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 = GET_32BIT(d);
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 };
315 unsigned char *keyblob;
316 int keyblob_len, keyblob_size;
319 static struct openssh_key *load_openssh_key(const Filename *filename,
320 const char **errmsg_p)
322 struct openssh_key *ret;
328 int base64_chars = 0;
330 ret = snew(struct openssh_key);
332 ret->keyblob_len = ret->keyblob_size = 0;
334 memset(ret->iv, 0, sizeof(ret->iv));
336 fp = f_open(*filename, "r", FALSE);
338 errmsg = "unable to open key file";
342 if (!(line = fgetline(fp))) {
343 errmsg = "unexpected end of file";
347 if (0 != strncmp(line, "-----BEGIN ", 11) ||
348 0 != strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) {
349 errmsg = "file does not begin with OpenSSH key header";
352 if (!strcmp(line, "-----BEGIN RSA PRIVATE KEY-----"))
353 ret->type = OSSH_RSA;
354 else if (!strcmp(line, "-----BEGIN DSA PRIVATE KEY-----"))
355 ret->type = OSSH_DSA;
357 errmsg = "unrecognised key type";
360 memset(line, 0, strlen(line));
366 if (!(line = fgetline(fp))) {
367 errmsg = "unexpected end of file";
371 if (0 == strncmp(line, "-----END ", 9) &&
372 0 == strcmp(line+strlen(line)-16, "PRIVATE KEY-----"))
374 if ((p = strchr(line, ':')) != NULL) {
376 errmsg = "header found in body of key data";
380 while (*p && isspace((unsigned char)*p)) p++;
381 if (!strcmp(line, "Proc-Type")) {
382 if (p[0] != '4' || p[1] != ',') {
383 errmsg = "Proc-Type is not 4 (only 4 is supported)";
387 if (!strcmp(p, "ENCRYPTED"))
389 } else if (!strcmp(line, "DEK-Info")) {
392 if (strncmp(p, "DES-EDE3-CBC,", 13)) {
393 errmsg = "ciphers other than DES-EDE3-CBC not supported";
397 for (i = 0; i < 8; i++) {
398 if (1 != sscanf(p, "%2x", &j))
404 errmsg = "expected 16-digit iv in DEK-Info";
412 while (isbase64(*p)) {
413 base64_bit[base64_chars++] = *p;
414 if (base64_chars == 4) {
415 unsigned char out[3];
420 len = base64_decode_atom(base64_bit, out);
423 errmsg = "invalid base64 encoding";
427 if (ret->keyblob_len + len > ret->keyblob_size) {
428 ret->keyblob_size = ret->keyblob_len + len + 256;
429 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
433 memcpy(ret->keyblob + ret->keyblob_len, out, len);
434 ret->keyblob_len += len;
436 memset(out, 0, sizeof(out));
442 memset(line, 0, strlen(line));
447 if (ret->keyblob_len == 0 || !ret->keyblob) {
448 errmsg = "key body not present";
452 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
453 errmsg = "encrypted key blob is not a multiple of cipher block size";
457 memset(base64_bit, 0, sizeof(base64_bit));
458 if (errmsg_p) *errmsg_p = NULL;
463 memset(line, 0, strlen(line));
467 memset(base64_bit, 0, sizeof(base64_bit));
470 memset(ret->keyblob, 0, ret->keyblob_size);
473 memset(ret, 0, sizeof(*ret));
476 if (errmsg_p) *errmsg_p = errmsg;
480 int openssh_encrypted(const Filename *filename)
482 struct openssh_key *key = load_openssh_key(filename, NULL);
487 ret = key->encrypted;
488 memset(key->keyblob, 0, key->keyblob_size);
490 memset(key, 0, sizeof(*key));
495 struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
496 const char **errmsg_p)
498 struct openssh_key *key = load_openssh_key(filename, errmsg_p);
499 struct ssh2_userkey *retkey;
501 int ret, id, len, flags;
503 struct ssh2_userkey *retval = NULL;
506 int blobsize = 0, blobptr, privptr;
515 if (key->encrypted) {
517 * Derive encryption key from passphrase and iv/salt:
519 * - let block A equal MD5(passphrase || iv)
520 * - let block B equal MD5(A || passphrase || iv)
521 * - block C would be MD5(B || passphrase || iv) and so on
522 * - encryption key is the first N bytes of A || B
524 struct MD5Context md5c;
525 unsigned char keybuf[32];
528 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
529 MD5Update(&md5c, (unsigned char *)key->iv, 8);
530 MD5Final(keybuf, &md5c);
533 MD5Update(&md5c, keybuf, 16);
534 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
535 MD5Update(&md5c, (unsigned char *)key->iv, 8);
536 MD5Final(keybuf+16, &md5c);
539 * Now decrypt the key blob.
