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);
112 /* ----------------------------------------------------------------------
113 * Helper routines. (The base64 ones are defined in sshpubk.c.)
116 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
117 ((c) >= 'a' && (c) <= 'z') || \
118 ((c) >= '0' && (c) <= '9') || \
119 (c) == '+' || (c) == '/' || (c) == '=' \
123 * Read an ASN.1/BER identifier and length pair.
125 * Flags are a combination of the #defines listed below.
127 * Returns -1 if unsuccessful; otherwise returns the number of
128 * bytes used out of the source data.
131 /* ASN.1 tag classes. */
132 #define ASN1_CLASS_UNIVERSAL (0 << 6)
133 #define ASN1_CLASS_APPLICATION (1 << 6)
134 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
135 #define ASN1_CLASS_PRIVATE (3 << 6)
136 #define ASN1_CLASS_MASK (3 << 6)
138 /* Primitive versus constructed bit. */
139 #define ASN1_CONSTRUCTED (1 << 5)
141 static int ber_read_id_len(void *source, int sourcelen,
142 int *id, int *length, int *flags)
144 unsigned char *p = (unsigned char *) source;
149 *flags = (*p & 0xE0);
150 if ((*p & 0x1F) == 0x1F) {
156 *id = (*id << 7) | (*p & 0x7F);
174 *length = (*length << 8) | (*p++);
181 return p - (unsigned char *) source;
185 * Write an ASN.1/BER identifier and length pair. Returns the
186 * number of bytes consumed. Assumes dest contains enough space.
187 * Will avoid writing anything if dest is NULL, but still return
188 * amount of space required.
190 static int ber_write_id_len(void *dest, int id, int length, int flags)
192 unsigned char *d = (unsigned char *)dest;
197 * Identifier is one byte.
200 if (d) *d++ = id | flags;
204 * Identifier is multiple bytes: the first byte is 11111
205 * plus the flags, and subsequent bytes encode the value of
206 * the identifier, 7 bits at a time, with the top bit of
207 * each byte 1 except the last one which is 0.
210 if (d) *d++ = 0x1F | flags;
211 for (n = 1; (id >> (7*n)) > 0; n++)
212 continue; /* count the bytes */
215 if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
221 * Length is one byte.
224 if (d) *d++ = length;
228 * Length is multiple bytes. The first is 0x80 plus the
229 * number of subsequent bytes, and the subsequent bytes
230 * encode the actual length.
232 for (n = 1; (length >> (8*n)) > 0; n++)
233 continue; /* count the bytes */
235 if (d) *d++ = 0x80 | n;
238 if (d) *d++ = (length >> (8*n)) & 0xFF;
245 static int put_string(void *target, void *data, int len)
247 unsigned char *d = (unsigned char *)target;
250 memcpy(d+4, data, len);
254 static int put_mp(void *target, void *data, int len)
256 unsigned char *d = (unsigned char *)target;
257 unsigned char *i = (unsigned char *)data;
262 memcpy(d+5, data, len);
266 memcpy(d+4, data, len);
271 /* Simple structure to point to an mp-int within a blob. */
272 struct mpint_pos { void *start; int bytes; };
274 static int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
277 unsigned char *d = (unsigned char *) data;
281 bytes = GET_32BIT(d);
292 return len; /* ensure further calls fail as well */
295 /* ----------------------------------------------------------------------
296 * Code to read and write OpenSSH private keys.
