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simplesshd/dropbear/keyimport.c
Greg Alexander 9d7c6ffbfb stock dropbear-2019.78 source tree
2019-06-09 16:44:26 -04:00

1947 lines
50 KiB
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/*
* Based on PuTTY's import.c for importing/exporting OpenSSH and SSH.com
* keyfiles.
*
* Modifications copyright 2003 Matt Johnston
*
* PuTTY is copyright 1997-2003 Simon Tatham.
*
* Portions copyright Robert de Bath, Joris van Rantwijk, Delian
* Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry,
* Justin Bradford, and CORE SDI S.A.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE
* FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "keyimport.h"
#include "bignum.h"
#include "buffer.h"
#include "dbutil.h"
#include "ecc.h"
#if DROPBEAR_ECDSA
static const unsigned char OID_SEC256R1_BLOB[] = {0x2a, 0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07};
static const unsigned char OID_SEC384R1_BLOB[] = {0x2b, 0x81, 0x04, 0x00, 0x22};
static const unsigned char OID_SEC521R1_BLOB[] = {0x2b, 0x81, 0x04, 0x00, 0x23};
#endif
#define PUT_32BIT(cp, value) do { \
(cp)[3] = (unsigned char)(value); \
(cp)[2] = (unsigned char)((value) >> 8); \
(cp)[1] = (unsigned char)((value) >> 16); \
(cp)[0] = (unsigned char)((value) >> 24); } while (0)
#define GET_32BIT(cp) \
(((unsigned long)(unsigned char)(cp)[0] << 24) | \
((unsigned long)(unsigned char)(cp)[1] << 16) | \
((unsigned long)(unsigned char)(cp)[2] << 8) | \
((unsigned long)(unsigned char)(cp)[3]))
static int openssh_encrypted(const char *filename);
static sign_key *openssh_read(const char *filename, const char *passphrase);
static int openssh_write(const char *filename, sign_key *key,
const char *passphrase);
static int dropbear_write(const char*filename, sign_key * key);
static sign_key *dropbear_read(const char* filename);
static int toint(unsigned u);
#if 0
static int sshcom_encrypted(const char *filename, char **comment);
static struct ssh2_userkey *sshcom_read(const char *filename, char *passphrase);
static int sshcom_write(const char *filename, struct ssh2_userkey *key,
char *passphrase);
#endif
int import_encrypted(const char* filename, int filetype) {
if (filetype == KEYFILE_OPENSSH) {
return openssh_encrypted(filename);
#if 0
} else if (filetype == KEYFILE_SSHCOM) {
return sshcom_encrypted(filename, NULL);
#endif
}
return 0;
}
sign_key *import_read(const char *filename, const char *passphrase, int filetype) {
if (filetype == KEYFILE_OPENSSH) {
return openssh_read(filename, passphrase);
} else if (filetype == KEYFILE_DROPBEAR) {
return dropbear_read(filename);
#if 0
} else if (filetype == KEYFILE_SSHCOM) {
return sshcom_read(filename, passphrase);
#endif
}
return NULL;
}
int import_write(const char *filename, sign_key *key, const char *passphrase,
int filetype) {
if (filetype == KEYFILE_OPENSSH) {
return openssh_write(filename, key, passphrase);
} else if (filetype == KEYFILE_DROPBEAR) {
return dropbear_write(filename, key);
#if 0
} else if (filetype == KEYFILE_SSHCOM) {
return sshcom_write(filename, key, passphrase);
#endif
}
return 0;
}
static sign_key *dropbear_read(const char* filename) {
buffer * buf = NULL;
sign_key *ret = NULL;
enum signkey_type type;
buf = buf_new(MAX_PRIVKEY_SIZE);
if (buf_readfile(buf, filename) == DROPBEAR_FAILURE) {
goto error;
}
buf_setpos(buf, 0);
ret = new_sign_key();
type = DROPBEAR_SIGNKEY_ANY;
if (buf_get_priv_key(buf, ret, &type) == DROPBEAR_FAILURE){
goto error;
}
buf_free(buf);
ret->type = type;
return ret;
error:
if (buf) {
buf_free(buf);
}
if (ret) {
sign_key_free(ret);
}
return NULL;
}
/* returns 0 on fail, 1 on success */
static int dropbear_write(const char*filename, sign_key * key) {
buffer * buf;
FILE*fp;
int len;
int ret;
buf = buf_new(MAX_PRIVKEY_SIZE);
buf_put_priv_key(buf, key, key->type);
fp = fopen(filename, "w");
if (!fp) {
ret = 0;
goto out;
}
buf_setpos(buf, 0);
do {
len = fwrite(buf_getptr(buf, buf->len - buf->pos),
1, buf->len - buf->pos, fp);
buf_incrpos(buf, len);
} while (len > 0 && buf->len != buf->pos);
fclose(fp);
if (buf->pos != buf->len) {
ret = 0;
} else {
ret = 1;
}
out:
buf_free(buf);
return ret;
}
/* ----------------------------------------------------------------------
* 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) == '=' \
)
/* cpl has to be less than 100 */
static void base64_encode_fp(FILE * fp, const unsigned char *data,
int datalen, int cpl)
{
unsigned char out[100];
int n;
unsigned long outlen;
int rawcpl;
rawcpl = cpl * 3 / 4;
dropbear_assert((unsigned int)cpl < sizeof(out));
while (datalen > 0) {
n = (datalen < rawcpl ? datalen : rawcpl);
outlen = sizeof(out);
base64_encode(data, n, out, &outlen);
data += n;
datalen -= n;
fwrite(out, 1, outlen, fp);
fputc('\n', fp);
}
}
/*
* 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)
static int ber_read_id_len(void *source, int sourcelen,
int *id, int *length, int *flags)
{
unsigned char *p = (unsigned char *) source;
if (sourcelen == 0)
return -1;
*flags = (*p & 0xE0);
if ((*p & 0x1F) == 0x1F) {
*id = 0;
while (*p & 0x80) {
p++, sourcelen--;
if (sourcelen == 0)
return -1;
*id = (*id << 7) | (*p & 0x7F);
}
p++, sourcelen--;
} else {
*id = *p & 0x1F;
p++, sourcelen--;
}
if (sourcelen == 0)
return -1;
if (*p & 0x80) {
unsigned len;
int n = *p & 0x7F;
p++, sourcelen--;
if (sourcelen < n)
return -1;
len = 0;
while (n--)
len = (len << 8) | (*p++);
sourcelen -= n;
*length = toint(len);
} else {
*length = *p;
p++, sourcelen--;
}
if (*length < 0) {
printf("Negative ASN.1 length\n");
return -1;
}
return p - (unsigned char *) source;
}
/*
* 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 int ber_write_id_len(void *dest, int id, int length, int flags)
{
unsigned char *d = (unsigned char *)dest;
int len = 0;
if (id <= 30) {
/*
* Identifier is one byte.
