2 * Code for PuTTY to import and export private key files in other
3 * SSH clients' formats.
15 #define PUT_32BIT(cp, value) do { \
16 (cp)[3] = (unsigned char)(value); \
17 (cp)[2] = (unsigned char)((value) >> 8); \
18 (cp)[1] = (unsigned char)((value) >> 16); \
19 (cp)[0] = (unsigned char)((value) >> 24); } while (0)
21 #define GET_32BIT(cp) \
22 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
23 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
24 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
25 ((unsigned long)(unsigned char)(cp)[3]))
27 int openssh_encrypted(const Filename *filename);
28 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
29 const char **errmsg_p);
30 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
33 int sshcom_encrypted(const Filename *filename, char **comment);
34 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
35 const char **errmsg_p);
36 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
40 * Given a key type, determine whether we know how to import it.
42 int import_possible(int type)
44 if (type == SSH_KEYTYPE_OPENSSH)
46 if (type == SSH_KEYTYPE_SSHCOM)
52 * Given a key type, determine what native key type
53 * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
56 int import_target_type(int type)
59 * There are no known foreign SSH-1 key formats.
61 return SSH_KEYTYPE_SSH2;
65 * Determine whether a foreign key is encrypted.
67 int import_encrypted(const Filename *filename, int type, char **comment)
69 if (type == SSH_KEYTYPE_OPENSSH) {
70 /* OpenSSH doesn't do key comments */
71 *comment = dupstr(filename_to_str(filename));
72 return openssh_encrypted(filename);
74 if (type == SSH_KEYTYPE_SSHCOM) {
75 return sshcom_encrypted(filename, comment);
81 * Import an SSH-1 key.
83 int import_ssh1(const Filename *filename, int type,
84 struct RSAKey *key, char *passphrase, const char **errmsg_p)
90 * Import an SSH-2 key.
92 struct ssh2_userkey *import_ssh2(const Filename *filename, int type,
93 char *passphrase, const char **errmsg_p)
95 if (type == SSH_KEYTYPE_OPENSSH)
96 return openssh_read(filename, passphrase, errmsg_p);
97 if (type == SSH_KEYTYPE_SSHCOM)
98 return sshcom_read(filename, passphrase, errmsg_p);
103 * Export an SSH-1 key.
105 int export_ssh1(const Filename *filename, int type, struct RSAKey *key,
112 * Export an SSH-2 key.
114 int export_ssh2(const Filename *filename, int type,
115 struct ssh2_userkey *key, char *passphrase)
117 if (type == SSH_KEYTYPE_OPENSSH)
118 return openssh_write(filename, key, passphrase);
119 if (type == SSH_KEYTYPE_SSHCOM)
120 return sshcom_write(filename, key, passphrase);
124 /* ----------------------------------------------------------------------
125 * Helper routines. (The base64 ones are defined in sshpubk.c.)
128 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
129 ((c) >= 'a' && (c) <= 'z') || \
130 ((c) >= '0' && (c) <= '9') || \
131 (c) == '+' || (c) == '/' || (c) == '=' \
135 * Read an ASN.1/BER identifier and length pair.
137 * Flags are a combination of the #defines listed below.
139 * Returns -1 if unsuccessful; otherwise returns the number of
140 * bytes used out of the source data.
143 /* ASN.1 tag classes. */
144 #define ASN1_CLASS_UNIVERSAL (0 << 6)
145 #define ASN1_CLASS_APPLICATION (1 << 6)
146 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
147 #define ASN1_CLASS_PRIVATE (3 << 6)
148 #define ASN1_CLASS_MASK (3 << 6)
150 /* Primitive versus constructed bit. */
151 #define ASN1_CONSTRUCTED (1 << 5)
153 static int ber_read_id_len(void *source, int sourcelen,
154 int *id, int *length, int *flags)
156 unsigned char *p = (unsigned char *) source;
161 *flags = (*p & 0xE0);
162 if ((*p & 0x1F) == 0x1F) {
168 *id = (*id << 7) | (*p & 0x7F);
186 *length = (*length << 8) | (*p++);
193 return p - (unsigned char *) source;
197 * Write an ASN.1/BER identifier and length pair. Returns the
198 * number of bytes consumed. Assumes dest contains enough space.
199 * Will avoid writing anything if dest is NULL, but still return
200 * amount of space required.