299 enum { OSSH_DSA, OSSH_RSA };
304 unsigned char *keyblob;
305 int keyblob_len, keyblob_size;
308 static struct openssh_key *load_openssh_key(const Filename *filename,
309 const char **errmsg_p)
311 struct openssh_key *ret;
317 int base64_chars = 0;
319 ret = snew(struct openssh_key);
321 ret->keyblob_len = ret->keyblob_size = 0;
323 memset(ret->iv, 0, sizeof(ret->iv));
325 fp = f_open(*filename, "r");
327 errmsg = "unable to open key file";
330 if (!fgets(buffer, sizeof(buffer), fp) ||
331 0 != strncmp(buffer, "-----BEGIN ", 11) ||
332 0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) {
333 errmsg = "file does not begin with OpenSSH key header";
336 if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n"))
337 ret->type = OSSH_RSA;
338 else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n"))
339 ret->type = OSSH_DSA;
341 errmsg = "unrecognised key type";
347 if (!fgets(buffer, sizeof(buffer), fp)) {
348 errmsg = "unexpected end of file";
351 if (0 == strncmp(buffer, "-----END ", 9) &&
352 0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n"))
354 if ((p = strchr(buffer, ':')) != NULL) {
356 errmsg = "header found in body of key data";
360 while (*p && isspace((unsigned char)*p)) p++;
361 if (!strcmp(buffer, "Proc-Type")) {
362 if (p[0] != '4' || p[1] != ',') {
363 errmsg = "Proc-Type is not 4 (only 4 is supported)";
367 if (!strcmp(p, "ENCRYPTED\n"))
369 } else if (!strcmp(buffer, "DEK-Info")) {
372 if (strncmp(p, "DES-EDE3-CBC,", 13)) {
373 errmsg = "ciphers other than DES-EDE3-CBC not supported";
377 for (i = 0; i < 8; i++) {
378 if (1 != sscanf(p, "%2x", &j))
384 errmsg = "expected 16-digit iv in DEK-Info";
392 while (isbase64(*p)) {
393 base64_bit[base64_chars++] = *p;
394 if (base64_chars == 4) {
395 unsigned char out[3];
400 len = base64_decode_atom(base64_bit, out);
403 errmsg = "invalid base64 encoding";
407 if (ret->keyblob_len + len > ret->keyblob_size) {
408 ret->keyblob_size = ret->keyblob_len + len + 256;
409 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
413 memcpy(ret->keyblob + ret->keyblob_len, out, len);
414 ret->keyblob_len += len;
416 memset(out, 0, sizeof(out));
424 if (ret->keyblob_len == 0 || !ret->keyblob) {
425 errmsg = "key body not present";
429 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
430 errmsg = "encrypted key blob is not a multiple of cipher block size";
434 memset(buffer, 0, sizeof(buffer));
435 memset(base64_bit, 0, sizeof(base64_bit));
436 if (errmsg_p) *errmsg_p = NULL;
440 memset(buffer, 0, sizeof(buffer));
441 memset(base64_bit, 0, sizeof(base64_bit));
444 memset(ret->keyblob, 0, ret->keyblob_size);
447 memset(&ret, 0, sizeof(ret));
450 if (errmsg_p) *errmsg_p = errmsg;
454 int openssh_encrypted(const Filename *filename)
456 struct openssh_key *key = load_openssh_key(filename, NULL);
461 ret = key->encrypted;
462 memset(key->keyblob, 0, key->keyblob_size);
464 memset(&key, 0, sizeof(key));
469 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
470 const char **errmsg_p)
472 struct openssh_key *key = load_openssh_key(filename, errmsg_p);
473 struct ssh2_userkey *retkey;
475 int ret, id, len, flags;
477 struct ssh2_userkey *retval = NULL;
480 int blobsize = 0, blobptr, privptr;
489 if (key->encrypted) {
491 * Derive encryption key from passphrase and iv/salt:
493 * - let block A equal MD5(passphrase || iv)
494 * - let block B equal MD5(A || passphrase || iv)
495 * - block C would be MD5(B || passphrase || iv) and so on
496 * - encryption key is the first N bytes of A || B
498 struct MD5Context md5c;
499 unsigned char keybuf[32];
502 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
503 MD5Update(&md5c, (unsigned char *)key->iv, 8);
504 MD5Final(keybuf, &md5c);
507 MD5Update(&md5c, keybuf, 16);
508 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
509 MD5Update(&md5c, (unsigned char *)key->iv, 8);
510 MD5Final(keybuf+16, &md5c);
513 * Now decrypt the key blob.
515 des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv,
516 key->keyblob, key->keyblob_len);
518 memset(&md5c, 0, sizeof(md5c));
519 memset(keybuf, 0, sizeof(keybuf));
523 * Now we have a decrypted key blob, which contains an ASN.1
524 * encoded private key. We must now untangle the ASN.1.
