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putty
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putty/sshpubk.c

1224 строки
30 KiB
C
Исходник Ответственный История

/*
* Generic SSH public-key handling operations. In particular,
* reading of SSH public-key files, and also the generic `sign'
* operation for ssh2 (which checks the type of the key and
* dispatches to the appropriate key-type specific function).
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "putty.h"
#include "ssh.h"
#include "misc.h"
#define PUT_32BIT(cp, value) do { \
(cp)[3] = (value); \
(cp)[2] = (value) >> 8; \
(cp)[1] = (value) >> 16; \
(cp)[0] = (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]))
#define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n"
#define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\
(x)-'a'<26 ? (x)-'a'+26 :\
(x)-'0'<10 ? (x)-'0'+52 :\
(x)=='+' ? 62 : \
(x)=='/' ? 63 : 0 )
static int loadrsakey_main(FILE * fp, struct RSAKey *key, int pub_only,
char **commentptr, char *passphrase,
const char **error)
{
unsigned char buf[16384];
unsigned char keybuf[16];
int len;
int i, j, ciphertype;
int ret = 0;
struct MD5Context md5c;
char *comment;
*error = NULL;
/* Slurp the whole file (minus the header) into a buffer. */
len = fread(buf, 1, sizeof(buf), fp);
fclose(fp);
if (len < 0 || len == sizeof(buf)) {
*error = "error reading file";
goto end; /* file too big or not read */
}
i = 0;
*error = "file format error";
/*
* A zero byte. (The signature includes a terminating NUL.)
*/
if (len - i < 1 || buf[i] != 0)
goto end;
i++;
/* One byte giving encryption type, and one reserved uint32. */
if (len - i < 1)
goto end;
ciphertype = buf[i];
if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES)
goto end;
i++;
if (len - i < 4)
goto end; /* reserved field not present */
if (buf[i] != 0 || buf[i + 1] != 0 || buf[i + 2] != 0
|| buf[i + 3] != 0) goto end; /* reserved field nonzero, panic! */
i += 4;
/* Now the serious stuff. An ordinary SSH 1 public key. */
i += makekey(buf + i, len, key, NULL, 1);
if (i < 0)
goto end; /* overran */
if (pub_only) {
ret = 1;
goto end;
}
/* Next, the comment field. */
j = GET_32BIT(buf + i);
i += 4;
if (len - i < j)
goto end;
comment = snewn(j + 1, char);
if (comment) {
memcpy(comment, buf + i, j);
comment[j] = '\0';
}
i += j;
if (commentptr)
*commentptr = comment;
if (key)
key->comment = comment;
if (!key) {
ret = ciphertype != 0;
*error = NULL;
goto end;
}
/*
* Decrypt remainder of buffer.
*/
if (ciphertype) {
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
des3_decrypt_pubkey(keybuf, buf + i, (len - i + 7) & ~7);
memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
}
/*
* We are now in the secret part of the key. The first four
* bytes should be of the form a, b, a, b.
*/
if (len - i < 4)
goto end;
if (buf[i] != buf[i + 2] || buf[i + 1] != buf[i + 3]) {
*error = "wrong passphrase";
ret = -1;
goto end;
}
i += 4;
/*
* After that, we have one further bignum which is our
* decryption exponent, and then the three auxiliary values
* (iqmp, q, p).
*/
j = makeprivate(buf + i, len - i, key);
if (j < 0) goto end;
i += j;
j = ssh1_read_bignum(buf + i, len - i, &key->iqmp);
if (j < 0) goto end;
i += j;
j = ssh1_read_bignum(buf + i, len - i, &key->q);
if (j < 0) goto end;
i += j;
j = ssh1_read_bignum(buf + i, len - i, &key->p);
if (j < 0) goto end;
i += j;
if (!rsa_verify(key)) {
*error = "rsa_verify failed";
freersakey(key);
ret = 0;
} else
ret = 1;
end:
memset(buf, 0, sizeof(buf)); /* burn the evidence */
return ret;
}
int loadrsakey(const Filename *filename, struct RSAKey *key, char *passphrase,
const char **errorstr)
{
FILE *fp;
char buf[64];
int ret = 0;
const char *error = NULL;
fp = f_open(*filename, "rb");
if (!fp) {
error = "can't open file";
goto end;
}
/*
* Read the first line of the file and see if it's a v1 private
* key file.
