2 * Code for PuTTY to import and export private key files in other
3 * SSH clients' formats.
14 #define PUT_32BIT(cp, value) do { \
15 (cp)[3] = (unsigned char)(value); \
16 (cp)[2] = (unsigned char)((value) >> 8); \
17 (cp)[1] = (unsigned char)((value) >> 16); \
18 (cp)[0] = (unsigned char)((value) >> 24); } while (0)
20 #define GET_32BIT(cp) \
21 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
22 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
23 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
24 ((unsigned long)(unsigned char)(cp)[3]))
26 int openssh_encrypted(char *filename);
27 struct ssh2_userkey *openssh_read(char *filename, char *passphrase);
28 int openssh_write(char *filename, struct ssh2_userkey *key, char *passphrase);
30 int sshcom_encrypted(char *filename, char **comment);
31 struct ssh2_userkey *sshcom_read(char *filename, char *passphrase);
32 int sshcom_write(char *filename, struct ssh2_userkey *key, char *passphrase);
35 * Given a key type, determine whether we know how to import it.
37 int import_possible(int type)
39 if (type == SSH_KEYTYPE_OPENSSH)
41 if (type == SSH_KEYTYPE_SSHCOM)
47 * Given a key type, determine what native key type
48 * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
51 int import_target_type(int type)
54 * There are no known foreign SSH1 key formats.
56 return SSH_KEYTYPE_SSH2;
60 * Determine whether a foreign key is encrypted.
62 int import_encrypted(char *filename, int type, char **comment)
64 if (type == SSH_KEYTYPE_OPENSSH) {
65 *comment = dupstr(filename); /* OpenSSH doesn't do key comments */
66 return openssh_encrypted(filename);
68 if (type == SSH_KEYTYPE_SSHCOM) {
69 return sshcom_encrypted(filename, comment);
77 int import_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase)
85 struct ssh2_userkey *import_ssh2(char *filename, int type, char *passphrase)
87 if (type == SSH_KEYTYPE_OPENSSH)
88 return openssh_read(filename, passphrase);
89 if (type == SSH_KEYTYPE_SSHCOM)
90 return sshcom_read(filename, passphrase);
97 int export_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase)
103 * Export an SSH2 key.
105 int export_ssh2(char *filename, int type,
106 struct ssh2_userkey *key, char *passphrase)
108 if (type == SSH_KEYTYPE_OPENSSH)
109 return openssh_write(filename, key, passphrase);
110 if (type == SSH_KEYTYPE_SSHCOM)
111 return sshcom_write(filename, key, passphrase);
115 /* ----------------------------------------------------------------------
116 * Helper routines. (The base64 ones are defined in sshpubk.c.)
119 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
120 ((c) >= 'a' && (c) <= 'z') || \
121 ((c) >= '0' && (c) <= '9') || \
122 (c) == '+' || (c) == '/' || (c) == '=' \
125 extern int base64_decode_atom(char *atom, unsigned char *out);
126 extern int base64_lines(int datalen);
127 extern void base64_encode_atom(unsigned char *data, int n, char *out);
128 extern void base64_encode(FILE *fp, unsigned char *data, int datalen, int cpl);
131 * Read an ASN.1/BER identifier and length pair.
133 * Flags are a combination of the #defines listed below.
135 * Returns -1 if unsuccessful; otherwise returns the number of
136 * bytes used out of the source data.
139 /* ASN.1 tag classes. */
140 #define ASN1_CLASS_UNIVERSAL (0 << 6)
141 #define ASN1_CLASS_APPLICATION (1 << 6)
142 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
143 #define ASN1_CLASS_PRIVATE (3 << 6)
144 #define ASN1_CLASS_MASK (3 << 6)
146 /* Primitive versus constructed bit. */
147 #define ASN1_CONSTRUCTED (1 << 5)
149 int ber_read_id_len(void *source, int sourcelen,
150 int *id, int *length, int *flags)
152 unsigned char *p = (unsigned char *) source;
157 *flags = (*p & 0xE0);
158 if ((*p & 0x1F) == 0x1F) {
161 *id = (*id << 7) | (*p & 0x7F);
166 *id = (*id << 7) | (*p & 0x7F);
183 *length = (*length << 8) | (*p++);
190 return p - (unsigned char *) source;
194 * Write an ASN.1/BER identifier and length pair. Returns the
195 * number of bytes consumed. Assumes dest contains enough space.
196 * Will avoid writing anything if dest is NULL, but still return
197 * amount of space required.