541 des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv,
542 key->keyblob, key->keyblob_len);
544 memset(&md5c, 0, sizeof(md5c));
545 memset(keybuf, 0, sizeof(keybuf));
549 * Now we have a decrypted key blob, which contains an ASN.1
550 * encoded private key. We must now untangle the ASN.1.
552 * We expect the whole key blob to be formatted as a SEQUENCE
553 * (0x30 followed by a length code indicating that the rest of
554 * the blob is part of the sequence). Within that SEQUENCE we
555 * expect to see a bunch of INTEGERs. What those integers mean
556 * depends on the key type:
558 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
559 * dmp1, dmq1, iqmp in that order. (The last three are d mod
560 * (p-1), d mod (q-1), inverse of q mod p respectively.)
562 * - For DSA, we expect them to be 0, p, q, g, y, x in that
568 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
569 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
571 if (ret < 0 || id != 16) {
572 errmsg = "ASN.1 decoding failure";
573 retval = SSH2_WRONG_PASSPHRASE;
577 /* Expect a load of INTEGERs. */
578 if (key->type == OSSH_RSA)
580 else if (key->type == OSSH_DSA)
583 num_integers = 0; /* placate compiler warnings */
586 * Space to create key blob in.
588 blobsize = 256+key->keyblob_len;
589 blob = snewn(blobsize, unsigned char);
591 if (key->type == OSSH_DSA)
592 memcpy(blob+4, "ssh-dss", 7);
593 else if (key->type == OSSH_RSA)
594 memcpy(blob+4, "ssh-rsa", 7);
598 for (i = 0; i < num_integers; i++) {
599 ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
602 if (ret < 0 || id != 2 ||
603 key->keyblob+key->keyblob_len-p < len) {
604 errmsg = "ASN.1 decoding failure";
605 retval = SSH2_WRONG_PASSPHRASE;
611 * The first integer should be zero always (I think
612 * this is some sort of version indication).
614 if (len != 1 || p[0] != 0) {
615 errmsg = "version number mismatch";
618 } else if (key->type == OSSH_RSA) {
620 * Integers 1 and 2 go into the public blob but in the
621 * opposite order; integers 3, 4, 5 and 8 go into the
622 * private blob. The other two (6 and 7) are ignored.
625 /* Save the details for after we deal with number 2. */
628 } else if (i != 6 && i != 7) {
629 PUT_32BIT(blob+blobptr, len);
630 memcpy(blob+blobptr+4, p, len);
633 PUT_32BIT(blob+blobptr, modlen);
634 memcpy(blob+blobptr+4, modptr, modlen);
639 } else if (key->type == OSSH_DSA) {
641 * Integers 1-4 go into the public blob; integer 5 goes
642 * into the private blob.
644 PUT_32BIT(blob+blobptr, len);
645 memcpy(blob+blobptr+4, p, len);
651 /* Skip past the number. */
656 * Now put together the actual key. Simplest way to do this is
657 * to assemble our own key blobs and feed them to the createkey
658 * functions; this is a bit faffy but it does mean we get all
659 * the sanity checks for free.
661 assert(privptr > 0); /* should have bombed by now if not */
662 retkey = snew(struct ssh2_userkey);
663 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
664 retkey->data = retkey->alg->createkey(blob, privptr,
665 blob+privptr, blobptr-privptr);
668 errmsg = "unable to create key data structure";
672 retkey->comment = dupstr("imported-openssh-key");
673 errmsg = NULL; /* no error */
678 memset(blob, 0, blobsize);
681 memset(key->keyblob, 0, key->keyblob_size);
683 memset(key, 0, sizeof(*key));
685 if (errmsg_p) *errmsg_p = errmsg;
689 int openssh_write(const Filename *filename, struct ssh2_userkey *key,
692 unsigned char *pubblob, *privblob, *spareblob;
693 int publen, privlen, sparelen = 0;
694 unsigned char *outblob;
696 struct mpint_pos numbers[9];
697 int nnumbers, pos, len, seqlen, i;
698 char *header, *footer;
705 * Fetch the key blobs.
