2 * Code for PuTTY to import and export private key files in other
3 * SSH clients' formats.
15 #define PUT_32BIT(cp, value) do { \
16 (cp)[3] = (unsigned char)(value); \
17 (cp)[2] = (unsigned char)((value) >> 8); \
18 (cp)[1] = (unsigned char)((value) >> 16); \
19 (cp)[0] = (unsigned char)((value) >> 24); } while (0)
21 #define GET_32BIT(cp) \
22 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
23 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
24 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
25 ((unsigned long)(unsigned char)(cp)[3]))
27 int openssh_encrypted(const Filename
*filename
);
28 struct ssh2_userkey
*openssh_read(const Filename
*filename
, char *passphrase
);
29 int openssh_write(const Filename
*filename
, struct ssh2_userkey
*key
,
32 int sshcom_encrypted(const Filename
*filename
, char **comment
);
33 struct ssh2_userkey
*sshcom_read(const Filename
*filename
, char *passphrase
);
34 int sshcom_write(const Filename
*filename
, struct ssh2_userkey
*key
,
38 * Given a key type, determine whether we know how to import it.
40 int import_possible(int type
)
42 if (type
== SSH_KEYTYPE_OPENSSH
)
44 if (type
== SSH_KEYTYPE_SSHCOM
)
50 * Given a key type, determine what native key type
51 * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
54 int import_target_type(int type
)
57 * There are no known foreign SSH1 key formats.
59 return SSH_KEYTYPE_SSH2
;
63 * Determine whether a foreign key is encrypted.
65 int import_encrypted(const Filename
*filename
, int type
, char **comment
)
67 if (type
== SSH_KEYTYPE_OPENSSH
) {
68 /* OpenSSH doesn't do key comments */
69 *comment
= dupstr(filename_to_str(filename
));
70 return openssh_encrypted(filename
);
72 if (type
== SSH_KEYTYPE_SSHCOM
) {
73 return sshcom_encrypted(filename
, comment
);
81 int import_ssh1(const Filename
*filename
, int type
,
82 struct RSAKey
*key
, char *passphrase
)
90 struct ssh2_userkey
*import_ssh2(const Filename
*filename
, int type
,
93 if (type
== SSH_KEYTYPE_OPENSSH
)
94 return openssh_read(filename
, passphrase
);
95 if (type
== SSH_KEYTYPE_SSHCOM
)
96 return sshcom_read(filename
, passphrase
);
101 * Export an SSH1 key.
103 int export_ssh1(const Filename
*filename
, int type
, struct RSAKey
*key
,
110 * Export an SSH2 key.
112 int export_ssh2(const Filename
*filename
, int type
,
113 struct ssh2_userkey
*key
, char *passphrase
)
115 if (type
== SSH_KEYTYPE_OPENSSH
)
116 return openssh_write(filename
, key
, passphrase
);
117 if (type
== SSH_KEYTYPE_SSHCOM
)
118 return sshcom_write(filename
, key
, passphrase
);
122 /* ----------------------------------------------------------------------
123 * Helper routines. (The base64 ones are defined in sshpubk.c.)
126 #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
127 ((c) >= 'a' && (c) <= 'z') || \
128 ((c) >= '0' && (c) <= '9') || \
129 (c) == '+' || (c) == '/' || (c) == '=' \
133 * Read an ASN.1/BER identifier and length pair.
135 * Flags are a combination of the #defines listed below.
137 * Returns -1 if unsuccessful; otherwise returns the number of
138 * bytes used out of the source data.
141 /* ASN.1 tag classes. */
142 #define ASN1_CLASS_UNIVERSAL (0 << 6)
143 #define ASN1_CLASS_APPLICATION (1 << 6)
144 #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
145 #define ASN1_CLASS_PRIVATE (3 << 6)
146 #define ASN1_CLASS_MASK (3 << 6)
148 /* Primitive versus constructed bit. */
149 #define ASN1_CONSTRUCTED (1 << 5)
151 static int ber_read_id_len(void *source
, int sourcelen
,
152 int *id
, int *length
, int *flags
)
154 unsigned char *p
= (unsigned char *) source
;
159 *flags
= (*p
& 0xE0);
160 if ((*p
& 0x1F) == 0x1F) {
163 *id
= (*id
<< 7) | (*p
& 0x7F);
168 *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
)
321 struct openssh_key
*ret
;
327 int base64_chars
= 0;
329 ret
= snew(struct openssh_key
);
331 ret
->keyblob_len
= ret
->keyblob_size
= 0;
333 memset(ret
->iv
, 0, sizeof(ret
->iv
));
335 fp
= f_open(*filename
, "r");
337 errmsg
= "Unable to open key file";
340 if (!fgets(buffer
, sizeof(buffer
), fp
) ||
341 0 != strncmp(buffer
, "-----BEGIN ", 11) ||
342 0 != strcmp(buffer
+strlen(buffer