*/
len++;
if (d) *d++ = 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.
*/
len++;
if (d) *d++ = 0x1F | flags;
for (n = 1; (id >> (7*n)) > 0; n++)
continue; /* count the bytes */
while (n--) {
len++;
if (d) *d++ = (n ? 0x80 : 0) | ((id >> (7*n)) & 0x7F);
}
}
if (length < 128) {
/*
* Length is one byte.
*/
len++;
if (d) *d++ = 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 */
len++;
if (d) *d++ = 0x80 | n;
while (n--) {
len++;
if (d) *d++ = (length >> (8*n)) & 0xFF;
}
}
return len;
}
/* Simple structure to point to an mp-int within a blob. */
struct mpint_pos { void *start; int bytes; };
/* ----------------------------------------------------------------------
* Code to read and write OpenSSH private keys.
*/
enum { OSSH_DSA, OSSH_RSA, OSSH_EC };
struct openssh_key {
int type;
int encrypted;
char iv[32];
unsigned char *keyblob;
unsigned int keyblob_len, keyblob_size;
};
static struct openssh_key *load_openssh_key(const char *filename)
{
struct openssh_key *ret;
FILE *fp = NULL;
char buffer[256];
char *errmsg = NULL, *p = NULL;
int headers_done;
unsigned long len, outlen;
ret = (struct openssh_key*)m_malloc(sizeof(struct openssh_key));
ret->keyblob = NULL;
ret->keyblob_len = ret->keyblob_size = 0;
ret->encrypted = 0;
memset(ret->iv, 0, sizeof(ret->iv));
if (strlen(filename) == 1 && filename[0] == '-') {
fp = stdin;
} else {
fp = fopen(filename, "r");
}
if (!fp) {
errmsg = "Unable to open key file";
goto error;
}
if (!fgets(buffer, sizeof(buffer), fp) ||
0 != strncmp(buffer, "-----BEGIN ", 11) ||
0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) {
errmsg = "File does not begin with OpenSSH key header";
goto error;
}
if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n"))
ret->type = OSSH_RSA;
else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n"))
ret->type = OSSH_DSA;
else if (!strcmp(buffer, "-----BEGIN EC PRIVATE KEY-----\n"))
ret->type = OSSH_EC;
else {
errmsg = "Unrecognised key type";
goto error;
}
headers_done = 0;
while (1) {
if (!fgets(buffer, sizeof(buffer), fp)) {
errmsg = "Unexpected end of file";
goto error;
}
if (0 == strncmp(buffer, "-----END ", 9) &&
0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n"))
break; /* done */
if ((p = strchr(buffer, ':')) != 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(buffer, "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\n"))
ret->encrypted = 1;
} else if (!strcmp(buffer, "DEK-Info")) {
int i, j;
if (strncmp(p, "DES-EDE3-CBC,", 13)) {
errmsg = "Ciphers other than DES-EDE3-CBC not supported";
goto error;
}
p += 13;
for (i = 0; i < 8; i++) {
if (1 != sscanf(p, "%2x", &j))
break;
ret->iv[i] = j;
p += 2;
}
if (i < 8) {
errmsg = "Expected 16-digit iv in DEK-Info";
goto error;
}
}
} else {
headers_done = 1;
len = strlen(buffer);
outlen = len*4/3;
if (ret->keyblob_len + outlen > ret->keyblob_size) {
ret->keyblob_size = ret->keyblob_len + outlen + 256;
ret->keyblob = (unsigned char*)m_realloc(ret->keyblob,
ret->keyblob_size);
}
outlen = ret->keyblob_size - ret->keyblob_len;
if (base64_decode((const unsigned char *)buffer, len,
ret->keyblob + ret->keyblob_len, &outlen) != CRYPT_OK){
errmsg = "Error decoding base64";
goto error;
}
ret->keyblob_len += outlen;
}
}
if (ret->keyblob_len == 0 || !ret->keyblob) {
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;
}
m_burn(buffer, sizeof(buffer));
return ret;
error:
m_burn(buffer, sizeof(buffer));
if (ret) {
if (ret->keyblob) {
m_burn(ret->keyblob, ret->keyblob_size);
m_free(ret->keyblob);
}
m_free(ret);
}
if (fp) {
fclose(fp);
}
if (errmsg) {
fprintf(stderr, "Error: %s\n", errmsg);
}
return NULL;
}
static int openssh_encrypted(const char *filename)
{
struct openssh_key *key = load_openssh_key(filename);
int ret;
if (!key)
return 0;
ret = key->encrypted;
m_burn(key->keyblob, key->keyblob_size);
m_free(key->keyblob);
m_free(key);
return ret;
}
static sign_key *openssh_read(const char *filename, const char * UNUSED(passphrase))
{
struct openssh_key *key;
unsigned char *p;
int ret, id, len, flags;
int i, num_integers = 0;
sign_key *retval = NULL;
char *errmsg;
unsigned char *modptr = NULL;
int modlen = -9999;
enum signkey_type type;
sign_key *retkey;
buffer * blobbuf = NULL;
retkey = new_sign_key();
key = load_openssh_key(filename);
if (!key)
return NULL;
if (key->encrypted) {
errmsg = "encrypted keys not supported currently";
goto error;
#if 0
/* matt TODO */
/*
* 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
*/
struct MD5Context md5c;
unsigned char keybuf[32];
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Update(&md5c, (unsigned char *)key->iv, 8);
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
MD5Update(&md5c, keybuf, 16);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Update(&md5c, (unsigned char *)key->iv, 8);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob.
