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putty
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putty/import.c

2373 строки
69 KiB
C
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/*
* Code for PuTTY to import and export private key files in other
* SSH clients' formats.
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <ctype.h>
#include "putty.h"
#include "ssh.h"
#include "misc.h"
static bool openssh_pem_encrypted(const Filename *file);
static bool openssh_new_encrypted(const Filename *file);
static struct ssh2_userkey *openssh_pem_read(
const Filename *file, const char *passphrase, const char **errmsg_p);
static struct ssh2_userkey *openssh_new_read(
const Filename *file, const char *passphrase, const char **errmsg_p);
static bool openssh_auto_write(
const Filename *file, struct ssh2_userkey *key, const char *passphrase);
static bool openssh_pem_write(
const Filename *file, struct ssh2_userkey *key, const char *passphrase);
static bool openssh_new_write(
const Filename *file, struct ssh2_userkey *key, const char *passphrase);
static bool sshcom_encrypted(const Filename *file, char **comment);
static struct ssh2_userkey *sshcom_read(
const Filename *file, const char *passphrase, const char **errmsg_p);
static bool sshcom_write(
const Filename *file, struct ssh2_userkey *key, const char *passphrase);
/*
* Given a key type, determine whether we know how to import it.
*/
bool import_possible(int type)
{
if (type == SSH_KEYTYPE_OPENSSH_PEM)
return true;
if (type == SSH_KEYTYPE_OPENSSH_NEW)
return true;
if (type == SSH_KEYTYPE_SSHCOM)
return true;
return false;
}
/*
* Given a key type, determine what native key type
* (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once
* we've imported it.
*/
int import_target_type(int type)
{
/*
* There are no known foreign SSH-1 key formats.
*/
return SSH_KEYTYPE_SSH2;
}
/*
* Determine whether a foreign key is encrypted.
*/
bool import_encrypted(const Filename *filename, int type, char **comment)
{
if (type == SSH_KEYTYPE_OPENSSH_PEM) {
/* OpenSSH PEM format doesn't contain a key comment at all */
*comment = dupstr(filename_to_str(filename));
return openssh_pem_encrypted(filename);
} else if (type == SSH_KEYTYPE_OPENSSH_NEW) {
/* OpenSSH new format does, but it's inside the encrypted
* section for some reason */
*comment = dupstr(filename_to_str(filename));
return openssh_new_encrypted(filename);
} else if (type == SSH_KEYTYPE_SSHCOM) {
return sshcom_encrypted(filename, comment);
}
return false;
}
/*
* Import an SSH-1 key.
*/
int import_ssh1(const Filename *filename, int type,
struct RSAKey *key, char *passphrase, const char **errmsg_p)
{
return 0;
}
/*
* Import an SSH-2 key.
*/
struct ssh2_userkey *import_ssh2(const Filename *filename, int type,
char *passphrase, const char **errmsg_p)
{
if (type == SSH_KEYTYPE_OPENSSH_PEM)
return openssh_pem_read(filename, passphrase, errmsg_p);
else if (type == SSH_KEYTYPE_OPENSSH_NEW)
return openssh_new_read(filename, passphrase, errmsg_p);
if (type == SSH_KEYTYPE_SSHCOM)
return sshcom_read(filename, passphrase, errmsg_p);
return NULL;
}
/*
* Export an SSH-1 key.
*/
bool export_ssh1(const Filename *filename, int type, struct RSAKey *key,
char *passphrase)
{
return false;
}
/*
* Export an SSH-2 key.
*/
bool export_ssh2(const Filename *filename, int type,
struct ssh2_userkey *key, char *passphrase)
{
if (type == SSH_KEYTYPE_OPENSSH_AUTO)
return openssh_auto_write(filename, key, passphrase);
if (type == SSH_KEYTYPE_OPENSSH_NEW)
return openssh_new_write(filename, key, passphrase);
if (type == SSH_KEYTYPE_SSHCOM)
return sshcom_write(filename, key, passphrase);
return false;
}
/*
* Strip trailing CRs and LFs at the end of a line of text.
*/
void strip_crlf(char *str)
{
char *p = str + strlen(str);
while (p > str && (p[-1] == '\r' || p[-1] == '\n'))
*--p = '\0';
}
/* ----------------------------------------------------------------------
* Helper routines. (The base64 ones are defined in sshpubk.c.)
*/
#define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \
((c) >= 'a' && (c) <= 'z') || \
((c) >= '0' && (c) <= '9') || \
(c) == '+' || (c) == '/' || (c) == '=' \
)
/*
* Read an ASN.1/BER identifier and length pair.
*
* Flags are a combination of the #defines listed below.
*
* Returns -1 if unsuccessful; otherwise returns the number of
* bytes used out of the source data.
*/
/* ASN.1 tag classes. */
#define ASN1_CLASS_UNIVERSAL (0 << 6)
#define ASN1_CLASS_APPLICATION (1 << 6)
#define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6)
#define ASN1_CLASS_PRIVATE (3 << 6)
#define ASN1_CLASS_MASK (3 << 6)
/* Primitive versus constructed bit. */
#define ASN1_CONSTRUCTED (1 << 5)
/*
* Write an ASN.1/BER identifier and length pair. Returns the
* number of bytes consumed. Assumes dest contains enough space.
* Will avoid writing anything if dest is NULL, but still return
* amount of space required.
*/
static void BinarySink_put_ber_id_len(BinarySink *bs,
int id, int length, int flags)
{
if (id <= 30) {
/*
* Identifier is one byte.
*/
put_byte(bs, id | flags);
} else {
int n;
/*
* Identifier is multiple bytes: the first byte is 11111
* plus the flags, and subsequent bytes encode the value of
* the identifier, 7 bits at a time, with the top bit of
* each byte 1 except the last one which is 0.
*/
put_byte(bs, 0x1F | flags);
for (n = 1; (id >> (7*n)) > 0; n++)
continue; /* count the bytes */
while (n--)
put_byte(bs, (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F));
}
if (length < 128) {
/*
* Length is one byte.
*/
put_byte(bs, length);
} else {
int n;
/*
* Length is multiple bytes. The first is 0x80 plus the
* number of subsequent bytes, and the subsequent bytes
* encode the actual length.
*/
for (n = 1; (length >> (8*n)) > 0; n++)
continue; /* count the bytes */
put_byte(bs, 0x80 | n);
while (n--)
put_byte(bs, (length >> (8*n)) & 0xFF);
}
}
#define put_ber_id_len(bs, id, len, flags) \
BinarySink_put_ber_id_len(BinarySink_UPCAST(bs), id, len, flags)
typedef struct ber_item {
int id;
int flags;
ptrlen data;
} ber_item;
static ber_item BinarySource_get_ber(BinarySource *src)
{
ber_item toret;
unsigned char leadbyte, lenbyte;
size_t length;
leadbyte = get_byte(src);
toret.flags = (leadbyte & 0xE0);
if ((leadbyte & 0x1F) == 0x1F) {
unsigned char idbyte;
toret.id = 0;
do {
idbyte = get_byte(src);
toret.id = (toret.id << 7) | (idbyte & 0x7F);
} while (idbyte & 0x80);
} else {
toret.id = leadbyte & 0x1F;
}
lenbyte = get_byte(src);
if (lenbyte & 0x80) {
int nbytes = lenbyte & 0x7F;
length = 0;
while (nbytes-- > 0)
length = (length << 8) | get_byte(src);
} else {
length = lenbyte;
}
toret.data = get_data(src, length);
return toret;
}
#define get_ber(bs) BinarySource_get_ber(BinarySource_UPCAST(bs))
/* ----------------------------------------------------------------------
* Code to read and write OpenSSH private keys, in the old-style PEM
* format.