202 static int ber_write_id_len(void *dest, int id, int length, int flags)
204 unsigned char *d = (unsigned char *)dest;
209 * Identifier is one byte.
212 if (d) *d++ = id | flags;
216 * Identifier is multiple bytes: the first byte is 11111
217 * plus the flags, and subsequent bytes encode the value of
218 * the identifier, 7 bits at a time, with the top bit of
219 * each byte 1 except the last one which is 0.
222 if (d) *d++ = 0x1F | flags;
223 for (n = 1; (id >> (7*n)) > 0; n++)
224 continue; /* count the bytes */
227 if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
233 * Length is one byte.
236 if (d) *d++ = length;
240 * Length is multiple bytes. The first is 0x80 plus the
241 * number of subsequent bytes, and the subsequent bytes
242 * encode the actual length.
244 for (n = 1; (length >> (8*n)) > 0; n++)
245 continue; /* count the bytes */
247 if (d) *d++ = 0x80 | n;
250 if (d) *d++ = (length >> (8*n)) & 0xFF;
257 static int put_string(void *target, void *data, int len)
259 unsigned char *d = (unsigned char *)target;
262 memcpy(d+4, data, len);
266 static int put_mp(void *target, void *data, int len)
268 unsigned char *d = (unsigned char *)target;
269 unsigned char *i = (unsigned char *)data;
274 memcpy(d+5, data, len);
278 memcpy(d+4, data, len);
283 /* Simple structure to point to an mp-int within a blob. */
284 struct mpint_pos { void *start; int bytes; };
286 static int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
289 unsigned char *d = (unsigned char *) data;
293 bytes = GET_32BIT(d);
304 return len; /* ensure further calls fail as well */
307 /* ----------------------------------------------------------------------
308 * Code to read and write OpenSSH private keys.
311 enum { OSSH_DSA, OSSH_RSA };
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");
339 errmsg = "unable to open key file";
342 if (!fgets(buffer, sizeof(buffer), fp) ||
343 0 != strncmp(buffer, "-----BEGIN ", 11) ||
344 0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) {
345 errmsg = "file does not begin with OpenSSH key header";
348 if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n"))
349 ret->type = OSSH_RSA;
350 else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n"))
351 ret->type = OSSH_DSA;
353 errmsg = "unrecognised key type";
359 if (!fgets(buffer, sizeof(buffer), fp)) {
360 errmsg = "unexpected end of file";
363 if (0 == strncmp(buffer, "-----END ", 9) &&
364 0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n"))
366 if ((p = strchr(buffer, ':')) != NULL) {
368 errmsg = "header found in body of key data";
372 while (*p && isspace((unsigned char)*p)) p++;
373 if (!strcmp(buffer, "Proc-Type")) {
374 if (p[0] != '4' || p[1] != ',') {
375 errmsg = "Proc-Type is not 4 (only 4 is supported)";
379 if (!strcmp(p, "ENCRYPTED\n"))
381 } else if (!strcmp(buffer, "DEK-Info")) {
384 if (strncmp(p, "DES-EDE3-CBC,", 13)) {
385 errmsg = "ciphers other than DES-EDE3-CBC not supported";
389 for (i = 0; i < 8; i++) {
390 if (1 != sscanf(p, "%2x", &j))
396 errmsg = "expected 16-digit iv in DEK-Info";
404 while (isbase64(*p)) {
405 base64_bit[base64_chars++] = *p;
406 if (base64_chars == 4) {
407 unsigned char out[3];
412 len = base64_decode_atom(base64_bit, out);
415 errmsg = "invalid base64 encoding";
419 if (ret->keyblob_len + len > ret->keyblob_size) {
420 ret->keyblob_size = ret->keyblob_len + len + 256;
421 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
425 memcpy(ret->keyblob + ret->keyblob_len, out, len);
426 ret->keyblob_len += len;
428 memset(out, 0, sizeof(out));
436 if (ret->keyblob_len == 0 || !ret->keyblob) {
437 errmsg = "key body not present";
441 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
442 errmsg = "encrypted key blob is not a multiple of cipher block size";
446 memset(buffer, 0, sizeof(buffer));
447 memset(base64_bit, 0, sizeof(base64_bit));
448 if (errmsg_p) *errmsg_p = NULL;
452 memset(buffer, 0, sizeof(buffer));
453 memset(base64_bit, 0, sizeof(base64_bit));
456 memset(ret->keyblob, 0, ret->keyblob_size);
459 memset(&ret, 0, sizeof(ret));
