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/*
*
* authfile.c
*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* Created: Mon Mar 27 03:52:05 1995 ylo
*
* This file contains functions for reading and writing identity files, and
* for reading the passphrase from the user.
*
*/
#include "includes.h"
RCSID("$Id: authfile.c,v 1.6 1999/12/07 04:38:32 damien Exp $");
#ifdef HAVE_OPENSSL
#include <openssl/bn.h>
#endif
#ifdef HAVE_SSL
#include <ssl/bn.h>
#endif
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "cipher.h"
#include "ssh.h"
/* Version identification string for identity files. */
#define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
/*
* Saves the authentication (private) key in a file, encrypting it with
* passphrase. The identification of the file (lowest 64 bits of n) will
* precede the key to provide identification of the key without needing a
* passphrase.
*/
int
save_private_key(const char *filename, const char *passphrase,
RSA *key, const char *comment)
{
Buffer buffer, encrypted;
char buf[100], *cp;
int fd, i;
CipherContext cipher;
int cipher_type;
u_int32_t rand;
/*
* If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
* to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
*/
if (strcmp(passphrase, "") == 0)
cipher_type = SSH_CIPHER_NONE;
else
cipher_type = SSH_AUTHFILE_CIPHER;
/* This buffer is used to built the secret part of the private key. */
buffer_init(&buffer);
/* Put checkbytes for checking passphrase validity. */
rand = arc4random();
buf[0] = rand & 0xff;
buf[1] = (rand >> 8) & 0xff;
buf[2] = buf[0];
buf[3] = buf[1];
buffer_append(&buffer, buf, 4);
/*
* Store the private key (n and e will not be stored because they
* will be stored in plain text, and storing them also in encrypted
* format would just give known plaintext).
*/
buffer_put_bignum(&buffer, key->d);
buffer_put_bignum(&buffer, key->iqmp);
buffer_put_bignum(&buffer, key->q); /* reverse from SSL p */
buffer_put_bignum(&buffer, key->p); /* reverse from SSL q */
/* Pad the part to be encrypted until its size is a multiple of 8. */
while (buffer_len(&buffer) % 8 != 0)
buffer_put_char(&buffer, 0);
/* This buffer will be used to contain the data in the file. */
buffer_init(&encrypted);
/* First store keyfile id string. */
cp = AUTHFILE_ID_STRING;
for (i = 0; cp[i]; i++)
buffer_put_char(&encrypted, cp[i]);
buffer_put_char(&encrypted, 0);
/* Store cipher type. */
buffer_put_char(&encrypted, cipher_type);
buffer_put_int(&encrypted, 0); /* For future extension */
/* Store public key. This will be in plain text. */
buffer_put_int(&encrypted, BN_num_bits(key->n));
buffer_put_bignum(&encrypted, key->n);
buffer_put_bignum(&encrypted, key->e);
buffer_put_string(&encrypted, comment, strlen(comment));
/* Allocate space for the private part of the key in the buffer. */
buffer_append_space(&encrypted, &cp, buffer_len(&buffer));
cipher_set_key_string(&cipher, cipher_type, passphrase, 1);
cipher_encrypt(&cipher, (unsigned char *) cp,
(unsigned char *) buffer_ptr(&buffer),
buffer_len(&buffer));
memset(&cipher, 0, sizeof(cipher));
/* Destroy temporary data. */
memset(buf, 0, sizeof(buf));
buffer_free(&buffer);
fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
if (fd < 0)
return 0;
if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) !=
buffer_len(&encrypted)) {
debug("Write to key file %.200s failed: %.100s", filename,
strerror(errno));
buffer_free(&encrypted);
close(fd);
remove(filename);
return 0;
}
close(fd);
buffer_free(&encrypted);
return 1;
}
/*
* Loads the public part of the key file. Returns 0 if an error was
* encountered (the file does not exist or is not readable), and non-zero
* otherwise.
*/
int
load_public_key(const char *filename, RSA * pub,
char **comment_return)
{
int fd, i;
off_t len;
Buffer buffer;
char *cp;
fd = open(filename, O_RDONLY);
if (fd < 0)
return 0;
len = lseek(fd, (off_t) 0, SEEK_END);
lseek(fd, (off_t) 0, SEEK_SET);
buffer_init(&buffer);
buffer_append_space(&buffer, &cp, len);
if (read(fd, cp, (size_t) len) != (size_t) len) {
debug("Read from key file %.200s failed: %.100s", filename,
strerror(errno));
buffer_free(&buffer);
close(fd);
return 0;
}
close(fd);
/* Check that it is at least big enought to contain the ID string. */
if (len < strlen(AUTHFILE_ID_STRING) + 1) {
debug("Bad key file %.200s.", filename);
buffer_free(&buffer);
return 0;
}
/*
* Make sure it begins with the id string. Consume the id string
* from the buffer.