*/
typedef enum {
OP_DSA, OP_RSA, OP_ECDSA
} openssh_pem_keytype;
typedef enum {
OP_E_3DES, OP_E_AES
} openssh_pem_enc;
struct openssh_pem_key {
openssh_pem_keytype keytype;
bool encrypted;
openssh_pem_enc encryption;
char iv[32];
strbuf *keyblob;
};
void BinarySink_put_mp_ssh2_from_string(
BinarySink *bs, const void *bytesv, int nbytes)
{
const unsigned char *bytes = (const unsigned char *)bytesv;
while (nbytes > 0 && bytes[0] == 0) {
nbytes--;
bytes++;
}
if (nbytes > 0 && bytes[0] & 0x80) {
put_uint32(bs, nbytes + 1);
put_byte(bs, 0);
} else {
put_uint32(bs, nbytes);
}
put_data(bs, bytes, nbytes);
}
#define put_mp_ssh2_from_string(bs, val, len) \
BinarySink_put_mp_ssh2_from_string(BinarySink_UPCAST(bs), val, len)
static struct openssh_pem_key *load_openssh_pem_key(const Filename *filename,
const char **errmsg_p)
{
struct openssh_pem_key *ret;
FILE *fp = NULL;
char *line = NULL;
const char *errmsg;
char *p;
bool headers_done;
char base64_bit[4];
int base64_chars = 0;
ret = snew(struct openssh_pem_key);
ret->keyblob = strbuf_new();
fp = f_open(filename, "r", false);
if (!fp) {
errmsg = "unable to open key file";
goto error;
}
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (!strstartswith(line, "-----BEGIN ") ||
!strendswith(line, "PRIVATE KEY-----")) {
errmsg = "file does not begin with OpenSSH key header";
goto error;
}
/*
* Parse the BEGIN line. For old-format keys, this tells us the
* type of the key; for new-format keys, all it tells us is the
* format, and we'll find out the key type once we parse the
* base64.
*/
if (!strcmp(line, "-----BEGIN RSA PRIVATE KEY-----")) {
ret->keytype = OP_RSA;
} else if (!strcmp(line, "-----BEGIN DSA PRIVATE KEY-----")) {
ret->keytype = OP_DSA;
} else if (!strcmp(line, "-----BEGIN EC PRIVATE KEY-----")) {
ret->keytype = OP_ECDSA;
} else if (!strcmp(line, "-----BEGIN OPENSSH PRIVATE KEY-----")) {
errmsg = "this is a new-style OpenSSH key";
goto error;
} else {
errmsg = "unrecognised key type";
goto error;
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
ret->encrypted = false;
memset(ret->iv, 0, sizeof(ret->iv));
headers_done = false;
while (1) {
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (strstartswith(line, "-----END ") &&
strendswith(line, "PRIVATE KEY-----")) {
sfree(line);
line = NULL;
break; /* done */
}
if ((p = strchr(line, ':')) != NULL) {
if (headers_done) {
errmsg = "header found in body of key data";
goto error;
}
*p++ = '\0';
while (*p && isspace((unsigned char)*p)) p++;
if (!strcmp(line, "Proc-Type")) {
if (p[0] != '4' || p[1] != ',') {
errmsg = "Proc-Type is not 4 (only 4 is supported)";
goto error;
}
p += 2;
if (!strcmp(p, "ENCRYPTED"))
ret->encrypted = true;
} else if (!strcmp(line, "DEK-Info")) {
int i, ivlen;
if (!strncmp(p, "DES-EDE3-CBC,", 13)) {
ret->encryption = OP_E_3DES;
ivlen = 8;
} else if (!strncmp(p, "AES-128-CBC,", 12)) {
ret->encryption = OP_E_AES;
ivlen = 16;
} else {
errmsg = "unsupported cipher";
goto error;
}
p = strchr(p, ',') + 1;/* always non-NULL, by above checks */
for (i = 0; i < ivlen; i++) {
unsigned j;
if (1 != sscanf(p, "%2x", &j)) {
errmsg = "expected more iv data in DEK-Info";
goto error;
}
ret->iv[i] = j;
p += 2;
}
if (*p) {
errmsg = "more iv data than expected in DEK-Info";
goto error;
}
}
} else {
headers_done = true;
p = line;
while (isbase64(*p)) {
base64_bit[base64_chars++] = *p;
if (base64_chars == 4) {
unsigned char out[3];
int len;
base64_chars = 0;
len = base64_decode_atom(base64_bit, out);
if (len <= 0) {
errmsg = "invalid base64 encoding";
goto error;
}
put_data(ret->keyblob, out, len);
smemclr(out, sizeof(out));
}
p++;
}
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
fclose(fp);
fp = NULL;
if (!ret->keyblob || ret->keyblob->len == 0) {
errmsg = "key body not present";
goto error;
}
if (ret->encrypted && ret->keyblob->len % 8 != 0) {
errmsg = "encrypted key blob is not a multiple of "
"cipher block size";
goto error;
}
smemclr(base64_bit, sizeof(base64_bit));
if (errmsg_p) *errmsg_p = NULL;
return ret;
error:
if (line) {
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
smemclr(base64_bit, sizeof(base64_bit));
if (ret) {
if (ret->keyblob)
strbuf_free(ret->keyblob);
smemclr(ret, sizeof(*ret));
sfree(ret);
}
if (errmsg_p) *errmsg_p = errmsg;
if (fp) fclose(fp);
return NULL;
}
static bool openssh_pem_encrypted(const Filename *filename)
{
struct openssh_pem_key *key = load_openssh_pem_key(filename, NULL);
bool ret;
if (!key)
return false;
ret = key->encrypted;
strbuf_free(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
return ret;
}
static struct ssh2_userkey *openssh_pem_read(
const Filename *filename, const char *passphrase, const char **errmsg_p)
{
struct openssh_pem_key *key = load_openssh_pem_key(filename, errmsg_p);
struct ssh2_userkey *retkey;
const ssh_keyalg *alg;
BinarySource src[1];
int i, num_integers;
struct ssh2_userkey *retval = NULL;
const char *errmsg;
strbuf *blob = strbuf_new();
int privptr = 0, publen;
const char *modptr = NULL;
int modlen = 0;
if (!key)
return NULL;
if (key->encrypted) {
/*
* Derive encryption key from passphrase and iv/salt:
*
* - let block A equal MD5(passphrase || iv)
* - let block B equal MD5(A || passphrase || iv)
* - block C would be MD5(B || passphrase || iv) and so on
* - encryption key is the first N bytes of A || B
*
* (Note that only 8 bytes of the iv are used for key
* derivation, even when the key is encrypted with AES and
* hence there are 16 bytes available.)
*/
struct MD5Context md5c;
unsigned char keybuf[32];
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, key->iv, 8);
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
put_data(&md5c, keybuf, 16);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, key->iv, 8);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob.
*/
if (key->encryption == OP_E_3DES)
des3_decrypt_pubkey_ossh(keybuf, key->iv,
key->keyblob->u, key->keyblob->len);
else {
AESContext *ctx;
assert(key->encryption == OP_E_AES);
ctx = aes_make_context();
aes128_key(ctx, keybuf);
aes_iv(ctx, key->iv);
aes_ssh2_decrypt_blk(ctx, key->keyblob->u, key->keyblob->len);
aes_free_context(ctx);
}
smemclr(&md5c, sizeof(md5c));
smemclr(keybuf, sizeof(keybuf));
}
/*
* Now we have a decrypted key blob, which contains an ASN.1
* encoded private key. We must now untangle the ASN.1.
*
* We expect the whole key blob to be formatted as a SEQUENCE
* (0x30 followed by a length code indicating that the rest of
* the blob is part of the sequence). Within that SEQUENCE we
* expect to see a bunch of INTEGERs. What those integers mean
* depends on the key type:
*
* - For RSA, we expect the integers to be 0, n, e, d, p, q,
* dmp1, dmq1, iqmp in that order. (The last three are d mod
* (p-1), d mod (q-1), inverse of q mod p respectively.)
*
* - For DSA, we expect them to be 0, p, q, g, y, x in that
* order.
