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
;
493 if (key
->encrypted
) {
495 * Derive encryption key from passphrase and iv/salt:
497 * - let block A equal MD5(passphrase || iv)
498 * - let block B equal MD5(A || passphrase || iv)
499 * - block C would be MD5(B || passphrase || iv) and so on
500 * - encryption key is the first N bytes of A || B
502 struct MD5Context md5c
;
503 unsigned char keybuf
[32];
506 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
507 MD5Update(&md5c
, key
->iv
, 8);
508 MD5Final(keybuf
, &md5c
);
511 MD5Update(&md5c
, keybuf
, 16);
512 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
513 MD5Update(&md5c
, key
->iv
, 8);
514 MD5Final(keybuf
+16, &md5c
);
517 * Now decrypt the key blob.
519 des3_decrypt_pubkey_ossh(keybuf
, key
->iv
,
520 key
->keyblob
, key
->keyblob_len
);
522 memset(&md5c
, 0, sizeof(md5c
));
523 memset(keybuf
, 0, sizeof(keybuf
));
527 * Now we have a decrypted key blob, which contains an ASN.1
528 * encoded private key. We must now untangle the ASN.1.
530 * We expect the whole key blob to be formatted as a SEQUENCE
531 * (0x30 followed by a length code indicating that the rest of
532 * the blob is part of the sequence). Within that SEQUENCE we
533 * expect to see a bunch of INTEGERs. What those integers mean
534 * depends on the key type:
536 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
537 * dmp1, dmq1, iqmp in that order. (The last three are d mod
538 * (p-1), d mod (q-1), inverse of q mod p respectively.)
540 * - For DSA, we expect them to be 0, p, q, g, y, x in that
546 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
547 ret
= ber_read_id_len(p
, key
->keyblob_len
, &id
, &len
, &flags
);
549 if (ret
< 0 || id
!= 16) {
550 errmsg
= "ASN.1 decoding failure";
551 retval
= SSH2_WRONG_PASSPHRASE
;
555 /* Expect a load of INTEGERs. */
556 if (key
->type
== OSSH_RSA
)
558 else if (key
->type
== OSSH_DSA
)
562 * Space to create key blob in.
564 blobsize
= 256+key
->keyblob_len
;
565 blob
= smalloc(blobsize
);
567 if (key
->type
== OSSH_DSA
)
568 memcpy(blob
+4, "ssh-dss", 7);
569 else if (key
->type
== OSSH_RSA
)
570 memcpy(blob
+4, "ssh-rsa", 7);
574 for (i
= 0; i
< num_integers
; i
++) {
575 ret
= ber_read_id_len(p
, key
->keyblob
+key
->keyblob_len
-p
,
578 if (ret
< 0 || id
!= 2 ||
579 key
->keyblob
+key
->keyblob_len
-p
< len
) {
580 errmsg
= "ASN.1 decoding failure";
586 * The first integer should be zero always (I think
587 * this is some sort of version indication).
589 if (len
!= 1 || p
[0] != 0) {
590 errmsg
= "Version number mismatch";
593 } else if (key
->type
== OSSH_RSA
) {
595 * Integers 1 and 2 go into the public blob but in the
596 * opposite order; integers 3, 4, 5 and 8 go into the
597 * private blob. The other two (6 and 7) are ignored.
600 /* Save the details for after we deal with number 2. */
603 } else if (i
!= 6 && i
!= 7) {
604 PUT_32BIT(blob
+blobptr
, len
);
605 memcpy(blob
+blobptr
+4, p
, len
);
608 PUT_32BIT(blob
+blobptr
, modlen
);
609 memcpy(blob
+blobptr
+4, modptr
, modlen
);
614 } else if (key
->type
== OSSH_DSA
) {
616 * Integers 1-4 go into the public blob; integer 5 goes
617 * into the private blob.