199 int ber_write_id_len(void *dest, int id, int length, int flags)
201 unsigned char *d = (unsigned char *)dest;
206 * Identifier is one byte.
209 if (d) *d++ = id | flags;
213 * Identifier is multiple bytes: the first byte is 11111
214 * plus the flags, and subsequent bytes encode the value of
215 * the identifier, 7 bits at a time, with the top bit of
216 * each byte 1 except the last one which is 0.
219 if (d) *d++ = 0x1F | flags;
220 for (n = 1; (id >> (7*n)) > 0; n++)
221 continue; /* count the bytes */
224 if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
230 * Length is one byte.
233 if (d) *d++ = length;
237 * Length is multiple bytes. The first is 0x80 plus the
238 * number of subsequent bytes, and the subsequent bytes
239 * encode the actual length.
241 for (n = 1; (length >> (8*n)) > 0; n++)
242 continue; /* count the bytes */
244 if (d) *d++ = 0x80 | n;
247 if (d) *d++ = (length >> (8*n)) & 0xFF;
254 static int put_string(void *target, void *data, int len)
256 unsigned char *d = (unsigned char *)target;
259 memcpy(d+4, data, len);
263 static int put_mp(void *target, void *data, int len)
265 unsigned char *d = (unsigned char *)target;
266 unsigned char *i = (unsigned char *)data;
271 memcpy(d+5, data, len);
275 memcpy(d+4, data, len);
280 /* Simple structure to point to an mp-int within a blob. */
281 struct mpint_pos { void *start; int bytes; };
283 int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
286 unsigned char *d = (unsigned char *) data;
290 bytes = GET_32BIT(d);
301 return len; /* ensure further calls fail as well */
304 /* ----------------------------------------------------------------------
305 * Code to read and write OpenSSH private keys.
308 enum { OSSH_DSA, OSSH_RSA };
313 unsigned char *keyblob;
314 int keyblob_len, keyblob_size;
317 struct openssh_key *load_openssh_key(char *filename)
319 struct openssh_key *ret;
325 int base64_chars = 0;
327 ret = smalloc(sizeof(*ret));
329 ret->keyblob_len = ret->keyblob_size = 0;
331 memset(ret->iv, 0, sizeof(ret->iv));
333 fp = fopen(filename, "r");
335 errmsg = "Unable to open key file";
338 if (!fgets(buffer, sizeof(buffer), fp) ||
339 0 != strncmp(buffer, "-----BEGIN ", 11) ||
340 0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) {
341 errmsg = "File does not begin with OpenSSH key header";
344 if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n"))
345 ret->type = OSSH_RSA;
346 else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n"))
347 ret->type = OSSH_DSA;
349 errmsg = "Unrecognised key type";
355 if (!fgets(buffer, sizeof(buffer), fp)) {
356 errmsg = "Unexpected end of file";
359 if (0 == strncmp(buffer, "-----END ", 9) &&
360 0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n"))
362 if ((p = strchr(buffer, ':')) != NULL) {
364 errmsg = "Header found in body of key data";
368 while (*p && isspace((unsigned char)*p)) p++;
369 if (!strcmp(buffer, "Proc-Type")) {
370 if (p[0] != '4' || p[1] != ',') {
371 errmsg = "Proc-Type is not 4 (only 4 is supported)";
375 if (!strcmp(p, "ENCRYPTED\n"))
377 } else if (!strcmp(buffer, "DEK-Info")) {
380 if (strncmp(p, "DES-EDE3-CBC,", 13)) {
381 errmsg = "Ciphers other than DES-EDE3-CBC not supported";
385 for (i = 0; i < 8; i++) {
386 if (1 != sscanf(p, "%2x", &j))
392 errmsg = "Expected 16-digit iv in DEK-Info";
400 while (isbase64(*p)) {
401 base64_bit[base64_chars++] = *p;
402 if (base64_chars == 4) {
403 unsigned char out[3];
408 len = base64_decode_atom(base64_bit, out);
411 errmsg = "Invalid base64 encoding";
415 if (ret->keyblob_len + len > ret->keyblob_size) {
416 ret->keyblob_size = ret->keyblob_len + len + 256;
417 ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size);
420 memcpy(ret->keyblob + ret->keyblob_len, out, len);
421 ret->keyblob_len += len;
423 memset(out, 0, sizeof(out));
431 if (ret->keyblob_len == 0 || !ret->keyblob) {
432 errmsg = "Key body not present";