*
* - In ECDSA the format is totally different: we see the
* SEQUENCE, but beneath is an INTEGER 1, OCTET STRING priv
* EXPLICIT [0] OID curve, EXPLICIT [1] BIT STRING pubPoint
*/
BinarySource_BARE_INIT(src, key->keyblob->u, key->keyblob->len);
{
/* Expect the SEQUENCE header. Take its absence as a failure to
* decrypt, if the key was encrypted. */
ber_item seq = get_ber(src);
if (get_err(src) || seq.id != 16) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
goto error;
}
/* Reinitialise our BinarySource to parse just the inside of that
* SEQUENCE. */
BinarySource_BARE_INIT(src, seq.data.ptr, seq.data.len);
}
/* Expect a load of INTEGERs. */
if (key->keytype == OP_RSA)
num_integers = 9;
else if (key->keytype == OP_DSA)
num_integers = 6;
else
num_integers = 0; /* placate compiler warnings */
if (key->keytype == OP_ECDSA) {
/* And now for something completely different */
ber_item integer, privkey, sub0, sub1, oid, pubkey;
const ssh_keyalg *alg;
const struct ec_curve *curve;
/* Parse the outer layer of things inside the containing SEQUENCE */
integer = get_ber(src);
privkey = get_ber(src);
sub0 = get_ber(src);
sub1 = get_ber(src);
/* Now look inside sub0 for the curve OID */
BinarySource_BARE_INIT(src, sub0.data.ptr, sub0.data.len);
oid = get_ber(src);
/* And inside sub1 for the public-key BIT STRING */
BinarySource_BARE_INIT(src, sub1.data.ptr, sub1.data.len);
pubkey = get_ber(src);
if (get_err(src) ||
integer.id != 2 ||
integer.data.len != 1 ||
((const unsigned char *)integer.data.ptr)[0] != 1 ||
privkey.id != 4 ||
sub0.id != 0 ||
sub1.id != 1 ||
oid.id != 6 ||
pubkey.id != 3) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
goto error;
}
alg = ec_alg_by_oid(oid.data.len, oid.data.ptr, &curve);
if (!alg) {
errmsg = "Unsupported ECDSA curve.";
retval = NULL;
goto error;
}
if (pubkey.data.len != ((((curve->fieldBits + 7) / 8) * 2) + 2)) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
goto error;
}
/* Skip 0x00 before point */
pubkey.data.ptr = (const char *)pubkey.data.ptr + 1;
pubkey.data.len -= 1;
/* Construct the key */
retkey = snew(struct ssh2_userkey);
put_stringz(blob, alg->ssh_id);
put_stringz(blob, curve->name);
put_stringpl(blob, pubkey.data);
publen = blob->len;
put_mp_ssh2_from_string(blob, privkey.data.ptr, privkey.data.len);
retkey->key = ssh_key_new_priv(
alg, make_ptrlen(blob->u, publen),
make_ptrlen(blob->u + publen, blob->len - publen));
if (!retkey->key) {
sfree(retkey);
errmsg = "unable to create key data structure";
goto error;
}
} else if (key->keytype == OP_RSA || key->keytype == OP_DSA) {
put_stringz(blob, key->keytype == OP_DSA ? "ssh-dss" : "ssh-rsa");
for (i = 0; i < num_integers; i++) {
ber_item integer = get_ber(src);
if (get_err(src) || integer.id != 2) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
goto error;
}
if (i == 0) {
/*
* The first integer should be zero always (I think
* this is some sort of version indication).
*/
if (integer.data.len != 1 ||
((const unsigned char *)integer.data.ptr)[0] != 0) {
errmsg = "version number mismatch";
goto error;
}
} else if (key->keytype == OP_RSA) {
/*
* Integers 1 and 2 go into the public blob but in the
* opposite order; integers 3, 4, 5 and 8 go into the
* private blob. The other two (6 and 7) are ignored.
*/
if (i == 1) {
/* Save the details for after we deal with number 2. */
modptr = integer.data.ptr;
modlen = integer.data.len;
} else if (i != 6 && i != 7) {
put_mp_ssh2_from_string(blob, integer.data.ptr,
integer.data.len);
if (i == 2) {
put_mp_ssh2_from_string(blob, modptr, modlen);
privptr = blob->len;
}
}
} else if (key->keytype == OP_DSA) {
/*
* Integers 1-4 go into the public blob; integer 5 goes
* into the private blob.
*/
put_mp_ssh2_from_string(blob, integer.data.ptr,
integer.data.len);
if (i == 4)
privptr = blob->len;
}
}
/*
* Now put together the actual key. Simplest way to do this is
* to assemble our own key blobs and feed them to the createkey
* functions; this is a bit faffy but it does mean we get all
* the sanity checks for free.
*/
assert(privptr > 0); /* should have bombed by now if not */
retkey = snew(struct ssh2_userkey);
alg = (key->keytype == OP_RSA ? &ssh_rsa : &ssh_dss);
retkey->key = ssh_key_new_priv(
alg, make_ptrlen(blob->u, privptr),
make_ptrlen(blob->u+privptr, blob->len-privptr));
if (!retkey->key) {
sfree(retkey);
errmsg = "unable to create key data structure";
goto error;
}
} else {
assert(0 && "Bad key type from load_openssh_pem_key");
errmsg = "Bad key type from load_openssh_pem_key";
goto error;
}
/*
* The old key format doesn't include a comment in the private
* key file.
*/
retkey->comment = dupstr("imported-openssh-key");
errmsg = NULL; /* no error */
retval = retkey;
error:
strbuf_free(blob);
strbuf_free(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
if (errmsg_p) *errmsg_p = errmsg;
return retval;
}
static bool openssh_pem_write(
const Filename *filename, struct ssh2_userkey *key, const char *passphrase)
{
strbuf *pubblob, *privblob, *outblob;
unsigned char *spareblob;
int sparelen = 0;
ptrlen numbers[9];
int nnumbers, i;
const char *header, *footer;
char zero[1];
unsigned char iv[8];
bool ret = false;
FILE *fp;
BinarySource src[1];
/*
* Fetch the key blobs.
*/
pubblob = strbuf_new();
ssh_key_public_blob(key->key, BinarySink_UPCAST(pubblob));
privblob = strbuf_new();
ssh_key_private_blob(key->key, BinarySink_UPCAST(privblob));
spareblob = NULL;
outblob = strbuf_new();
/*
* Encode the OpenSSH key blob, and also decide on the header
* line.
*/
if (ssh_key_alg(key->key) == &ssh_rsa ||
ssh_key_alg(key->key) == &ssh_dss) {
strbuf *seq;
/*
* The RSA and DSS handlers share some code because the two
* key types have very similar ASN.1 representations, as a
* plain SEQUENCE of big integers. So we set up a list of
* bignums per key type and then construct the actual blob in
* common code after that.
*/
if (ssh_key_alg(key->key) == &ssh_rsa) {
ptrlen n, e, d, p, q, iqmp, dmp1, dmq1;
Bignum bd, bp, bq, bdmp1, bdmq1;
/*
* These blobs were generated from inside PuTTY, so we needn't
* treat them as untrusted.
*/
BinarySource_BARE_INIT(src, pubblob->u, pubblob->len);
get_string(src); /* skip algorithm name */
e = get_string(src);
n = get_string(src);
BinarySource_BARE_INIT(src, privblob->u, privblob->len);
d = get_string(src);
p = get_string(src);
q = get_string(src);
iqmp = get_string(src);
assert(!get_err(src)); /* can't go wrong */
/* We also need d mod (p-1) and d mod (q-1). */
bd = bignum_from_bytes(d.ptr, d.len);
bp = bignum_from_bytes(p.ptr, p.len);
bq = bignum_from_bytes(q.ptr, q.len);
decbn(bp);
decbn(bq);
bdmp1 = bigmod(bd, bp);
bdmq1 = bigmod(bd, bq);
freebn(bd);
freebn(bp);
freebn(bq);
dmp1.len = (bignum_bitcount(bdmp1)+8)/8;
dmq1.len = (bignum_bitcount(bdmq1)+8)/8;
sparelen = dmp1.len + dmq1.len;
spareblob = snewn(sparelen, unsigned char);
dmp1.ptr = spareblob;
dmq1.ptr = spareblob + dmp1.len;
for (i = 0; i < dmp1.len; i++)
spareblob[i] = bignum_byte(bdmp1, dmp1.len-1 - i);
for (i = 0; i < dmq1.len; i++)
spareblob[i+dmp1.len] = bignum_byte(bdmq1, dmq1.len-1 - i);
freebn(bdmp1);
freebn(bdmq1);
numbers[0] = make_ptrlen(zero, 1); zero[0] = '\0';
numbers[1] = n;
numbers[2] = e;
numbers[3] = d;
numbers[4] = p;
numbers[5] = q;
numbers[6] = dmp1;
numbers[7] = dmq1;
numbers[8] = iqmp;
nnumbers = 9;
header = "-----BEGIN RSA PRIVATE KEY-----\n";
footer = "-----END RSA PRIVATE KEY-----\n";
} else { /* ssh-dss */
ptrlen p, q, g, y, x;
/*
* These blobs were generated from inside PuTTY, so we needn't
* treat them as untrusted.