462 if (errmsg_p) *errmsg_p = errmsg;
466 int openssh_encrypted(const Filename *filename)
468 struct openssh_key *key = load_openssh_key(filename, NULL);
473 ret = key->encrypted;
474 memset(key->keyblob, 0, key->keyblob_size);
476 memset(&key, 0, sizeof(key));
481 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
482 const char **errmsg_p)
484 struct openssh_key *key = load_openssh_key(filename, errmsg_p);
485 struct ssh2_userkey *retkey;
487 int ret, id, len, flags;
489 struct ssh2_userkey *retval = NULL;
492 int blobsize = 0, blobptr, privptr;
501 if (key->encrypted) {
503 * Derive encryption key from passphrase and iv/salt:
505 * - let block A equal MD5(passphrase || iv)
506 * - let block B equal MD5(A || passphrase || iv)
507 * - block C would be MD5(B || passphrase || iv) and so on
508 * - encryption key is the first N bytes of A || B
510 struct MD5Context md5c;
511 unsigned char keybuf[32];
514 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
515 MD5Update(&md5c, (unsigned char *)key->iv, 8);
516 MD5Final(keybuf, &md5c);
519 MD5Update(&md5c, keybuf, 16);
520 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
521 MD5Update(&md5c, (unsigned char *)key->iv, 8);
522 MD5Final(keybuf+16, &md5c);
525 * Now decrypt the key blob.
527 des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv,
528 key->keyblob, key->keyblob_len);
530 memset(&md5c, 0, sizeof(md5c));
531 memset(keybuf, 0, sizeof(keybuf));
535 * Now we have a decrypted key blob, which contains an ASN.1
536 * encoded private key. We must now untangle the ASN.1.
538 * We expect the whole key blob to be formatted as a SEQUENCE
539 * (0x30 followed by a length code indicating that the rest of
540 * the blob is part of the sequence). Within that SEQUENCE we
541 * expect to see a bunch of INTEGERs. What those integers mean
542 * depends on the key type:
544 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
545 * dmp1, dmq1, iqmp in that order. (The last three are d mod
546 * (p-1), d mod (q-1), inverse of q mod p respectively.)
548 * - For DSA, we expect them to be 0, p, q, g, y, x in that
554 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
555 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
557 if (ret < 0 || id != 16) {
558 errmsg = "ASN.1 decoding failure";
559 retval = SSH2_WRONG_PASSPHRASE;
563 /* Expect a load of INTEGERs. */
564 if (key->type == OSSH_RSA)
566 else if (key->type == OSSH_DSA)
569 num_integers = 0; /* placate compiler warnings */
572 * Space to create key blob in.
574 blobsize = 256+key->keyblob_len;
575 blob = snewn(blobsize, unsigned char);
577 if (key->type == OSSH_DSA)
578 memcpy(blob+4, "ssh-dss", 7);
579 else if (key->type == OSSH_RSA)
580 memcpy(blob+4, "ssh-rsa", 7);
584 for (i = 0; i < num_integers; i++) {
585 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
588 if (ret < 0 || id != 2 ||
589 key->keyblob+key->keyblob_len-p < len) {
590 errmsg = "ASN.1 decoding failure";
591 retval = SSH2_WRONG_PASSPHRASE;
597 * The first integer should be zero always (I think
598 * this is some sort of version indication).
600 if (len != 1 || p[0] != 0) {
601 errmsg = "version number mismatch";
604 } else if (key->type == OSSH_RSA) {
606 * Integers 1 and 2 go into the public blob but in the
607 * opposite order; integers 3, 4, 5 and 8 go into the
608 * private blob. The other two (6 and 7) are ignored.
611 /* Save the details for after we deal with number 2. */
614 } else if (i != 6 && i != 7) {
615 PUT_32BIT(blob+blobptr, len);
616 memcpy(blob+blobptr+4, p, len);
619 PUT_32BIT(blob+blobptr, modlen);
620 memcpy(blob+blobptr+4, modptr, modlen);
625 } else if (key->type == OSSH_DSA) {
627 * Integers 1-4 go into the public blob; integer 5 goes
628 * into the private blob.
630 PUT_32BIT(blob+blobptr, len);
631 memcpy(blob+blobptr+4, p, len);
637 /* Skip past the number. */
642 * Now put together the actual key. Simplest way to do this is
643 * to assemble our own key blobs and feed them to the createkey
644 * functions; this is a bit faffy but it does mean we get all
645 * the sanity checks for free.