436 if (ret->encrypted && ret->keyblob_len % 8 != 0) {
437 errmsg = "Encrypted key blob is not a multiple of cipher block size";
441 memset(buffer, 0, sizeof(buffer));
442 memset(base64_bit, 0, sizeof(base64_bit));
446 memset(buffer, 0, sizeof(buffer));
447 memset(base64_bit, 0, sizeof(base64_bit));
450 memset(ret->keyblob, 0, ret->keyblob_size);
453 memset(&ret, 0, sizeof(ret));
459 int openssh_encrypted(char *filename)
461 struct openssh_key *key = load_openssh_key(filename);
466 ret = key->encrypted;
467 memset(key->keyblob, 0, key->keyblob_size);
469 memset(&key, 0, sizeof(key));
474 struct ssh2_userkey *openssh_read(char *filename, char *passphrase)
476 struct openssh_key *key = load_openssh_key(filename);
477 struct ssh2_userkey *retkey;
479 int ret, id, len, flags;
481 struct ssh2_userkey *retval = NULL;
484 int blobsize, blobptr, privptr;
491 if (key->encrypted) {
493 * Derive encryption key from passphrase and iv/salt:
495 * - let block A equal MD5(passphrase || iv)
496 * - let block B equal MD5(A || passphrase || iv)
497 * - block C would be MD5(B || passphrase || iv) and so on
498 * - encryption key is the first N bytes of A || B
500 struct MD5Context md5c;
501 unsigned char keybuf[32];
504 MD5Update(&md5c, passphrase, strlen(passphrase));
505 MD5Update(&md5c, key->iv, 8);
506 MD5Final(keybuf, &md5c);
509 MD5Update(&md5c, keybuf, 16);
510 MD5Update(&md5c, passphrase, strlen(passphrase));
511 MD5Update(&md5c, key->iv, 8);
512 MD5Final(keybuf+16, &md5c);
515 * Now decrypt the key blob.
517 des3_decrypt_pubkey_ossh(keybuf, key->iv,
518 key->keyblob, key->keyblob_len);
520 memset(&md5c, 0, sizeof(md5c));
521 memset(keybuf, 0, sizeof(keybuf));
525 * Now we have a decrypted key blob, which contains an ASN.1
526 * encoded private key. We must now untangle the ASN.1.
528 * We expect the whole key blob to be formatted as a SEQUENCE
529 * (0x30 followed by a length code indicating that the rest of
530 * the blob is part of the sequence). Within that SEQUENCE we
531 * expect to see a bunch of INTEGERs. What those integers mean
532 * depends on the key type:
534 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
535 * dmp1, dmq1, iqmp in that order. (The last three are d mod
536 * (p-1), d mod (q-1), inverse of q mod p respectively.)
538 * - For DSA, we expect them to be 0, p, q, g, y, x in that
544 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
545 ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
547 if (ret < 0 || id != 16) {
548 errmsg = "ASN.1 decoding failure";
549 retval = SSH2_WRONG_PASSPHRASE;
553 /* Expect a load of INTEGERs. */
554 if (key->type == OSSH_RSA)
556 else if (key->type == OSSH_DSA)
560 * Space to create key blob in.
562 blobsize = 256+key->keyblob_len;
563 blob = smalloc(blobsize);
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";
584 * The first integer should be zero always (I think
585 * this is some sort of version indication).
587 if (len != 1 || p[0] != 0) {
588 errmsg = "Version number mismatch";
591 } else if (key->type == OSSH_RSA) {
593 * Integers 1 and 2 go into the public blob but in the
594 * opposite order; integers 3, 4, 5 and 8 go into the
595 * private blob. The other two (6 and 7) are ignored.
598 /* Save the details for after we deal with number 2. */
601 } else if (i != 6 && i != 7) {
602 PUT_32BIT(blob+blobptr, len);
603 memcpy(blob+blobptr+4, p, len);
606 PUT_32BIT(blob+blobptr, modlen);
607 memcpy(blob+blobptr+4, modptr, modlen);
612 } else if (key->type == OSSH_DSA) {
614 * Integers 1-4 go into the public blob; integer 5 goes
615 * into the private blob.
617 PUT_32BIT(blob+blobptr, len);
618 memcpy(blob+blobptr+4, p, len);
624 /* Skip past the number. */
629 * Now put together the actual key. Simplest way to do this is
630 * to assemble our own key blobs and feed them to the createkey
631 * functions; this is a bit faffy but it does mean we get all
632 * the sanity checks for free.