*/
BinarySource_BARE_INIT(src, pubblob->u, pubblob->len);
get_string(src); /* skip algorithm name */
p = get_string(src);
q = get_string(src);
g = get_string(src);
y = get_string(src);
BinarySource_BARE_INIT(src, privblob->u, privblob->len);
x = get_string(src);
assert(!get_err(src)); /* can't go wrong */
numbers[0].ptr = zero; numbers[0].len = 1; zero[0] = '\0';
numbers[1] = p;
numbers[2] = q;
numbers[3] = g;
numbers[4] = y;
numbers[5] = x;
nnumbers = 6;
header = "-----BEGIN DSA PRIVATE KEY-----\n";
footer = "-----END DSA PRIVATE KEY-----\n";
}
seq = strbuf_new();
for (i = 0; i < nnumbers; i++) {
put_ber_id_len(seq, 2, numbers[i].len, 0);
put_data(seq, numbers[i].ptr, numbers[i].len);
}
put_ber_id_len(outblob, 16, seq->len, ASN1_CONSTRUCTED);
put_data(outblob, seq->s, seq->len);
strbuf_free(seq);
} else if (ssh_key_alg(key->key) == &ssh_ecdsa_nistp256 ||
ssh_key_alg(key->key) == &ssh_ecdsa_nistp384 ||
ssh_key_alg(key->key) == &ssh_ecdsa_nistp521) {
const unsigned char *oid;
struct ec_key *ec = container_of(key->key, struct ec_key, sshk);
int oidlen;
int pointlen;
strbuf *seq, *sub;
/*
* Structure of asn1:
* SEQUENCE
* INTEGER 1
* OCTET STRING (private key)
* [0]
* OID (curve)
* [1]
* BIT STRING (0x00 public key point)
*/
oid = ec_alg_oid(ssh_key_alg(key->key), &oidlen);
pointlen = (ec->publicKey.curve->fieldBits + 7) / 8 * 2;
seq = strbuf_new();
/* INTEGER 1 */
put_ber_id_len(seq, 2, 1, 0);
put_byte(seq, 1);
/* OCTET STRING private key */
put_ber_id_len(seq, 4, privblob->len - 4, 0);
put_data(seq, privblob->s + 4, privblob->len - 4);
/* Subsidiary OID */
sub = strbuf_new();
put_ber_id_len(sub, 6, oidlen, 0);
put_data(sub, oid, oidlen);
/* Append the OID to the sequence */
put_ber_id_len(seq, 0, sub->len,
ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
put_data(seq, sub->s, sub->len);
strbuf_free(sub);
/* Subsidiary BIT STRING */
sub = strbuf_new();
put_ber_id_len(sub, 3, 2 + pointlen, 0);
put_byte(sub, 0);
put_data(sub, pubblob->s+39, 1 + pointlen);
/* Append the BIT STRING to the sequence */
put_ber_id_len(seq, 1, sub->len,
ASN1_CLASS_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED);
put_data(seq, sub->s, sub->len);
strbuf_free(sub);
/* Write the full sequence with header to the output blob. */
put_ber_id_len(outblob, 16, seq->len, ASN1_CONSTRUCTED);
put_data(outblob, seq->s, seq->len);
strbuf_free(seq);
header = "-----BEGIN EC PRIVATE KEY-----\n";
footer = "-----END EC PRIVATE KEY-----\n";
} else {
assert(0); /* zoinks! */
exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
}
/*
* Encrypt the key.
*
* For the moment, we still encrypt our OpenSSH keys using
* old-style 3DES.
*/
if (passphrase) {
struct MD5Context md5c;
unsigned char keybuf[32];
int origlen, outlen, pad, i;
/*
* Padding on OpenSSH keys is deterministic. The number of
* padding bytes is always more than zero, and always at most
* the cipher block length. The value of each padding byte is
* equal to the number of padding bytes. So a plaintext that's
* an exact multiple of the block size will be padded with 08
* 08 08 08 08 08 08 08 (assuming a 64-bit block cipher); a
* plaintext one byte less than a multiple of the block size
* will be padded with just 01.
*
* This enables the OpenSSL key decryption function to strip
* off the padding algorithmically and return the unpadded
* plaintext to the next layer: it looks at the final byte, and
* then expects to find that many bytes at the end of the data
* with the same value. Those are all removed and the rest is
* returned.
*/
origlen = outblob->len;
outlen = (origlen + 8) &~ 7;
pad = outlen - origlen;
put_padding(outblob, pad, pad);
/*
* Invent an iv. Then derive encryption key from passphrase
* and iv/salt:
*
* - let block A equal MD5(passphrase || iv)
* - let block B equal MD5(A || passphrase || iv)
* - block C would be MD5(B || passphrase || iv) and so on
* - encryption key is the first N bytes of A || B
*/
for (i = 0; i < 8; i++) iv[i] = random_byte();
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, iv, 8);
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
put_data(&md5c, keybuf, 16);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, iv, 8);
MD5Final(keybuf+16, &md5c);
/*
* Now encrypt the key blob.
*/
des3_encrypt_pubkey_ossh(keybuf, iv,
outblob->u, outlen);
smemclr(&md5c, sizeof(md5c));
smemclr(keybuf, sizeof(keybuf));
}
/*
* And save it. We'll use Unix line endings just in case it's
* subsequently transferred in binary mode.
*/
fp = f_open(filename, "wb", true); /* ensure Unix line endings */
if (!fp)
goto error;
fputs(header, fp);
if (passphrase) {
fprintf(fp, "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,");
for (i = 0; i < 8; i++)
fprintf(fp, "%02X", iv[i]);
fprintf(fp, "\n\n");
}
base64_encode(fp, outblob->u, outblob->len, 64);
fputs(footer, fp);
fclose(fp);
ret = true;
error:
if (outblob)
strbuf_free(outblob);
if (spareblob) {
smemclr(spareblob, sparelen);
sfree(spareblob);
}
if (privblob)
strbuf_free(privblob);
if (pubblob)
strbuf_free(pubblob);
return ret;
}
/* ----------------------------------------------------------------------
* Code to read and write OpenSSH private keys in the new-style format.