*/
for (i = 0; i < (unsigned int) strlen(AUTHFILE_ID_STRING) + 1; i++)
if (buffer_get_char(&buffer) != (u_char) AUTHFILE_ID_STRING[i]) {
debug("Bad key file %.200s.", filename);
buffer_free(&buffer);
return 0;
}
/* Skip cipher type and reserved data. */
(void) buffer_get_char(&buffer); /* cipher type */
(void) buffer_get_int(&buffer); /* reserved */
/* Read the public key from the buffer. */
buffer_get_int(&buffer);
pub->n = BN_new();
buffer_get_bignum(&buffer, pub->n);
pub->e = BN_new();
buffer_get_bignum(&buffer, pub->e);
if (comment_return)
*comment_return = buffer_get_string(&buffer, NULL);
/* The encrypted private part is not parsed by this function. */
buffer_free(&buffer);
return 1;
}
/*
* Loads the private key from the file. Returns 0 if an error is encountered
* (file does not exist or is not readable, or passphrase is bad). This
* initializes the private key.
* Assumes we are called under uid of the owner of the file.
*/
int
load_private_key(const char *filename, const char *passphrase,
RSA * prv, char **comment_return)
{
int fd, i, check1, check2, cipher_type;
off_t len;
Buffer buffer, decrypted;
char *cp;
CipherContext cipher;
BN_CTX *ctx;
BIGNUM *aux;
struct stat st;
fd = open(filename, O_RDONLY);
if (fd < 0)
return 0;
/* check owner and modes */
if (fstat(fd, &st) < 0 ||
(st.st_uid != 0 && st.st_uid != getuid()) ||
(st.st_mode & 077) != 0) {
close(fd);
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @");
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("Bad ownership or mode(0%3.3o) for '%s'.",
st.st_mode & 0777, filename);
error("It is recommended that your private key files are NOT accessible by others.");
return 0;
}
len = lseek(fd, (off_t) 0, SEEK_END);
lseek(fd, (off_t) 0, SEEK_SET);
buffer_init(&buffer);
buffer_append_space(&buffer, &cp, len);
if (read(fd, cp, (size_t) len) != (size_t) len) {
debug("Read from key file %.200s failed: %.100s", filename,
strerror(errno));
buffer_free(&buffer);
close(fd);
return 0;
}
close(fd);
/* Check that it is at least big enought to contain the ID string. */
if (len < strlen(AUTHFILE_ID_STRING) + 1) {
debug("Bad key file %.200s.", filename);
buffer_free(&buffer);
return 0;
}
/*
* Make sure it begins with the id string. Consume the id string
* from the buffer.
*/
for (i = 0; i < (unsigned int) strlen(AUTHFILE_ID_STRING) + 1; i++)
if (buffer_get_char(&buffer) != (unsigned char) AUTHFILE_ID_STRING[i]) {
debug("Bad key file %.200s.", filename);
buffer_free(&buffer);
return 0;
}
/* Read cipher type. */
cipher_type = buffer_get_char(&buffer);
(void) buffer_get_int(&buffer); /* Reserved data. */
/* Read the public key from the buffer. */
buffer_get_int(&buffer);
prv->n = BN_new();
buffer_get_bignum(&buffer, prv->n);
prv->e = BN_new();
buffer_get_bignum(&buffer, prv->e);
if (comment_return)
*comment_return = buffer_get_string(&buffer, NULL);
else
xfree(buffer_get_string(&buffer, NULL));
/* Check that it is a supported cipher. */
if (((cipher_mask() | SSH_CIPHER_NONE | SSH_AUTHFILE_CIPHER) &
(1 << cipher_type)) == 0) {
debug("Unsupported cipher %.100s used in key file %.200s.",
cipher_name(cipher_type), filename);
buffer_free(&buffer);
goto fail;
}
/* Initialize space for decrypted data. */
buffer_init(&decrypted);
buffer_append_space(&decrypted, &cp, buffer_len(&buffer));
/* Rest of the buffer is encrypted. Decrypt it using the passphrase. */
cipher_set_key_string(&cipher, cipher_type, passphrase, 0);
cipher_decrypt(&cipher, (unsigned char *) cp,
(unsigned char *) buffer_ptr(&buffer),
buffer_len(&buffer));
buffer_free(&buffer);
check1 = buffer_get_char(&decrypted);
check2 = buffer_get_char(&decrypted);
if (check1 != buffer_get_char(&decrypted) ||
check2 != buffer_get_char(&decrypted)) {
if (strcmp(passphrase, "") != 0)
debug("Bad passphrase supplied for key file %.200s.", filename);
/* Bad passphrase. */
buffer_free(&decrypted);
fail:
BN_clear_free(prv->n);
BN_clear_free(prv->e);
if (comment_return)
xfree(*comment_return);
return 0;
}
/* Read the rest of the private key. */
prv->d = BN_new();
buffer_get_bignum(&decrypted, prv->d);
prv->iqmp = BN_new();
buffer_get_bignum(&decrypted, prv->iqmp); /* u */
/* in SSL and SSH p and q are exchanged */
prv->q = BN_new();
buffer_get_bignum(&decrypted, prv->q); /* p */
prv->p = BN_new();
buffer_get_bignum(&decrypted, prv->p); /* q */
ctx = BN_CTX_new();
aux = BN_new();
BN_sub(aux, prv->q, BN_value_one());
prv->dmq1 = BN_new();
BN_mod(prv->dmq1, prv->d, aux, ctx);
BN_sub(aux, prv->p, BN_value_one());
prv->dmp1 = BN_new();
BN_mod(prv->dmp1, prv->d, aux, ctx);
BN_clear_free(aux);
BN_CTX_free(ctx);
buffer_free(&decrypted);
return 1;
}