*/
if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) {
/*
* This routine will take care of calling fclose() for us.
*/
ret = loadrsakey_main(fp, key, FALSE, NULL, passphrase, &error);
fp = NULL;
goto end;
}
/*
* Otherwise, we have nothing. Return empty-handed.
*/
error = "not an SSH-1 RSA file";
end:
if (fp)
fclose(fp);
if ((ret != 1) && errorstr)
*errorstr = error;
return ret;
}
/*
* See whether an RSA key is encrypted. Return its comment field as
* well.
*/
int rsakey_encrypted(const Filename *filename, char **comment)
{
FILE *fp;
char buf[64];
fp = f_open(*filename, "rb");
if (!fp)
return 0; /* doesn't even exist */
/*
* Read the first line of the file and see if it's a v1 private
* key file.
*/
if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) {
const char *dummy;
/*
* This routine will take care of calling fclose() for us.
*/
return loadrsakey_main(fp, NULL, FALSE, comment, NULL, &dummy);
}
fclose(fp);
return 0; /* wasn't the right kind of file */
}
/*
* Return a malloc'ed chunk of memory containing the public blob of
* an RSA key, as given in the agent protocol (modulus bits,
* exponent, modulus).
*/
int rsakey_pubblob(const Filename *filename, void **blob, int *bloblen,
const char **errorstr)
{
FILE *fp;
char buf[64];
struct RSAKey key;
int ret;
const char *error = NULL;
/* Default return if we fail. */
*blob = NULL;
*bloblen = 0;
ret = 0;
fp = f_open(*filename, "rb");
if (!fp) {
error = "can't open file";
goto end;
}
/*
* Read the first line of the file and see if it's a v1 private
* key file.
*/
if (fgets(buf, sizeof(buf), fp) && !strcmp(buf, rsa_signature)) {
memset(&key, 0, sizeof(key));
if (loadrsakey_main(fp, &key, TRUE, NULL, NULL, &error)) {
*blob = rsa_public_blob(&key, bloblen);
freersakey(&key);
ret = 1;
fp = NULL;
}
} else {
error = "not an SSH-1 RSA file";
}
end:
if (fp)
fclose(fp);
if ((ret != 1) && errorstr)
*errorstr = error;
return ret;
}
/*
* Save an RSA key file. Return nonzero on success.
*/
int saversakey(const Filename *filename, struct RSAKey *key, char *passphrase)
{
unsigned char buf[16384];
unsigned char keybuf[16];
struct MD5Context md5c;
unsigned char *p, *estart;
FILE *fp;
/*
* Write the initial signature.
*/
p = buf;
memcpy(p, rsa_signature, sizeof(rsa_signature));
p += sizeof(rsa_signature);
/*
* One byte giving encryption type, and one reserved (zero)
* uint32.
*/
*p++ = (passphrase ? SSH_CIPHER_3DES : 0);
PUT_32BIT(p, 0);
p += 4;
/*
* An ordinary SSH 1 public key consists of: a uint32
* containing the bit count, then two bignums containing the
* modulus and exponent respectively.
*/
PUT_32BIT(p, bignum_bitcount(key->modulus));
p += 4;
p += ssh1_write_bignum(p, key->modulus);
p += ssh1_write_bignum(p, key->exponent);
/*
* A string containing the comment field.
*/
if (key->comment) {
PUT_32BIT(p, strlen(key->comment));
p += 4;
memcpy(p, key->comment, strlen(key->comment));
p += strlen(key->comment);
} else {
PUT_32BIT(p, 0);
p += 4;
}
/*
* The encrypted portion starts here.
*/
estart = p;
/*
* Two bytes, then the same two bytes repeated.
*/
*p++ = random_byte();
*p++ = random_byte();
p[0] = p[-2];
p[1] = p[-1];
p += 2;
/*
* Four more bignums: the decryption exponent, then iqmp, then
* q, then p.