647 assert(privptr > 0); /* should have bombed by now if not */
648 retkey = snew(struct ssh2_userkey);
649 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
650 retkey->data = retkey->alg->createkey(blob, privptr,
651 blob+privptr, blobptr-privptr);
654 errmsg = "unable to create key data structure";
658 retkey->comment = dupstr("imported-openssh-key");
659 errmsg = NULL; /* no error */
664 memset(blob, 0, blobsize);
667 memset(key->keyblob, 0, key->keyblob_size);
669 memset(&key, 0, sizeof(key));
671 if (errmsg_p) *errmsg_p = errmsg;
675 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
678 unsigned char *pubblob, *privblob, *spareblob;
679 int publen, privlen, sparelen = 0;
680 unsigned char *outblob;
682 struct mpint_pos numbers[9];
683 int nnumbers, pos, len, seqlen, i;
684 char *header, *footer;
691 * Fetch the key blobs.
693 pubblob = key->alg->public_blob(key->data, &publen);
694 privblob = key->alg->private_blob(key->data, &privlen);
695 spareblob = outblob = NULL;
698 * Find the sequence of integers to be encoded into the OpenSSH
699 * key blob, and also decide on the header line.
701 if (key->alg == &ssh_rsa) {
703 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
704 Bignum bd, bp, bq, bdmp1, bdmq1;
706 pos = 4 + GET_32BIT(pubblob);
707 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
708 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
710 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
711 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
712 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
713 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
715 assert(e.start && iqmp.start); /* can't go wrong */
717 /* We also need d mod (p-1) and d mod (q-1). */
718 bd = bignum_from_bytes(d.start, d.bytes);
719 bp = bignum_from_bytes(p.start, p.bytes);
720 bq = bignum_from_bytes(q.start, q.bytes);
723 bdmp1 = bigmod(bd, bp);
724 bdmq1 = bigmod(bd, bq);
729 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
730 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
731 sparelen = dmp1.bytes + dmq1.bytes;
732 spareblob = snewn(sparelen, unsigned char);
733 dmp1.start = spareblob;
734 dmq1.start = spareblob + dmp1.bytes;
735 for (i = 0; i < dmp1.bytes; i++)
736 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
737 for (i = 0; i < dmq1.bytes; i++)
738 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
742 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
753 header = "-----BEGIN RSA PRIVATE KEY-----\n";
754 footer = "-----END RSA PRIVATE KEY-----\n";
755 } else if (key->alg == &ssh_dss) {
757 struct mpint_pos p, q, g, y, x;
759 pos = 4 + GET_32BIT(pubblob);
760 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
761 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
762 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
763 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
765 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
767 assert(y.start && x.start); /* can't go wrong */
769 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
777 header = "-----BEGIN DSA PRIVATE KEY-----\n";
778 footer = "-----END DSA PRIVATE KEY-----\n";
780 assert(0); /* zoinks! */
784 * Now count up the total size of the ASN.1 encoded integers,
785 * so as to determine the length of the containing SEQUENCE.
788 for (i = 0; i < nnumbers; i++) {
789 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
790 len += numbers[i].bytes;
793 /* Now add on the SEQUENCE header. */
794 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
795 /* Round up to the cipher block size, ensuring we have at least one
796 * byte of padding (see below). */
799 outlen = (outlen+8) &~ 7;
802 * Now we know how big outblob needs to be. Allocate it.
804 outblob = snewn(outlen, unsigned char);
807 * And write the data into it.
810 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
811 for (i = 0; i < nnumbers; i++) {
812 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
813 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
814 pos += numbers[i].bytes;
818 * Padding on OpenSSH keys is deterministic. The number of
819 * padding bytes is always more than zero, and always at most
820 * the cipher block length. The value of each padding byte is
821 * equal to the number of padding bytes. So a plaintext that's
822 * an exact multiple of the block size will be padded with 08
823 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
824 * plaintext one byte less than a multiple of the block size
825 * will be padded with just 01.