526 * We expect the whole key blob to be formatted as a SEQUENCE
527 * (0x30 followed by a length code indicating that the rest of
528 * the blob is part of the sequence). Within that SEQUENCE we
529 * expect to see a bunch of INTEGERs. What those integers mean
530 * depends on the key type:
532 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
533 * dmp1, dmq1, iqmp in that order. (The last three are d mod
534 * (p-1), d mod (q-1), inverse of q mod p respectively.)
536 * - For DSA, we expect them to be 0, p, q, g, y, x in that
542 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
543 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
545 if (ret < 0 || id != 16) {
546 errmsg = "ASN.1 decoding failure";
547 retval = SSH2_WRONG_PASSPHRASE;
551 /* Expect a load of INTEGERs. */
552 if (key->type == OSSH_RSA)
554 else if (key->type == OSSH_DSA)
557 num_integers = 0; /* placate compiler warnings */
560 * Space to create key blob in.
562 blobsize = 256+key->keyblob_len;
563 blob = snewn(blobsize, unsigned char);
565 if (key->type == OSSH_DSA)
566 memcpy(blob+4, "ssh-dss", 7);
567 else if (key->type == OSSH_RSA)
568 memcpy(blob+4, "ssh-rsa", 7);
572 for (i = 0; i < num_integers; i++) {
573 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
576 if (ret < 0 || id != 2 ||
577 key->keyblob+key->keyblob_len-p < len) {
578 errmsg = "ASN.1 decoding failure";
579 retval = SSH2_WRONG_PASSPHRASE;
585 * The first integer should be zero always (I think
586 * this is some sort of version indication).
588 if (len != 1 || p[0] != 0) {
589 errmsg = "version number mismatch";
592 } else if (key->type == OSSH_RSA) {
594 * Integers 1 and 2 go into the public blob but in the
595 * opposite order; integers 3, 4, 5 and 8 go into the
596 * private blob. The other two (6 and 7) are ignored.
599 /* Save the details for after we deal with number 2. */
602 } else if (i != 6 && i != 7) {
603 PUT_32BIT(blob+blobptr, len);
604 memcpy(blob+blobptr+4, p, len);
607 PUT_32BIT(blob+blobptr, modlen);
608 memcpy(blob+blobptr+4, modptr, modlen);
613 } else if (key->type == OSSH_DSA) {
615 * Integers 1-4 go into the public blob; integer 5 goes
616 * into the private blob.
618 PUT_32BIT(blob+blobptr, len);
619 memcpy(blob+blobptr+4, p, len);
625 /* Skip past the number. */
630 * Now put together the actual key. Simplest way to do this is
631 * to assemble our own key blobs and feed them to the createkey
632 * functions; this is a bit faffy but it does mean we get all
633 * the sanity checks for free.
635 assert(privptr > 0); /* should have bombed by now if not */
636 retkey = snew(struct ssh2_userkey);
637 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
638 retkey->data = retkey->alg->createkey(blob, privptr,
639 blob+privptr, blobptr-privptr);
642 errmsg = "unable to create key data structure";
646 retkey->comment = dupstr("imported-openssh-key");
647 errmsg = NULL; /* no error */
652 memset(blob, 0, blobsize);
655 memset(key->keyblob, 0, key->keyblob_size);
657 memset(&key, 0, sizeof(key));
659 if (errmsg_p) *errmsg_p = errmsg;
663 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
666 unsigned char *pubblob, *privblob, *spareblob;
667 int publen, privlen, sparelen = 0;
668 unsigned char *outblob;
670 struct mpint_pos numbers[9];
671 int nnumbers, pos, len, seqlen, i;
672 char *header, *footer;
679 * Fetch the key blobs.
681 pubblob = key->alg->public_blob(key->data, &publen);
682 privblob = key->alg->private_blob(key->data, &privlen);
683 spareblob = outblob = NULL;
686 * Find the sequence of integers to be encoded into the OpenSSH
687 * key blob, and also decide on the header line.