*/
p += ssh1_write_bignum(p, key->private_exponent);
p += ssh1_write_bignum(p, key->iqmp);
p += ssh1_write_bignum(p, key->q);
p += ssh1_write_bignum(p, key->p);
/*
* Now write zeros until the encrypted portion is a multiple of
* 8 bytes.
*/
while ((p - estart) % 8)
*p++ = '\0';
/*
* Now encrypt the encrypted portion.
*/
if (passphrase) {
MD5Init(&md5c);
MD5Update(&md5c, (unsigned char *)passphrase, strlen(passphrase));
MD5Final(keybuf, &md5c);
des3_encrypt_pubkey(keybuf, estart, p - estart);
memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */
}
/*
* Done. Write the result to the file.
*/
fp = f_open(*filename, "wb");
if (fp) {
int ret = (fwrite(buf, 1, p - buf, fp) == (size_t) (p - buf));
ret = ret && (fclose(fp) == 0);
return ret;
} else
return 0;
}
/* ----------------------------------------------------------------------
* SSH2 private key load/store functions.
*/
/*
* PuTTY's own format for SSH2 keys is as follows:
*
* The file is text. Lines are terminated by CRLF, although CR-only
* and LF-only are tolerated on input.
*
* The first line says "PuTTY-User-Key-File-2: " plus the name of the
* algorithm ("ssh-dss", "ssh-rsa" etc).
*
* The next line says "Encryption: " plus an encryption type.
* Currently the only supported encryption types are "aes256-cbc"
* and "none".
*
* The next line says "Comment: " plus the comment string.
*
* Next there is a line saying "Public-Lines: " plus a number N.
* The following N lines contain a base64 encoding of the public
* part of the key. This is encoded as the standard SSH2 public key
* blob (with no initial length): so for RSA, for example, it will
* read
*
* string "ssh-rsa"
* mpint exponent
* mpint modulus
*
* Next, there is a line saying "Private-Lines: " plus a number N,
* and then N lines containing the (potentially encrypted) private
* part of the key. For the key type "ssh-rsa", this will be
* composed of
*
* mpint private_exponent
* mpint p (the larger of the two primes)
* mpint q (the smaller prime)
* mpint iqmp (the inverse of q modulo p)
* data padding (to reach a multiple of the cipher block size)
*
* And for "ssh-dss", it will be composed of
*
* mpint x (the private key parameter)
* [ string hash 20-byte hash of mpints p || q || g only in old format ]
*
* Finally, there is a line saying "Private-MAC: " plus a hex
* representation of a HMAC-SHA-1 of:
*
* string name of algorithm ("ssh-dss", "ssh-rsa")
* string encryption type
* string comment
* string public-blob
* string private-plaintext (the plaintext version of the
* private part, including the final
* padding)
*
* The key to the MAC is itself a SHA-1 hash of:
*
* data "putty-private-key-file-mac-key"
* data passphrase
*
* (An empty passphrase is used for unencrypted keys.)
*
* If the key is encrypted, the encryption key is derived from the
* passphrase by means of a succession of SHA-1 hashes. Each hash
* is the hash of:
*
* uint32 sequence-number
* data passphrase
*
* where the sequence-number increases from zero. As many of these
* hashes are used as necessary.