*/
typedef enum {
ON_E_NONE, ON_E_AES256CBC, ON_E_AES256CTR
} openssh_new_cipher;
typedef enum {
ON_K_NONE, ON_K_BCRYPT
} openssh_new_kdf;
struct openssh_new_key {
openssh_new_cipher cipher;
openssh_new_kdf kdf;
union {
struct {
int rounds;
/* This points to a position within keyblob, not a
* separately allocated thing */
ptrlen salt;
} bcrypt;
} kdfopts;
int nkeys, key_wanted;
/* This too points to a position within keyblob */
ptrlen private;
unsigned char *keyblob;
int keyblob_len, keyblob_size;
};
static struct openssh_new_key *load_openssh_new_key(const Filename *filename,
const char **errmsg_p)
{
struct openssh_new_key *ret;
FILE *fp = NULL;
char *line = NULL;
const char *errmsg;
char *p;
char base64_bit[4];
int base64_chars = 0;
BinarySource src[1];
ptrlen str;
unsigned key_index;
ret = snew(struct openssh_new_key);
ret->keyblob = NULL;
ret->keyblob_len = ret->keyblob_size = 0;
fp = f_open(filename, "r", false);
if (!fp) {
errmsg = "unable to open key file";
goto error;
}
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (0 != strcmp(line, "-----BEGIN OPENSSH PRIVATE KEY-----")) {
errmsg = "file does not begin with OpenSSH new-style key header";
goto error;
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
while (1) {
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (0 == strcmp(line, "-----END OPENSSH PRIVATE KEY-----")) {
sfree(line);
line = NULL;
break; /* done */
}
p = line;
while (isbase64(*p)) {
base64_bit[base64_chars++] = *p;
if (base64_chars == 4) {
unsigned char out[3];
int len;
base64_chars = 0;
len = base64_decode_atom(base64_bit, out);
if (len <= 0) {
errmsg = "invalid base64 encoding";
goto error;
}
if (ret->keyblob_len + len > ret->keyblob_size) {
ret->keyblob_size = ret->keyblob_len + len + 256;
ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
unsigned char);
}
memcpy(ret->keyblob + ret->keyblob_len, out, len);
ret->keyblob_len += len;
smemclr(out, sizeof(out));
}
p++;
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
fclose(fp);
fp = NULL;
if (ret->keyblob_len == 0 || !ret->keyblob) {
errmsg = "key body not present";
goto error;
}
BinarySource_BARE_INIT(src, ret->keyblob, ret->keyblob_len);
if (strcmp(get_asciz(src), "openssh-key-v1") != 0) {
errmsg = "new-style OpenSSH magic number missing\n";
goto error;
}
/* Cipher name */
str = get_string(src);
if (ptrlen_eq_string(str, "none")) {
ret->cipher = ON_E_NONE;
} else if (ptrlen_eq_string(str, "aes256-cbc")) {
ret->cipher = ON_E_AES256CBC;
} else if (ptrlen_eq_string(str, "aes256-ctr")) {
ret->cipher = ON_E_AES256CTR;
} else {
errmsg = get_err(src) ? "no cipher name found" :
"unrecognised cipher name\n";
goto error;
}
/* Key derivation function name */
str = get_string(src);
if (ptrlen_eq_string(str, "none")) {
ret->kdf = ON_K_NONE;
} else if (ptrlen_eq_string(str, "bcrypt")) {
ret->kdf = ON_K_BCRYPT;
} else {
errmsg = get_err(src) ? "no kdf name found" :
"unrecognised kdf name\n";
goto error;
}
/* KDF extra options */
str = get_string(src);
switch (ret->kdf) {
case ON_K_NONE:
if (str.len != 0) {
errmsg = "expected empty options string for 'none' kdf";
goto error;
}
break;
case ON_K_BCRYPT:
{
BinarySource opts[1];
BinarySource_BARE_INIT(opts, str.ptr, str.len);
ret->kdfopts.bcrypt.salt = get_string(opts);
ret->kdfopts.bcrypt.rounds = get_uint32(opts);
if (get_err(opts)) {
errmsg = "failed to parse bcrypt options string";
goto error;
}
}
break;
}
/*
* At this point we expect a uint32 saying how many keys are
* stored in this file. OpenSSH new-style key files can
* contain more than one. Currently we don't have any user
* interface to specify which one we're trying to extract, so
* we just bomb out with an error if more than one is found in
* the file. However, I've put in all the mechanism here to
* extract the nth one for a given n, in case we later connect
* up some UI to that mechanism. Just arrange that the
* 'key_wanted' field is set to a value in the range [0,
* nkeys) by some mechanism.
*/
ret->nkeys = toint(get_uint32(src));
if (ret->nkeys != 1) {
errmsg = get_err(src) ? "no key count found" :
"multiple keys in new-style OpenSSH key file not supported\n";
goto error;
}
ret->key_wanted = 0;
/* Read and ignore a string per public key. */
for (key_index = 0; key_index < ret->nkeys; key_index++)
str = get_string(src);
/*
* Now we expect a string containing the encrypted part of the
* key file.
*/
ret->private = get_string(src);
if (get_err(src)) {
errmsg = "no private key container string found\n";
goto error;
}
/*
* And now we're done, until asked to actually decrypt.
*/
smemclr(base64_bit, sizeof(base64_bit));
if (errmsg_p) *errmsg_p = NULL;
return ret;
error:
if (line) {
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
smemclr(base64_bit, sizeof(base64_bit));
if (ret) {
if (ret->keyblob) {
smemclr(ret->keyblob, ret->keyblob_size);
sfree(ret->keyblob);
}
smemclr(ret, sizeof(*ret));
sfree(ret);
}
if (errmsg_p) *errmsg_p = errmsg;
if (fp) fclose(fp);
return NULL;
}
static bool openssh_new_encrypted(const Filename *filename)
{
struct openssh_new_key *key = load_openssh_new_key(filename, NULL);
bool ret;
if (!key)
return false;
ret = (key->cipher != ON_E_NONE);
smemclr(key->keyblob, key->keyblob_size);
sfree(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
return ret;
}
static struct ssh2_userkey *openssh_new_read(
const Filename *filename, const char *passphrase, const char **errmsg_p)
{
struct openssh_new_key *key = load_openssh_new_key(filename, errmsg_p);
struct ssh2_userkey *retkey = NULL;
struct ssh2_userkey *retval = NULL;
const char *errmsg;
unsigned checkint;
BinarySource src[1];
int key_index;
const ssh_keyalg *alg = NULL;
if (!key)
return NULL;
if (key->cipher != ON_E_NONE) {
unsigned char keybuf[48];
int keysize;
/*
* Construct the decryption key, and decrypt the string.
*/
switch (key->cipher) {
case ON_E_NONE:
keysize = 0;
break;
case ON_E_AES256CBC:
case ON_E_AES256CTR:
keysize = 48; /* 32 byte key + 16 byte IV */
break;
default:
assert(0 && "Bad cipher enumeration value");
}
assert(keysize <= sizeof(keybuf));
switch (key->kdf) {
case ON_K_NONE:
memset(keybuf, 0, keysize);
break;
case ON_K_BCRYPT:
openssh_bcrypt(passphrase,
key->kdfopts.bcrypt.salt.ptr,
key->kdfopts.bcrypt.salt.len,
key->kdfopts.bcrypt.rounds,
keybuf, keysize);
break;
default:
assert(0 && "Bad kdf enumeration value");
}
switch (key->cipher) {
case ON_E_NONE:
break;
case ON_E_AES256CBC:
case ON_E_AES256CTR:
if (key->private.len % 16 != 0) {
errmsg = "private key container length is not a"
" multiple of AES block size\n";
goto error;
}
{
void *ctx = aes_make_context();
aes256_key(ctx, keybuf);
aes_iv(ctx, keybuf + 32);
/* Decrypt the private section in place, casting away
* the const from key->private being a ptrlen */
if (key->cipher == ON_E_AES256CBC) {
aes_ssh2_decrypt_blk(ctx, (char *)key->private.ptr,
key->private.len);
}
else {
aes_ssh2_sdctr(ctx, (char *)key->private.ptr,
key->private.len);
}
aes_free_context(ctx);
}
break;
default:
assert(0 && "Bad cipher enumeration value");
}
}
/*
* Now parse the entire encrypted section, and extract the key
* identified by key_wanted.
*/
BinarySource_BARE_INIT(src, key->private.ptr, key->private.len);
checkint = get_uint32(src);
if (get_uint32(src) != checkint || get_err(src)) {
errmsg = "decryption check failed";
goto error;
}
retkey = snew(struct ssh2_userkey);
retkey->key = NULL;
retkey->comment = NULL;
for (key_index = 0; key_index < key->nkeys; key_index++) {
ptrlen comment;
/*
* Identify the key type.
*/
alg = find_pubkey_alg_len(get_string(src));
if (!alg) {
errmsg = "private key type not recognised\n";
goto error;
}
/*
* Read the key. We have to do this even if it's not the one
* we want, because it's the only way to find out how much
* data to skip past to get to the next key in the file.
*/
retkey->key = ssh_key_new_priv_openssh(alg, src);
if (get_err(src)) {
errmsg = "unable to read entire private key";
goto error;
}
if (!retkey->key) {
errmsg = "unable to create key data structure";
goto error;
}
if (key_index != key->key_wanted) {
/*
* If this isn't the key we're looking for, throw it away.
*/
ssh_key_free(retkey->key);
retkey->key = NULL;
}
/*
* Read the key comment.
*/
comment = get_string(src);
if (get_err(src)) {
errmsg = "unable to read key comment";
goto error;
}
if (key_index == key->key_wanted) {
assert(retkey);
retkey->comment = mkstr(comment);
}
}
if (!retkey) {
errmsg = "key index out of range";
goto error;
}
/*
* Now we expect nothing left but padding.