827 * This enables the OpenSSL key decryption function to strip
828 * off the padding algorithmically and return the unpadded
829 * plaintext to the next layer: it looks at the final byte, and
830 * then expects to find that many bytes at the end of the data
831 * with the same value. Those are all removed and the rest is
835 while (pos < outlen) {
836 outblob[pos++] = outlen - len;
844 * Invent an iv. Then derive encryption key from passphrase
847 * - let block A equal MD5(passphrase || iv)
848 * - let block B equal MD5(A || passphrase || iv)
849 * - block C would be MD5(B || passphrase || iv) and so on
850 * - encryption key is the first N bytes of A || B
852 struct MD5Context md5c;
853 unsigned char keybuf[32];
855 for (i = 0; i < 8; i++) iv[i] = random_byte();
858 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
859 MD5Update(&md5c, iv, 8);
860 MD5Final(keybuf, &md5c);
863 MD5Update(&md5c, keybuf, 16);
864 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
865 MD5Update(&md5c, iv, 8);
866 MD5Final(keybuf+16, &md5c);
869 * Now encrypt the key blob.
871 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
873 memset(&md5c, 0, sizeof(md5c));
874 memset(keybuf, 0, sizeof(keybuf));
878 * And save it. We'll use Unix line endings just in case it's
879 * subsequently transferred in binary mode.
881 fp = f_open(*filename, "wb"); /* ensure Unix line endings */
886 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
887 for (i = 0; i < 8; i++)
888 fprintf(fp, "%02X", iv[i]);
891 base64_encode(fp, outblob, outlen, 64);
898 memset(outblob, 0, outlen);
902 memset(spareblob, 0, sparelen);
906 memset(privblob, 0, privlen);
910 memset(pubblob, 0, publen);
916 /* ----------------------------------------------------------------------
917 * Code to read ssh.com private keys.
921 * The format of the base64 blob is largely SSH-2-packet-formatted,
922 * except that mpints are a bit different: they're more like the
923 * old SSH-1 mpint. You have a 32-bit bit count N, followed by
924 * (N+7)/8 bytes of data.
926 * So. The blob contains:
928 * - uint32 0x3f6ff9eb (magic number)
929 * - uint32 size (total blob size)
930 * - string key-type (see below)
931 * - string cipher-type (tells you if key is encrypted)
932 * - string encrypted-blob
934 * (The first size field includes the size field itself and the
935 * magic number before it. All other size fields are ordinary SSH-2
936 * strings, so the size field indicates how much data is to
939 * The encrypted blob, once decrypted, contains a single string
940 * which in turn contains the payload. (This allows padding to be
941 * added after that string while still making it clear where the
942 * real payload ends. Also it probably makes for a reasonable
945 * The payload blob, for an RSA key, contains:
948 * - mpint n (yes, the public and private stuff is intermixed)
949 * - mpint u (presumably inverse of p mod q)
950 * - mpint p (p is the smaller prime)
951 * - mpint q (q is the larger)
953 * For a DSA key, the payload blob contains:
961 * Alternatively, if the parameters are `predefined', that
962 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
963 * containing some predefined parameter specification. *shudder*,
964 * but I doubt we'll encounter this in real life.
966 * The key type strings are ghastly. The RSA key I looked at had a
969 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
971 * and the DSA key wasn't much better:
973 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
975 * It isn't clear that these will always be the same. I think it
976 * might be wise just to look at the `if-modn{sign{rsa' and
977 * `dl-modp{sign{dsa' prefixes.