689 if (key->alg == &ssh_rsa) {
691 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
692 Bignum bd, bp, bq, bdmp1, bdmq1;
694 pos = 4 + GET_32BIT(pubblob);
695 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
696 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
698 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
699 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
700 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
701 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
703 assert(e.start && iqmp.start); /* can't go wrong */
705 /* We also need d mod (p-1) and d mod (q-1). */
706 bd = bignum_from_bytes(d.start, d.bytes);
707 bp = bignum_from_bytes(p.start, p.bytes);
708 bq = bignum_from_bytes(q.start, q.bytes);
711 bdmp1 = bigmod(bd, bp);
712 bdmq1 = bigmod(bd, bq);
717 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
718 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
719 sparelen = dmp1.bytes + dmq1.bytes;
720 spareblob = snewn(sparelen, unsigned char);
721 dmp1.start = spareblob;
722 dmq1.start = spareblob + dmp1.bytes;
723 for (i = 0; i < dmp1.bytes; i++)
724 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
725 for (i = 0; i < dmq1.bytes; i++)
726 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
730 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
741 header = "-----BEGIN RSA PRIVATE KEY-----\n";
742 footer = "-----END RSA PRIVATE KEY-----\n";
743 } else if (key->alg == &ssh_dss) {
745 struct mpint_pos p, q, g, y, x;
747 pos = 4 + GET_32BIT(pubblob);
748 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
749 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
750 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
751 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
753 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
755 assert(y.start && x.start); /* can't go wrong */
757 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
765 header = "-----BEGIN DSA PRIVATE KEY-----\n";
766 footer = "-----END DSA PRIVATE KEY-----\n";
768 assert(0); /* zoinks! */
769 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
773 * Now count up the total size of the ASN.1 encoded integers,
774 * so as to determine the length of the containing SEQUENCE.
777 for (i = 0; i < nnumbers; i++) {
778 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
779 len += numbers[i].bytes;
782 /* Now add on the SEQUENCE header. */
783 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
784 /* Round up to the cipher block size, ensuring we have at least one
785 * byte of padding (see below). */
788 outlen = (outlen+8) &~ 7;
791 * Now we know how big outblob needs to be. Allocate it.
793 outblob = snewn(outlen, unsigned char);
796 * And write the data into it.
799 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
800 for (i = 0; i < nnumbers; i++) {
801 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
802 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
803 pos += numbers[i].bytes;
807 * Padding on OpenSSH keys is deterministic. The number of
808 * padding bytes is always more than zero, and always at most
809 * the cipher block length. The value of each padding byte is
810 * equal to the number of padding bytes. So a plaintext that's
811 * an exact multiple of the block size will be padded with 08
812 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
813 * plaintext one byte less than a multiple of the block size
814 * will be padded with just 01.
816 * This enables the OpenSSL key decryption function to strip
817 * off the padding algorithmically and return the unpadded
818 * plaintext to the next layer: it looks at the final byte, and
819 * then expects to find that many bytes at the end of the data
820 * with the same value. Those are all removed and the rest is
824 while (pos < outlen) {
825 outblob[pos++] = outlen - len;
833 * Invent an iv. Then derive encryption key from passphrase
836 * - let block A equal MD5(passphrase || iv)
837 * - let block B equal MD5(A || passphrase || iv)
838 * - block C would be MD5(B || passphrase || iv) and so on
839 * - encryption key is the first N bytes of A || B
841 struct MD5Context md5c;
842 unsigned char keybuf[32];
844 for (i = 0; i < 8; i++) iv[i] = random_byte();
847 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
848 MD5Update(&md5c, iv, 8);
849 MD5Final(keybuf, &md5c);
852 MD5Update(&md5c, keybuf, 16);
853 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
854 MD5Update(&md5c, iv, 8);
855 MD5Final(keybuf+16, &md5c);
858 * Now encrypt the key blob.
860 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
862 memset(&md5c, 0, sizeof(md5c));
863 memset(keybuf, 0, sizeof(keybuf));
867 * And save it. We'll use Unix line endings just in case it's
868 * subsequently transferred in binary mode.