*/
des3_decrypt_pubkey_ossh(keybuf, (unsigned char *)key->iv,
key->keyblob, key->keyblob_len);
memset(&md5c, 0, sizeof(md5c));
memset(keybuf, 0, sizeof(keybuf));
#endif
}
/*
* 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.
*/
p = key->keyblob;
/* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */
ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
p += ret;
if (ret < 0 || id != 16 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
goto error;
}
/* Expect a load of INTEGERs. */
if (key->type == OSSH_RSA)
num_integers = 9;
else if (key->type == OSSH_DSA)
num_integers = 6;
else if (key->type == OSSH_EC)
num_integers = 1;
/*
* Space to create key blob in.
*/
blobbuf = buf_new(3000);
#if DROPBEAR_DSS
if (key->type == OSSH_DSA) {
buf_putstring(blobbuf, "ssh-dss", 7);
retkey->type = DROPBEAR_SIGNKEY_DSS;
}
#endif
#if DROPBEAR_RSA
if (key->type == OSSH_RSA) {
buf_putstring(blobbuf, "ssh-rsa", 7);
retkey->type = DROPBEAR_SIGNKEY_RSA;
}
#endif
for (i = 0; i < num_integers; i++) {
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
if (ret < 0 || id != 2 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
goto error;
}
if (i == 0) {
/* First integer is a version indicator */
int expected = -1;
switch (key->type) {
case OSSH_RSA:
case OSSH_DSA:
expected = 0;
break;
case OSSH_EC:
expected = 1;
break;
}
if (len != 1 || p[0] != expected) {
errmsg = "Version number mismatch";
goto error;
}
} else if (key->type == OSSH_RSA) {
/*
* OpenSSH key order is n, e, d, p, q, dmp1, dmq1, iqmp
* but we want e, n, d, p, q
*/
if (i == 1) {
/* Save the details for after we deal with number 2. */
modptr = p;
modlen = len;
} else if (i >= 2 && i <= 5) {
buf_putstring(blobbuf, (const char*)p, len);
if (i == 2) {
buf_putstring(blobbuf, (const char*)modptr, modlen);
}
}
} else if (key->type == OSSH_DSA) {
/*
* OpenSSH key order is p, q, g, y, x,
* we want the same.
*/
buf_putstring(blobbuf, (const char*)p, len);
}
/* Skip past the number. */
p += len;
}
#if DROPBEAR_ECDSA
if (key->type == OSSH_EC) {
unsigned char* private_key_bytes = NULL;
int private_key_len = 0;
unsigned char* public_key_bytes = NULL;
int public_key_len = 0;
ecc_key *ecc = NULL;
const struct dropbear_ecc_curve *curve = NULL;
/* See SEC1 v2, Appendix C.4 */
/* OpenSSL (so OpenSSH) seems to include the optional parts. */
/* privateKey OCTET STRING, */
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
/* id==4 for octet string */
if (ret < 0 || id != 4 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
goto error;
}
private_key_bytes = p;
private_key_len = len;
p += len;
/* parameters [0] ECDomainParameters {{ SECGCurveNames }} OPTIONAL, */
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
/* id==0 */
if (ret < 0 || id != 0 || len < 0) {
errmsg = "ASN.1 decoding failure";
goto error;
}
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
/* id==6 for object */
if (ret < 0 || id != 6 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
goto error;
}
if (0) {}
#if DROPBEAR_ECC_256
else if (len == sizeof(OID_SEC256R1_BLOB)
&& memcmp(p, OID_SEC256R1_BLOB, len) == 0) {
retkey->type = DROPBEAR_SIGNKEY_ECDSA_NISTP256;
curve = &ecc_curve_nistp256;
}
#endif
#if DROPBEAR_ECC_384
else if (len == sizeof(OID_SEC384R1_BLOB)
&& memcmp(p, OID_SEC384R1_BLOB, len) == 0) {
retkey->type = DROPBEAR_SIGNKEY_ECDSA_NISTP384;
curve = &ecc_curve_nistp384;
}
#endif
#if DROPBEAR_ECC_521
else if (len == sizeof(OID_SEC521R1_BLOB)
&& memcmp(p, OID_SEC521R1_BLOB, len) == 0) {
retkey->type = DROPBEAR_SIGNKEY_ECDSA_NISTP521;
curve = &ecc_curve_nistp521;
}
#endif
else {
errmsg = "Unknown ECC key type";
goto error;
}
p += len;
/* publicKey [1] BIT STRING OPTIONAL */
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
/* id==1 */
if (ret < 0 || id != 1 || len < 0) {
errmsg = "ASN.1 decoding failure";
goto error;
}
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
/* id==3 for bit string */
if (ret < 0 || id != 3 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
goto error;
}
public_key_bytes = p+1;
public_key_len = len-1;
p += len;
buf_putbytes(blobbuf, public_key_bytes, public_key_len);
ecc = buf_get_ecc_raw_pubkey(blobbuf, curve);
if (!ecc) {
errmsg = "Error parsing ECC key";
goto error;
}
m_mp_alloc_init_multi((mp_int**)&ecc->k, NULL);
if (mp_read_unsigned_bin(ecc->k, private_key_bytes, private_key_len)
!= MP_OKAY) {
errmsg = "Error parsing ECC key";
goto error;
}
*signkey_key_ptr(retkey, retkey->type) = ecc;
}
#endif /* DROPBEAR_ECDSA */
/*
* 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.