707 pubblob = key->alg->public_blob(key->data, &publen);
708 privblob = key->alg->private_blob(key->data, &privlen);
709 spareblob = outblob = NULL;
712 * Find the sequence of integers to be encoded into the OpenSSH
713 * key blob, and also decide on the header line.
715 if (key->alg == &ssh_rsa) {
717 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
718 Bignum bd, bp, bq, bdmp1, bdmq1;
720 pos = 4 + GET_32BIT(pubblob);
721 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
722 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
724 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
725 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
726 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
727 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
729 assert(e.start && iqmp.start); /* can't go wrong */
731 /* We also need d mod (p-1) and d mod (q-1). */
732 bd = bignum_from_bytes(d.start, d.bytes);
733 bp = bignum_from_bytes(p.start, p.bytes);
734 bq = bignum_from_bytes(q.start, q.bytes);
737 bdmp1 = bigmod(bd, bp);
738 bdmq1 = bigmod(bd, bq);
743 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
744 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
745 sparelen = dmp1.bytes + dmq1.bytes;
746 spareblob = snewn(sparelen, unsigned char);
747 dmp1.start = spareblob;
748 dmq1.start = spareblob + dmp1.bytes;
749 for (i = 0; i < dmp1.bytes; i++)
750 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
751 for (i = 0; i < dmq1.bytes; i++)
752 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
756 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
767 header = "-----BEGIN RSA PRIVATE KEY-----\n";
768 footer = "-----END RSA PRIVATE KEY-----\n";
769 } else if (key->alg == &ssh_dss) {
771 struct mpint_pos p, q, g, y, x;
773 pos = 4 + GET_32BIT(pubblob);
774 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
775 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
776 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
777 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
779 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
781 assert(y.start && x.start); /* can't go wrong */
783 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
791 header = "-----BEGIN DSA PRIVATE KEY-----\n";
792 footer = "-----END DSA PRIVATE KEY-----\n";
794 assert(0); /* zoinks! */
795 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
799 * Now count up the total size of the ASN.1 encoded integers,
800 * so as to determine the length of the containing SEQUENCE.
803 for (i = 0; i < nnumbers; i++) {
804 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
805 len += numbers[i].bytes;
808 /* Now add on the SEQUENCE header. */
809 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
810 /* Round up to the cipher block size, ensuring we have at least one
811 * byte of padding (see below). */
814 outlen = (outlen+8) &~ 7;
817 * Now we know how big outblob needs to be. Allocate it.
819 outblob = snewn(outlen, unsigned char);
822 * And write the data into it.
825 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
826 for (i = 0; i < nnumbers; i++) {
827 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
828 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
829 pos += numbers[i].bytes;
833 * Padding on OpenSSH keys is deterministic. The number of
834 * padding bytes is always more than zero, and always at most
835 * the cipher block length. The value of each padding byte is
836 * equal to the number of padding bytes. So a plaintext that's
837 * an exact multiple of the block size will be padded with 08
838 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
839 * plaintext one byte less than a multiple of the block size
840 * will be padded with just 01.
842 * This enables the OpenSSL key decryption function to strip
843 * off the padding algorithmically and return the unpadded
844 * plaintext to the next layer: it looks at the final byte, and
845 * then expects to find that many bytes at the end of the data
846 * with the same value. Those are all removed and the rest is
850 while (pos < outlen) {
851 outblob[pos++] = outlen - len;
859 * Invent an iv. Then derive encryption key from passphrase
862 * - let block A equal MD5(passphrase || iv)
863 * - let block B equal MD5(A || passphrase || iv)
864 * - block C would be MD5(B || passphrase || iv) and so on
865 * - encryption key is the first N bytes of A || B
867 struct MD5Context md5c;
868 unsigned char keybuf[32];
870 for (i = 0; i < 8; i++) iv[i] = random_byte();
873 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
874 MD5Update(&md5c, iv, 8);
875 MD5Final(keybuf, &md5c);
878 MD5Update(&md5c, keybuf, 16);
879 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
880 MD5Update(&md5c, iv, 8);
881 MD5Final(keybuf+16, &md5c);
884 * Now encrypt the key blob.