)-17, "PRIVATE KEY-----\n")) {
343 errmsg
= "File does not begin with OpenSSH key header";
346 if (!strcmp(buffer
, "-----BEGIN RSA PRIVATE KEY-----\n"))
347 ret
->type
= OSSH_RSA
;
348 else if (!strcmp(buffer
, "-----BEGIN DSA PRIVATE KEY-----\n"))
349 ret
->type
= OSSH_DSA
;
351 errmsg
= "Unrecognised key type";
357 if (!fgets(buffer
, sizeof(buffer
), fp
)) {
358 errmsg
= "Unexpected end of file";
361 if (0 == strncmp(buffer
, "-----END ", 9) &&
362 0 == strcmp(buffer
+strlen(buffer
)-17, "PRIVATE KEY-----\n"))
364 if ((p
= strchr(buffer
, ':')) != NULL
) {
366 errmsg
= "Header found in body of key data";
370 while (*p
&& isspace((unsigned char)*p
)) p
++;
371 if (!strcmp(buffer
, "Proc-Type")) {
372 if (p
[0] != '4' || p
[1] != ',') {
373 errmsg
= "Proc-Type is not 4 (only 4 is supported)";
377 if (!strcmp(p
, "ENCRYPTED\n"))
379 } else if (!strcmp(buffer
, "DEK-Info")) {
382 if (strncmp(p
, "DES-EDE3-CBC,", 13)) {
383 errmsg
= "Ciphers other than DES-EDE3-CBC not supported";
387 for (i
= 0; i
< 8; i
++) {
388 if (1 != sscanf(p
, "%2x", &j
))
394 errmsg
= "Expected 16-digit iv in DEK-Info";
402 while (isbase64(*p
)) {
403 base64_bit
[base64_chars
++] = *p
;
404 if (base64_chars
== 4) {
405 unsigned char out
[3];
410 len
= base64_decode_atom(base64_bit
, out
);
413 errmsg
= "Invalid base64 encoding";
417 if (ret
->keyblob_len
+ len
> ret
->keyblob_size
) {
418 ret
->keyblob_size
= ret
->keyblob_len
+ len
+ 256;
419 ret
->keyblob
= sresize(ret
->keyblob
, ret
->keyblob_size
,
423 memcpy(ret
->keyblob
+ ret
->keyblob_len
, out
, len
);
424 ret
->keyblob_len
+= len
;
426 memset(out
, 0, sizeof(out
));
434 if (ret
->keyblob_len
== 0 || !ret
->keyblob
) {
435 errmsg
= "Key body not present";
439 if (ret
->encrypted
&& ret
->keyblob_len
% 8 != 0) {
440 errmsg
= "Encrypted key blob is not a multiple of cipher block size";
444 memset(buffer
, 0, sizeof(buffer
));
445 memset(base64_bit
, 0, sizeof(base64_bit
));
449 memset(buffer
, 0, sizeof(buffer
));
450 memset(base64_bit
, 0, sizeof(base64_bit
));
453 memset(ret
->keyblob
, 0, ret
->keyblob_size
);
456 memset(&ret
, 0, sizeof(ret
));
462 int openssh_encrypted(const Filename
*filename
)
464 struct openssh_key
*key
= load_openssh_key(filename
);
469 ret
= key
->encrypted
;
470 memset(key
->keyblob
, 0, key
->keyblob_size
);
472 memset(&key
, 0, sizeof(key
));
477 struct ssh2_userkey
*openssh_read(const Filename
*filename
, char *passphrase
)
479 struct openssh_key
*key
= load_openssh_key(filename
);
480 struct ssh2_userkey
*retkey
;
482 int ret
, id
, len
, flags
;
484 struct ssh2_userkey
*retval
= NULL
;
487 int blobsize
, blobptr
, privptr
;
496 if (key
->encrypted
) {
498 * Derive encryption key from passphrase and iv/salt:
500 * - let block A equal MD5(passphrase || iv)
501 * - let block B equal MD5(A || passphrase || iv)
502 * - block C would be MD5(B || passphrase || iv) and so on
503 * - encryption key is the first N bytes of A || B
505 struct MD5Context md5c
;
506 unsigned char keybuf
[32];
509 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
510 MD5Update(&md5c
, (unsigned char *)key
->iv
, 8);
511 MD5Final(keybuf
, &md5c
);
514 MD5Update(&md5c
, keybuf
, 16);
515 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
516 MD5Update(&md5c
, (unsigned char *)key
->iv
, 8);
517 MD5Final(keybuf
+16, &md5c
);
520 * Now decrypt the key blob.
522 des3_decrypt_pubkey_ossh(keybuf
, (unsigned char *)key
->iv
,
523 key
->keyblob
, key
->keyblob_len
);
525 memset(&md5c
, 0, sizeof(md5c
));
526 memset(keybuf
, 0, sizeof(keybuf
));
530 * Now we have a decrypted key blob, which contains an ASN.1
531 * encoded private key. We must now untangle the ASN.1.
533 * We expect the whole key blob to be formatted as a SEQUENCE
534 * (0x30 followed by a length code indicating that the rest of
535 * the blob is part of the sequence). Within that SEQUENCE we
536 * expect to see a bunch of INTEGERs. What those integers mean
537 * depends on the key type:
539 * - For RSA, we expect the integers to be 0, n, e, d, p, q,
540 * dmp1, dmq1, iqmp in that order. (The last three are d mod
541 * (p-1), d mod (q-1), inverse of q mod p respectively.)
