 errmsg = NULL; /* no error */
1531 smemclr(blob, blobsize);
1534 smemclr(key->keyblob, key->keyblob_size);
1535 sfree(key->keyblob);
1536 smemclr(key, sizeof(*key));
1538 if (errmsg_p) *errmsg_p = errmsg;
1542 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
1545 unsigned char *pubblob, *privblob;
1546 int publen, privlen;
1547 unsigned char *outblob;
1549 struct mpint_pos numbers[6];
1550 int nnumbers, initial_zero, pos, lenpos, i;
1558 * Fetch the key blobs.
1560 pubblob = key->alg->public_blob(key->data, &publen);
1561 privblob = key->alg->private_blob(key->data, &privlen);
1565 * Find the sequence of integers to be encoded into the OpenSSH
1566 * key blob, and also decide on the header line.
1568 if (key->alg == &ssh_rsa) {
1570 struct mpint_pos n, e, d, p, q, iqmp;
1573 * These blobs were generated from inside PuTTY, so we needn't
1574 * treat them as untrusted.
1576 pos = 4 + GET_32BIT(pubblob);
1577 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1578 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1580 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1581 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1582 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1583 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1585 assert(e.start && iqmp.start); /* can't go wrong */
1596 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1597 } else if (key->alg == &ssh_dss) {
1599 struct mpint_pos p, q, g, y, x;
1602 * These blobs were generated from inside PuTTY, so we needn't
1603 * treat them as untrusted.
1605 pos = 4 + GET_32BIT(pubblob);
1606 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1607 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1608 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1609 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1611 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1613 assert(y.start && x.start); /* can't go wrong */
1623 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1625 assert(0); /* zoinks! */
1626 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
1630 * Total size of key blob will be somewhere under 512 plus
1631 * combined length of integers. We'll calculate the more
1632 * precise size as we construct the blob.
1635 for (i = 0; i < nnumbers; i++)
1636 outlen += 4 + numbers[i].bytes;
1637 outblob = snewn(outlen, unsigned char);
1640 * Create the unencrypted key blob.
1643 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1644 pos += 4; /* length field, fill in later */
1645 pos += put_string(outblob+pos, type, strlen(type));
1647 char *ciphertype = passphrase ? "3des-cbc" : "none";
1648 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1650 lenpos = pos; /* remember this position */
1651 pos += 4; /* encrypted-blob size */
1652 pos += 4; /* encrypted-payload size */
1654 PUT_32BIT(outblob+pos, 0);
1657 for (i = 0; i < nnumbers; i++)
1658 pos += sshcom_put_mpint(outblob+pos,
1659 numbers[i].start, numbers[i].bytes);
1660 /* Now wrap up the encrypted payload. */
1661 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1662 /* Pad encrypted blob to a multiple of cipher block size. */
1664 int padding = -(pos - (lenpos+4)) & 7;
1666 outblob[pos++] = random_byte();
1668 ciphertext = (char *)outblob+lenpos+4;
1669 cipherlen = pos - (lenpos+4);
1670 assert(!passphrase || cipherlen % 8 == 0);
1671 /* Wrap up the encrypted blob string. */
1672 PUT_32BIT(outblob+lenpos, cipherlen);
1673 /* And finally fill in the total length field. */
1674 PUT_32BIT(outblob+4, pos);
1676 assert(pos < outlen);
1683 * Derive encryption key from passphrase and iv/salt:
1685 * - let block A equal MD5(passphrase)
1686 * - let block B equal MD5(passphrase || A)
1687 * - block C would be MD5(passphrase || A || B) and so on
1688 * - encryption key is the first N bytes of A || B
1690 struct MD5Context md5c;
1691 unsigned char keybuf[32], iv[8];
1694 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1695 MD5Final(keybuf, &md5c);
1698 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1699 MD5Update(&md5c, keybuf, 16);
1700 MD5Final(keybuf+16, &md5c);
1703 * Now decrypt the key blob.
1705 memset(iv, 0, sizeof(iv));
1706 des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1709 smemclr(&md5c, sizeof(md5c));
1710 smemclr(keybuf, sizeof(keybuf));
1714 * And save it. We'll use Unix line endings just in case it's
1715 * subsequently transferred in binary mode.
1717 fp = f_open(filename, "wb", TRUE); /* ensure Unix line endings */
1720 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1721 fprintf(fp, "Comment: \"");
1723 * Comment header is broken with backslash-newline if it goes
1724 * over 70 chars. Although it's surrounded by quotes, it
1725 * _doesn't_ escape backslashes or quotes within the string.
1726 * Don't ask me, I didn't design it.
1729 int slen = 60; /* starts at 60 due to "Comment: " */
1730 char *c = key->comment;
1731 while ((int)strlen(c) > slen) {
1732 fprintf(fp, "%.*s\\\n", slen, c);
1734 slen = 70; /* allow 70 chars on subsequent lines */
1736 fprintf(fp, "%s\"\n", c);
1738 base64_encode(fp, outblob, pos, 70);
1739 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1745 smemclr(outblob, outlen);
1749 smemclr(privblob, privlen);
1753 smemclr(pubblob, publen);