*/
if (key->type == OSSH_RSA || key->type == OSSH_DSA) {
buf_setpos(blobbuf, 0);
type = DROPBEAR_SIGNKEY_ANY;
if (buf_get_priv_key(blobbuf, retkey, &type)
!= DROPBEAR_SUCCESS) {
errmsg = "unable to create key structure";
sign_key_free(retkey);
retkey = NULL;
goto error;
}
}
errmsg = NULL; /* no error */
retval = retkey;
error:
if (blobbuf) {
buf_burn(blobbuf);
buf_free(blobbuf);
}
m_burn(key->keyblob, key->keyblob_size);
m_free(key->keyblob);
m_burn(key, sizeof(*key));
m_free(key);
if (errmsg) {
fprintf(stderr, "Error: %s\n", errmsg);
}
return retval;
}
static int openssh_write(const char *filename, sign_key *key,
const char *passphrase)
{
buffer * keyblob = NULL;
buffer * extrablob = NULL; /* used for calculated values to write */
unsigned char *outblob = NULL;
int outlen = -9999;
struct mpint_pos numbers[9];
int nnumbers = -1, pos = 0, len = 0, seqlen, i;
char *header = NULL, *footer = NULL;
char zero[1];
int ret = 0;
FILE *fp;
#if DROPBEAR_RSA
mp_int dmp1, dmq1, iqmp, tmpval; /* for rsa */
#endif
if (
#if DROPBEAR_RSA
key->type == DROPBEAR_SIGNKEY_RSA ||
#endif
#if DROPBEAR_DSS
key->type == DROPBEAR_SIGNKEY_DSS ||
#endif
0)
{
/*
* Fetch the key blobs.
*/
keyblob = buf_new(3000);
buf_put_priv_key(keyblob, key, key->type);
buf_setpos(keyblob, 0);
/* skip the "ssh-rsa" or "ssh-dss" header */
buf_incrpos(keyblob, buf_getint(keyblob));
/*
* Find the sequence of integers to be encoded into the OpenSSH
* key blob, and also decide on the header line.
*/
numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
#if DROPBEAR_RSA
if (key->type == DROPBEAR_SIGNKEY_RSA) {
if (key->rsakey->p == NULL || key->rsakey->q == NULL) {
fprintf(stderr, "Pre-0.33 Dropbear keys cannot be converted to OpenSSH keys.\n");
goto error;
}
/* e */
numbers[2].bytes = buf_getint(keyblob);
numbers[2].start = buf_getptr(keyblob, numbers[2].bytes);
buf_incrpos(keyblob, numbers[2].bytes);
/* n */
numbers[1].bytes = buf_getint(keyblob);
numbers[1].start = buf_getptr(keyblob, numbers[1].bytes);
buf_incrpos(keyblob, numbers[1].bytes);
/* d */
numbers[3].bytes = buf_getint(keyblob);
numbers[3].start = buf_getptr(keyblob, numbers[3].bytes);
buf_incrpos(keyblob, numbers[3].bytes);
/* p */
numbers[4].bytes = buf_getint(keyblob);
numbers[4].start = buf_getptr(keyblob, numbers[4].bytes);
buf_incrpos(keyblob, numbers[4].bytes);
/* q */
numbers[5].bytes = buf_getint(keyblob);
numbers[5].start = buf_getptr(keyblob, numbers[5].bytes);
buf_incrpos(keyblob, numbers[5].bytes);
/* now calculate some extra parameters: */
m_mp_init(&tmpval);
m_mp_init(&dmp1);
m_mp_init(&dmq1);
m_mp_init(&iqmp);
/* dmp1 = d mod (p-1) */
if (mp_sub_d(key->rsakey->p, 1, &tmpval) != MP_OKAY) {
fprintf(stderr, "Bignum error for p-1\n");
goto error;
}
if (mp_mod(key->rsakey->d, &tmpval, &dmp1) != MP_OKAY) {
fprintf(stderr, "Bignum error for dmp1\n");
goto error;
}
/* dmq1 = d mod (q-1) */
if (mp_sub_d(key->rsakey->q, 1, &tmpval) != MP_OKAY) {
fprintf(stderr, "Bignum error for q-1\n");
goto error;
}
if (mp_mod(key->rsakey->d, &tmpval, &dmq1) != MP_OKAY) {
fprintf(stderr, "Bignum error for dmq1\n");
goto error;
}
/* iqmp = (q^-1) mod p */
if (mp_invmod(key->rsakey->q, key->rsakey->p, &iqmp) != MP_OKAY) {
fprintf(stderr, "Bignum error for iqmp\n");
goto error;
}
extrablob = buf_new(2000);
buf_putmpint(extrablob, &dmp1);
buf_putmpint(extrablob, &dmq1);
buf_putmpint(extrablob, &iqmp);
buf_setpos(extrablob, 0);
mp_clear(&dmp1);
mp_clear(&dmq1);
mp_clear(&iqmp);
mp_clear(&tmpval);
/* dmp1 */
numbers[6].bytes = buf_getint(extrablob);
numbers[6].start = buf_getptr(extrablob, numbers[6].bytes);
buf_incrpos(extrablob, numbers[6].bytes);
/* dmq1 */
numbers[7].bytes = buf_getint(extrablob);
numbers[7].start = buf_getptr(extrablob, numbers[7].bytes);
buf_incrpos(extrablob, numbers[7].bytes);
/* iqmp */
numbers[8].bytes = buf_getint(extrablob);
numbers[8].start = buf_getptr(extrablob, numbers[8].bytes);
buf_incrpos(extrablob, numbers[8].bytes);
nnumbers = 9;
header = "-----BEGIN RSA PRIVATE KEY-----\n";
footer = "-----END RSA PRIVATE KEY-----\n";
}
#endif /* DROPBEAR_RSA */
#if DROPBEAR_DSS
if (key->type == DROPBEAR_SIGNKEY_DSS) {
/* p */
numbers[1].bytes = buf_getint(keyblob);
numbers[1].start = buf_getptr(keyblob, numbers[1].bytes);
buf_incrpos(keyblob, numbers[1].bytes);
/* q */