543 * - For DSA, we expect them to be 0, p, q, g, y, x in that
549 /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
550 ret
= ber_read_id_len(p
, key
->keyblob_len
, &id
, &len
, &flags
);
552 if (ret
< 0 || id
!= 16) {
553 errmsg
= "ASN.1 decoding failure";
554 retval
= SSH2_WRONG_PASSPHRASE
;
558 /* Expect a load of INTEGERs. */
559 if (key
->type
== OSSH_RSA
)
561 else if (key
->type
== OSSH_DSA
)
565 * Space to create key blob in.
567 blobsize
= 256+key
->keyblob_len
;
568 blob
= snewn(blobsize
, unsigned char);
570 if (key
->type
== OSSH_DSA
)
571 memcpy(blob
+4, "ssh-dss", 7);
572 else if (key
->type
== OSSH_RSA
)
573 memcpy(blob
+4, "ssh-rsa", 7);
577 for (i
= 0; i
< num_integers
; i
++) {
578 ret
= ber_read_id_len(p
, key
->keyblob
+key
->keyblob_len
-p
,
581 if (ret
< 0 || id
!= 2 ||
582 key
->keyblob
+key
->keyblob_len
-p
< len
) {
583 errmsg
= "ASN.1 decoding failure";
589 * The first integer should be zero always (I think
590 * this is some sort of version indication).
592 if (len
!= 1 || p
[0] != 0) {
593 errmsg
= "Version number mismatch";
596 } else if (key
->type
== OSSH_RSA
) {
598 * Integers 1 and 2 go into the public blob but in the
599 * opposite order; integers 3, 4, 5 and 8 go into the
600 * private blob. The other two (6 and 7) are ignored.
603 /* Save the details for after we deal with number 2. */
606 } else if (i
!= 6 && i
!= 7) {
607 PUT_32BIT(blob
+blobptr
, len
);
608 memcpy(blob
+blobptr
+4, p
, len
);
611 PUT_32BIT(blob
+blobptr
, modlen
);
612 memcpy(blob
+blobptr
+4, modptr
, modlen
);
617 } else if (key
->type
== OSSH_DSA
) {
619 * Integers 1-4 go into the public blob; integer 5 goes
620 * into the private blob.
622 PUT_32BIT(blob
+blobptr
, len
);
623 memcpy(blob
+blobptr
+4, p
, len
);
629 /* Skip past the number. */
634 * Now put together the actual key. Simplest way to do this is
635 * to assemble our own key blobs and feed them to the createkey
636 * functions; this is a bit faffy but it does mean we get all
637 * the sanity checks for free.
639 assert(privptr
> 0); /* should have bombed by now if not */
640 retkey
= snew(struct ssh2_userkey
);
641 retkey
->alg
= (key
->type
== OSSH_RSA ?
&ssh_rsa
: &ssh_dss
);
642 retkey
->data
= retkey
->alg
->createkey(blob
, privptr
,
643 blob
+privptr
, blobptr
-privptr
);
646 errmsg
= "unable to create key data structure";
650 retkey
->comment
= dupstr("imported-openssh-key");
651 errmsg
= NULL
; /* no error */
656 memset(blob
, 0, blobsize
);
659 memset(key
->keyblob
, 0, key
->keyblob_size
);
661 memset(&key
, 0, sizeof(key
));
666 int openssh_write(const Filename
*filename
, struct ssh2_userkey
*key
,
669 unsigned char *pubblob
, *privblob
, *spareblob
;
670 int publen
, privlen
, sparelen
;
671 unsigned char *outblob
;
673 struct mpint_pos numbers
[9];
674 int nnumbers
, pos
, len
, seqlen
, i
;
675 char *header
, *footer
;
682 * Fetch the key blobs.
684 pubblob
= key
->alg
->public_blob(key
->data
, &publen
);
685 privblob
= key
->alg
->private_blob(key
->data
, &privlen
);
686 spareblob
= outblob
= NULL
;
689 * Find the sequence of integers to be encoded into the OpenSSH
690 * key blob, and also decide on the header line.