870 fp = f_open(*filename, "wb"); /* ensure Unix line endings */
875 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
876 for (i = 0; i < 8; i++)
877 fprintf(fp, "%02X", iv[i]);
880 base64_encode(fp, outblob, outlen, 64);
887 memset(outblob, 0, outlen);
891 memset(spareblob, 0, sparelen);
895 memset(privblob, 0, privlen);
899 memset(pubblob, 0, publen);
905 /* ----------------------------------------------------------------------
906 * Code to read ssh.com private keys.
910 * The format of the base64 blob is largely SSH-2-packet-formatted,
911 * except that mpints are a bit different: they're more like the
912 * old SSH-1 mpint. You have a 32-bit bit count N, followed by
913 * (N+7)/8 bytes of data.
915 * So. The blob contains:
917 * - uint32 0x3f6ff9eb (magic number)
918 * - uint32 size (total blob size)
919 * - string key-type (see below)
920 * - string cipher-type (tells you if key is encrypted)
921 * - string encrypted-blob
923 * (The first size field includes the size field itself and the
924 * magic number before it. All other size fields are ordinary SSH-2
925 * strings, so the size field indicates how much data is to
928 * The encrypted blob, once decrypted, contains a single string
929 * which in turn contains the payload. (This allows padding to be
930 * added after that string while still making it clear where the
931 * real payload ends. Also it probably makes for a reasonable
934 * The payload blob, for an RSA key, contains:
937 * - mpint n (yes, the public and private stuff is intermixed)
938 * - mpint u (presumably inverse of p mod q)
939 * - mpint p (p is the smaller prime)
940 * - mpint q (q is the larger)
942 * For a DSA key, the payload blob contains:
950 * Alternatively, if the parameters are `predefined', that
951 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
952 * containing some predefined parameter specification. *shudder*,
953 * but I doubt we'll encounter this in real life.
955 * The key type strings are ghastly. The RSA key I looked at had a
958 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
960 * and the DSA key wasn't much better:
962 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
964 * It isn't clear that these will always be the same. I think it
965 * might be wise just to look at the `if-modn{sign{rsa' and
966 * `dl-modp{sign{dsa' prefixes.
968 * Finally, the encryption. The cipher-type string appears to be
969 * either `none' or `3des-cbc'. Looks as if this is SSH-2-style
970 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
971 * from the passphrase by means of yet another hashing faff:
973 * - first 16 bytes are MD5(passphrase)
974 * - next 16 bytes are MD5(passphrase || first 16 bytes)
975 * - if there were more, they'd be MD5(passphrase || first 32),
979 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
982 char comment[256]; /* allowing any length is overkill */
983 unsigned char *keyblob;
984 int keyblob_len, keyblob_size;
987 static struct sshcom_key *load_sshcom_key(const Filename *filename,
988 const char **errmsg_p)
990 struct sshcom_key *ret;
997 int base64_chars = 0;
999 ret = snew(struct sshcom_key);
1000 ret->comment[0] = '\0';
1001 ret->keyblob = NULL;
1002 ret->keyblob_len = ret->keyblob_size = 0;
1004 fp = f_open(*filename, "r");
1006 errmsg = "unable to open key file";
1009 if (!fgets(buffer, sizeof(buffer), fp) ||
1010 0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1011 errmsg = "file does not begin with ssh.com key header";
1017 if (!fgets(buffer, sizeof(buffer), fp)) {
1018 errmsg = "unexpected end of file";
1021 if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1023 if ((p = strchr(buffer, ':')) != NULL) {
1025 errmsg = "header found in body of key data";
1029 while (*p && isspace((unsigned char)*p)) p++;
1031 * Header lines can end in a trailing backslash for
1034 while ((len = strlen(p)) > (int)(sizeof(buffer) - (p-buffer) -1) ||
1035 p[len-1] != '\n' || p[len-2] == '\\') {
1036 if (len > (int)((p-buffer) + sizeof(buffer)-2)) {
1037 errmsg = "header line too long to deal with";
1040 if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) {
1041 errmsg = "unexpected end of file";