numbers[2].bytes = buf_getint(keyblob);
numbers[2].start = buf_getptr(keyblob, numbers[2].bytes);
buf_incrpos(keyblob, numbers[2].bytes);
/* g */
numbers[3].bytes = buf_getint(keyblob);
numbers[3].start = buf_getptr(keyblob, numbers[3].bytes);
buf_incrpos(keyblob, numbers[3].bytes);
/* y */
numbers[4].bytes = buf_getint(keyblob);
numbers[4].start = buf_getptr(keyblob, numbers[4].bytes);
buf_incrpos(keyblob, numbers[4].bytes);
/* x */
numbers[5].bytes = buf_getint(keyblob);
numbers[5].start = buf_getptr(keyblob, numbers[5].bytes);
buf_incrpos(keyblob, numbers[5].bytes);
nnumbers = 6;
header = "-----BEGIN DSA PRIVATE KEY-----\n";
footer = "-----END DSA PRIVATE KEY-----\n";
}
#endif /* DROPBEAR_DSS */
/*
* Now count up the total size of the ASN.1 encoded integers,
* so as to determine the length of the containing SEQUENCE.
*/
len = 0;
for (i = 0; i < nnumbers; i++) {
len += ber_write_id_len(NULL, 2, numbers[i].bytes, 0);
len += numbers[i].bytes;
}
seqlen = len;
/* Now add on the SEQUENCE header. */
len += ber_write_id_len(NULL, 16, seqlen, ASN1_CONSTRUCTED);
/* Round up to the cipher block size, ensuring we have at least one
* byte of padding (see below). */
outlen = len;
if (passphrase)
outlen = (outlen+8) &~ 7;
/*
* Now we know how big outblob needs to be. Allocate it.
*/
outblob = (unsigned char*)m_malloc(outlen);
/*
* And write the data into it.
*/
pos = 0;
pos += ber_write_id_len(outblob+pos, 16, seqlen, ASN1_CONSTRUCTED);
for (i = 0; i < nnumbers; i++) {
pos += ber_write_id_len(outblob+pos, 2, numbers[i].bytes, 0);
memcpy(outblob+pos, numbers[i].start, numbers[i].bytes);
pos += numbers[i].bytes;
}
} /* end RSA and DSS handling */
#if DROPBEAR_ECDSA
if (key->type == DROPBEAR_SIGNKEY_ECDSA_NISTP256
|| key->type == DROPBEAR_SIGNKEY_ECDSA_NISTP384
|| key->type == DROPBEAR_SIGNKEY_ECDSA_NISTP521) {
/* SEC1 V2 appendix c.4
ECPrivateKey ::= SEQUENCE {
version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
privateKey OCTET STRING,
parameters [0] ECDomainParameters {{ SECGCurveNames }} OPTIONAL,
publicKey [1] BIT STRING OPTIONAL
}
*/
buffer *seq_buf = buf_new(400);
ecc_key **eck = (ecc_key**)signkey_key_ptr(key, key->type);
const long curve_size = (*eck)->dp->size;
int curve_oid_len = 0;
const void* curve_oid = NULL;
unsigned long pubkey_size = 2*curve_size+1;
int k_size;
int err = 0;
/* version. less than 10 bytes */
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 2, 1, 0));
buf_putbyte(seq_buf, 1);
/* privateKey */
k_size = mp_unsigned_bin_size((*eck)->k);
dropbear_assert(k_size <= curve_size);
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 4, k_size, 0));
mp_to_unsigned_bin((*eck)->k, buf_getwriteptr(seq_buf, k_size));
buf_incrwritepos(seq_buf, k_size);
/* SECGCurveNames */
switch (key->type)
{
case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
curve_oid_len = sizeof(OID_SEC256R1_BLOB);
curve_oid = OID_SEC256R1_BLOB;
break;
case DROPBEAR_SIGNKEY_ECDSA_NISTP384:
curve_oid_len = sizeof(OID_SEC384R1_BLOB);
curve_oid = OID_SEC384R1_BLOB;
break;
case DROPBEAR_SIGNKEY_ECDSA_NISTP521:
curve_oid_len = sizeof(OID_SEC521R1_BLOB);
curve_oid = OID_SEC521R1_BLOB;
break;
default:
dropbear_exit("Internal error");
}
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 0, 2+curve_oid_len, 0xa0));
/* object == 6 */
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 6, curve_oid_len, 0));
buf_putbytes(seq_buf, curve_oid, curve_oid_len);
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 1,
(pubkey_size +1 < 128 ? 2 : 3 ) +1 +pubkey_size, 0xa0));
buf_incrwritepos(seq_buf,
ber_write_id_len(buf_getwriteptr(seq_buf, 10), 3, 1+pubkey_size, 0));
buf_putbyte(seq_buf, 0);
err = ecc_ansi_x963_export(*eck, buf_getwriteptr(seq_buf, pubkey_size), &pubkey_size);
if (err != CRYPT_OK) {
dropbear_exit("ECC error");
}
buf_incrwritepos(seq_buf, pubkey_size);
buf_setpos(seq_buf, 0);
outblob = (unsigned char*)m_malloc(1000);
pos = 0;
pos += ber_write_id_len(outblob+pos, 16, seq_buf->len, ASN1_CONSTRUCTED);
memcpy(&outblob[pos], seq_buf->data, seq_buf->len);
pos += seq_buf->len;
len = pos;
outlen = len;
buf_burn(seq_buf);
buf_free(seq_buf);
seq_buf = NULL;
header = "-----BEGIN EC PRIVATE KEY-----\n";
footer = "-----END EC PRIVATE KEY-----\n";
}
#endif
/*
* 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.