692 if (key
->alg
== &ssh_rsa
) {
694 struct mpint_pos n
, e
, d
, p
, q
, iqmp
, dmp1
, dmq1
;
695 Bignum bd
, bp
, bq
, bdmp1
, bdmq1
;
697 pos
= 4 + GET_32BIT(pubblob
);
698 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &e
);
699 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &n
);
701 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &d
);
702 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &p
);
703 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &q
);
704 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &iqmp
);
706 assert(e
.start
&& iqmp
.start
); /* can't go wrong */
708 /* We also need d mod (p-1) and d mod (q-1). */
709 bd
= bignum_from_bytes(d
.start
, d
.bytes
);
710 bp
= bignum_from_bytes(p
.start
, p
.bytes
);
711 bq
= bignum_from_bytes(q
.start
, q
.bytes
);
714 bdmp1
= bigmod(bd
, bp
);
715 bdmq1
= bigmod(bd
, bq
);
720 dmp1
.bytes
= (bignum_bitcount(bdmp1
)+8)/8;
721 dmq1
.bytes
= (bignum_bitcount(bdmq1
)+8)/8;
722 sparelen
= dmp1
.bytes
+ dmq1
.bytes
;
723 spareblob
= snewn(sparelen
, unsigned char);
724 dmp1
.start
= spareblob
;
725 dmq1
.start
= spareblob
+ dmp1
.bytes
;
726 for (i
= 0; i
< dmp1
.bytes
; i
++)
727 spareblob
[i
] = bignum_byte(bdmp1
, dmp1
.bytes
-1 - i
);
728 for (i
= 0; i
< dmq1
.bytes
; i
++)
729 spareblob
[i
+dmp1
.bytes
] = bignum_byte(bdmq1
, dmq1
.bytes
-1 - i
);
733 numbers
[0].start
= zero
; numbers
[0].bytes
= 1; zero
[0] = '\0';
744 header
= "-----BEGIN RSA PRIVATE KEY-----\n";
745 footer
= "-----END RSA PRIVATE KEY-----\n";
746 } else if (key
->alg
== &ssh_dss
) {
748 struct mpint_pos p
, q
, g
, y
, x
;
750 pos
= 4 + GET_32BIT(pubblob
);
751 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &p
);
752 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &q
);
753 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &g
);
754 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &y
);
756 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &x
);
758 assert(y
.start
&& x
.start
); /* can't go wrong */
760 numbers
[0].start
= zero
; numbers
[0].bytes
= 1; zero
[0] = '\0';
768 header
= "-----BEGIN DSA PRIVATE KEY-----\n";
769 footer
= "-----END DSA PRIVATE KEY-----\n";
771 assert(0); /* zoinks! */
775 * Now count up the total size of the ASN.1 encoded integers,
776 * so as to determine the length of the containing SEQUENCE.
779 for (i
= 0; i
< nnumbers
; i
++) {
780 len
+= ber_write_id_len(NULL
, 2, numbers
[i
].bytes
, 0);
781 len
+= numbers
[i
].bytes
;
784 /* Now add on the SEQUENCE header. */
785 len
+= ber_write_id_len(NULL
, 16, seqlen
, ASN1_CONSTRUCTED
);
786 /* Round up to the cipher block size, ensuring we have at least one
787 * byte of padding (see below). */
790 outlen
= (outlen
+8) &~ 7;
793 * Now we know how big outblob needs to be. Allocate it.
795 outblob
= snewn(outlen
, unsigned char);
798 * And write the data into it.
801 pos
+= ber_write_id_len(outblob
+pos
, 16, seqlen
, ASN1_CONSTRUCTED
);
802 for (i
= 0; i
< nnumbers
; i
++) {
803 pos
+= ber_write_id_len(outblob
+pos
, 2, numbers
[i
].bytes
, 0);
804 memcpy(outblob
+pos
, numbers
[i
].start
, numbers
[i
].bytes
);
805 pos
+= numbers
[i
].bytes
;
809 * Padding on OpenSSH keys is deterministic. The number of
810 * padding bytes is always more than zero, and always at most
811 * the cipher block length. The value of each padding byte is
812 * equal to the number of padding bytes. So a plaintext that's
813 * an exact multiple of the block size will be padded with 08
814 * 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
815 * plaintext one byte less than a multiple of the block size
816 * will be padded with just 01.
818 * This enables the OpenSSL key decryption function to strip
819 * off the padding algorithmically and return the unpadded
820 * plaintext to the next layer: it looks at the final byte, and
821 * then expects to find that many bytes at the end of the data
822 * with the same value. Those are all removed and the rest is
826 while (pos
< outlen
) {
827 outblob
[pos
++] = outlen
- len
;
835 * Invent an iv. Then derive encryption key from passphrase
838 * - let block A equal MD5(passphrase || iv)
839 * - let block B equal MD5(A || passphrase || iv)
840 * - block C would be MD5(B || passphrase || iv) and so on
841 * - encryption key is the first N bytes of A || B
843 struct MD5Context md5c
;
844 unsigned char keybuf
[32];
846 for (i
= 0; i
< 8; i
++) iv
[i
] = random_byte();
849 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
850 MD5Update(&md5c
, iv
, 8);
851 MD5Final(keybuf
, &md5c
);
854 MD5Update(&md5c
, keybuf
, 16);
855 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
856 MD5Update(&md5c
, iv
, 8);
857 MD5Final(keybuf
+16, &md5c
);
860 * Now encrypt the key blob.
862 des3_encrypt_pubkey_ossh(keybuf
, iv
, outblob
, outlen
);
864 memset(&md5c
, 0, sizeof(md5c
));
865 memset(keybuf
, 0, sizeof(keybuf
));
869 * And save it. We'll use Unix line endings just in case it's
870 * subsequently transferred in binary mode.
872 fp
= f_open(*filename
, "wb"); /* ensure Unix line endings */
877 fprintf(fp
, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
878 for (i
= 0; i
< 8; i
++)
879 fprintf(fp
, "%02X", iv
[i
]);
882 base64_encode(fp
, outblob
, outlen
, 64);
889 memset(outblob
, 0, outlen
);
893 memset(spareblob
, 0, sparelen
);
897 memset(privblob
, 0, privlen
);
901 memset(pubblob
, 0, publen
);
907 /* ----------------------------------------------------------------------
908 * Code to read ssh.com private keys.