979 * Finally, the encryption. The cipher-type string appears to be
980 * either `none' or `3des-cbc'. Looks as if this is SSH-2-style
981 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
982 * from the passphrase by means of yet another hashing faff:
984 * - first 16 bytes are MD5(passphrase)
985 * - next 16 bytes are MD5(passphrase || first 16 bytes)
986 * - if there were more, they'd be MD5(passphrase || first 32),
990 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
993 char comment[256]; /* allowing any length is overkill */
994 unsigned char *keyblob;
995 int keyblob_len, keyblob_size;
998 static struct sshcom_key *load_sshcom_key(const Filename *filename,
999 const char **errmsg_p)
1001 struct sshcom_key *ret;
1008 int base64_chars = 0;
1010 ret = snew(struct sshcom_key);
1011 ret->comment[0] = '\0';
1012 ret->keyblob = NULL;
1013 ret->keyblob_len = ret->keyblob_size = 0;
1015 fp = f_open(*filename, "r");
1017 errmsg = "unable to open key file";
1020 if (!fgets(buffer, sizeof(buffer), fp) ||
1021 0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1022 errmsg = "file does not begin with ssh.com key header";
1028 if (!fgets(buffer, sizeof(buffer), fp)) {
1029 errmsg = "unexpected end of file";
1032 if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1034 if ((p = strchr(buffer, ':')) != NULL) {
1036 errmsg = "header found in body of key data";
1040 while (*p && isspace((unsigned char)*p)) p++;
1042 * Header lines can end in a trailing backslash for
1045 while ((len = strlen(p)) > (int)(sizeof(buffer) - (p-buffer) -1) ||
1046 p[len-1] != '\n' || p[len-2] == '\\') {
1047 if (len > (int)((p-buffer) + sizeof(buffer)-2)) {
1048 errmsg = "header line too long to deal with";
1051 if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) {
1052 errmsg = "unexpected end of file";
1056 p[strcspn(p, "\n")] = '\0';
1057 if (!strcmp(buffer, "Comment")) {
1058 /* Strip quotes in comment if present. */
1059 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1061 p[strlen(p)-1] = '\0';
1063 strncpy(ret->comment, p, sizeof(ret->comment));
1064 ret->comment[sizeof(ret->comment)-1] = '\0';
1070 while (isbase64(*p)) {
1071 base64_bit[base64_chars++] = *p;
1072 if (base64_chars == 4) {
1073 unsigned char out[3];
1077 len = base64_decode_atom(base64_bit, out);
1080 errmsg = "invalid base64 encoding";
1084 if (ret->keyblob_len + len > ret->keyblob_size) {
1085 ret->keyblob_size = ret->keyblob_len + len + 256;
1086 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
1090 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1091 ret->keyblob_len += len;
1099 if (ret->keyblob_len == 0 || !ret->keyblob) {
1100 errmsg = "key body not present";
1104 if (errmsg_p) *errmsg_p = NULL;
1110 memset(ret->keyblob, 0, ret->keyblob_size);
1111 sfree(ret->keyblob);
1113 memset(&ret, 0, sizeof(ret));
1116 if (errmsg_p) *errmsg_p = errmsg;
1120 int sshcom_encrypted(const Filename *filename, char **comment)
1122 struct sshcom_key *key = load_sshcom_key(filename, NULL);
1123 int pos, len, answer;
1130 * Check magic number.
1132 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
1133 return 0; /* key is invalid */
1136 * Find the cipher-type string.
1140 if (key->keyblob_len < pos+4)
1141 goto done; /* key is far too short */
1142 pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */
1143 if (key->keyblob_len < pos+4)
1144 goto done; /* key is far too short */
1145 len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */
1146 if (key->keyblob_len < pos+4+len)
1147 goto done; /* cipher type string is incomplete */
1148 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1152 *comment = dupstr(key->comment);
1153 memset(key->keyblob, 0, key->keyblob_size);
1154 sfree(key->keyblob);
1155 memset(&key, 0, sizeof(key));
1160 static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1164 unsigned char *d = (unsigned char *) data;
1168 bits = GET_32BIT(d);
1170 bytes = (bits + 7) / 8;
1181 return len; /* ensure further calls fail as well */
1184 static int sshcom_put_mpint(void *target, void *data, int len)
1186 unsigned char *d = (unsigned char *)target;
1187 unsigned char *i = (unsigned char *)data;
1188 int bits = len * 8 - 1;
1191 if (*i & (1 << (bits & 7)))
1197 PUT_32BIT(d, bits+1);
1198 memcpy(d+4, i, len);
1202 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
1203 const char **errmsg_p)
1205 struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
1208 const char prefix_rsa[] = "if-modn{sign{rsa";
1209 const char prefix_dsa[] = "dl-modp{sign{dsa";
1210 enum { RSA, DSA } type;
1214 struct ssh2_userkey *ret = NULL, *retkey;
1215 const struct ssh_signkey *alg;
1216 unsigned char *blob = NULL;
1217 int blobsize = 0, publen, privlen;
1223 * Check magic number.
1225 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1226 errmsg = "key does not begin with magic number";
1231 * Determine the key type.
1234 if (key->keyblob_len < pos+4 ||
1235 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1236 errmsg = "key blob does not contain a key type string";
1239 if (len > sizeof(prefix_rsa) - 1 &&
1240 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1242 } else if (len > sizeof(prefix_dsa) - 1 &&
1243 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1246 errmsg = "key is of unknown type";
1252 * Determine the cipher type.