886 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
888 memset(&md5c, 0, sizeof(md5c));
889 memset(keybuf, 0, sizeof(keybuf));
893 * And save it. We'll use Unix line endings just in case it's
894 * subsequently transferred in binary mode.
896 fp = f_open(*filename, "wb", TRUE); /* ensure Unix line endings */
901 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
902 for (i = 0; i < 8; i++)
903 fprintf(fp, "%02X", iv[i]);
906 base64_encode(fp, outblob, outlen, 64);
913 memset(outblob, 0, outlen);
917 memset(spareblob, 0, sparelen);
921 memset(privblob, 0, privlen);
925 memset(pubblob, 0, publen);
931 /* ----------------------------------------------------------------------
932 * Code to read ssh.com private keys.
936 * The format of the base64 blob is largely SSH-2-packet-formatted,
937 * except that mpints are a bit different: they're more like the
938 * old SSH-1 mpint. You have a 32-bit bit count N, followed by
939 * (N+7)/8 bytes of data.
941 * So. The blob contains:
943 * - uint32 0x3f6ff9eb (magic number)
944 * - uint32 size (total blob size)
945 * - string key-type (see below)
946 * - string cipher-type (tells you if key is encrypted)
947 * - string encrypted-blob
949 * (The first size field includes the size field itself and the
950 * magic number before it. All other size fields are ordinary SSH-2
951 * strings, so the size field indicates how much data is to
954 * The encrypted blob, once decrypted, contains a single string
955 * which in turn contains the payload. (This allows padding to be
956 * added after that string while still making it clear where the
957 * real payload ends. Also it probably makes for a reasonable
960 * The payload blob, for an RSA key, contains:
963 * - mpint n (yes, the public and private stuff is intermixed)
964 * - mpint u (presumably inverse of p mod q)
965 * - mpint p (p is the smaller prime)
966 * - mpint q (q is the larger)
968 * For a DSA key, the payload blob contains:
976 * Alternatively, if the parameters are `predefined', that
977 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
978 * containing some predefined parameter specification. *shudder*,
979 * but I doubt we'll encounter this in real life.
981 * The key type strings are ghastly. The RSA key I looked at had a
984 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
986 * and the DSA key wasn't much better:
988 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
990 * It isn't clear that these will always be the same. I think it
991 * might be wise just to look at the `if-modn{sign{rsa' and
992 * `dl-modp{sign{dsa' prefixes.
994 * Finally, the encryption. The cipher-type string appears to be
995 * either `none' or `3des-cbc'. Looks as if this is SSH-2-style
996 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
997 * from the passphrase by means of yet another hashing faff:
999 * - first 16 bytes are MD5(passphrase)
1000 * - next 16 bytes are MD5(passphrase || first 16 bytes)
1001 * - if there were more, they'd be MD5(passphrase || first 32),
1005 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
1008 char comment[256]; /* allowing any length is overkill */
1009 unsigned char *keyblob;
1010 int keyblob_len, keyblob_size;
1013 static struct sshcom_key *load_sshcom_key(const Filename *filename,
1014 const char **errmsg_p)
1016 struct sshcom_key *ret;
1023 int base64_chars = 0;
1025 ret = snew(struct sshcom_key);
1026 ret->comment[0] = '\0';
1027 ret->keyblob = NULL;
1028 ret->keyblob_len = ret->keyblob_size = 0;
1030 fp = f_open(*filename, "r", FALSE);
1032 errmsg = "unable to open key file";
1035 if (!(line = fgetline(fp))) {
1036 errmsg = "unexpected end of file";
1040 if (0 != strcmp(line, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")) {
1041 errmsg = "file does not begin with ssh.com key header";
1044 memset(line, 0, strlen(line));
1050 if (!(line = fgetline(fp))) {
1051 errmsg = "unexpected end of file";
1055 if (!strcmp(line, "---- END SSH2 ENCRYPTED PRIVATE KEY ----"))
1057 if ((p = strchr(line, ':')) != NULL) {
1059 errmsg = "header found in body of key data";
1063 while (*p && isspace((unsigned char)*p)) p++;
1064 hdrstart = p - line;
1067 * Header lines can end in a trailing backslash for
1070 len = hdrstart + strlen(line+hdrstart);