1045 p[strcspn(p, "\n")] = '\0';
1046 if (!strcmp(buffer, "Comment")) {
1047 /* Strip quotes in comment if present. */
1048 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1050 p[strlen(p)-1] = '\0';
1052 strncpy(ret->comment, p, sizeof(ret->comment));
1053 ret->comment[sizeof(ret->comment)-1] = '\0';
1059 while (isbase64(*p)) {
1060 base64_bit[base64_chars++] = *p;
1061 if (base64_chars == 4) {
1062 unsigned char out[3];
1066 len = base64_decode_atom(base64_bit, out);
1069 errmsg = "invalid base64 encoding";
1073 if (ret->keyblob_len + len > ret->keyblob_size) {
1074 ret->keyblob_size = ret->keyblob_len + len + 256;
1075 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
1079 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1080 ret->keyblob_len += len;
1088 if (ret->keyblob_len == 0 || !ret->keyblob) {
1089 errmsg = "key body not present";
1093 if (errmsg_p) *errmsg_p = NULL;
1099 memset(ret->keyblob, 0, ret->keyblob_size);
1100 sfree(ret->keyblob);
1102 memset(&ret, 0, sizeof(ret));
1105 if (errmsg_p) *errmsg_p = errmsg;
1109 int sshcom_encrypted(const Filename *filename, char **comment)
1111 struct sshcom_key *key = load_sshcom_key(filename, NULL);
1112 int pos, len, answer;
1119 * Check magic number.
1121 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
1122 return 0; /* key is invalid */
1125 * Find the cipher-type string.
1129 if (key->keyblob_len < pos+4)
1130 goto done; /* key is far too short */
1131 pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */
1132 if (key->keyblob_len < pos+4)
1133 goto done; /* key is far too short */
1134 len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */
1135 if (key->keyblob_len < pos+4+len)
1136 goto done; /* cipher type string is incomplete */
1137 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1141 *comment = dupstr(key->comment);
1142 memset(key->keyblob, 0, key->keyblob_size);
1143 sfree(key->keyblob);
1144 memset(&key, 0, sizeof(key));
1149 static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1153 unsigned char *d = (unsigned char *) data;
1157 bits = GET_32BIT(d);
1159 bytes = (bits + 7) / 8;
1170 return len; /* ensure further calls fail as well */
1173 static int sshcom_put_mpint(void *target, void *data, int len)
1175 unsigned char *d = (unsigned char *)target;
1176 unsigned char *i = (unsigned char *)data;
1177 int bits = len * 8 - 1;
1180 if (*i & (1 << (bits & 7)))
1186 PUT_32BIT(d, bits+1);
1187 memcpy(d+4, i, len);
1191 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
1192 const char **errmsg_p)
1194 struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
1197 const char prefix_rsa[] = "if-modn{sign{rsa";
1198 const char prefix_dsa[] = "dl-modp{sign{dsa";
1199 enum { RSA, DSA } type;
1203 struct ssh2_userkey *ret = NULL, *retkey;
1204 const struct ssh_signkey *alg;
1205 unsigned char *blob = NULL;
1206 int blobsize = 0, publen, privlen;
1212 * Check magic number.
1214 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1215 errmsg = "key does not begin with magic number";
1220 * Determine the key type.
1223 if (key->keyblob_len < pos+4 ||
1224 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1225 errmsg = "key blob does not contain a key type string";
1228 if (len > sizeof(prefix_rsa) - 1 &&
1229 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1231 } else if (len > sizeof(prefix_dsa) - 1 &&
1232 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1235 errmsg = "key is of unknown type";
1241 * Determine the cipher type.
1243 if (key->keyblob_len < pos+4 ||
1244 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1245 errmsg = "key blob does not contain a cipher type string";
1248 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1250 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1253 errmsg = "key encryption is of unknown type";
1259 * Get hold of the encrypted part of the key.
1261 if (key->keyblob_len < pos+4 ||
1262 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1263 errmsg = "key blob does not contain actual key data";
1266 ciphertext = (char *)key->keyblob + pos + 4;
1268 if (cipherlen == 0) {
1269 errmsg = "length of key data is zero";
1274 * Decrypt it if necessary.