619 PUT_32BIT(blob
+blobptr
, len
);
620 memcpy(blob
+blobptr
+4, p
, len
);
626 /* Skip past the number. */
631 * Now put together the actual key. Simplest way to do this is
632 * to assemble our own key blobs and feed them to the createkey
633 * functions; this is a bit faffy but it does mean we get all
634 * the sanity checks for free.
636 assert(privptr
> 0); /* should have bombed by now if not */
637 retkey
= smalloc(sizeof(struct ssh2_userkey
));
638 retkey
->alg
= (key
->type
== OSSH_RSA ?
&ssh_rsa
: &ssh_dss
);
639 retkey
->data
= retkey
->alg
->createkey(blob
, privptr
,
640 blob
+privptr
, blobptr
-privptr
);
643 errmsg
= "unable to create key data structure";
647 retkey
->comment
= dupstr("imported-openssh-key");
648 errmsg
= NULL
; /* no error */
653 memset(blob
, 0, blobsize
);
656 memset(key
->keyblob
, 0, key
->keyblob_size
);
658 memset(&key
, 0, sizeof(key
));
663 int openssh_write(char *filename
, struct ssh2_userkey
*key
, char *passphrase
)
665 unsigned char *pubblob
, *privblob
, *spareblob
;
666 int publen
, privlen
, sparelen
;
667 unsigned char *outblob
;
669 struct mpint_pos numbers
[9];
670 int nnumbers
, pos
, len
, seqlen
, i
;
671 char *header
, *footer
;
678 * Fetch the key blobs.
680 pubblob
= key
->alg
->public_blob(key
->data
, &publen
);
681 privblob
= key
->alg
->private_blob(key
->data
, &privlen
);
682 spareblob
= outblob
= NULL
;
685 * Find the sequence of integers to be encoded into the OpenSSH
686 * key blob, and also decide on the header line.
688 if (key
->alg
== &ssh_rsa
) {
690 struct mpint_pos n
, e
, d
, p
, q
, iqmp
, dmp1
, dmq1
;
691 Bignum bd
, bp
, bq
, bdmp1
, bdmq1
;
693 pos
= 4 + GET_32BIT(pubblob
);
694 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &e
);
695 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &n
);
697 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &d
);
698 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &p
);
699 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &q
);
700 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &iqmp
);
702 assert(e
.start
&& iqmp
.start
); /* can't go wrong */
704 /* We also need d mod (p-1) and d mod (q-1). */
705 bd
= bignum_from_bytes(d
.start
, d
.bytes
);
706 bp
= bignum_from_bytes(p
.start
, p
.bytes
);
707 bq
= bignum_from_bytes(q
.start
, q
.bytes
);
710 bdmp1
= bigmod(bd
, bp
);
711 bdmq1
= bigmod(bd
, bq
);
716 dmp1
.bytes
= (bignum_bitcount(bdmp1
)+8)/8;
717 dmq1
.bytes
= (bignum_bitcount(bdmq1
)+8)/8;
718 sparelen
= dmp1
.bytes
+ dmq1
.bytes
;
719 spareblob
= smalloc(sparelen
);
720 dmp1
.start
= spareblob
;
721 dmq1
.start
= spareblob
+ dmp1
.bytes
;
722 for (i
= 0; i
< dmp1
.bytes
; i
++)
723 spareblob
[i
] = bignum_byte(bdmp1
, dmp1
.bytes
-1 - i
);
724 for (i
= 0; i
< dmq1
.bytes
; i
++)
725 spareblob
[i
+dmp1
.bytes
] = bignum_byte(bdmq1
, dmq1
.bytes
-1 - i
);
729 numbers
[0].start
= zero
; numbers
[0].bytes
= 1; zero
[0] = '\0';
740 header
= "-----BEGIN RSA PRIVATE KEY-----\n";
741 footer
= "-----END RSA PRIVATE KEY-----\n";
742 } else if (key
->alg
== &ssh_dss
) {
744 struct mpint_pos p
, q
, g
, y
, x
;
746 pos
= 4 + GET_32BIT(pubblob
);
747 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &p
);
748 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &q
);
749 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &g
);
750 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &y
);
752 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &x
);
754 assert(y
.start
&& x
.start
); /* can't go wrong */
756 numbers
[0].start
= zero
; numbers
[0].bytes
= 1; zero
[0] = '\0';
764 header
= "-----BEGIN DSA PRIVATE KEY-----\n";
765 footer
= "-----END DSA PRIVATE KEY-----\n";
767 assert(0); /* zoinks! */
771 * Now count up the total size of the ASN.1 encoded integers,
772 * so as to determine the length of the containing SEQUENCE.