1072 while (line[len-1] == '\\') {
1076 line2 = fgetline(fp);
1078 errmsg = "unexpected end of file";
1083 line2len = strlen(line2);
1084 line = sresize(line, len + line2len + 1, char);
1085 strcpy(line + len - 1, line2);
1086 len += line2len - 1;
1089 memset(line2, 0, strlen(line2));
1093 p = line + hdrstart;
1095 if (!strcmp(line, "Comment")) {
1096 /* Strip quotes in comment if present. */
1097 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1099 p[strlen(p)-1] = '\0';
1101 strncpy(ret->comment, p, sizeof(ret->comment));
1102 ret->comment[sizeof(ret->comment)-1] = '\0';
1108 while (isbase64(*p)) {
1109 base64_bit[base64_chars++] = *p;
1110 if (base64_chars == 4) {
1111 unsigned char out[3];
1115 len = base64_decode_atom(base64_bit, out);
1118 errmsg = "invalid base64 encoding";
1122 if (ret->keyblob_len + len > ret->keyblob_size) {
1123 ret->keyblob_size = ret->keyblob_len + len + 256;
1124 ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
1128 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1129 ret->keyblob_len += len;
1135 memset(line, 0, strlen(line));
1140 if (ret->keyblob_len == 0 || !ret->keyblob) {
1141 errmsg = "key body not present";
1145 if (errmsg_p) *errmsg_p = NULL;
1150 memset(line, 0, strlen(line));
1156 memset(ret->keyblob, 0, ret->keyblob_size);
1157 sfree(ret->keyblob);
1159 memset(ret, 0, sizeof(*ret));
1162 if (errmsg_p) *errmsg_p = errmsg;
1166 int sshcom_encrypted(const Filename *filename, char **comment)
1168 struct sshcom_key *key = load_sshcom_key(filename, NULL);
1169 int pos, len, answer;
1176 * Check magic number.
1178 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
1179 return 0; /* key is invalid */
1182 * Find the cipher-type string.
1186 if (key->keyblob_len < pos+4)
1187 goto done; /* key is far too short */
1188 pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */
1189 if (key->keyblob_len < pos+4)
1190 goto done; /* key is far too short */
1191 len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */
1192 if (key->keyblob_len < pos+4+len)
1193 goto done; /* cipher type string is incomplete */
1194 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1198 *comment = dupstr(key->comment);
1199 memset(key->keyblob, 0, key->keyblob_size);
1200 sfree(key->keyblob);
1201 memset(key, 0, sizeof(*key));
1206 static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1210 unsigned char *d = (unsigned char *) data;
1214 bits = GET_32BIT(d);
1216 bytes = (bits + 7) / 8;
1227 return len; /* ensure further calls fail as well */
1230 static int sshcom_put_mpint(void *target, void *data, int len)
1232 unsigned char *d = (unsigned char *)target;
1233 unsigned char *i = (unsigned char *)data;
1234 int bits = len * 8 - 1;
1237 if (*i & (1 << (bits & 7)))
1243 PUT_32BIT(d, bits+1);
1244 memcpy(d+4, i, len);
1248 struct ssh2_userkey *sshcom_read(const Filename *filename, char *passphrase,
1249 const char **errmsg_p)
1251 struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
1254 const char prefix_rsa[] = "if-modn{sign{rsa";
1255 const char prefix_dsa[] = "dl-modp{sign{dsa";
1256 enum { RSA, DSA } type;
1260 struct ssh2_userkey *ret = NULL, *retkey;
1261 const struct ssh_signkey *alg;
1262 unsigned char *blob = NULL;
1263 int blobsize = 0, publen, privlen;
1269 * Check magic number.
1271 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1272 errmsg = "key does not begin with magic number";
1277 * Determine the key type.
1280 if (key->keyblob_len < pos+4 ||
1281 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1282 errmsg = "key blob does not contain a key type string";
1285 if (len > sizeof(prefix_rsa) - 1 &&
1286 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1288 } else if (len > sizeof(prefix_dsa) - 1 &&
1289 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1292 errmsg = "key is of unknown type";
1298 * Determine the cipher type.
1300 if (key->keyblob_len < pos+4 ||
1301 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1302 errmsg = "key blob does not contain a cipher type string";
1305 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1307 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1310 errmsg = "key encryption is of unknown type";
1316 * Get hold of the encrypted part of the key.