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 a cipher type string";
1259 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1261 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1264 errmsg = "key encryption is of unknown type";
1270 * Get hold of the encrypted part of the key.
1272 if (key->keyblob_len < pos+4 ||
1273 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1274 errmsg = "key blob does not contain actual key data";
1277 ciphertext = (char *)key->keyblob + pos + 4;
1279 if (cipherlen == 0) {
1280 errmsg = "length of key data is zero";
1285 * Decrypt it if necessary.
1289 * Derive encryption key from passphrase and iv/salt:
1291 * - let block A equal MD5(passphrase)
1292 * - let block B equal MD5(passphrase || A)
1293 * - block C would be MD5(passphrase || A || B) and so on
1294 * - encryption key is the first N bytes of A || B
1296 struct MD5Context md5c;
1297 unsigned char keybuf[32], iv[8];
1299 if (cipherlen % 8 != 0) {
1300 errmsg = "encrypted part of key is not a multiple of cipher block"
1306 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1307 MD5Final(keybuf, &md5c);
1310 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1311 MD5Update(&md5c, keybuf, 16);
1312 MD5Final(keybuf+16, &md5c);
1315 * Now decrypt the key blob.
1317 memset(iv, 0, sizeof(iv));
1318 des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1321 memset(&md5c, 0, sizeof(md5c));
1322 memset(keybuf, 0, sizeof(keybuf));
1325 * Hereafter we return WRONG_PASSPHRASE for any parsing
1326 * error. (But only if we've just tried to decrypt it!
1327 * Returning WRONG_PASSPHRASE for an unencrypted key is
1331 ret = SSH2_WRONG_PASSPHRASE;
1335 * Strip away the containing string to get to the real meat.
1337 len = GET_32BIT(ciphertext);
1338 if (len < 0 || len > cipherlen-4) {
1339 errmsg = "containing string was ill-formed";
1346 * Now we break down into RSA versus DSA. In either case we'll
1347 * construct public and private blobs in our own format, and
1348 * end up feeding them to alg->createkey().
1350 blobsize = cipherlen + 256;
1351 blob = snewn(blobsize, unsigned char);
1354 struct mpint_pos n, e, d, u, p, q;
1356 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1357 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1358 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1359 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1360 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1361 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1363 errmsg = "key data did not contain six integers";
1369 pos += put_string(blob+pos, "ssh-rsa", 7);
1370 pos += put_mp(blob+pos, e.start, e.bytes);
1371 pos += put_mp(blob+pos, n.start, n.bytes);
1373 pos += put_string(blob+pos, d.start, d.bytes);
1374 pos += put_mp(blob+pos, q.start, q.bytes);
1375 pos += put_mp(blob+pos, p.start, p.bytes);
1376 pos += put_mp(blob+pos, u.start, u.bytes);
1377 privlen = pos - publen;
1378 } else if (type == DSA) {
1379 struct mpint_pos p, q, g, x, y;
1381 if (GET_32BIT(ciphertext) != 0) {
1382 errmsg = "predefined DSA parameters not supported";
1385 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1386 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1387 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1388 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1389 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1391 errmsg = "key data did not contain five integers";
1397 pos += put_string(blob+pos, "ssh-dss", 7);
1398 pos += put_mp(blob+pos, p.start, p.bytes);
1399 pos += put_mp(blob+pos, q.start, q.bytes);
1400 pos += put_mp(blob+pos, g.start, g.bytes);
1401 pos += put_mp(blob+pos, y.start, y.bytes);
1403 pos += put_mp(blob+pos, x.start, x.bytes);
1404 privlen = pos - publen;
1408 assert(privlen > 0); /* should have bombed by now if not */
1410 retkey = snew(struct ssh2_userkey);
1412 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1413 if (!retkey->data) {
1415 errmsg = "unable to create key data structure";
1418 retkey->comment = dupstr(key->comment);
1420 errmsg = NULL; /* no error */
1425 memset(blob, 0, blobsize);
1428 memset(key->keyblob, 0, key->keyblob_size);
1429 sfree(key->keyblob);
1430 memset(&key, 0, sizeof(key));
1432 if (errmsg_p) *errmsg_p = errmsg;
1436 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
1439 unsigned char *pubblob, *privblob;
1440 int publen, privlen;
1441 unsigned char *outblob;
1443 struct mpint_pos numbers[6];
1444 int nnumbers, initial_zero, pos, lenpos, i;
1452 * Fetch the key blobs.