*/
dropbear_assert(pos == len);
while (pos < outlen) {
outblob[pos++] = outlen - len;
}
/*
* Encrypt the key.
*/
if (passphrase) {
fprintf(stderr, "Encrypted keys aren't supported currently\n");
goto error;
}
/*
* And save it. We'll use Unix line endings just in case it's
* subsequently transferred in binary mode.
*/
if (strlen(filename) == 1 && filename[0] == '-') {
fp = stdout;
} else {
fp = fopen(filename, "wb"); /* ensure Unix line endings */
}
if (!fp) {
fprintf(stderr, "Failed opening output file\n");
goto error;
}
fputs(header, fp);
base64_encode_fp(fp, outblob, outlen, 64);
fputs(footer, fp);
fclose(fp);
ret = 1;
error:
if (outblob) {
memset(outblob, 0, outlen);
m_free(outblob);
}
if (keyblob) {
buf_burn(keyblob);
buf_free(keyblob);
}
if (extrablob) {
buf_burn(extrablob);
buf_free(extrablob);
}
return ret;
}
#if 0
/* XXX TODO ssh.com stuff isn't going yet */
/* ----------------------------------------------------------------------
* Code to read ssh.com private keys.
*/
/*
* The format of the base64 blob is largely ssh2-packet-formatted,
* except that mpints are a bit different: they're more like the
* old ssh1 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 ssh2
* 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 SSH2-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 char *filename)
{
struct sshcom_key *ret;
FILE *fp;
char buffer[256];
int len;
char *errmsg, *p;
int 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 = fopen(filename, "r");
if (!fp) {
errmsg = "Unable to open key file";
goto error;
}
if (!fgets(buffer, sizeof(buffer), fp) ||
0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) {
errmsg = "File does not begin with ssh.com key header";
goto error;
}
headers_done = 0;
while (1) {
if (!fgets(buffer, sizeof(buffer), fp)) {
errmsg = "Unexpected end of file";
goto error;
}
if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n"))
break; /* done */
if ((p = strchr(buffer, ':')) != NULL) {
if (headers_done) {
errmsg = "Header found in body of key data";
goto error;
}
*p++ = '\0';
while (*p && isspace((unsigned char)*p)) p++;
/*
* Header lines can end in a trailing backslash for
* continuation.
*/
while ((len = strlen(p)) > (int)(sizeof(buffer) - (p-buffer) -1) ||
p[len-1] != '\n' || p[len-2] == '\\') {
if (len > (int)((p-buffer) + sizeof(buffer)-2)) {
errmsg = "Header line too long to deal with";
goto error;
}
if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) {
errmsg = "Unexpected end of file";
goto error;
}
}
p[strcspn(p, "\n")] = '\0';
if (!strcmp(buffer, "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 = 1;
p = buffer;
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++;
}
}
}
if (ret->keyblob_len == 0 || !ret->keyblob) {
errmsg = "Key body not present";
goto error;
}
return ret;
error:
if (ret) {
if (ret->keyblob) {
memset(ret->keyblob, 0, ret->keyblob_size);
m_free(ret->keyblob);
}
memset(ret, 0, sizeof(*ret));
m_free(ret);
}
return NULL;
}
int sshcom_encrypted(const char *filename, char **comment)
{
struct sshcom_key *key = load_sshcom_key(filename);
int pos, len, answer;
*comment = NULL;
if (!key)
return 0;
/*
* Check magic number.
*/
if (GET_32BIT(key->keyblob) != 0x3f6ff9eb)
return 0; /* key is invalid */
/*
* Find the cipher-type string.