1318 if (key->keyblob_len < pos+4 ||
1319 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1320 errmsg = "key blob does not contain actual key data";
1323 ciphertext = (char *)key->keyblob + pos + 4;
1325 if (cipherlen == 0) {
1326 errmsg = "length of key data is zero";
1331 * Decrypt it if necessary.
1335 * Derive encryption key from passphrase and iv/salt:
1337 * - let block A equal MD5(passphrase)
1338 * - let block B equal MD5(passphrase || A)
1339 * - block C would be MD5(passphrase || A || B) and so on
1340 * - encryption key is the first N bytes of A || B
1342 struct MD5Context md5c;
1343 unsigned char keybuf[32], iv[8];
1345 if (cipherlen % 8 != 0) {
1346 errmsg = "encrypted part of key is not a multiple of cipher block"
1352 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1353 MD5Final(keybuf, &md5c);
1356 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1357 MD5Update(&md5c, keybuf, 16);
1358 MD5Final(keybuf+16, &md5c);
1361 * Now decrypt the key blob.
1363 memset(iv, 0, sizeof(iv));
1364 des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1367 memset(&md5c, 0, sizeof(md5c));
1368 memset(keybuf, 0, sizeof(keybuf));
1371 * Hereafter we return WRONG_PASSPHRASE for any parsing
1372 * error. (But only if we've just tried to decrypt it!
1373 * Returning WRONG_PASSPHRASE for an unencrypted key is
1377 ret = SSH2_WRONG_PASSPHRASE;
1381 * Strip away the containing string to get to the real meat.
1383 len = GET_32BIT(ciphertext);
1384 if (len < 0 || len > cipherlen-4) {
1385 errmsg = "containing string was ill-formed";
1392 * Now we break down into RSA versus DSA. In either case we'll
1393 * construct public and private blobs in our own format, and
1394 * end up feeding them to alg->createkey().
1396 blobsize = cipherlen + 256;
1397 blob = snewn(blobsize, unsigned char);
1400 struct mpint_pos n, e, d, u, p, q;
1402 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1403 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1404 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1405 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1406 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1407 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1409 errmsg = "key data did not contain six integers";
1415 pos += put_string(blob+pos, "ssh-rsa", 7);
1416 pos += put_mp(blob+pos, e.start, e.bytes);
1417 pos += put_mp(blob+pos, n.start, n.bytes);
1419 pos += put_string(blob+pos, d.start, d.bytes);
1420 pos += put_mp(blob+pos, q.start, q.bytes);
1421 pos += put_mp(blob+pos, p.start, p.bytes);
1422 pos += put_mp(blob+pos, u.start, u.bytes);
1423 privlen = pos - publen;
1424 } else if (type == DSA) {
1425 struct mpint_pos p, q, g, x, y;
1427 if (GET_32BIT(ciphertext) != 0) {
1428 errmsg = "predefined DSA parameters not supported";
1431 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1432 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1433 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1434 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1435 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1437 errmsg = "key data did not contain five integers";
1443 pos += put_string(blob+pos, "ssh-dss", 7);
1444 pos += put_mp(blob+pos, p.start, p.bytes);
1445 pos += put_mp(blob+pos, q.start, q.bytes);
1446 pos += put_mp(blob+pos, g.start, g.bytes);
1447 pos += put_mp(blob+pos, y.start, y.bytes);
1449 pos += put_mp(blob+pos, x.start, x.bytes);
1450 privlen = pos - publen;
1454 assert(privlen > 0); /* should have bombed by now if not */
1456 retkey = snew(struct ssh2_userkey);
1458 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1459 if (!retkey->data) {
1461 errmsg = "unable to create key data structure";
1464 retkey->comment = dupstr(key->comment);
1466 errmsg = NULL; /* no error */
1471 memset(blob, 0, blobsize);
1474 memset(key->keyblob, 0, key->keyblob_size);
1475 sfree(key->keyblob);
1476 memset(key, 0, sizeof(*key));
1478 if (errmsg_p) *errmsg_p = errmsg;
1482 int sshcom_write(const Filename *filename, struct ssh2_userkey *key,
1485 unsigned char *pubblob, *privblob;
1486 int publen, privlen;
1487 unsigned char *outblob;
1489 struct mpint_pos numbers[6];
1490 int nnumbers, initial_zero, pos, lenpos, i;
1498 * Fetch the key blobs.