1278 * Derive encryption key from passphrase and iv/salt:
1280 * - let block A equal MD5(passphrase)
1281 * - let block B equal MD5(passphrase || A)
1282 * - block C would be MD5(passphrase || A || B) and so on
1283 * - encryption key is the first N bytes of A || B
1285 struct MD5Context md5c;
1286 unsigned char keybuf[32], iv[8];
1288 if (cipherlen % 8 != 0) {
1289 errmsg = "encrypted part of key is not a multiple of cipher block"
1295 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1296 MD5Final(keybuf, &md5c);
1299 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1300 MD5Update(&md5c, keybuf, 16);
1301 MD5Final(keybuf+16, &md5c);
1304 * Now decrypt the key blob.
1306 memset(iv, 0, sizeof(iv));
1307 des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1310 memset(&md5c, 0, sizeof(md5c));
1311 memset(keybuf, 0, sizeof(keybuf));
1314 * Hereafter we return WRONG_PASSPHRASE for any parsing
1315 * error. (But only if we've just tried to decrypt it!
1316 * Returning WRONG_PASSPHRASE for an unencrypted key is
1320 ret = SSH2_WRONG_PASSPHRASE;
1324 * Strip away the containing string to get to the real meat.
1326 len = GET_32BIT(ciphertext);
1327 if (len < 0 || len > cipherlen-4) {
1328 errmsg = "containing string was ill-formed";
1335 * Now we break down into RSA versus DSA. In either case we'll
1336 * construct public and private blobs in our own format, and
1337 * end up feeding them to alg->createkey().
1339 blobsize = cipherlen + 256;
1340 blob = snewn(blobsize, unsigned char);
1343 struct mpint_pos n, e, d, u, p, q;
1345 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1346 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1347 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1348 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1349 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1350 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1352 errmsg = "key data did not contain six integers";
1358 pos += put_string(blob+pos, "ssh-rsa", 7);
1359 pos += put_mp(blob+pos, e.start, e.bytes);
1360 pos += put_mp(blob+pos, n.start, n.bytes);
1362 pos += put_string(blob+pos, d.start, d.bytes);
1363 pos += put_mp(blob+pos, q.start, q.bytes);
1364 pos += put_mp(blob+pos, p.start, p.bytes);
1365 pos += put_mp(blob+pos, u.start, u.bytes);
1366 privlen = pos - publen;
1367 } else if (type == DSA) {
1368 struct mpint_pos p, q, g, x, y;
1370 if (GET_32BIT(ciphertext) != 0) {
1371 errmsg = "predefined DSA parameters not supported";
1374 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1375 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1376 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1377 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1378 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1380 errmsg = "key data did not contain five integers";
1386 pos += put_string(blob+pos, "ssh-dss", 7);
1387 pos += put_mp(blob+pos, p.start, p.bytes);
1388 pos += put_mp(blob+pos, q.start, q.bytes);
1389 pos += put_mp(blob+pos, g.start, g.bytes);
1390 pos += put_mp(blob+pos, y.start, y.bytes);
1392 pos += put_mp(blob+pos, x.start, x.bytes);
1393 privlen = pos - publen;
1397 assert(privlen > 0); /* should have bombed by now if not */
1399 retkey = snew(struct ssh2_userkey);
1401 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1402 if (!retkey->data) {
1404 errmsg = "unable to create key data structure";
1407 retkey->comment = dupstr(key->comment);
1409 errmsg = NULL; /* no error */
1414 memset(blob, 0, blobsize);
1417 memset(key->keyblob, 0, key->keyblob_size);
1418 sfree(key->keyblob);
1419 memset(&key, 0, sizeof(key));
1421 if (errmsg_p) *errmsg_p = errmsg;
1425 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
1428 unsigned char *pubblob, *privblob;
1429 int publen, privlen;
1430 unsigned char *outblob;
1432 struct mpint_pos numbers[6];
1433 int nnumbers, initial_zero, pos, lenpos, i;
1441 * Fetch the key blobs.
1443 pubblob = key->alg->public_blob(key->data, &publen);
1444 privblob = key->alg->private_blob(key->data, &privlen);
1448 * Find the sequence of integers to be encoded into the OpenSSH
1449 * key blob, and also decide on the header line.