912 * The format of the base64 blob is largely ssh2-packet-formatted,
913 * except that mpints are a bit different: they're more like the
914 * old ssh1 mpint. You have a 32-bit bit count N, followed by
915 * (N+7)/8 bytes of data.
917 * So. The blob contains:
919 * - uint32 0x3f6ff9eb (magic number)
920 * - uint32 size (total blob size)
921 * - string key-type (see below)
922 * - string cipher-type (tells you if key is encrypted)
923 * - string encrypted-blob
925 * (The first size field includes the size field itself and the
926 * magic number before it. All other size fields are ordinary ssh2
927 * strings, so the size field indicates how much data is to
930 * The encrypted blob, once decrypted, contains a single string
931 * which in turn contains the payload. (This allows padding to be
932 * added after that string while still making it clear where the
933 * real payload ends. Also it probably makes for a reasonable
936 * The payload blob, for an RSA key, contains:
939 * - mpint n (yes, the public and private stuff is intermixed)
940 * - mpint u (presumably inverse of p mod q)
941 * - mpint p (p is the smaller prime)
942 * - mpint q (q is the larger)
944 * For a DSA key, the payload blob contains:
952 * Alternatively, if the parameters are `predefined', that
953 * (0,p,g,q) sequence can be replaced by a uint32 1 and a string
954 * containing some predefined parameter specification. *shudder*,
955 * but I doubt we'll encounter this in real life.
957 * The key type strings are ghastly. The RSA key I looked at had a
960 * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
962 * and the DSA key wasn't much better:
964 * `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
966 * It isn't clear that these will always be the same. I think it
967 * might be wise just to look at the `if-modn{sign{rsa' and
968 * `dl-modp{sign{dsa' prefixes.
970 * Finally, the encryption. The cipher-type string appears to be
971 * either `none' or `3des-cbc'. Looks as if this is SSH2-style
972 * 3des-cbc (i.e. outer cbc rather than inner). The key is created
973 * from the passphrase by means of yet another hashing faff:
975 * - first 16 bytes are MD5(passphrase)
976 * - next 16 bytes are MD5(passphrase || first 16 bytes)
977 * - if there were more, they'd be MD5(passphrase || first 32),
981 #define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
984 char comment
[256]; /* allowing any length is overkill */
985 unsigned char *keyblob
;
986 int keyblob_len
, keyblob_size
;
989 static struct sshcom_key
*load_sshcom_key(const Filename
*filename
)
991 struct sshcom_key
*ret
;
998 int base64_chars
= 0;
1000 ret
= snew(struct sshcom_key
);
1001 ret
->comment
[0] = '\0';
1002 ret
->keyblob
= NULL
;
1003 ret
->keyblob_len
= ret
->keyblob_size
= 0;
1005 fp
= f_open(*filename
, "r");
1007 errmsg
= "Unable to open key file";
1010 if (!fgets(buffer
, sizeof(buffer
), fp
) ||
1011 0 != strcmp(buffer
, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
1012 errmsg
= "File does not begin with ssh.com key header";
1018 if (!fgets(buffer
, sizeof(buffer
), fp
)) {
1019 errmsg
= "Unexpected end of file";
1022 if (!strcmp(buffer
, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
1024 if ((p
= strchr(buffer
, ':')) != NULL
) {
1026 errmsg
= "Header found in body of key data";
1030 while (*p
&& isspace((unsigned char)*p
)) p
++;
1032 * Header lines can end in a trailing backslash for
1035 while ((len
= strlen(p
)) > (int)(sizeof(buffer
) - (p
-buffer
) -1) ||
1036 p
[len
-1] != '\n' || p
[len
-2] == '\\') {
1037 if (len
> (int)((p
-buffer
) + sizeof(buffer
)-2)) {
1038 errmsg
= "Header line too long to deal with";
1041 if (!fgets(p
+len
-2, sizeof(buffer
)-(p
-buffer
)-(len
-2), fp
)) {
1042 errmsg
= "Unexpected end of file";
1046 p
[strcspn(p
, "\n")] = '\0';
1047 if (!strcmp(buffer
, "Comment")) {
1048 /* Strip quotes in comment if present. */
1049 if (p
[0] == '"' && p
[strlen(p
)-1] == '"') {
1051 p
[strlen(p
)-1] = '\0';
1053 strncpy(ret
->comment
, p
, sizeof(ret
->comment
));
1054 ret
->comment
[sizeof(ret
->comment
)-1] = '\0';
1060 while (isbase64(*p
)) {
1061 base64_bit
[base64_chars
++] = *p
;
1062 if (base64_chars
== 4) {
1063 unsigned char out
[3];
1067 len
= base64_decode_atom(base64_bit
, out
);
1070 errmsg
= "Invalid base64 encoding";
1074 if (ret
->keyblob_len
+ len
> ret
->keyblob_size
) {
1075 ret
->keyblob_size
= ret
->keyblob_len
+ len
+ 256;
1076 ret
->keyblob
= sresize(ret
->keyblob
, ret
->keyblob_size
,
1080 memcpy(ret
->keyblob
+ ret
->keyblob_len
, out
, len
);
1081 ret
->keyblob_len
+= len
;
1089 if (ret
->keyblob_len
== 0 || !ret
->keyblob
) {
1090 errmsg
= "Key body not present";
1099 memset(ret
->keyblob
, 0, ret
->keyblob_size
);
1100 sfree(ret
->keyblob
);
1102 memset(&ret
, 0, sizeof(ret
));
1108 int sshcom_encrypted(const Filename
*filename
, char **comment
)
1110 struct sshcom_key
*key
= load_sshcom_key(filename
);
1111 int pos
, len
, answer
;
1118 * Check magic number.