*
* For backwards compatibility with snapshots between 0.51 and
* 0.52, we also support the older key file format, which begins
* with "PuTTY-User-Key-File-1" (version number differs). In this
* format the Private-MAC: field only covers the private-plaintext
* field and nothing else (and without the 4-byte string length on
* the front too). Moreover, for RSA keys the Private-MAC: field
* can be replaced with a Private-Hash: field which is a plain
* SHA-1 hash instead of an HMAC. This is not allowable in DSA
* keys. (Yes, the old format was a mess. Guess why it changed :-)
*/
static int read_header(FILE * fp, char *header)
{
int len = 39;
int c;
while (len > 0) {
c = fgetc(fp);
if (c == '\n' || c == '\r' || c == EOF)
return 0; /* failure */
if (c == ':') {
c = fgetc(fp);
if (c != ' ')
return 0;
*header = '\0';
return 1; /* success! */
}
if (len == 0)
return 0; /* failure */
*header++ = c;
len--;
}
return 0; /* failure */
}
static char *read_body(FILE * fp)
{
char *text;
int len;
int size;
int c;
size = 128;
text = snewn(size, char);
len = 0;
text[len] = '\0';
while (1) {
c = fgetc(fp);
if (c == '\r' || c == '\n') {
c = fgetc(fp);
if (c != '\r' && c != '\n' && c != EOF)
ungetc(c, fp);
return text;
}
if (c == EOF) {
sfree(text);
return NULL;
}
if (len + 1 > size) {
size += 128;
text = sresize(text, size, char);
}
text[len++] = c;
text[len] = '\0';
}
}
int base64_decode_atom(char *atom, unsigned char *out)
{
int vals[4];
int i, v, len;
unsigned word;
char c;
for (i = 0; i < 4; i++) {
c = atom[i];
if (c >= 'A' && c <= 'Z')
v = c - 'A';
else if (c >= 'a' && c <= 'z')
v = c - 'a' + 26;
else if (c >= '0' && c <= '9')
v = c - '0' + 52;
else if (c == '+')
v = 62;
else if (c == '/')
v = 63;
else if (c == '=')
v = -1;
else
return 0; /* invalid atom */
vals[i] = v;
}
if (vals[0] == -1 || vals[1] == -1)
return 0;
if (vals[2] == -1 && vals[3] != -1)
return 0;
if (vals[3] != -1)
len = 3;
else if (vals[2] != -1)
len = 2;
else
len = 1;
word = ((vals[0] << 18) |
(vals[1] << 12) | ((vals[2] & 0x3F) << 6) | (vals[3] & 0x3F));
out[0] = (word >> 16) & 0xFF;
if (len > 1)
out[1] = (word >> 8) & 0xFF;
if (len > 2)
out[2] = word & 0xFF;
return len;
}
static unsigned char *read_blob(FILE * fp, int nlines, int *bloblen)
{
unsigned char *blob;
char *line;
int linelen, len;
int i, j, k;
/* We expect at most 64 base64 characters, ie 48 real bytes, per line. */
blob = snewn(48 * nlines, unsigned char);
len = 0;
for (i = 0; i < nlines; i++) {
line = read_body(fp);
if (!line) {
sfree(blob);
return NULL;
}
linelen = strlen(line);
if (linelen % 4 != 0 || linelen > 64) {
sfree(blob);
sfree(line);
return NULL;
}
for (j = 0; j < linelen; j += 4) {
k = base64_decode_atom(line + j, blob + len);
if (!k) {
sfree(line);
sfree(blob);
return NULL;
}
len += k;
}
sfree(line);
}
*bloblen = len;
return blob;
}
/*
* Magic error return value for when the passphrase is wrong.
*/
struct ssh2_userkey ssh2_wrong_passphrase = {
NULL, NULL, NULL
};
const struct ssh_signkey *find_pubkey_alg(const char *name)
{
if (!strcmp(name, "ssh-rsa"))
return &ssh_rsa;
else if (!strcmp(name, "ssh-dss"))
return &ssh_dss;
else
return NULL;
}
struct ssh2_userkey *ssh2_load_userkey(const Filename *filename,
char *passphrase, const char **errorstr)
{
FILE *fp;
char header[40], *b, *encryption, *comment, *mac;
const struct ssh_signkey *alg;
struct ssh2_userkey *ret;
int cipher, cipherblk;
unsigned char *public_blob, *private_blob;
int public_blob_len, private_blob_len;
int i, is_mac, old_fmt;
int passlen = passphrase ? strlen(passphrase) : 0;
const char *error = NULL;
ret = NULL; /* return NULL for most errors */
encryption = comment = mac = NULL;
public_blob = private_blob = NULL;
fp = f_open(*filename, "rb");
if (!fp) {
error = "can't open file";
goto error;
}
/* Read the first header line which contains the key type. */
if (!read_header(fp, header))
goto error;
if (0 == strcmp(header, "PuTTY-User-Key-File-2")) {