*/
{
unsigned char expected_pad_byte = 1;
while (get_avail(src) > 0)
if (get_byte(src) != expected_pad_byte++) {
errmsg = "padding at end of private string did not match";
goto error;
}
}
errmsg = NULL; /* no error */
retval = retkey;
retkey = NULL; /* prevent the free */
error:
if (retkey) {
sfree(retkey->comment);
if (retkey->key)
ssh_key_free(retkey->key);
sfree(retkey);
}
smemclr(key->keyblob, key->keyblob_size);
sfree(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
if (errmsg_p) *errmsg_p = errmsg;
return retval;
}
static bool openssh_new_write(
const Filename *filename, struct ssh2_userkey *key, const char *passphrase)
{
strbuf *pubblob, *privblob, *cblob;
int padvalue, i;
unsigned checkint;
bool ret = false;
unsigned char bcrypt_salt[16];
const int bcrypt_rounds = 16;
FILE *fp;
/*
* Fetch the key blobs and find out the lengths of things.
*/
pubblob = strbuf_new();
ssh_key_public_blob(key->key, BinarySink_UPCAST(pubblob));
privblob = strbuf_new();
ssh_key_openssh_blob(key->key, BinarySink_UPCAST(privblob));
/*
* Construct the cleartext version of the blob.
*/
cblob = strbuf_new();
/* Magic number. */
put_asciz(cblob, "openssh-key-v1");
/* Cipher and kdf names, and kdf options. */
if (!passphrase) {
memset(bcrypt_salt, 0, sizeof(bcrypt_salt)); /* prevent warnings */
put_stringz(cblob, "none");
put_stringz(cblob, "none");
put_stringz(cblob, "");
} else {
strbuf *substr;
for (i = 0; i < (int)sizeof(bcrypt_salt); i++)
bcrypt_salt[i] = random_byte();
put_stringz(cblob, "aes256-ctr");
put_stringz(cblob, "bcrypt");
substr = strbuf_new();
put_string(substr, bcrypt_salt, sizeof(bcrypt_salt));
put_uint32(substr, bcrypt_rounds);
put_stringsb(cblob, substr);
}
/* Number of keys. */
put_uint32(cblob, 1);
/* Public blob. */
put_string(cblob, pubblob->s, pubblob->len);
/* Private section. */
{
strbuf *cpblob = strbuf_new();
/* checkint. */
checkint = 0;
for (i = 0; i < 4; i++)
checkint = (checkint << 8) + random_byte();
put_uint32(cpblob, checkint);
put_uint32(cpblob, checkint);
/* Private key. The main private blob goes inline, with no string
* wrapper. */
put_stringz(cpblob, ssh_key_ssh_id(key->key));
put_data(cpblob, privblob->s, privblob->len);
/* Comment. */
put_stringz(cpblob, key->comment);
/* Pad out the encrypted section. */
padvalue = 1;
do {
put_byte(cpblob, padvalue++);
} while (cpblob->len & 15);
if (passphrase) {
/*
* Encrypt the private section. We need 48 bytes of key
* material: 32 bytes AES key + 16 bytes iv.
*/
unsigned char keybuf[48];
void *ctx;
openssh_bcrypt(passphrase,
bcrypt_salt, sizeof(bcrypt_salt), bcrypt_rounds,
keybuf, sizeof(keybuf));
ctx = aes_make_context();
aes256_key(ctx, keybuf);
aes_iv(ctx, keybuf + 32);
aes_ssh2_sdctr(ctx, cpblob->u,
cpblob->len);
aes_free_context(ctx);
smemclr(keybuf, sizeof(keybuf));
}
put_stringsb(cblob, cpblob);
}
/*
* And save it. We'll use Unix line endings just in case it's
* subsequently transferred in binary mode.
*/
fp = f_open(filename, "wb", true); /* ensure Unix line endings */
if (!fp)
goto error;
fputs("-----BEGIN OPENSSH PRIVATE KEY-----\n", fp);
base64_encode(fp, cblob->u, cblob->len, 64);
fputs("-----END OPENSSH PRIVATE KEY-----\n", fp);
fclose(fp);
ret = true;
error:
if (cblob)
strbuf_free(cblob);
if (privblob)
strbuf_free(privblob);
if (pubblob)
strbuf_free(pubblob);
return ret;
}
/* ----------------------------------------------------------------------
* The switch function openssh_auto_write(), which chooses one of the
* concrete OpenSSH output formats based on the key type.
*/
static bool openssh_auto_write(
const Filename *filename, struct ssh2_userkey *key, const char *passphrase)
{
/*
* The old OpenSSH format supports a fixed list of key types. We
* assume that anything not in that fixed list is newer, and hence
* will use the new format.
*/
if (ssh_key_alg(key->key) == &ssh_dss ||
ssh_key_alg(key->key) == &ssh_rsa ||
ssh_key_alg(key->key) == &ssh_ecdsa_nistp256 ||
ssh_key_alg(key->key) == &ssh_ecdsa_nistp384 ||
ssh_key_alg(key->key) == &ssh_ecdsa_nistp521)
return openssh_pem_write(filename, key, passphrase);
else
return openssh_new_write(filename, key, passphrase);
}
/* ----------------------------------------------------------------------
* Code to read ssh.com private keys.
*/
/*
* The format of the base64 blob is largely SSH-2-packet-formatted,
* except that mpints are a bit different: they're more like the
* old SSH-1 mpint. You have a 32-bit bit count N, followed by
* (N+7)/8 bytes of data.
*
* So. The blob contains:
*
* - uint32 0x3f6ff9eb (magic number)
* - uint32 size (total blob size)
* - string key-type (see below)
* - string cipher-type (tells you if key is encrypted)
* - string encrypted-blob
*
* (The first size field includes the size field itself and the
* magic number before it. All other size fields are ordinary SSH-2
* strings, so the size field indicates how much data is to
* _follow_.)
*
* The encrypted blob, once decrypted, contains a single string
* which in turn contains the payload. (This allows padding to be
* added after that string while still making it clear where the
* real payload ends. Also it probably makes for a reasonable
* decryption check.)
*
* The payload blob, for an RSA key, contains:
* - mpint e
* - mpint d
* - mpint n (yes, the public and private stuff is intermixed)
* - mpint u (presumably inverse of p mod q)
* - mpint p (p is the smaller prime)
* - mpint q (q is the larger)
*
* For a DSA key, the payload blob contains:
* - uint32 0
* - mpint p
* - mpint g
* - mpint q
* - mpint y
* - mpint x
*
* Alternatively, if the parameters are `predefined', that
* (0,p,g,q) sequence can be replaced by a uint32 1 and a string
* containing some predefined parameter specification. *shudder*,
* but I doubt we'll encounter this in real life.
*
* The key type strings are ghastly. The RSA key I looked at had a
* type string of
*
* `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}'
*
* and the DSA key wasn't much better:
*
* `dl-modp{sign{dsa-nist-sha1},dh{plain}}'
*
* It isn't clear that these will always be the same. I think it
* might be wise just to look at the `if-modn{sign{rsa' and
* `dl-modp{sign{dsa' prefixes.
*
* Finally, the encryption. The cipher-type string appears to be
* either `none' or `3des-cbc'. Looks as if this is SSH-2-style
* 3des-cbc (i.e. outer cbc rather than inner). The key is created
* from the passphrase by means of yet another hashing faff:
*
* - first 16 bytes are MD5(passphrase)
* - next 16 bytes are MD5(passphrase || first 16 bytes)
* - if there were more, they'd be MD5(passphrase || first 32),
* and so on.
*/
#define SSHCOM_MAGIC_NUMBER 0x3f6ff9eb
struct sshcom_key {
char comment[256]; /* allowing any length is overkill */
unsigned char *keyblob;
int keyblob_len, keyblob_size;
};
static struct sshcom_key *load_sshcom_key(const Filename *filename,
const char **errmsg_p)
{
struct sshcom_key *ret;
FILE *fp;
char *line = NULL;
int hdrstart, len;
const char *errmsg;
char *p;
bool headers_done;
char base64_bit[4];
int base64_chars = 0;
ret = snew(struct sshcom_key);
ret->comment[0] = '\0';
ret->keyblob = NULL;
ret->keyblob_len = ret->keyblob_size = 0;
fp = f_open(filename, "r", false);
if (!fp) {
errmsg = "unable to open key file";
goto error;
}
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (0 != strcmp(line, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")) {
errmsg = "file does not begin with ssh.com key header";
goto error;
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
headers_done = false;
while (1) {
if (!(line = fgetline(fp))) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line);
if (!strcmp(line, "---- END SSH2 ENCRYPTED PRIVATE KEY ----")) {
sfree(line);
line = NULL;
break; /* done */
}
if ((p = strchr(line, ':')) != NULL) {
if (headers_done) {
errmsg = "header found in body of key data";
goto error;
}
*p++ = '\0';
while (*p && isspace((unsigned char)*p)) p++;
hdrstart = p - line;
/*
* Header lines can end in a trailing backslash for
* continuation.