*/
answer = 0;
pos = 8;
if (key->keyblob_len < pos+4)
goto done; /* key is far too short */
len = toint(GET_32BIT(key->keyblob + pos));
if (len < 0 || len > key->keyblob_len - pos - 4)
goto done; /* key is far too short */
pos += 4 + len; /* skip key type */
len = toint(GET_32BIT(key->keyblob + pos)); /* find cipher-type length */
if (len < 0 || len > key->keyblob_len - pos - 4)
goto done; /* cipher type string is incomplete */
if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4))
answer = 1;
done:
*comment = dupstr(key->comment);
memset(key->keyblob, 0, key->keyblob_size);
m_free(key->keyblob);
memset(key, 0, sizeof(*key));
m_free(key);
return answer;
}
static int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret)
{
unsigned bits, bytes;
unsigned char *d = (unsigned char *) data;
if (len < 4)
goto error;
bits = GET_32BIT(d);
bytes = (bits + 7) / 8;
if (len < 4+bytes)
goto error;
ret->start = d + 4;
ret->bytes = bytes;
return bytes+4;
error:
ret->start = NULL;
ret->bytes = -1;
return len; /* ensure further calls fail as well */
}
static int sshcom_put_mpint(void *target, void *data, int len)
{
unsigned char *d = (unsigned char *)target;
unsigned char *i = (unsigned char *)data;
int bits = len * 8 - 1;
while (bits > 0) {
if (*i & (1 << (bits & 7)))
break;
if (!(bits-- & 7))
i++, len--;
}
PUT_32BIT(d, bits+1);
memcpy(d+4, i, len);
return len+4;
}
sign_key *sshcom_read(const char *filename, char *passphrase)
{
struct sshcom_key *key = load_sshcom_key(filename);
char *errmsg;
int pos, len;
const char prefix_rsa[] = "if-modn{sign{rsa";
const char prefix_dsa[] = "dl-modp{sign{dsa";
enum { RSA, DSA } type;
int encrypted;
char *ciphertext;
int cipherlen;
struct ssh2_userkey *ret = NULL, *retkey;
const struct ssh_signkey *alg;
unsigned char *blob = NULL;
int blobsize = 0, publen, privlen;
if (!key)
return NULL;
/*
* Check magic number.
*/
if (GET_32BIT(key->keyblob) != SSHCOM_MAGIC_NUMBER) {
errmsg = "Key does not begin with magic number";
goto error;
}
/*
* Determine the key type.
*/
pos = 8;
if (key->keyblob_len < pos+4 ||
(len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
errmsg = "Key blob does not contain a key type string";
goto error;
}
if (len > sizeof(prefix_rsa) - 1 &&
!memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) {
type = RSA;
} else if (len > sizeof(prefix_dsa) - 1 &&
!memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) {
type = DSA;
} else {
errmsg = "Key is of unknown type";
goto error;
}
pos += 4+len;
/*
* Determine the cipher type.
*/
if (key->keyblob_len < pos+4 ||
(len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
errmsg = "Key blob does not contain a cipher type string";
goto error;
}
if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4))
encrypted = 0;
else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8))
encrypted = 1;
else {
errmsg = "Key encryption is of unknown type";
goto error;
}
pos += 4+len;
/*
* Get hold of the encrypted part of the key.
*/
if (key->keyblob_len < pos+4 ||
(len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) {
errmsg = "Key blob does not contain actual key data";
goto error;
}
ciphertext = (char *)key->keyblob + pos + 4;
cipherlen = len;
if (cipherlen == 0) {
errmsg = "Length of key data is zero";
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 (cipherlen % 8 != 0) {
errmsg = "Encrypted part of key is not a multiple of cipher block"
" size";
goto error;
}
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Update(&md5c, keybuf, 16);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob.
*/
memset(iv, 0, sizeof(iv));
des3_decrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
cipherlen);
memset(&md5c, 0, sizeof(md5c));
memset(keybuf, 0, 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;
}
/*
* Strip away the containing string to get to the real meat.
*/
len = toint(GET_32BIT(ciphertext));
if (len < 0 || len > cipherlen-4) {
errmsg = "containing string was ill-formed";
goto error;
}
ciphertext += 4;
cipherlen = 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 alg->createkey().
*/
blobsize = cipherlen + 256;
blob = snewn(blobsize, unsigned char);
privlen = 0;
if (type == RSA) {
struct mpint_pos n, e, d, u, p, q;
int pos = 0;
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
if (!q.start) {
errmsg = "key data did not contain six integers";
goto error;
}
alg = &ssh_rsa;
pos = 0;
pos += put_string(blob+pos, "ssh-rsa", 7);
pos += put_mp(blob+pos, e.start, e.bytes);
pos += put_mp(blob+pos, n.start, n.bytes);
publen = pos;
pos += put_string(blob+pos, d.start, d.bytes);
pos += put_mp(blob+pos, q.start, q.bytes);
pos += put_mp(blob+pos, p.start, p.bytes);
pos += put_mp(blob+pos, u.start, u.bytes);
privlen = pos - publen;
} else if (type == DSA) {
struct mpint_pos p, q, g, x, y;
int pos = 4;
if (GET_32BIT(ciphertext) != 0) {
errmsg = "predefined DSA parameters not supported";
goto error;
}
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y);
pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x);
if (!x.start) {
errmsg = "key data did not contain five integers";
goto error;
}
alg = &ssh_dss;
pos = 0;
pos += put_string(blob+pos, "ssh-dss", 7);
pos += put_mp(blob+pos, p.start, p.bytes);
pos += put_mp(blob+pos, q.start, q.bytes);
pos += put_mp(blob+pos, g.start, g.bytes);
pos += put_mp(blob+pos, y.start, y.bytes);
publen = pos;
pos += put_mp(blob+pos, x.start, x.bytes);
privlen = pos - publen;
} else
return NULL;
dropbear_assert(privlen > 0); /* should have bombed by now if not */
retkey = snew(struct ssh2_userkey);
retkey->alg = alg;
retkey->data = alg->createkey(blob, publen, blob+publen, privlen);
if (!retkey->data) {
m_free(retkey);
errmsg = "unable to create key data structure";
goto error;
}
retkey->comment = dupstr(key->comment);
errmsg = NULL; /* no error */
ret = retkey;
error:
if (blob) {
memset(blob, 0, blobsize);
m_free(blob);
}
memset(key->keyblob, 0, key->keyblob_size);
m_free(key->keyblob);
memset(key, 0, sizeof(*key));
m_free(key);
return ret;
}
int sshcom_write(const char *filename, sign_key *key,
char *passphrase)
{
unsigned char *pubblob, *privblob;
int publen, privlen;
unsigned char *outblob;
int outlen;
struct mpint_pos numbers[6];
int nnumbers, initial_zero, pos, lenpos, i;
char *type;
char *ciphertext;
int cipherlen;
int ret = 0;
FILE *fp;
/*
* Fetch the key blobs.