old_fmt = 0;
} else if (0 == strcmp(header, "PuTTY-User-Key-File-1")) {
/* this is an old key file; warn and then continue */
old_keyfile_warning();
old_fmt = 1;
} else {
error = "not a PuTTY SSH-2 private key";
goto error;
}
error = "file format error";
if ((b = read_body(fp)) == NULL)
goto error;
/* Select key algorithm structure. */
alg = find_pubkey_alg(b);
if (!alg) {
sfree(b);
goto error;
}
sfree(b);
/* Read the Encryption header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
goto error;
if ((encryption = read_body(fp)) == NULL)
goto error;
if (!strcmp(encryption, "aes256-cbc")) {
cipher = 1;
cipherblk = 16;
} else if (!strcmp(encryption, "none")) {
cipher = 0;
cipherblk = 1;
} else {
sfree(encryption);
goto error;
}
/* Read the Comment header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
goto error;
if ((comment = read_body(fp)) == NULL)
goto error;
/* Read the Public-Lines header line and the public blob. */
if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
goto error;
if ((b = read_body(fp)) == NULL)
goto error;
i = atoi(b);
sfree(b);
if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
goto error;
/* Read the Private-Lines header line and the Private blob. */
if (!read_header(fp, header) || 0 != strcmp(header, "Private-Lines"))
goto error;
if ((b = read_body(fp)) == NULL)
goto error;
i = atoi(b);
sfree(b);
if ((private_blob = read_blob(fp, i, &private_blob_len)) == NULL)
goto error;
/* Read the Private-MAC or Private-Hash header line. */
if (!read_header(fp, header))
goto error;
if (0 == strcmp(header, "Private-MAC")) {
if ((mac = read_body(fp)) == NULL)
goto error;
is_mac = 1;
} else if (0 == strcmp(header, "Private-Hash") &&
alg == &ssh_rsa && old_fmt) {
if ((mac = read_body(fp)) == NULL)
goto error;
is_mac = 0;
} else
goto error;
fclose(fp);
fp = NULL;
/*
* Decrypt the private blob.
*/
if (cipher) {
unsigned char key[40];
SHA_State s;
if (!passphrase)
goto error;
if (private_blob_len % cipherblk)
goto error;
SHA_Init(&s);
SHA_Bytes(&s, "\0\0\0\0", 4);
SHA_Bytes(&s, passphrase, passlen);
SHA_Final(&s, key + 0);
SHA_Init(&s);
SHA_Bytes(&s, "\0\0\0\1", 4);
SHA_Bytes(&s, passphrase, passlen);
SHA_Final(&s, key + 20);
aes256_decrypt_pubkey(key, private_blob, private_blob_len);
}
/*
* Verify the MAC.
*/
{
char realmac[41];
unsigned char binary[20];
unsigned char *macdata;
int maclen;
int free_macdata;
if (old_fmt) {
/* MAC (or hash) only covers the private blob. */
macdata = private_blob;
maclen = private_blob_len;
free_macdata = 0;
} else {
unsigned char *p;
int namelen = strlen(alg->name);
int enclen = strlen(encryption);
int commlen = strlen(comment);
maclen = (4 + namelen +
4 + enclen +
4 + commlen +
4 + public_blob_len +
4 + private_blob_len);
macdata = snewn(maclen, unsigned char);
p = macdata;
#define DO_STR(s,len) PUT_32BIT(p,(len));memcpy(p+4,(s),(len));p+=4+(len)
DO_STR(alg->name, namelen);
DO_STR(encryption, enclen);
DO_STR(comment, commlen);
DO_STR(public_blob, public_blob_len);
DO_STR(private_blob, private_blob_len);
free_macdata = 1;
}
if (is_mac) {
SHA_State s;
unsigned char mackey[20];
char header[] = "putty-private-key-file-mac-key";
SHA_Init(&s);
SHA_Bytes(&s, header, sizeof(header)-1);
if (cipher && passphrase)
SHA_Bytes(&s, passphrase, passlen);
SHA_Final(&s, mackey);
hmac_sha1_simple(mackey, 20, macdata, maclen, binary);
memset(mackey, 0, sizeof(mackey));
memset(&s, 0, sizeof(s));
} else {
SHA_Simple(macdata, maclen, binary);
}
if (free_macdata) {
memset(macdata, 0, maclen);
sfree(macdata);
}
for (i = 0; i < 20; i++)
sprintf(realmac + 2 * i, "%02x", binary[i]);
if (strcmp(mac, realmac)) {
/* An incorrect MAC is an unconditional Error if the key is
* unencrypted. Otherwise, it means Wrong Passphrase. */
if (cipher) {
error = "wrong passphrase";
ret = SSH2_WRONG_PASSPHRASE;
} else {
error = "MAC failed";
ret = NULL;
}
goto error;
}
}
sfree(mac);
/*
* Create and return the key.