1500 pubblob = key->alg->public_blob(key->data, &publen);
1501 privblob = key->alg->private_blob(key->data, &privlen);
1505 * Find the sequence of integers to be encoded into the OpenSSH
1506 * key blob, and also decide on the header line.
1508 if (key->alg == &ssh_rsa) {
1510 struct mpint_pos n, e, d, p, q, iqmp;
1512 pos = 4 + GET_32BIT(pubblob);
1513 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1514 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1516 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1517 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1518 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1519 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1521 assert(e.start && iqmp.start); /* can't go wrong */
1532 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1533 } else if (key->alg == &ssh_dss) {
1535 struct mpint_pos p, q, g, y, x;
1537 pos = 4 + GET_32BIT(pubblob);
1538 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1539 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1540 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1541 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1543 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1545 assert(y.start && x.start); /* can't go wrong */
1555 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1557 assert(0); /* zoinks! */
1558 exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
1562 * Total size of key blob will be somewhere under 512 plus
1563 * combined length of integers. We'll calculate the more
1564 * precise size as we construct the blob.
1567 for (i = 0; i < nnumbers; i++)
1568 outlen += 4 + numbers[i].bytes;
1569 outblob = snewn(outlen, unsigned char);
1572 * Create the unencrypted key blob.
1575 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1576 pos += 4; /* length field, fill in later */
1577 pos += put_string(outblob+pos, type, strlen(type));
1579 char *ciphertype = passphrase ? "3des-cbc" : "none";
1580 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1582 lenpos = pos; /* remember this position */
1583 pos += 4; /* encrypted-blob size */
1584 pos += 4; /* encrypted-payload size */
1586 PUT_32BIT(outblob+pos, 0);
1589 for (i = 0; i < nnumbers; i++)
1590 pos += sshcom_put_mpint(outblob+pos,
1591 numbers[i].start, numbers[i].bytes);
1592 /* Now wrap up the encrypted payload. */
1593 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1594 /* Pad encrypted blob to a multiple of cipher block size. */
1596 int padding = -(pos - (lenpos+4)) & 7;
1598 outblob[pos++] = random_byte();
1600 ciphertext = (char *)outblob+lenpos+4;
1601 cipherlen = pos - (lenpos+4);
1602 assert(!passphrase || cipherlen % 8 == 0);
1603 /* Wrap up the encrypted blob string. */
1604 PUT_32BIT(outblob+lenpos, cipherlen);
1605 /* And finally fill in the total length field. */
1606 PUT_32BIT(outblob+4, pos);
1608 assert(pos < outlen);
1615 * Derive encryption key from passphrase and iv/salt:
1617 * - let block A equal MD5(passphrase)
1618 * - let block B equal MD5(passphrase || A)
1619 * - block C would be MD5(passphrase || A || B) and so on
1620 * - encryption key is the first N bytes of A || B
1622 struct MD5Context md5c;
1623 unsigned char keybuf[32], iv[8];
1626 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1627 MD5Final(keybuf, &md5c);
1630 MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
1631 MD5Update(&md5c, keybuf, 16);
1632 MD5Final(keybuf+16, &md5c);
1635 * Now decrypt the key blob.
1637 memset(iv, 0, sizeof(iv));
1638 des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
1641 memset(&md5c, 0, sizeof(md5c));
1642 memset(keybuf, 0, sizeof(keybuf));
1646 * And save it. We'll use Unix line endings just in case it's
1647 * subsequently transferred in binary mode.
1649 fp = f_open(*filename, "wb", TRUE); /* ensure Unix line endings */
1652 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1653 fprintf(fp, "Comment: \"");
1655 * Comment header is broken with backslash-newline if it goes
1656 * over 70 chars. Although it's surrounded by quotes, it
1657 * _doesn't_ escape backslashes or quotes within the string.
1658 * Don't ask me, I didn't design it.
1661 int slen = 60; /* starts at 60 due to "Comment: " */
1662 char *c = key->comment;
1663 while ((int)strlen(c) > slen) {
1664 fprintf(fp, "%.*s\\\n", slen, c);
1666 slen = 70; /* allow 70 chars on subsequent lines */
1668 fprintf(fp, "%s\"\n", c);
1670 base64_encode(fp, outblob, pos, 70);
1671 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1677 memset(outblob, 0, outlen);
1681 memset(privblob, 0, privlen);
1685 memset(pubblob, 0, publen);