*/
pubblob = key->alg->public_blob(key->data, &publen);
privblob = key->alg->private_blob(key->data, &privlen);
outblob = NULL;
/*
* Find the sequence of integers to be encoded into the OpenSSH
* key blob, and also decide on the header line.
*/
if (key->alg == &ssh_rsa) {
int pos;
struct mpint_pos n, e, d, p, q, iqmp;
pos = 4 + GET_32BIT(pubblob);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &e);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &n);
pos = 0;
pos += ssh2_read_mpint(privblob+pos, privlen-pos, &d);
pos += ssh2_read_mpint(privblob+pos, privlen-pos, &p);
pos += ssh2_read_mpint(privblob+pos, privlen-pos, &q);
pos += ssh2_read_mpint(privblob+pos, privlen-pos, &iqmp);
dropbear_assert(e.start && iqmp.start); /* 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 = 0;
type = "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}";
} else if (key->alg == &ssh_dss) {
int pos;
struct mpint_pos p, q, g, y, x;
pos = 4 + GET_32BIT(pubblob);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &p);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &q);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &g);
pos += ssh2_read_mpint(pubblob+pos, publen-pos, &y);
pos = 0;
pos += ssh2_read_mpint(privblob+pos, privlen-pos, &x);
dropbear_assert(y.start && x.start); /* can't go wrong */
numbers[0] = p;
numbers[1] = g;
numbers[2] = q;
numbers[3] = y;
numbers[4] = x;
nnumbers = 5;
initial_zero = 1;
type = "dl-modp{sign{dsa-nist-sha1},dh{plain}}";
} else {
dropbear_assert(0); /* zoinks! */
}
/*
* Total size of key blob will be somewhere under 512 plus
* combined length of integers. We'll calculate the more
* precise size as we construct the blob.
*/
outlen = 512;
for (i = 0; i < nnumbers; i++)
outlen += 4 + numbers[i].bytes;
outblob = snewn(outlen, unsigned char);
/*
* Create the unencrypted key blob.
*/
pos = 0;
PUT_32BIT(outblob+pos, SSHCOM_MAGIC_NUMBER); pos += 4;
pos += 4; /* length field, fill in later */
pos += put_string(outblob+pos, type, strlen(type));
{
char *ciphertype = passphrase ? "3des-cbc" : "none";
pos += put_string(outblob+pos, ciphertype, strlen(ciphertype));
}
lenpos = pos; /* remember this position */
pos += 4; /* encrypted-blob size */
pos += 4; /* encrypted-payload size */
if (initial_zero) {
PUT_32BIT(outblob+pos, 0);
pos += 4;
}
for (i = 0; i < nnumbers; i++)
pos += sshcom_put_mpint(outblob+pos,
numbers[i].start, numbers[i].bytes);
/* Now wrap up the encrypted payload. */
PUT_32BIT(outblob+lenpos+4, pos - (lenpos+8));
/* Pad encrypted blob to a multiple of cipher block size. */
if (passphrase) {
int padding = -(pos - (lenpos+4)) & 7;
while (padding--)
outblob[pos++] = random_byte();
}
ciphertext = (char *)outblob+lenpos+4;
cipherlen = pos - (lenpos+4);
dropbear_assert(!passphrase || cipherlen % 8 == 0);
/* Wrap up the encrypted blob string. */
PUT_32BIT(outblob+lenpos, cipherlen);
/* And finally fill in the total length field. */
PUT_32BIT(outblob+4, pos);
dropbear_assert(pos < outlen);
/*
* 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);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Update(&md5c, keybuf, 16);
MD5Final(keybuf+16, &md5c);
/*
* Now decrypt the key blob.
*/
memset(iv, 0, sizeof(iv));
des3_encrypt_pubkey_ossh(keybuf, iv, (unsigned char *)ciphertext,
cipherlen);
memset(&md5c, 0, sizeof(md5c));
memset(keybuf, 0, sizeof(keybuf));
}
/*
* And save it. We'll use Unix line endings just in case it's
* subsequently transferred in binary mode.
*/
fp = fopen(filename, "wb"); /* 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(fp, outblob, pos, 70);
fputs("---- END SSH2 ENCRYPTED PRIVATE KEY ----\n", fp);
fclose(fp);
ret = 1;
error:
if (outblob) {
memset(outblob, 0, outlen);
m_free(outblob);
}
if (privblob) {
memset(privblob, 0, privlen);
m_free(privblob);
}
if (pubblob) {
memset(pubblob, 0, publen);
m_free(pubblob);
}
return ret;
}
#endif /* ssh.com stuff disabled */
/* From PuTTY misc.c */
static int toint(unsigned u)
{
/*
* Convert an unsigned to an int, without running into the
* undefined behaviour which happens by the strict C standard if
* the value overflows. You'd hope that sensible compilers would
* do the sensible thing in response to a cast, but actually I
* don't trust modern compilers not to do silly things like
* assuming that _obviously_ you wouldn't have caused an overflow
* and so they can elide an 'if (i < 0)' test immediately after
* the cast.
*
* Sensible compilers ought of course to optimise this entire
* function into 'just return the input value'!
*/
if (u <= (unsigned)INT_MAX)
return (int)u;
else if (u >= (unsigned)INT_MIN) /* wrap in cast _to_ unsigned is OK */
return INT_MIN + (int)(u - (unsigned)INT_MIN);
else
return INT_MIN; /* fallback; should never occur on binary machines */
}
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