775 for (i
= 0; i
< nnumbers
; i
++) {
776 len
+= ber_write_id_len(NULL
, 2, numbers
[i
].bytes
, 0);
777 len
+= numbers
[i
].bytes
;
780 /* Now add on the SEQUENCE header. */
781 len
+= ber_write_id_len(NULL
, 16, seqlen
, ASN1_CONSTRUCTED
);
782 /* Round up to the cipher block size, ensuring we have at least one
783 * byte of padding (see below). */
786 outlen
= (outlen
+8) &~ 7;
789 * Now we know how big outblob needs to be. Allocate it.
791 outblob
= smalloc(outlen
);
794 * And write the data into it.
797 pos
+= ber_write_id_len(outblob
+pos
, 16, seqlen
, ASN1_CONSTRUCTED
);
798 for (i
= 0; i
< nnumbers
; i
++) {
799 pos
+= ber_write_id_len(outblob
+pos
, 2, numbers
[i
].bytes
, 0);
800 memcpy(outblob
+pos
, numbers
[i
].start
, numbers
[i
].bytes
);
801 pos
+= numbers
[i
].bytes
;
805 * Padding on OpenSSH keys is deterministic. The number of
806 * padding bytes is always more than zero, and always at most
807 * the cipher block length. The value of each padding byte is
808 * equal to the number of padding bytes. So a plaintext that's
809 * an exact multiple of the block size will be padded with 08
810 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
811 * plaintext one byte less than a multiple of the block size
812 * will be padded with just 01.
814 * This enables the OpenSSL key decryption function to strip
815 * off the padding algorithmically and return the unpadded
816 * plaintext to the next layer: it looks at the final byte, and
817 * then expects to find that many bytes at the end of the data
818 * with the same value. Those are all removed and the rest is
822 while (pos
< outlen
) {
823 outblob
[pos
++] = outlen
- len
;
831 * Invent an iv. Then derive encryption key from passphrase
834 * - let block A equal MD5(passphrase || iv)
835 * - let block B equal MD5(A || passphrase || iv)
836 * - block C would be MD5(B || passphrase || iv) and so on
837 * - encryption key is the first N bytes of A || B
839 struct MD5Context md5c
;
840 unsigned char keybuf
[32];
842 for (i
= 0; i
< 8; i
++) iv
[i
] = random_byte();
845 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
846 MD5Update(&md5c
, iv
, 8);
847 MD5Final(keybuf
, &md5c
);
850 MD5Update(&md5c
, keybuf
, 16);
851 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
852 MD5Update(&md5c
, iv
, 8);
853 MD5Final(keybuf
+16, &md5c
);
856 * Now encrypt the key blob.
858 des3_encrypt_pubkey_ossh(keybuf
, iv
, outblob
, outlen
);
860 memset(&md5c
, 0, sizeof(md5c
));
861 memset(keybuf
, 0, sizeof(keybuf
));
865 * And save it. We'll use Unix line endings just in case it's
866 * subsequently transferred in binary mode.
868 fp
= fopen(filename
, "wb"); /* ensure Unix line endings */
873 fprintf(fp
, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
874 for (i
= 0; i
< 8; i
++)
875 fprintf(fp
, "%02X", iv
[i
]);
878 base64_encode(fp
, outblob
, outlen
, 64);
885 memset(outblob
, 0, outlen
);
889 memset(spareblob
, 0, sparelen
);
893 memset(privblob
, 0, privlen
);
897 memset(pubblob
, 0, publen
);
903 /* ----------------------------------------------------------------------
904 * Code to read ssh.com private keys.