*/
ret = snew(struct ssh2_userkey);
ret->alg = alg;
ret->comment = comment;
ret->data = alg->createkey(public_blob, public_blob_len,
private_blob, private_blob_len);
if (!ret->data) {
sfree(ret->comment);
sfree(ret);
ret = NULL;
error = "createkey failed";
goto error;
}
sfree(public_blob);
sfree(private_blob);
sfree(encryption);
if (errorstr)
*errorstr = NULL;
return ret;
/*
* Error processing.
*/
error:
if (fp)
fclose(fp);
if (comment)
sfree(comment);
if (encryption)
sfree(encryption);
if (mac)
sfree(mac);
if (public_blob)
sfree(public_blob);
if (private_blob)
sfree(private_blob);
if (errorstr)
*errorstr = error;
return ret;
}
char *ssh2_userkey_loadpub(const Filename *filename, char **algorithm,
int *pub_blob_len, const char **errorstr)
{
FILE *fp;
char header[40], *b;
const struct ssh_signkey *alg;
unsigned char *public_blob;
int public_blob_len;
int i;
const char *error = NULL;
public_blob = NULL;
fp = f_open(*filename, "rb");
if (!fp) {
error = "can't open file";
goto error;
}
/* Read the first header line which contains the key type. */
if (!read_header(fp, header)
|| (0 != strcmp(header, "PuTTY-User-Key-File-2") &&
0 != strcmp(header, "PuTTY-User-Key-File-1"))) {
error = "not a PuTTY SSH-2 private key";
goto error;
}
error = "file format error";
if ((b = read_body(fp)) == NULL)
goto error;
/* Select key algorithm structure. Currently only ssh-rsa. */
alg = find_pubkey_alg(b);
if (!alg) {
sfree(b);
goto error;
}
sfree(b);
/* Read the Encryption header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Encryption"))
goto error;
if ((b = read_body(fp)) == NULL)
goto error;
sfree(b); /* we don't care */
/* Read the Comment header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Comment"))
goto error;
if ((b = read_body(fp)) == NULL)
goto error;
sfree(b); /* we don't care */
/* Read the Public-Lines header line and the public blob. */
if (!read_header(fp, header) || 0 != strcmp(header, "Public-Lines"))
goto error;
if ((b = read_body(fp)) == NULL)
goto error;
i = atoi(b);
sfree(b);
if ((public_blob = read_blob(fp, i, &public_blob_len)) == NULL)
goto error;
fclose(fp);
if (pub_blob_len)
*pub_blob_len = public_blob_len;
if (algorithm)
*algorithm = alg->name;
return (char *)public_blob;
/*
* Error processing.