1454 pubblob = key->alg->public_blob(key->data, &publen);
1455 privblob = key->alg->private_blob(key->data, &privlen);
1459 * Find the sequence of integers to be encoded into the OpenSSH
1460 * key blob, and also decide on the header line.
1462 if (key->alg == &ssh_rsa) {
1464 struct mpint_pos n, e, d, p, q, iqmp;
1466 pos = 4 + GET_32BIT(pubblob);
1467 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1468 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1470 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1471 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1472 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1473 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1475 assert(e.start && iqmp.start); /* can't go wrong */
1486 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1487 } else if (key->alg == &ssh_dss) {
1489 struct mpint_pos p, q, g, y, x;
1491 pos = 4 + GET_32BIT(pubblob);
1492 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1493 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1494 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1495 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1497 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1499 assert(y.start && x.start); /* can't go wrong */
1509 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1511 assert(0); /* zoinks! */
1515 * Total size of key blob will be somewhere under 512 plus
1516 * combined length of integers. We'll calculate the more
1517 * precise size as we construct the blob.
1520 for (i = 0; i < nnumbers; i++)
1521 outlen += 4 + numbers[i].bytes;
1522 outblob = snewn(outlen, unsigned char);
1525 * Create the unencrypted key blob.
1528 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1529 pos += 4; /* length field, fill in later */
1530 pos += put_string(outblob+pos, type, strlen(type));
1532 char *ciphertype = passphrase ? "3des-cbc" : "none";
1533 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1535 lenpos = pos; /* remember this position */
1536 pos += 4; /* encrypted-blob size */
1537 pos += 4; /* encrypted-payload size */
1539 PUT_32BIT(outblob+pos, 0);
1542 for (i = 0; i < nnumbers; i++)
1543 pos += sshcom_put_mpint(outblob+pos,
1544 numbers[i].start, numbers[i].bytes);
1545 /* Now wrap up the encrypted payload. */
1546 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1547 /* Pad encrypted blob to a multiple of cipher block size. */
1549 int padding = -(pos - (lenpos+4)) & 7;
1551 outblob[pos++] = random_byte();
1553 ciphertext = (char *)outblob+lenpos+4;
1554 cipherlen = pos - (lenpos+4);
1555 assert(!passphrase || cipherlen % 8 == 0);
1556 /* Wrap up the encrypted blob string. */
1557 PUT_32BIT(outblob+lenpos, cipherlen);
1558 /* And finally fill in the total length field. */
1559 PUT_32BIT(outblob+4, pos);
1561 assert(pos < outlen);
1568 * Derive encryption key from passphrase and iv/salt:
1570 * - let block A equal MD5(passphrase)
1571 * - let block B equal MD5(passphrase || A)
1572 * - block C would be MD5(passphrase || A || B) and so on
1573 * - encryption key is the first N bytes of A || B
1575 struct MD5Context md5c;
1576 unsigned char keybuf[32], iv[8];
1579 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1580 MD5Final(keybuf, &md5c);
1583 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1584 MD5Update(&md5c, keybuf, 16);
1585 MD5Final(keybuf+16, &md5c);
1588 * Now decrypt the key blob.
1590 memset(iv, 0, sizeof(iv));
1591 des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1594 memset(&md5c, 0, sizeof(md5c));
1595 memset(keybuf, 0, sizeof(keybuf));
1599 * And save it. We'll use Unix line endings just in case it's
1600 * subsequently transferred in binary mode.
1602 fp = f_open(*filename, "wb"); /* ensure Unix line endings */
1605 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1606 fprintf(fp, "Comment: \"");
1608 * Comment header is broken with backslash-newline if it goes
1609 * over 70 chars. Although it's surrounded by quotes, it
1610 * _doesn't_ escape backslashes or quotes within the string.
1611 * Don't ask me, I didn't design it.
1614 int slen = 60; /* starts at 60 due to "Comment: " */
1615 char *c = key->comment;
1616 while ((int)strlen(c) > slen) {
1617 fprintf(fp, "%.*s\\\n", slen, c);
1619 slen = 70; /* allow 70 chars on subsequent lines */
1621 fprintf(fp, "%s\"\n", c);
1623 base64_encode(fp, outblob, pos, 70);
1624 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1630 memset(outblob, 0, outlen);
1634 memset(privblob, 0, privlen);
1638 memset(pubblob, 0, publen);