908 * The format of the base64 blob is largely ssh2-packet-formatted,
909 * except that mpints are a bit different: they're more like the
910 * old ssh1 mpint. You have a 32-bit bit count N, followed by
911 * (N+7)/8 bytes of data.
913 * So. The blob contains:
915 * - uint32 0x3f6ff9eb (magic number)
916 * - uint32 size (total blob size)
917 * - string key-type (see below)
918 * - string cipher-type (tells you if key is encrypted)
919 * - string encrypted-blob
921 * (The first size field includes the size field itself and the
922 * magic number before it. All other size fields are ordinary ssh2
923 * strings, so the size field indicates how much data is to
926 * The encrypted blob, once decrypted, contains a single string
927 * which in turn contains the payload. (This allows padding to be
928 * added after that string while still making it clear where the
929 * real payload ends. Also it probably makes for a reasonable
932 * The payload blob, for an RSA key, contains:
935 * - mpint n (yes, the public and private stuff is intermixed)
936 * - mpint u (presumably inverse of p mod q)
937 * - mpint p (p is the smaller prime)
938 * - mpint q (q is the larger)
940 * For a DSA key, the payload blob contains:
948 * Alternatively, if the parameters are `predefined', that
949 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
950 * containing some predefined parameter specification. *shudder*,
951 * but I doubt we'll encounter this in real life.
953 * The key type strings are ghastly. The RSA key I looked at had a
956 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
958 * and the DSA key wasn't much better:
960 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
962 * It isn't clear that these will always be the same. I think it
963 * might be wise just to look at the `if-modn{sign{rsa' and
964 * `dl-modp{sign{dsa' prefixes.
966 * Finally, the encryption. The cipher-type string appears to be
967 * either `none' or `3des-cbc'. Looks as if this is SSH2-style
968 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
969 * from the passphrase by means of yet another hashing faff:
971 * - first 16 bytes are MD5(passphrase)
972 * - next 16 bytes are MD5(passphrase || first 16 bytes)
973 * - if there were more, they'd be MD5(passphrase || first 32),
977 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
980 char comment
[256]; /* allowing any length is overkill */
981 unsigned char *keyblob
;
982 int keyblob_len
, keyblob_size
;
985 struct sshcom_key
*load_sshcom_key(char *filename
)
987 struct sshcom_key
*ret
;
994 int base64_chars
= 0;
996 ret
= smalloc(sizeof(*ret
));
997 ret
->comment
[0] = '\0';
999 ret
->keyblob_len
= ret
->keyblob_size
= 0;
1001 fp
= fopen(filename
, "r");
1003 errmsg
= "Unable to open key file";
1006 if (!fgets(buffer
, sizeof(buffer
), fp
) ||
1007 0 != strcmp(buffer
, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1008 errmsg
= "File does not begin with ssh.com key header";
1014 if (!fgets(buffer
, sizeof(buffer
), fp
)) {
1015 errmsg
= "Unexpected end of file";
1018 if (!strcmp(buffer
, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1020 if ((p
= strchr(buffer
, ':')) != NULL
) {
1022 errmsg
= "Header found in body of key data";
1026 while (*p
&& isspace((unsigned char)*p
)) p
++;