*/
len = hdrstart + strlen(line+hdrstart);
assert(!line[len]);
while (line[len-1] == '\\') {
char *line2;
int line2len;
line2 = fgetline(fp);
if (!line2) {
errmsg = "unexpected end of file";
goto error;
}
strip_crlf(line2);
line2len = strlen(line2);
line = sresize(line, len + line2len + 1, char);
strcpy(line + len - 1, line2);
len += line2len - 1;
assert(!line[len]);
smemclr(line2, strlen(line2));
sfree(line2);
line2 = NULL;
}
p = line + hdrstart;
strip_crlf(p);
if (!strcmp(line, "Comment")) {
/* Strip quotes in comment if present. */
if (p[0] == '"' && p[strlen(p)-1] == '"') {
p++;
p[strlen(p)-1] = '\0';
}
strncpy(ret->comment, p, sizeof(ret->comment));
ret->comment[sizeof(ret->comment)-1] = '\0';
}
} else {
headers_done = true;
p = line;
while (isbase64(*p)) {
base64_bit[base64_chars++] = *p;
if (base64_chars == 4) {
unsigned char out[3];
base64_chars = 0;
len = base64_decode_atom(base64_bit, out);
if (len <= 0) {
errmsg = "invalid base64 encoding";
goto error;
}
if (ret->keyblob_len + len > ret->keyblob_size) {
ret->keyblob_size = ret->keyblob_len + len + 256;
ret->keyblob = sresize(ret->keyblob, ret->keyblob_size,
unsigned char);
}
memcpy(ret->keyblob + ret->keyblob_len, out, len);
ret->keyblob_len += len;
}
p++;
}
}
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
if (ret->keyblob_len == 0 || !ret->keyblob) {
errmsg = "key body not present";
goto error;
}
fclose(fp);
if (errmsg_p) *errmsg_p = NULL;
return ret;
error:
if (fp)
fclose(fp);
if (line) {
smemclr(line, strlen(line));
sfree(line);
line = NULL;
}
if (ret) {
if (ret->keyblob) {
smemclr(ret->keyblob, ret->keyblob_size);
sfree(ret->keyblob);
}
smemclr(ret, sizeof(*ret));
sfree(ret);
}
if (errmsg_p) *errmsg_p = errmsg;
return NULL;
}
static bool sshcom_encrypted(const Filename *filename, char **comment)
{
struct sshcom_key *key = load_sshcom_key(filename, NULL);
BinarySource src[1];
ptrlen str;
bool answer = false;
*comment = NULL;
if (!key)
goto done;
BinarySource_BARE_INIT(src, key->keyblob, key->keyblob_len);
if (get_uint32(src) != SSHCOM_MAGIC_NUMBER)
goto done; /* key is invalid */
get_uint32(src); /* skip length field */
get_string(src); /* skip key type */
str = get_string(src); /* cipher type */
if (get_err(src))
goto done; /* key is invalid */
if (!ptrlen_eq_string(str, "none"))
answer = true;
done:
if (key) {
*comment = dupstr(key->comment);
smemclr(key->keyblob, key->keyblob_size);
sfree(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
} else {
*comment = dupstr("");
}
return answer;
}
void BinarySink_put_mp_sshcom_from_string(
BinarySink *bs, const void *bytesv, int nbytes)
{
const unsigned char *bytes = (const unsigned char *)bytesv;
int bits = nbytes * 8 - 1;
while (bits > 0) {
if (*bytes & (1 << (bits & 7)))
break;
if (!(bits-- & 7))
bytes++, nbytes--;
}
put_uint32(bs, bits+1);
put_data(bs, bytes, nbytes);
}
#define put_mp_sshcom_from_string(bs, val, len) \
BinarySink_put_mp_sshcom_from_string(BinarySink_UPCAST(bs), val, len)
static ptrlen BinarySource_get_mp_sshcom_as_string(BinarySource *src)
{
unsigned bits = get_uint32(src);
return get_data(src, (bits + 7) / 8);
}
#define get_mp_sshcom_as_string(bs) \
BinarySource_get_mp_sshcom_as_string(BinarySource_UPCAST(bs))
static struct ssh2_userkey *sshcom_read(
const Filename *filename, const char *passphrase, const char **errmsg_p)
{
struct sshcom_key *key = load_sshcom_key(filename, errmsg_p);
const char *errmsg;
BinarySource src[1];
ptrlen str, ciphertext;
int publen;
const char prefix_rsa[] = "if-modn{sign{rsa";
const char prefix_dsa[] = "dl-modp{sign{dsa";
enum { RSA, DSA } type;
bool encrypted;
struct ssh2_userkey *ret = NULL, *retkey;
const ssh_keyalg *alg;
strbuf *blob = NULL;
if (!key)
return NULL;
BinarySource_BARE_INIT(src, key->keyblob, key->keyblob_len);
if (get_uint32(src) != SSHCOM_MAGIC_NUMBER) {
errmsg = "key does not begin with magic number";
goto error;
}
get_uint32(src); /* skip length field */
/*
* Determine the key type.
*/
str = get_string(src);
if (str.len > sizeof(prefix_rsa) - 1 &&
!memcmp(str.ptr, prefix_rsa, sizeof(prefix_rsa) - 1)) {
type = RSA;
} else if (str.len > sizeof(prefix_dsa) - 1 &&
!memcmp(str.ptr, prefix_dsa, sizeof(prefix_dsa) - 1)) {
type = DSA;
} else {
errmsg = "key is of unknown type";
goto error;
}
/*
* Determine the cipher type.
*/
str = get_string(src);
if (ptrlen_eq_string(str, "none"))
encrypted = false;
else if (ptrlen_eq_string(str, "3des-cbc"))
encrypted = true;
else {
errmsg = "key encryption is of unknown type";
goto error;
}
/*
* Get hold of the encrypted part of the key.
*/
ciphertext = get_string(src);
if (ciphertext.len == 0) {
errmsg = "no key data found";
goto error;
}
/*
* Decrypt it if necessary.
*/
if (encrypted) {
/*
* Derive encryption key from passphrase and iv/salt:
*
* - let block A equal MD5(passphrase)
* - let block B equal MD5(passphrase || A)
* - block C would be MD5(passphrase || A || B) and so on
* - encryption key is the first N bytes of A || B
*/
struct MD5Context md5c;
unsigned char keybuf[32], iv[8];
if (ciphertext.len % 8 != 0) {
errmsg = "encrypted part of key is not a multiple of cipher block"
" size";
goto error;
}
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, keybuf, 16);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob in place (casting away const from
* ciphertext being a ptrlen).
*/
memset(iv, 0, sizeof(iv));
des3_decrypt_pubkey_ossh(keybuf, iv,
(char *)ciphertext.ptr, ciphertext.len);
smemclr(&md5c, sizeof(md5c));
smemclr(keybuf, sizeof(keybuf));
/*
* Hereafter we return WRONG_PASSPHRASE for any parsing
* error. (But only if we've just tried to decrypt it!
* Returning WRONG_PASSPHRASE for an unencrypted key is
* automatic doom.)
*/
if (encrypted)
ret = SSH2_WRONG_PASSPHRASE;
}
/*
* Expect the ciphertext to be formatted as a containing string,
* and reinitialise src to start parsing the inside of that string.
*/
BinarySource_BARE_INIT(src, ciphertext.ptr, ciphertext.len);
str = get_string(src);
if (get_err(src)) {
errmsg = "containing string was ill-formed";
goto error;
}
BinarySource_BARE_INIT(src, str.ptr, str.len);
/*
* Now we break down into RSA versus DSA. In either case we'll
* construct public and private blobs in our own format, and
* end up feeding them to ssh_key_new_priv().