634 assert(privptr > 0); /* should have bombed by now if not */
635 retkey = smalloc(sizeof(struct ssh2_userkey));
636 retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss);
637 retkey->data = retkey->alg->createkey(blob, privptr,
638 blob+privptr, blobptr-privptr);
641 errmsg = "unable to create key data structure";
645 retkey->comment = dupstr("imported-openssh-key");
646 errmsg = NULL; /* no error */
651 memset(blob, 0, blobsize);
654 memset(key->keyblob, 0, key->keyblob_size);
656 memset(&key, 0, sizeof(key));
661 int openssh_write(char *filename, struct ssh2_userkey *key, char *passphrase)
663 unsigned char *pubblob, *privblob, *spareblob;
664 int publen, privlen, sparelen;
665 unsigned char *outblob;
667 struct mpint_pos numbers[9];
668 int nnumbers, pos, len, seqlen, i;
669 char *header, *footer;
676 * Fetch the key blobs.
678 pubblob = key->alg->public_blob(key->data, &publen);
679 privblob = key->alg->private_blob(key->data, &privlen);
680 spareblob = outblob = NULL;
683 * Find the sequence of integers to be encoded into the OpenSSH
684 * key blob, and also decide on the header line.
686 if (key->alg == &ssh_rsa) {
688 struct mpint_pos n, e, d, p, q, iqmp, dmp1, dmq1;
689 Bignum bd, bp, bq, bdmp1, bdmq1;
691 pos = 4 + GET_32BIT(pubblob);
692 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
693 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
695 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
696 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
697 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
698 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
700 assert(e.start && iqmp.start); /* can't go wrong */
702 /* We also need d mod (p-1) and d mod (q-1). */
703 bd = bignum_from_bytes(d.start, d.bytes);
704 bp = bignum_from_bytes(p.start, p.bytes);
705 bq = bignum_from_bytes(q.start, q.bytes);
708 bdmp1 = bigmod(bd, bp);
709 bdmq1 = bigmod(bd, bq);
714 dmp1.bytes = (bignum_bitcount(bdmp1)+8)/8;
715 dmq1.bytes = (bignum_bitcount(bdmq1)+8)/8;
716 sparelen = dmp1.bytes + dmq1.bytes;
717 spareblob = smalloc(sparelen);
718 dmp1.start = spareblob;
719 dmq1.start = spareblob + dmp1.bytes;
720 for (i = 0; i < dmp1.bytes; i++)
721 spareblob[i] = bignum_byte(bdmp1, dmp1.bytes-1 - i);
722 for (i = 0; i < dmq1.bytes; i++)
723 spareblob[i+dmp1.bytes] = bignum_byte(bdmq1, dmq1.bytes-1 - i);
727 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
738 header = "-----BEGIN RSA PRIVATE KEY-----\n";
739 footer = "-----END RSA PRIVATE KEY-----\n";
740 } else if (key->alg == &ssh_dss) {
742 struct mpint_pos p, q, g, y, x;
744 pos = 4 + GET_32BIT(pubblob);
745 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
746 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
747 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
748 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
750 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
752 assert(y.start && x.start); /* can't go wrong */
754 numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
762 header = "-----BEGIN DSA PRIVATE KEY-----\n";
763 footer = "-----END DSA PRIVATE KEY-----\n";
765 assert(0); /* zoinks! */
769 * Now count up the total size of the ASN.1 encoded integers,
770 * so as to determine the length of the containing SEQUENCE.
773 for (i = 0; i < nnumbers; i++) {
774 len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
775 len += numbers[i].bytes;
778 /* Now add on the SEQUENCE header. */
779 len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
780 /* Round up to the cipher block size, ensuring we have at least one
781 * byte of padding (see below). */
784 outlen = (outlen+8) &~ 7;
787 * Now we know how big outblob needs to be. Allocate it.
789 outblob = smalloc(outlen);
792 * And write the data into it.
795 pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
796 for (i = 0; i < nnumbers; i++) {
797 pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
798 memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
799 pos += numbers[i].bytes;
803 * Padding on OpenSSH keys is deterministic. The number of
804 * padding bytes is always more than zero, and always at most
805 * the cipher block length. The value of each padding byte is
806 * equal to the number of padding bytes. So a plaintext that's
807 * an exact multiple of the block size will be padded with 08
808 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
809 * plaintext one byte less than a multiple of the block size
810 * will be padded with just 01.