1028 * Header lines can end in a trailing backslash for
1031 while ((len
= strlen(p
)) > sizeof(buffer
) - (p
-buffer
) -1 ||
1032 p
[len
-1] != '\n' || p
[len
-2] == '\\') {
1033 if (len
> (p
-buffer
) + sizeof(buffer
)-2) {
1034 errmsg
= "Header line too long to deal with";
1037 if (!fgets(p
+len
-2, sizeof(buffer
)-(p
-buffer
)-(len
-2), fp
)) {
1038 errmsg
= "Unexpected end of file";
1042 p
[strcspn(p
, "\n")] = '\0';
1043 if (!strcmp(buffer
, "Comment")) {
1044 /* Strip quotes in comment if present. */
1045 if (p
[0] == '"' && p
[strlen(p
)-1] == '"') {
1047 p
[strlen(p
)-1] = '\0';
1049 strncpy(ret
->comment
, p
, sizeof(ret
->comment
));
1050 ret
->comment
[sizeof(ret
->comment
)-1] = '\0';
1056 while (isbase64(*p
)) {
1057 base64_bit
[base64_chars
++] = *p
;
1058 if (base64_chars
== 4) {
1059 unsigned char out
[3];
1063 len
= base64_decode_atom(base64_bit
, out
);
1066 errmsg
= "Invalid base64 encoding";
1070 if (ret
->keyblob_len
+ len
> ret
->keyblob_size
) {
1071 ret
->keyblob_size
= ret
->keyblob_len
+ len
+ 256;
1072 ret
->keyblob
= srealloc(ret
->keyblob
, ret
->keyblob_size
);
1075 memcpy(ret
->keyblob
+ ret
->keyblob_len
, out
, len
);
1076 ret
->keyblob_len
+= len
;
1084 if (ret
->keyblob_len
== 0 || !ret
->keyblob
) {
1085 errmsg
= "Key body not present";
1094 memset(ret
->keyblob
, 0, ret
->keyblob_size
);
1095 sfree(ret
->keyblob
);
1097 memset(&ret
, 0, sizeof(ret
));
1103 int sshcom_encrypted(char *filename
, char **comment
)
1105 struct sshcom_key
*key
= load_sshcom_key(filename
);
1106 int pos
, len
, answer
;
1113 * Check magic number.
1115 if (GET_32BIT(key
->keyblob
) != 0x3f6ff9eb)
1116 return 0; /* key is invalid */
1119 * Find the cipher-type string.
1123 if (key
->keyblob_len
< pos
+4)
1124 goto done
; /* key is far too short */
1125 pos
+= 4 + GET_32BIT(key
->keyblob
+ pos
); /* skip key type */
1126 if (key
->keyblob_len
< pos
+4)
1127 goto done
; /* key is far too short */
1128 len
= GET_32BIT(key
->keyblob
+ pos
); /* find cipher-type length */
1129 if (key
->keyblob_len
< pos
+4+len
)
1130 goto done
; /* cipher type string is incomplete */
1131 if (len
!= 4 || 0 != memcmp(key
->keyblob
+ pos
+ 4, "none", 4))
1135 *comment
= dupstr(key
->comment
);
1136 memset(key
->keyblob
, 0, key
->keyblob_size
);
1137 sfree(key
->keyblob
);
1138 memset(&key
, 0, sizeof(key
));
1143 int sshcom_read_mpint(void *data
, int len
, struct mpint_pos
*ret
)
1147 unsigned char *d
= (unsigned char *) data
;
1151 bits
= GET_32BIT(d
);
1153 bytes
= (bits
+ 7) / 8;
1164 return len
; /* ensure further calls fail as well */
1167 static int sshcom_put_mpint(void *target
, void *data
, int len
)
1169 unsigned char *d
= (unsigned char *)target
;
1170 unsigned char *i
= (unsigned char *)data
;
1171 int bits
= len
* 8 - 1;
1174 if (*i
& (1 << (bits
& 7)))
1180 PUT_32BIT(d
, bits
+1);
1181 memcpy(d
+4, i
, len
);
1185 struct ssh2_userkey
*sshcom_read(char *filename
, char *passphrase
)
1187 struct sshcom_key
*key
= load_sshcom_key(filename
);
1190 const char prefix_rsa
[] = "if-modn{sign{rsa";
1191 const char prefix_dsa
[] = "dl-modp{sign{dsa";
1192 enum { RSA
, DSA
} type
;
1196 struct ssh2_userkey
*ret
= NULL
, *retkey
;
1197 const struct ssh_signkey
*alg
;
1198 unsigned char *blob
= NULL
;
1199 int blobsize
, publen
, privlen
;
1205 * Check magic number.