1451 if (key->alg == &ssh_rsa) {
1453 struct mpint_pos n, e, d, p, q, iqmp;
1455 pos = 4 + GET_32BIT(pubblob);
1456 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1457 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1459 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1460 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1461 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1462 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1464 assert(e.start && iqmp.start); /* can't go wrong */
1475 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1476 } else if (key->alg == &ssh_dss) {
1478 struct mpint_pos p, q, g, y, x;
1480 pos = 4 + GET_32BIT(pubblob);
1481 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1482 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1483 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1484 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1486 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1488 assert(y.start && x.start); /* can't go wrong */
1498 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1500 assert(0); /* zoinks! */
1501 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
1505 * Total size of key blob will be somewhere under 512 plus
1506 * combined length of integers. We'll calculate the more
1507 * precise size as we construct the blob.
1510 for (i = 0; i < nnumbers; i++)
1511 outlen += 4 + numbers[i].bytes;
1512 outblob = snewn(outlen, unsigned char);
1515 * Create the unencrypted key blob.
1518 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1519 pos += 4; /* length field, fill in later */
1520 pos += put_string(outblob+pos, type, strlen(type));
1522 char *ciphertype = passphrase ? "3des-cbc" : "none";
1523 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1525 lenpos = pos; /* remember this position */
1526 pos += 4; /* encrypted-blob size */
1527 pos += 4; /* encrypted-payload size */
1529 PUT_32BIT(outblob+pos, 0);
1532 for (i = 0; i < nnumbers; i++)
1533 pos += sshcom_put_mpint(outblob+pos,
1534 numbers[i].start, numbers[i].bytes);
1535 /* Now wrap up the encrypted payload. */
1536 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1537 /* Pad encrypted blob to a multiple of cipher block size. */
1539 int padding = -(pos - (lenpos+4)) & 7;
1541 outblob[pos++] = random_byte();
1543 ciphertext = (char *)outblob+lenpos+4;
1544 cipherlen = pos - (lenpos+4);
1545 assert(!passphrase || cipherlen % 8 == 0);
1546 /* Wrap up the encrypted blob string. */
1547 PUT_32BIT(outblob+lenpos, cipherlen);
1548 /* And finally fill in the total length field. */
1549 PUT_32BIT(outblob+4, pos);
1551 assert(pos < outlen);
1558 * Derive encryption key from passphrase and iv/salt:
1560 * - let block A equal MD5(passphrase)
1561 * - let block B equal MD5(passphrase || A)
1562 * - block C would be MD5(passphrase || A || B) and so on
1563 * - encryption key is the first N bytes of A || B
1565 struct MD5Context md5c;
1566 unsigned char keybuf[32], iv[8];
1569 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1570 MD5Final(keybuf, &md5c);
1573 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1574 MD5Update(&md5c, keybuf, 16);
1575 MD5Final(keybuf+16, &md5c);
1578 * Now decrypt the key blob.
1580 memset(iv, 0, sizeof(iv));
1581 des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1584 memset(&md5c, 0, sizeof(md5c));
1585 memset(keybuf, 0, sizeof(keybuf));
1589 * And save it. We'll use Unix line endings just in case it's
1590 * subsequently transferred in binary mode.
1592 fp = f_open(*filename, "wb"); /* ensure Unix line endings */
1595 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1596 fprintf(fp, "Comment: \"");
1598 * Comment header is broken with backslash-newline if it goes
1599 * over 70 chars. Although it's surrounded by quotes, it
1600 * _doesn't_ escape backslashes or quotes within the string.
1601 * Don't ask me, I didn't design it.
1604 int slen = 60; /* starts at 60 due to "Comment: " */
1605 char *c = key->comment;
1606 while ((int)strlen(c) > slen) {
1607 fprintf(fp, "%.*s\\\n", slen, c);
1609 slen = 70; /* allow 70 chars on subsequent lines */
1611 fprintf(fp, "%s\"\n", c);
1613 base64_encode(fp, outblob, pos, 70);
1614 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1620 memset(outblob, 0, outlen);
1624 memset(privblob, 0, privlen);
1628 memset(pubblob, 0, publen);