*/
error:
if (fp)
fclose(fp);
if (public_blob)
sfree(public_blob);
if (errorstr)
*errorstr = error;
return NULL;
}
int ssh2_userkey_encrypted(const Filename *filename, char **commentptr)
{
FILE *fp;
char header[40], *b, *comment;
int ret;
if (commentptr)
*commentptr = NULL;
fp = f_open(*filename, "rb");
if (!fp)
return 0;
if (!read_header(fp, header)
|| (0 != strcmp(header, "PuTTY-User-Key-File-2") &&
0 != strcmp(header, "PuTTY-User-Key-File-1"))) {
fclose(fp);
return 0;
}
if ((b = read_body(fp)) == NULL) {
fclose(fp);
return 0;
}
sfree(b); /* we don't care about key type here */
/* Read the Encryption header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Encryption")) {
fclose(fp);
return 0;
}
if ((b = read_body(fp)) == NULL) {
fclose(fp);
return 0;
}
/* Read the Comment header line. */
if (!read_header(fp, header) || 0 != strcmp(header, "Comment")) {
fclose(fp);
sfree(b);
return 1;
}
if ((comment = read_body(fp)) == NULL) {
fclose(fp);
sfree(b);
return 1;
}
if (commentptr)
*commentptr = comment;
fclose(fp);
if (!strcmp(b, "aes256-cbc"))
ret = 1;
else
ret = 0;
sfree(b);
return ret;
}
int base64_lines(int datalen)
{
/* When encoding, we use 64 chars/line, which equals 48 real chars. */
return (datalen + 47) / 48;
}
void base64_encode(FILE * fp, unsigned char *data, int datalen, int cpl)
{
int linelen = 0;
char out[4];
int n, i;
while (datalen > 0) {
n = (datalen < 3 ? datalen : 3);
base64_encode_atom(data, n, out);
data += n;
datalen -= n;
for (i = 0; i < 4; i++) {
if (linelen >= cpl) {
linelen = 0;
fputc('\n', fp);
}
fputc(out[i], fp);
linelen++;
}
}
fputc('\n', fp);
}
int ssh2_save_userkey(const Filename *filename, struct ssh2_userkey *key,
char *passphrase)
{
FILE *fp;
unsigned char *pub_blob, *priv_blob, *priv_blob_encrypted;
int pub_blob_len, priv_blob_len, priv_encrypted_len;
int passlen;
int cipherblk;
int i;
char *cipherstr;
unsigned char priv_mac[20];
/*
* Fetch the key component blobs.
*/
pub_blob = key->alg->public_blob(key->data, &pub_blob_len);
priv_blob = key->alg->private_blob(key->data, &priv_blob_len);
if (!pub_blob || !priv_blob) {
sfree(pub_blob);
sfree(priv_blob);
return 0;
}
/*
* Determine encryption details, and encrypt the private blob.
*/
if (passphrase) {
cipherstr = "aes256-cbc";
cipherblk = 16;
} else {
cipherstr = "none";
cipherblk = 1;
}
priv_encrypted_len = priv_blob_len + cipherblk - 1;
priv_encrypted_len -= priv_encrypted_len % cipherblk;
priv_blob_encrypted = snewn(priv_encrypted_len, unsigned char);
memset(priv_blob_encrypted, 0, priv_encrypted_len);
memcpy(priv_blob_encrypted, priv_blob, priv_blob_len);
/* Create padding based on the SHA hash of the unpadded blob. This prevents
* too easy a known-plaintext attack on the last block. */
SHA_Simple(priv_blob, priv_blob_len, priv_mac);
assert(priv_encrypted_len - priv_blob_len < 20);
memcpy(priv_blob_encrypted + priv_blob_len, priv_mac,
priv_encrypted_len - priv_blob_len);
/* Now create the MAC. */
{
unsigned char *macdata;
int maclen;
unsigned char *p;
int namelen = strlen(key->alg->name);
int enclen = strlen(cipherstr);
int commlen = strlen(key->comment);
SHA_State s;
unsigned char mackey[20];
char header[] = "putty-private-key-file-mac-key";
maclen = (4 + namelen +
4 + enclen +
4 + commlen +
4 + pub_blob_len +
4 + priv_encrypted_len);