1207 if (GET_32BIT(key
->keyblob
) != SSHCOM_MAGIC_NUMBER
) {
1208 errmsg
= "Key does not begin with magic number";
1213 * Determine the key type.
1216 if (key
->keyblob_len
< pos
+4 ||
1217 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1218 errmsg
= "Key blob does not contain a key type string";
1221 if (len
> sizeof(prefix_rsa
) - 1 &&
1222 !memcmp(key
->keyblob
+pos
+4, prefix_rsa
, sizeof(prefix_rsa
) - 1)) {
1224 } else if (len
> sizeof(prefix_dsa
) - 1 &&
1225 !memcmp(key
->keyblob
+pos
+4, prefix_dsa
, sizeof(prefix_dsa
) - 1)) {
1228 errmsg
= "Key is of unknown type";
1234 * Determine the cipher type.
1236 if (key
->keyblob_len
< pos
+4 ||
1237 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1238 errmsg
= "Key blob does not contain a cipher type string";
1241 if (len
== 4 && !memcmp(key
->keyblob
+pos
+4, "none", 4))
1243 else if (len
== 8 && !memcmp(key
->keyblob
+pos
+4, "3des-cbc", 8))
1246 errmsg
= "Key encryption is of unknown type";
1252 * Get hold of the encrypted part of the key.
1254 if (key
->keyblob_len
< pos
+4 ||
1255 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1256 errmsg
= "Key blob does not contain actual key data";
1259 ciphertext
= key
->keyblob
+ pos
+ 4;
1261 if (cipherlen
== 0) {
1262 errmsg
= "Length of key data is zero";
1267 * Decrypt it if necessary.
1271 * Derive encryption key from passphrase and iv/salt:
1273 * - let block A equal MD5(passphrase)
1274 * - let block B equal MD5(passphrase || A)
1275 * - block C would be MD5(passphrase || A || B) and so on
1276 * - encryption key is the first N bytes of A || B
1278 struct MD5Context md5c
;
1279 unsigned char keybuf
[32], iv
[8];
1281 if (cipherlen
% 8 != 0) {
1282 errmsg
= "Encrypted part of key is not a multiple of cipher block"
1288 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
1289 MD5Final(keybuf
, &md5c
);
1292 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
1293 MD5Update(&md5c
, keybuf
, 16);
1294 MD5Final(keybuf
+16, &md5c
);
1297 * Now decrypt the key blob.
1299 memset(iv
, 0, sizeof(iv
));
1300 des3_decrypt_pubkey_ossh(keybuf
, iv
, ciphertext
, cipherlen
);
1302 memset(&md5c
, 0, sizeof(md5c
));
1303 memset(keybuf
, 0, sizeof(keybuf
));
1306 * Hereafter we return WRONG_PASSPHRASE for any parsing
1307 * error. (But only if we've just tried to decrypt it!
1308 * Returning WRONG_PASSPHRASE for an unencrypted key is
1312 ret
= SSH2_WRONG_PASSPHRASE
;
1316 * Strip away the containing string to get to the real meat.
1318 len
= GET_32BIT(ciphertext
);
1319 if (len
> cipherlen
-4) {
1320 errmsg
= "containing string was ill-formed";
1327 * Now we break down into RSA versus DSA. In either case we'll
1328 * construct public and private blobs in our own format, and
1329 * end up feeding them to alg->createkey().