812 * This enables the OpenSSL key decryption function to strip
813 * off the padding algorithmically and return the unpadded
814 * plaintext to the next layer: it looks at the final byte, and
815 * then expects to find that many bytes at the end of the data
816 * with the same value. Those are all removed and the rest is
820 while (pos < outlen) {
821 outblob[pos++] = outlen - len;
829 * Invent an iv. Then derive encryption key from passphrase
832 * - let block A equal MD5(passphrase || iv)
833 * - let block B equal MD5(A || passphrase || iv)
834 * - block C would be MD5(B || passphrase || iv) and so on
835 * - encryption key is the first N bytes of A || B
837 struct MD5Context md5c;
838 unsigned char keybuf[32];
840 for (i = 0; i < 8; i++) iv[i] = random_byte();
843 MD5Update(&md5c, passphrase, strlen(passphrase));
844 MD5Update(&md5c, iv, 8);
845 MD5Final(keybuf, &md5c);
848 MD5Update(&md5c, keybuf, 16);
849 MD5Update(&md5c, passphrase, strlen(passphrase));
850 MD5Update(&md5c, iv, 8);
851 MD5Final(keybuf+16, &md5c);
854 * Now encrypt the key blob.
856 des3_encrypt_pubkey_ossh(keybuf, iv, outblob, outlen);
858 memset(&md5c, 0, sizeof(md5c));
859 memset(keybuf, 0, sizeof(keybuf));
863 * And save it. We'll use Unix line endings just in case it's
864 * subsequently transferred in binary mode.
866 fp = fopen(filename, "wb"); /* ensure Unix line endings */
871 fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
872 for (i = 0; i < 8; i++)
873 fprintf(fp, "%02X", iv[i]);
876 base64_encode(fp, outblob, outlen, 64);
883 memset(outblob, 0, outlen);
887 memset(spareblob, 0, sparelen);
891 memset(privblob, 0, privlen);
895 memset(pubblob, 0, publen);
901 /* ----------------------------------------------------------------------
902 * Code to read ssh.com private keys.
906 * The format of the base64 blob is largely ssh2-packet-formatted,
907 * except that mpints are a bit different: they're more like the
908 * old ssh1 mpint. You have a 32-bit bit count N, followed by
909 * (N+7)/8 bytes of data.
911 * So. The blob contains:
913 * - uint32 0x3f6ff9eb (magic number)
914 * - uint32 size (total blob size)
915 * - string key-type (see below)
916 * - string cipher-type (tells you if key is encrypted)
917 * - string encrypted-blob
919 * (The first size field includes the size field itself and the
920 * magic number before it. All other size fields are ordinary ssh2
921 * strings, so the size field indicates how much data is to
924 * The encrypted blob, once decrypted, contains a single string
925 * which in turn contains the payload. (This allows padding to be
926 * added after that string while still making it clear where the
927 * real payload ends. Also it probably makes for a reasonable
930 * The payload blob, for an RSA key, contains:
933 * - mpint n (yes, the public and private stuff is intermixed)
934 * - mpint u (presumably inverse of p mod q)
935 * - mpint p (p is the smaller prime)
936 * - mpint q (q is the larger)
938 * For a DSA key, the payload blob contains:
946 * Alternatively, if the parameters are `predefined', that
947 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
948 * containing some predefined parameter specification. *shudder*,
949 * but I doubt we'll encounter this in real life.
951 * The key type strings are ghastly. The RSA key I looked at had a
954 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
956 * and the DSA key wasn't much better:
958 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
960 * It isn't clear that these will always be the same. I think it
961 * might be wise just to look at the `if-modn{sign{rsa' and
962 * `dl-modp{sign{dsa' prefixes.