1120 if (GET_32BIT(key
->keyblob
) != 0x3f6ff9eb)
1121 return 0; /* key is invalid */
1124 * Find the cipher-type string.
1128 if (key
->keyblob_len
< pos
+4)
1129 goto done
; /* key is far too short */
1130 pos
+= 4 + GET_32BIT(key
->keyblob
+ pos
); /* skip key type */
1131 if (key
->keyblob_len
< pos
+4)
1132 goto done
; /* key is far too short */
1133 len
= GET_32BIT(key
->keyblob
+ pos
); /* find cipher-type length */
1134 if (key
->keyblob_len
< pos
+4+len
)
1135 goto done
; /* cipher type string is incomplete */
1136 if (len
!= 4 || 0 != memcmp(key
->keyblob
+ pos
+ 4, "none", 4))
1140 *comment
= dupstr(key
->comment
);
1141 memset(key
->keyblob
, 0, key
->keyblob_size
);
1142 sfree(key
->keyblob
);
1143 memset(&key
, 0, sizeof(key
));
1148 static int sshcom_read_mpint(void *data
, int len
, struct mpint_pos
*ret
)
1152 unsigned char *d
= (unsigned char *) data
;
1156 bits
= GET_32BIT(d
);
1158 bytes
= (bits
+ 7) / 8;
1169 return len
; /* ensure further calls fail as well */
1172 static int sshcom_put_mpint(void *target
, void *data
, int len
)
1174 unsigned char *d
= (unsigned char *)target
;
1175 unsigned char *i
= (unsigned char *)data
;
1176 int bits
= len
* 8 - 1;
1179 if (*i
& (1 << (bits
& 7)))
1185 PUT_32BIT(d
, bits
+1);
1186 memcpy(d
+4, i
, len
);
1190 struct ssh2_userkey
*sshcom_read(const Filename
*filename
, char *passphrase
)
1192 struct sshcom_key
*key
= load_sshcom_key(filename
);
1195 const char prefix_rsa
[] = "if-modn{sign{rsa";
1196 const char prefix_dsa
[] = "dl-modp{sign{dsa";
1197 enum { RSA
, DSA
} type
;
1201 struct ssh2_userkey
*ret
= NULL
, *retkey
;
1202 const struct ssh_signkey
*alg
;
1203 unsigned char *blob
= NULL
;
1204 int blobsize
, publen
, privlen
;
1210 * Check magic number.
1212 if (GET_32BIT(key
->keyblob
) != SSHCOM_MAGIC_NUMBER
) {
1213 errmsg
= "Key does not begin with magic number";
1218 * Determine the key type.
1221 if (key
->keyblob_len
< pos
+4 ||
1222 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1223 errmsg
= "Key blob does not contain a key type string";
1226 if (len
> sizeof(prefix_rsa
) - 1 &&
1227 !memcmp(key
->keyblob
+pos
+4, prefix_rsa
, sizeof(prefix_rsa
) - 1)) {
1229 } else if (len
> sizeof(prefix_dsa
) - 1 &&
1230 !memcmp(key
->keyblob
+pos
+4, prefix_dsa
, sizeof(prefix_dsa
) - 1)) {
1233 errmsg
= "Key is of unknown type";
1239 * Determine the cipher type.
1241 if (key
->keyblob_len
< pos
+4 ||
1242 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1243 errmsg
= "Key blob does not contain a cipher type string";
1246 if (len
== 4 && !memcmp(key
->keyblob
+pos
+4, "none", 4))
1248 else if (len
== 8 && !memcmp(key
->keyblob
+pos
+4, "3des-cbc", 8))
1251 errmsg
= "Key encryption is of unknown type";
1257 * Get hold of the encrypted part of the key.
1259 if (key
->keyblob_len
< pos
+4 ||
1260 (len
= GET_32BIT(key
->keyblob
+ pos
)) > key
->keyblob_len
- pos
- 4) {
1261 errmsg
= "Key blob does not contain actual key data";
1264 ciphertext
= (char *)key
->keyblob
+ pos
+ 4;
1266 if (cipherlen
== 0) {
1267 errmsg
= "Length of key data is zero";
1272 * Decrypt it if necessary.