*/
blob = strbuf_new();
if (type == RSA) {
ptrlen n, e, d, u, p, q;
e = get_mp_sshcom_as_string(src);
d = get_mp_sshcom_as_string(src);
n = get_mp_sshcom_as_string(src);
u = get_mp_sshcom_as_string(src);
p = get_mp_sshcom_as_string(src);
q = get_mp_sshcom_as_string(src);
if (get_err(src)) {
errmsg = "key data did not contain six integers";
goto error;
}
alg = &ssh_rsa;
put_stringz(blob, "ssh-rsa");
put_mp_ssh2_from_string(blob, e.ptr, e.len);
put_mp_ssh2_from_string(blob, n.ptr, n.len);
publen = blob->len;
put_mp_ssh2_from_string(blob, d.ptr, d.len);
put_mp_ssh2_from_string(blob, q.ptr, q.len);
put_mp_ssh2_from_string(blob, p.ptr, p.len);
put_mp_ssh2_from_string(blob, u.ptr, u.len);
} else {
ptrlen p, q, g, x, y;
assert(type == DSA); /* the only other option from the if above */
if (get_uint32(src) != 0) {
errmsg = "predefined DSA parameters not supported";
goto error;
}
p = get_mp_sshcom_as_string(src);
g = get_mp_sshcom_as_string(src);
q = get_mp_sshcom_as_string(src);
y = get_mp_sshcom_as_string(src);
x = get_mp_sshcom_as_string(src);
if (get_err(src)) {
errmsg = "key data did not contain five integers";
goto error;
}
alg = &ssh_dss;
put_stringz(blob, "ssh-dss");
put_mp_ssh2_from_string(blob, p.ptr, p.len);
put_mp_ssh2_from_string(blob, q.ptr, q.len);
put_mp_ssh2_from_string(blob, g.ptr, g.len);
put_mp_ssh2_from_string(blob, y.ptr, y.len);
publen = blob->len;
put_mp_ssh2_from_string(blob, x.ptr, x.len);
}
retkey = snew(struct ssh2_userkey);
retkey->key = ssh_key_new_priv(
alg, make_ptrlen(blob->u, publen),
make_ptrlen(blob->u + publen, blob->len - publen));
if (!retkey->key) {
sfree(retkey);
errmsg = "unable to create key data structure";
goto error;
}
retkey->comment = dupstr(key->comment);
errmsg = NULL; /* no error */
ret = retkey;
error:
if (blob) {
strbuf_free(blob);
}
smemclr(key->keyblob, key->keyblob_size);
sfree(key->keyblob);
smemclr(key, sizeof(*key));
sfree(key);
if (errmsg_p) *errmsg_p = errmsg;
return ret;
}
static bool sshcom_write(
const Filename *filename, struct ssh2_userkey *key, const char *passphrase)
{
strbuf *pubblob, *privblob, *outblob;
ptrlen numbers[6];
int nnumbers, lenpos, i;
bool initial_zero;
BinarySource src[1];
const char *type;
char *ciphertext;
int cipherlen;
bool ret = false;
FILE *fp;
/*
* Fetch the key blobs.
*/
pubblob = strbuf_new();
ssh_key_public_blob(key->key, BinarySink_UPCAST(pubblob));
privblob = strbuf_new();
ssh_key_private_blob(key->key, BinarySink_UPCAST(privblob));
outblob = NULL;
/*
* Find the sequence of integers to be encoded into the OpenSSH
* key blob, and also decide on the header line.
*/
if (ssh_key_alg(key->key) == &ssh_rsa) {
ptrlen n, e, d, p, q, iqmp;
/*
* These blobs were generated from inside PuTTY, so we needn't
* treat them as untrusted.
*/
BinarySource_BARE_INIT(src, pubblob->u, pubblob->len);
get_string(src); /* skip algorithm name */
e = get_string(src);
n = get_string(src);
BinarySource_BARE_INIT(src, privblob->u, privblob->len);
d = get_string(src);
p = get_string(src);
q = get_string(src);
iqmp = get_string(src);
assert(!get_err(src)); /* can't go wrong */
numbers[0] = e;
numbers[1] = d;
numbers[2] = n;
numbers[3] = iqmp;
numbers[4] = q;
numbers[5] = p;
nnumbers = 6;
initial_zero = false;
type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
} else if (ssh_key_alg(key->key) == &ssh_dss) {
ptrlen p, q, g, y, x;
/*
* These blobs were generated from inside PuTTY, so we needn't
* treat them as untrusted.
*/
BinarySource_BARE_INIT(src, pubblob->u, pubblob->len);
get_string(src); /* skip algorithm name */
p = get_string(src);
q = get_string(src);
g = get_string(src);
y = get_string(src);
BinarySource_BARE_INIT(src, privblob->u, privblob->len);
x = get_string(src);
assert(!get_err(src)); /* can't go wrong */
numbers[0] = p;
numbers[1] = g;
numbers[2] = q;
numbers[3] = y;
numbers[4] = x;
nnumbers = 5;
initial_zero = true;
type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
} else {
goto error; /* unsupported key type */
}
outblob = strbuf_new();
/*
* Create the unencrypted key blob.
*/
put_uint32(outblob, SSHCOM_MAGIC_NUMBER);
put_uint32(outblob, 0); /* length field, fill in later */
put_stringz(outblob, type);
put_stringz(outblob, passphrase ? "3des-cbc" : "none");
lenpos = outblob->len; /* remember this position */
put_uint32(outblob, 0); /* encrypted-blob size */
put_uint32(outblob, 0); /* encrypted-payload size */
if (initial_zero)
put_uint32(outblob, 0);
for (i = 0; i < nnumbers; i++)
put_mp_sshcom_from_string(outblob, numbers[i].ptr, numbers[i].len);
/* Now wrap up the encrypted payload. */
PUT_32BIT(outblob->s + lenpos + 4,
outblob->len - (lenpos + 8));
/* Pad encrypted blob to a multiple of cipher block size. */
if (passphrase) {
int padding = -(outblob->len - (lenpos+4)) & 7;
while (padding--)
put_byte(outblob, random_byte());
}
ciphertext = outblob->s + lenpos + 4;
cipherlen = outblob->len - (lenpos + 4);
assert(!passphrase || cipherlen % 8 == 0);
/* Wrap up the encrypted blob string. */
PUT_32BIT(outblob->s + lenpos, cipherlen);
/* And finally fill in the total length field. */
PUT_32BIT(outblob->s + 4, outblob->len);
/*
* Encrypt the key.
*/
if (passphrase) {
/*
* Derive encryption key from passphrase and iv/salt:
*
* - let block A equal MD5(passphrase)
* - let block B equal MD5(passphrase || A)
* - block C would be MD5(passphrase || A || B) and so on
* - encryption key is the first N bytes of A || B
*/
struct MD5Context md5c;
unsigned char keybuf[32], iv[8];
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
put_data(&md5c, passphrase, strlen(passphrase));
put_data(&md5c, keybuf, 16);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob.
*/
memset(iv, 0, sizeof(iv));
des3_encrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen);
smemclr(&md5c, sizeof(md5c));
smemclr(keybuf, sizeof(keybuf));
}
/*
* And save it. We'll use Unix line endings just in case it's
* subsequently transferred in binary mode.
*/
fp = f_open(filename, "wb", true); /* ensure Unix line endings */
if (!fp)
goto error;
fputs("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
fprintf(fp, "Comment: \"");
/*
* Comment header is broken with backslash-newline if it goes
* over 70 chars. Although it's surrounded by quotes, it
* _doesn't_ escape backslashes or quotes within the string.
* Don't ask me, I didn't design it.
*/
{
int slen = 60; /* starts at 60 due to "Comment: " */
char *c = key->comment;
while ((int)strlen(c) > slen) {
fprintf(fp, "%.*s\\\n", slen, c);
c += slen;
slen = 70; /* allow 70 chars on subsequent lines */
}
fprintf(fp, "%s\"\n", c);
}
base64_encode(fp, outblob->u, outblob->len, 70);
fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
fclose(fp);
ret = true;
error:
if (outblob)
strbuf_free(outblob);
if (privblob)
strbuf_free(privblob);
if (pubblob)
strbuf_free(pubblob);
return ret;
}
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