macdata = snewn(maclen, unsigned char);
p = macdata;
#define DO_STR(s,len) PUT_32BIT(p,(len));memcpy(p+4,(s),(len));p+=4+(len)
DO_STR(key->alg->name, namelen);
DO_STR(cipherstr, enclen);
DO_STR(key->comment, commlen);
DO_STR(pub_blob, pub_blob_len);
DO_STR(priv_blob_encrypted, priv_encrypted_len);
SHA_Init(&s);
SHA_Bytes(&s, header, sizeof(header)-1);
if (passphrase)
SHA_Bytes(&s, passphrase, strlen(passphrase));
SHA_Final(&s, mackey);
hmac_sha1_simple(mackey, 20, macdata, maclen, priv_mac);
memset(macdata, 0, maclen);
sfree(macdata);
memset(mackey, 0, sizeof(mackey));
memset(&s, 0, sizeof(s));
}
if (passphrase) {
unsigned char key[40];
SHA_State s;
passlen = strlen(passphrase);
SHA_Init(&s);
SHA_Bytes(&s, "\0\0\0\0", 4);
SHA_Bytes(&s, passphrase, passlen);
SHA_Final(&s, key + 0);
SHA_Init(&s);
SHA_Bytes(&s, "\0\0\0\1", 4);
SHA_Bytes(&s, passphrase, passlen);
SHA_Final(&s, key + 20);
aes256_encrypt_pubkey(key, priv_blob_encrypted,
priv_encrypted_len);
memset(key, 0, sizeof(key));
memset(&s, 0, sizeof(s));
}
fp = f_open(*filename, "w");
if (!fp)
return 0;
fprintf(fp, "PuTTY-User-Key-File-2: %s\n", key->alg->name);
fprintf(fp, "Encryption: %s\n", cipherstr);
fprintf(fp, "Comment: %s\n", key->comment);
fprintf(fp, "Public-Lines: %d\n", base64_lines(pub_blob_len));
base64_encode(fp, pub_blob, pub_blob_len, 64);
fprintf(fp, "Private-Lines: %d\n", base64_lines(priv_encrypted_len));
base64_encode(fp, priv_blob_encrypted, priv_encrypted_len, 64);
fprintf(fp, "Private-MAC: ");
for (i = 0; i < 20; i++)
fprintf(fp, "%02x", priv_mac[i]);
fprintf(fp, "\n");
fclose(fp);
sfree(pub_blob);
memset(priv_blob, 0, priv_blob_len);
sfree(priv_blob);
sfree(priv_blob_encrypted);
return 1;
}
/* ----------------------------------------------------------------------
* A function to determine the type of a private key file. Returns
* 0 on failure, 1 or 2 on success.
*/
int key_type(const Filename *filename)
{
FILE *fp;
char buf[32];
const char putty2_sig[] = "PuTTY-User-Key-File-";
const char sshcom_sig[] = "---- BEGIN SSH2 ENCRYPTED PRIVAT";
const char openssh_sig[] = "-----BEGIN ";
int i;
fp = f_open(*filename, "r");
if (!fp)
return SSH_KEYTYPE_UNOPENABLE;
i = fread(buf, 1, sizeof(buf), fp);
fclose(fp);
if (i < 0)
return SSH_KEYTYPE_UNOPENABLE;
if (i < 32)
return SSH_KEYTYPE_UNKNOWN;
if (!memcmp(buf, rsa_signature, sizeof(rsa_signature)-1))
return SSH_KEYTYPE_SSH1;
if (!memcmp(buf, putty2_sig, sizeof(putty2_sig)-1))
return SSH_KEYTYPE_SSH2;
if (!memcmp(buf, openssh_sig, sizeof(openssh_sig)-1))
return SSH_KEYTYPE_OPENSSH;
if (!memcmp(buf, sshcom_sig, sizeof(sshcom_sig)-1))
return SSH_KEYTYPE_SSHCOM;
return SSH_KEYTYPE_UNKNOWN; /* unrecognised or EOF */
}
/*
* Convert the type word to a string, for `wrong type' error
* messages.
*/
char *key_type_to_str(int type)
{
switch (type) {
case SSH_KEYTYPE_UNOPENABLE: return "unable to open file"; break;
case SSH_KEYTYPE_UNKNOWN: return "not a private key"; break;
case SSH_KEYTYPE_SSH1: return "SSH1 private key"; break;
case SSH_KEYTYPE_SSH2: return "PuTTY SSH2 private key"; break;
case SSH_KEYTYPE_OPENSSH: return "OpenSSH SSH2 private key"; break;
case SSH_KEYTYPE_SSHCOM: return "ssh.com SSH2 private key"; break;
default: return "INTERNAL ERROR"; break;
}
}
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