1331 blobsize
= cipherlen
+ 256;
1332 blob
= smalloc(blobsize
);
1335 struct mpint_pos n
, e
, d
, u
, p
, q
;
1337 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &e
);
1338 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &d
);
1339 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &n
);
1340 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &u
);
1341 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &p
);
1342 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &q
);
1344 errmsg
= "key data did not contain six integers";
1350 pos
+= put_string(blob
+pos
, "ssh-rsa", 7);
1351 pos
+= put_mp(blob
+pos
, e
.start
, e
.bytes
);
1352 pos
+= put_mp(blob
+pos
, n
.start
, n
.bytes
);
1354 pos
+= put_string(blob
+pos
, d
.start
, d
.bytes
);
1355 pos
+= put_mp(blob
+pos
, q
.start
, q
.bytes
);
1356 pos
+= put_mp(blob
+pos
, p
.start
, p
.bytes
);
1357 pos
+= put_mp(blob
+pos
, u
.start
, u
.bytes
);
1358 privlen
= pos
- publen
;
1359 } else if (type
== DSA
) {
1360 struct mpint_pos p
, q
, g
, x
, y
;
1362 if (GET_32BIT(ciphertext
) != 0) {
1363 errmsg
= "predefined DSA parameters not supported";
1366 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &p
);
1367 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &g
);
1368 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &q
);
1369 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &y
);
1370 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &x
);
1372 errmsg
= "key data did not contain five integers";
1378 pos
+= put_string(blob
+pos
, "ssh-dss", 7);
1379 pos
+= put_mp(blob
+pos
, p
.start
, p
.bytes
);
1380 pos
+= put_mp(blob
+pos
, q
.start
, q
.bytes
);
1381 pos
+= put_mp(blob
+pos
, g
.start
, g
.bytes
);
1382 pos
+= put_mp(blob
+pos
, y
.start
, y
.bytes
);
1384 pos
+= put_mp(blob
+pos
, x
.start
, x
.bytes
);
1385 privlen
= pos
- publen
;
1388 assert(privlen
> 0); /* should have bombed by now if not */
1390 retkey
= smalloc(sizeof(struct ssh2_userkey
));
1392 retkey
->data
= alg
->createkey(blob
, publen
, blob
+publen
, privlen
);
1393 if (!retkey
->data
) {
1395 errmsg
= "unable to create key data structure";
1398 retkey
->comment
= dupstr(key
->comment
);
1400 errmsg
= NULL
; /* no error */
1405 memset(blob
, 0, blobsize
);
1408 memset(key
->keyblob
, 0, key
->keyblob_size
);
1409 sfree(key
->keyblob
);
1410 memset(&key
, 0, sizeof(key
));
1415 int sshcom_write(char *filename
, struct ssh2_userkey
*key
, char *passphrase
)
1417 unsigned char *pubblob
, *privblob
;
1418 int publen
, privlen
;
1419 unsigned char *outblob
;
1421 struct mpint_pos numbers
[6];
1422 int nnumbers
, initial_zero
, pos
, lenpos
, i
;
1430 * Fetch the key blobs.
1432 pubblob
= key
->alg
->public_blob(key
->data
, &publen
);
1433 privblob
= key
->alg
->private_blob(key
->data
, &privlen
);
1437 * Find the sequence of integers to be encoded into the OpenSSH
1438 * key blob, and also decide on the header line.
1440 if (key
->alg
== &ssh_rsa
) {
1442 struct mpint_pos n
, e
, d
, p
, q
, iqmp
;
1444 pos
= 4 + GET_32BIT(pubblob
);
1445 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &e
);
1446 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &n
);
1448 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &d
);
1449 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &p
);
1450 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &q
);
1451 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &iqmp
);
1453 assert(e
.start
&& iqmp
.start
); /* can't go wrong */
1464 type
= "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1465 } else if (key
->alg
== &ssh_dss
) {
1467 struct mpint_pos p
, q
, g
, y
, x
;
1469 pos
= 4 + GET_32BIT(pubblob
);
1470 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &p
);
1471 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &q
);
1472 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &g
);
1473 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &y
);
1475 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &x
);
1477 assert(y
.start
&& x
.start
); /* can't go wrong */
1487 type
= "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1489 assert(0); /* zoinks! */
1493 * Total size of key blob will be somewhere under 512 plus
1494 * combined length of integers. We'll calculate the more
1495 * precise size as we construct the blob.