964 * Finally, the encryption. The cipher-type string appears to be
965 * either `none' or `3des-cbc'. Looks as if this is SSH2-style
966 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
967 * from the passphrase by means of yet another hashing faff:
969 * - first 16 bytes are MD5(passphrase)
970 * - next 16 bytes are MD5(passphrase || first 16 bytes)
971 * - if there were more, they'd be MD5(passphrase || first 32),
975 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
978 char comment[256]; /* allowing any length is overkill */
979 unsigned char *keyblob;
980 int keyblob_len, keyblob_size;
983 struct sshcom_key *load_sshcom_key(char *filename)
985 struct sshcom_key *ret;
992 int base64_chars = 0;
994 ret = smalloc(sizeof(*ret));
995 ret->comment[0] = '\0';
997 ret->keyblob_len = ret->keyblob_size = 0;
999 fp = fopen(filename, "r");
1001 errmsg = "Unable to open key file";
1004 if (!fgets(buffer, sizeof(buffer), fp) ||
1005 0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1006 errmsg = "File does not begin with ssh.com key header";
1012 if (!fgets(buffer, sizeof(buffer), fp)) {
1013 errmsg = "Unexpected end of file";
1016 if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1018 if ((p = strchr(buffer, ':')) != NULL) {
1020 errmsg = "Header found in body of key data";
1024 while (*p && isspace((unsigned char)*p)) p++;
1026 * Header lines can end in a trailing backslash for
1029 while ((len = strlen(p)) > sizeof(buffer) - (p-buffer) -1 ||
1030 p[len-1] != '\n' || p[len-2] == '\\') {
1031 if (len > (p-buffer) + sizeof(buffer)-2) {
1032 errmsg = "Header line too long to deal with";
1035 if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) {
1036 errmsg = "Unexpected end of file";
1040 p[strcspn(p, "\n")] = '\0';
1041 if (!strcmp(buffer, "Comment")) {
1042 /* Strip quotes in comment if present. */
1043 if (p[0] == '"' && p[strlen(p)-1] == '"') {
1045 p[strlen(p)-1] = '\0';
1047 strncpy(ret->comment, p, sizeof(ret->comment));
1048 ret->comment[sizeof(ret->comment)-1] = '\0';
1054 while (isbase64(*p)) {
1055 base64_bit[base64_chars++] = *p;
1056 if (base64_chars == 4) {
1057 unsigned char out[3];
1061 len = base64_decode_atom(base64_bit, out);
1064 errmsg = "Invalid base64 encoding";
1068 if (ret->keyblob_len + len > ret->keyblob_size) {
1069 ret->keyblob_size = ret->keyblob_len + len + 256;
1070 ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size);
1073 memcpy(ret->keyblob + ret->keyblob_len, out, len);
1074 ret->keyblob_len += len;
1082 if (ret->keyblob_len == 0 || !ret->keyblob) {
1083 errmsg = "Key body not present";
1092 memset(ret->keyblob, 0, ret->keyblob_size);
1093 sfree(ret->keyblob);
1095 memset(&ret, 0, sizeof(ret));
1101 int sshcom_encrypted(char *filename, char **comment)
1103 struct sshcom_key *key = load_sshcom_key(filename);
1104 int pos, len, answer;
1111 * Check magic number.
1113 if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
1114 return 0; /* key is invalid */
1117 * Find the cipher-type string.
1121 if (key->keyblob_len < pos+4)
1122 goto done; /* key is far too short */
1123 pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */
1124 if (key->keyblob_len < pos+4)
1125 goto done; /* key is far too short */
1126 len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */
1127 if (key->keyblob_len < pos+4+len)
1128 goto done; /* cipher type string is incomplete */
1129 if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
1133 *comment = dupstr(key->comment);
1134 memset(key->keyblob, 0, key->keyblob_size);
1135 sfree(key->keyblob);
1136 memset(&key, 0, sizeof(key));
1141 int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
1145 unsigned char *d = (unsigned char *) data;
1149 bits = GET_32BIT(d);
1151 bytes = (bits + 7) / 8;
1162 return len; /* ensure further calls fail as well */
1165 static int sshcom_put_mpint(void *target, void *data, int len)
1167 unsigned char *d = (unsigned char *)target;
1168 unsigned char *i = (unsigned char *)data;
1169 int bits = len * 8 - 1;
1172 if (*i & (1 << (bits & 7)))
1178 PUT_32BIT(d, bits+1);
1179 memcpy(d+4, i, len);
1183 struct ssh2_userkey *sshcom_read(char *filename, char *passphrase)
1185 struct sshcom_key *key = load_sshcom_key(filename);
1188 const char prefix_rsa[] = "if-modn{sign{rsa";
1189 const char prefix_dsa[] = "dl-modp{sign{dsa";
1190 enum { RSA, DSA } type;
1194 struct ssh2_userkey *ret = NULL, *retkey;
1195 const struct ssh_signkey *alg;
1196 unsigned char *blob = NULL;
1197 int blobsize, publen, privlen;
1203 * Check magic number.
1205 if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
1206 errmsg = "Key does not begin with magic number";
1211 * Determine the key type.
1214 if (key->keyblob_len < pos+4 ||
1215 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1216 errmsg = "Key blob does not contain a key type string";
1219 if (len > sizeof(prefix_rsa) - 1 &&
1220 !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
1222 } else if (len > sizeof(prefix_dsa) - 1 &&
1223 !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
1226 errmsg = "Key is of unknown type";
1232 * Determine the cipher 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 cipher type string";
1239 if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
1241 else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
1244 errmsg = "Key encryption is of unknown type";
1250 * Get hold of the encrypted part of the key.