1276 * Derive encryption key from passphrase and iv/salt:
1278 * - let block A equal MD5(passphrase)
1279 * - let block B equal MD5(passphrase || A)
1280 * - block C would be MD5(passphrase || A || B) and so on
1281 * - encryption key is the first N bytes of A || B
1283 struct MD5Context md5c
;
1284 unsigned char keybuf
[32], iv
[8];
1286 if (cipherlen
% 8 != 0) {
1287 errmsg
= "Encrypted part of key is not a multiple of cipher block"
1293 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
1294 MD5Final(keybuf
, &md5c
);
1297 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
1298 MD5Update(&md5c
, keybuf
, 16);
1299 MD5Final(keybuf
+16, &md5c
);
1302 * Now decrypt the key blob.
1304 memset(iv
, 0, sizeof(iv
));
1305 des3_decrypt_pubkey_ossh(keybuf
, iv
, (unsigned char *)ciphertext
,
1308 memset(&md5c
, 0, sizeof(md5c
));
1309 memset(keybuf
, 0, sizeof(keybuf
));
1312 * Hereafter we return WRONG_PASSPHRASE for any parsing
1313 * error. (But only if we've just tried to decrypt it!
1314 * Returning WRONG_PASSPHRASE for an unencrypted key is
1318 ret
= SSH2_WRONG_PASSPHRASE
;
1322 * Strip away the containing string to get to the real meat.
1324 len
= GET_32BIT(ciphertext
);
1325 if (len
> cipherlen
-4) {
1326 errmsg
= "containing string was ill-formed";
1333 * Now we break down into RSA versus DSA. In either case we'll
1334 * construct public and private blobs in our own format, and
1335 * end up feeding them to alg->createkey().
1337 blobsize
= cipherlen
+ 256;
1338 blob
= snewn(blobsize
, unsigned char);
1341 struct mpint_pos n
, e
, d
, u
, p
, q
;
1343 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &e
);
1344 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &d
);
1345 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &n
);
1346 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &u
);
1347 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &p
);
1348 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &q
);
1350 errmsg
= "key data did not contain six integers";
1356 pos
+= put_string(blob
+pos
, "ssh-rsa", 7);
1357 pos
+= put_mp(blob
+pos
, e
.start
, e
.bytes
);
1358 pos
+= put_mp(blob
+pos
, n
.start
, n
.bytes
);
1360 pos
+= put_string(blob
+pos
, d
.start
, d
.bytes
);
1361 pos
+= put_mp(blob
+pos
, q
.start
, q
.bytes
);
1362 pos
+= put_mp(blob
+pos
, p
.start
, p
.bytes
);
1363 pos
+= put_mp(blob
+pos
, u
.start
, u
.bytes
);
1364 privlen
= pos
- publen
;
1365 } else if (type
== DSA
) {
1366 struct mpint_pos p
, q
, g
, x
, y
;
1368 if (GET_32BIT(ciphertext
) != 0) {
1369 errmsg
= "predefined DSA parameters not supported";
1372 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &p
);
1373 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &g
);
1374 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &q
);
1375 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &y
);
1376 pos
+= sshcom_read_mpint(ciphertext
+pos
, cipherlen
-pos
, &x
);
1378 errmsg
= "key data did not contain five integers";
1384 pos
+= put_string(blob
+pos
, "ssh-dss", 7);
1385 pos
+= put_mp(blob
+pos
, p
.start
, p
.bytes
);
1386 pos
+= put_mp(blob
+pos
, q
.start
, q
.bytes
);
1387 pos
+= put_mp(blob
+pos
, g
.start
, g
.bytes
);
1388 pos
+= put_mp(blob
+pos
, y
.start
, y
.bytes
);
1390 pos
+= put_mp(blob
+pos
, x
.start
, x
.bytes
);
1391 privlen
= pos
- publen
;
1394 assert(privlen
> 0); /* should have bombed by now if not */
1396 retkey
= snew(struct ssh2_userkey
);
1398 retkey
->data
= alg
->createkey(blob
, publen
, blob
+publen
, privlen
);
1399 if (!retkey
->data
) {
1401 errmsg
= "unable to create key data structure";
1404 retkey
->comment
= dupstr(key
->comment
);
1406 errmsg
= NULL
; /* no error */
1411 memset(blob
, 0, blobsize
);
1414 memset(key
->keyblob
, 0, key
->keyblob_size
);
1415 sfree(key
->keyblob
);
1416 memset(&key
, 0, sizeof(key
));
1421 int sshcom_write(const Filename
*filename
, struct ssh2_userkey
*key
,
1424 unsigned char *pubblob
, *privblob
;
1425 int publen
, privlen
;
1426 unsigned char *outblob
;
1428 struct mpint_pos numbers
[6];
1429 int nnumbers
, initial_zero
, pos
, lenpos
, i
;
1437 * Fetch the key blobs.
1439 pubblob
= key
->alg
->public_blob(key
->data
, &publen
);
1440 privblob
= key
->alg
->private_blob(key
->data
, &privlen
);
1444 * Find the sequence of integers to be encoded into the OpenSSH
1445 * key blob, and also decide on the header line.