1498 for (i
= 0; i
< nnumbers
; i
++)
1499 outlen
+= 4 + numbers
[i
].bytes
;
1500 outblob
= smalloc(outlen
);
1503 * Create the unencrypted key blob.
1506 PUT_32BIT(outblob
+pos
, SSHCOM_MAGIC_NUMBER
); pos
+= 4;
1507 pos
+= 4; /* length field, fill in later */
1508 pos
+= put_string(outblob
+pos
, type
, strlen(type
));
1510 char *ciphertype
= passphrase ?
"3des-cbc" : "none";
1511 pos
+= put_string(outblob
+pos
, ciphertype
, strlen(ciphertype
));
1513 lenpos
= pos
; /* remember this position */
1514 pos
+= 4; /* encrypted-blob size */
1515 pos
+= 4; /* encrypted-payload size */
1517 PUT_32BIT(outblob
+pos
, 0);
1520 for (i
= 0; i
< nnumbers
; i
++)
1521 pos
+= sshcom_put_mpint(outblob
+pos
,
1522 numbers
[i
].start
, numbers
[i
].bytes
);
1523 /* Now wrap up the encrypted payload. */
1524 PUT_32BIT(outblob
+lenpos
+4, pos
- (lenpos
+8));
1525 /* Pad encrypted blob to a multiple of cipher block size. */
1527 int padding
= -(pos
- (lenpos
+4)) & 7;
1529 outblob
[pos
++] = random_byte();
1531 ciphertext
= outblob
+lenpos
+4;
1532 cipherlen
= pos
- (lenpos
+4);
1533 assert(!passphrase
|| cipherlen
% 8 == 0);
1534 /* Wrap up the encrypted blob string. */
1535 PUT_32BIT(outblob
+lenpos
, cipherlen
);
1536 /* And finally fill in the total length field. */
1537 PUT_32BIT(outblob
+4, pos
);
1539 assert(pos
< outlen
);
1546 * Derive encryption key from passphrase and iv/salt:
1548 * - let block A equal MD5(passphrase)
1549 * - let block B equal MD5(passphrase || A)
1550 * - block C would be MD5(passphrase || A || B) and so on
1551 * - encryption key is the first N bytes of A || B
1553 struct MD5Context md5c
;
1554 unsigned char keybuf
[32], iv
[8];
1557 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
1558 MD5Final(keybuf
, &md5c
);
1561 MD5Update(&md5c
, passphrase
, strlen(passphrase
));
1562 MD5Update(&md5c
, keybuf
, 16);
1563 MD5Final(keybuf
+16, &md5c
);
1566 * Now decrypt the key blob.
1568 memset(iv
, 0, sizeof(iv
));
1569 des3_encrypt_pubkey_ossh(keybuf
, iv
, ciphertext
, cipherlen
);
1571 memset(&md5c
, 0, sizeof(md5c
));
1572 memset(keybuf
, 0, sizeof(keybuf
));
1576 * And save it. We'll use Unix line endings just in case it's
1577 * subsequently transferred in binary mode.
1579 fp
= fopen(filename
, "wb"); /* ensure Unix line endings */
1582 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp
);
1583 fprintf(fp
, "Comment: \"");
1585 * Comment header is broken with backslash-newline if it goes
1586 * over 70 chars. Although it's surrounded by quotes, it
1587 * _doesn't_ escape backslashes or quotes within the string.
1588 * Don't ask me, I didn't design it.
1591 int slen
= 60; /* starts at 60 due to "Comment: " */
1592 char *c
= key
->comment
;
1593 while (strlen(c
) > slen
) {
1594 fprintf(fp
, "%.*s\\\n", slen
, c
);
1596 slen
= 70; /* allow 70 chars on subsequent lines */
1598 fprintf(fp
, "%s\"\n", c
);
1600 base64_encode(fp
, outblob
, pos
, 70);
1601 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp
);
1607 memset(outblob
, 0, outlen
);
1611 memset(privblob
, 0, privlen
);
1615 memset(pubblob
, 0, publen
);