1252 if (key->keyblob_len < pos+4 ||
1253 (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
1254 errmsg = "Key blob does not contain actual key data";
1257 ciphertext = key->keyblob + pos + 4;
1259 if (cipherlen == 0) {
1260 errmsg = "Length of key data is zero";
1265 * Decrypt it if necessary.
1269 * Derive encryption key from passphrase and iv/salt:
1271 * - let block A equal MD5(passphrase)
1272 * - let block B equal MD5(passphrase || A)
1273 * - block C would be MD5(passphrase || A || B) and so on
1274 * - encryption key is the first N bytes of A || B
1276 struct MD5Context md5c;
1277 unsigned char keybuf[32], iv[8];
1279 if (cipherlen % 8 != 0) {
1280 errmsg = "Encrypted part of key is not a multiple of cipher block"
1286 MD5Update(&md5c, passphrase, strlen(passphrase));
1287 MD5Final(keybuf, &md5c);
1290 MD5Update(&md5c, passphrase, strlen(passphrase));
1291 MD5Update(&md5c, keybuf, 16);
1292 MD5Final(keybuf+16, &md5c);
1295 * Now decrypt the key blob.
1297 memset(iv, 0, sizeof(iv));
1298 des3_decrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen);
1300 memset(&md5c, 0, sizeof(md5c));
1301 memset(keybuf, 0, sizeof(keybuf));
1304 * Hereafter we return WRONG_PASSPHRASE for any parsing
1305 * error. (But only if we've just tried to decrypt it!
1306 * Returning WRONG_PASSPHRASE for an unencrypted key is
1310 ret = SSH2_WRONG_PASSPHRASE;
1314 * Strip away the containing string to get to the real meat.
1316 len = GET_32BIT(ciphertext);
1317 if (len > cipherlen-4) {
1318 errmsg = "containing string was ill-formed";
1325 * Now we break down into RSA versus DSA. In either case we'll
1326 * construct public and private blobs in our own format, and
1327 * end up feeding them to alg->createkey().
1329 blobsize = cipherlen + 256;
1330 blob = smalloc(blobsize);
1333 struct mpint_pos n, e, d, u, p, q;
1335 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
1336 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
1337 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
1338 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
1339 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1340 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1342 errmsg = "key data did not contain six integers";
1348 pos += put_string(blob+pos, "ssh-rsa", 7);
1349 pos += put_mp(blob+pos, e.start, e.bytes);
1350 pos += put_mp(blob+pos, n.start, n.bytes);
1352 pos += put_string(blob+pos, d.start, d.bytes);
1353 pos += put_mp(blob+pos, q.start, q.bytes);
1354 pos += put_mp(blob+pos, p.start, p.bytes);
1355 pos += put_mp(blob+pos, u.start, u.bytes);
1356 privlen = pos - publen;
1357 } else if (type == DSA) {
1358 struct mpint_pos p, q, g, x, y;
1360 if (GET_32BIT(ciphertext) != 0) {
1361 errmsg = "predefined DSA parameters not supported";
1364 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
1365 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
1366 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
1367 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
1368 pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
1370 errmsg = "key data did not contain five integers";
1376 pos += put_string(blob+pos, "ssh-dss", 7);
1377 pos += put_mp(blob+pos, p.start, p.bytes);
1378 pos += put_mp(blob+pos, q.start, q.bytes);
1379 pos += put_mp(blob+pos, g.start, g.bytes);
1380 pos += put_mp(blob+pos, y.start, y.bytes);
1382 pos += put_mp(blob+pos, x.start, x.bytes);
1383 privlen = pos - publen;
1386 assert(privlen > 0); /* should have bombed by now if not */
1388 retkey = smalloc(sizeof(struct ssh2_userkey));
1390 retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
1391 if (!retkey->data) {
1393 errmsg = "unable to create key data structure";
1396 retkey->comment = dupstr(key->comment);
1398 errmsg = NULL; /* no error */
1403 memset(blob, 0, blobsize);
1406 memset(key->keyblob, 0, key->keyblob_size);
1407 sfree(key->keyblob);
1408 memset(&key, 0, sizeof(key));
1413 int sshcom_write(char *filename, struct ssh2_userkey *key, char *passphrase)
1415 unsigned char *pubblob, *privblob;
1416 int publen, privlen;
1417 unsigned char *outblob;
1419 struct mpint_pos numbers[6];
1420 int nnumbers, initial_zero, pos, lenpos, i;
1428 * Fetch the key blobs.