1447 if (key
->alg
== &ssh_rsa
) {
1449 struct mpint_pos n
, e
, d
, p
, q
, iqmp
;
1451 pos
= 4 + GET_32BIT(pubblob
);
1452 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &e
);
1453 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &n
);
1455 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &d
);
1456 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &p
);
1457 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &q
);
1458 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &iqmp
);
1460 assert(e
.start
&& iqmp
.start
); /* can't go wrong */
1471 type
= "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
1472 } else if (key
->alg
== &ssh_dss
) {
1474 struct mpint_pos p
, q
, g
, y
, x
;
1476 pos
= 4 + GET_32BIT(pubblob
);
1477 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &p
);
1478 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &q
);
1479 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &g
);
1480 pos
+= ssh2_read_mpint(pubblob
+pos
, publen
-pos
, &y
);
1482 pos
+= ssh2_read_mpint(privblob
+pos
, privlen
-pos
, &x
);
1484 assert(y
.start
&& x
.start
); /* can't go wrong */
1494 type
= "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
1496 assert(0); /* zoinks! */
1500 * Total size of key blob will be somewhere under 512 plus
1501 * combined length of integers. We'll calculate the more
1502 * precise size as we construct the blob.
1505 for (i
= 0; i
< nnumbers
; i
++)
1506 outlen
+= 4 + numbers
[i
].bytes
;
1507 outblob
= snewn(outlen
, unsigned char);
1510 * Create the unencrypted key blob.
1513 PUT_32BIT(outblob
+pos
, SSHCOM_MAGIC_NUMBER
); pos
+= 4;
1514 pos
+= 4; /* length field, fill in later */
1515 pos
+= put_string(outblob
+pos
, type
, strlen(type
));
1517 char *ciphertype
= passphrase ?
"3des-cbc" : "none";
1518 pos
+= put_string(outblob
+pos
, ciphertype
, strlen(ciphertype
));
1520 lenpos
= pos
; /* remember this position */
1521 pos
+= 4; /* encrypted-blob size */
1522 pos
+= 4; /* encrypted-payload size */
1524 PUT_32BIT(outblob
+pos
, 0);
1527 for (i
= 0; i
< nnumbers
; i
++)
1528 pos
+= sshcom_put_mpint(outblob
+pos
,
1529 numbers
[i
].start
, numbers
[i
].bytes
);
1530 /* Now wrap up the encrypted payload. */
1531 PUT_32BIT(outblob
+lenpos
+4, pos
- (lenpos
+8));
1532 /* Pad encrypted blob to a multiple of cipher block size. */
1534 int padding
= -(pos
- (lenpos
+4)) & 7;
1536 outblob
[pos
++] = random_byte();
1538 ciphertext
= (char *)outblob
+lenpos
+4;
1539 cipherlen
= pos
- (lenpos
+4);
1540 assert(!passphrase
|| cipherlen
% 8 == 0);
1541 /* Wrap up the encrypted blob string. */
1542 PUT_32BIT(outblob
+lenpos
, cipherlen
);
1543 /* And finally fill in the total length field. */
1544 PUT_32BIT(outblob
+4, pos
);
1546 assert(pos
< outlen
);
1553 * Derive encryption key from passphrase and iv/salt:
1555 * - let block A equal MD5(passphrase)
1556 * - let block B equal MD5(passphrase || A)
1557 * - block C would be MD5(passphrase || A || B) and so on
1558 * - encryption key is the first N bytes of A || B
1560 struct MD5Context md5c
;
1561 unsigned char keybuf
[32], iv
[8];
1564 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
1565 MD5Final(keybuf
, &md5c
);
1568 MD5Update(&md5c
, (unsigned char *)passphrase
, strlen(passphrase
));
1569 MD5Update(&md5c
, keybuf
, 16);
1570 MD5Final(keybuf
+16, &md5c
);
1573 * Now decrypt the key blob.
1575 memset(iv
, 0, sizeof(iv
));
1576 des3_encrypt_pubkey_ossh(keybuf
, iv
, (unsigned char *)ciphertext
,
1579 memset(&md5c
, 0, sizeof(md5c
));
1580 memset(keybuf
, 0, sizeof(keybuf
));
1584 * And save it. We'll use Unix line endings just in case it's
1585 * subsequently transferred in binary mode.
1587 fp
= f_open(*filename
, "wb"); /* ensure Unix line endings */
1590 fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp
);
1591 fprintf(fp
, "Comment: \"");
1593 * Comment header is broken with backslash-newline if it goes
1594 * over 70 chars. Although it's surrounded by quotes, it
1595 * _doesn't_ escape backslashes or quotes within the string.
1596 * Don't ask me, I didn't design it.
1599 int slen
= 60; /* starts at 60 due to "Comment: " */
1600 char *c
= key
->comment
;
1601 while ((int)strlen(c
) > slen
) {
1602 fprintf(fp
, "%.*s\\\n", slen
, c
);
1604 slen
= 70; /* allow 70 chars on subsequent lines */
1606 fprintf(fp
, "%s\"\n", c
);
1608 base64_encode(fp
, outblob
, pos
, 70);
1609 fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp
);
1615 memset(outblob
, 0, outlen
);
1619 memset(privblob
, 0, privlen
);
1623 memset(pubblob
, 0, publen
);