1430 pubblob = key->alg->public_blob(key->data, &publen);
1431 privblob = key->alg->private_blob(key->data, &privlen);
1435 * Find the sequence of integers to be encoded into the OpenSSH
1436 * key blob, and also decide on the header line.
1438 if (key->alg == &ssh_rsa) {
1440 struct mpint_pos n, e, d, p, q, iqmp;
1442 pos = 4 + GET_32BIT(pubblob);
1443 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
1444 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
1446 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
1447 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
1448 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
1449 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
1451 assert(e.start && iqmp.start); /* can't go wrong */
1462 type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1463 } else if (key->alg == &ssh_dss) {
1465 struct mpint_pos p, q, g, y, x;
1467 pos = 4 + GET_32BIT(pubblob);
1468 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
1469 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
1470 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
1471 pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
1473 pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
1475 assert(y.start && x.start); /* can't go wrong */
1485 type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1487 assert(0); /* zoinks! */
1491 * Total size of key blob will be somewhere under 512 plus
1492 * combined length of integers. We'll calculate the more
1493 * precise size as we construct the blob.
1496 for (i = 0; i < nnumbers; i++)
1497 outlen += 4 + numbers[i].bytes;
1498 outblob = smalloc(outlen);
1501 * Create the unencrypted key blob.
1504 PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
1505 pos += 4; /* length field, fill in later */
1506 pos += put_string(outblob+pos, type, strlen(type));
1508 char *ciphertype = passphrase ? "3des-cbc" : "none";
1509 pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
1511 lenpos = pos; /* remember this position */
1512 pos += 4; /* encrypted-blob size */
1513 pos += 4; /* encrypted-payload size */
1515 PUT_32BIT(outblob+pos, 0);
1518 for (i = 0; i < nnumbers; i++)
1519 pos += sshcom_put_mpint(outblob+pos,
1520 numbers[i].start, numbers[i].bytes);
1521 /* Now wrap up the encrypted payload. */
1522 PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
1523 /* Pad encrypted blob to a multiple of cipher block size. */
1525 int padding = -(pos - (lenpos+4)) & 7;
1527 outblob[pos++] = random_byte();
1529 ciphertext = outblob+lenpos+4;
1530 cipherlen = pos - (lenpos+4);
1531 assert(!passphrase || cipherlen % 8 == 0);
1532 /* Wrap up the encrypted blob string. */
1533 PUT_32BIT(outblob+lenpos, cipherlen);
1534 /* And finally fill in the total length field. */
1535 PUT_32BIT(outblob+4, pos);
1537 assert(pos < outlen);
1544 * Derive encryption key from passphrase and iv/salt:
1546 * - let block A equal MD5(passphrase)
1547 * - let block B equal MD5(passphrase || A)
1548 * - block C would be MD5(passphrase || A || B) and so on
1549 * - encryption key is the first N bytes of A || B
1551 struct MD5Context md5c;
1552 unsigned char keybuf[32], iv[8];
1555 MD5Update(&md5c, passphrase, strlen(passphrase));
1556 MD5Final(keybuf, &md5c);
1559 MD5Update(&md5c, passphrase, strlen(passphrase));
1560 MD5Update(&md5c, keybuf, 16);
1561 MD5Final(keybuf+16, &md5c);
1564 * Now decrypt the key blob.
1566 memset(iv, 0, sizeof(iv));
1567 des3_encrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen);
1569 memset(&md5c, 0, sizeof(md5c));
1570 memset(keybuf, 0, sizeof(keybuf));
1574 * And save it. We'll use Unix line endings just in case it's
1575 * subsequently transferred in binary mode.
1577 fp = fopen(filename, "wb"); /* ensure Unix line endings */
1580 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1581 fprintf(fp, "Comment: \"");
1583 * Comment header is broken with backslash-newline if it goes
1584 * over 70 chars. Although it's surrounded by quotes, it
1585 * _doesn't_ escape backslashes or quotes within the string.
1586 * Don't ask me, I didn't design it.
1589 int slen = 60; /* starts at 60 due to "Comment: " */
1590 char *c = key->comment;
1591 while (strlen(c) > slen) {
1592 fprintf(fp, "%.*s\\\n", slen, c);
1594 slen = 70; /* allow 70 chars on subsequent lines */
1596 fprintf(fp, "%s\"\n", c);
1598 base64_encode(fp, outblob, pos, 70);
1599 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
1605 memset(outblob, 0, outlen);
1609 memset(privblob, 0, privlen);
1613 memset(pubblob, 0, publen);