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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* This file contains functions for reading and writing identity files, and
* for reading the passphrase from the user.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <sys/param.h>
#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/pem.h>

#include <config.h>
#include "cipher.h"
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "key.h"
#include "log.h"

/* Version identification string for SSH v1 identity files. */
static const char authfile_id_string[] =
    "SSH PRIVATE KEY FILE FORMAT 1.1\n";


/*
* Loads the public part of the ssh v1 key file. Returns NULL if an error was
* encountered (the file does not exist or is not readable), and the key
* otherwise.
*/

static Key *
key_load_public_rsa1(int fd, const char *filename, char **commentp)
{
Buffer buffer;
Key *pub;
struct stat st;
char *cp;
int i;
off_t len;

if (fstat(fd, &st) < 0) {
error("fstat for key file %.200s failed: %.100s",
filename, strerror(errno));
return NULL;
}
len = st.st_size;

buffer_init(&buffer);
cp = buffer_append_space(&buffer, 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);
return NULL;
}

/* Check that it is at least big enough to contain the ID string. */
if (len < sizeof(authfile_id_string)) {
debug3("Not a RSA1 key file %.200s.", filename);
buffer_free(&buffer);
return NULL;
}
/*
* Make sure it begins with the id string. Consume the id string
* from the buffer.
*/
for (i = 0; i < sizeof(authfile_id_string); i++)
if (buffer_get_char(&buffer) != authfile_id_string[i]) {
debug3("Not a RSA1 key file %.200s.", filename);
buffer_free(&buffer);
return NULL;
}
/* 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. */
(void) buffer_get_int(&buffer);
pub = key_new(KEY_RSA1);
buffer_get_bignum(&buffer, pub->rsa->n);
buffer_get_bignum(&buffer, pub->rsa->e);
if (commentp)
*commentp = buffer_get_string(&buffer, NULL);
/* The encrypted private part is not parsed by this function. */

buffer_free(&buffer);
return pub;
}

/* load public key from private-key file, works only for SSH v1 */
Key *
key_load_public_type(int type, const char *filename, char **commentp)
{
Key *pub;
int fd;

if (type == KEY_RSA1) {
fd = open(filename, O_RDONLY);
if (fd < 0)
return NULL;
pub = key_load_public_rsa1(fd, filename, commentp);
close(fd);
return pub;
}
return NULL;
}

/* calculate p-1 and q-1 */
void
rsa_generate_additional_parameters(RSA *rsa)
{
BIGNUM *aux;
BN_CTX *ctx;

if ((aux = BN_new()) == NULL)
fatal("rsa_generate_additional_parameters: BN_new failed");
if ((ctx = BN_CTX_new()) == NULL)
fatal("rsa_generate_additional_parameters: BN_CTX_new failed");

BN_sub(aux, rsa->q, BN_value_one());
BN_mod(rsa->dmq1, rsa->d, aux, ctx);

BN_sub(aux, rsa->p, BN_value_one());
BN_mod(rsa->dmp1, rsa->d, aux, ctx);

BN_clear_free(aux);
BN_CTX_free(ctx);
}

/*
* 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.
*/

static Key *
key_load_private_rsa1(int fd, const char *filename, const char *passphrase,
    char **commentp)
{
int i, check1, check2, cipher_type;
off_t len;
Buffer buffer, decrypted;
u_char *cp;
CipherContext ciphercontext;
Cipher *cipher;
Key *prv = NULL;
struct stat st;

if (fstat(fd, &st) < 0) {
error("fstat for key file %.200s failed: %.100s",
filename, strerror(errno));
close(fd);
return NULL;
}
len = st.st_size;

buffer_init(&buffer);
cp = buffer_append_space(&buffer, 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 NULL;
}

/* Check that it is at least big enough to contain the ID string. */
if (len < sizeof(authfile_id_string)) {
debug3("Not a RSA1 key file %.200s.", filename);
buffer_free(&buffer);
close(fd);
return NULL;
}
/*
* Make sure it begins with the id string. Consume the id string
* from the buffer.
*/
for (i = 0; i < sizeof(authfile_id_string); i++)
if (buffer_get_char(&buffer) != authfile_id_string[i]) {
debug3("Not a RSA1 key file %.200s.", filename);
buffer_free(&buffer);
close(fd);
return NULL;
}

/* Read cipher type. */
cipher_type = buffer_get_char(&buffer);
(void) buffer_get_int(&buffer); /* Reserved data. */

/* Read the public key from the buffer. */
(void) buffer_get_int(&buffer);
prv = key_new_private(KEY_RSA1);

buffer_get_bignum(&buffer, prv->rsa->n);
buffer_get_bignum(&buffer, prv->rsa->e);
if (commentp)
*commentp = buffer_get_string(&buffer, NULL);
else
xfree(buffer_get_string(&buffer, NULL));

/* Check that it is a supported cipher. */
cipher = cipher_by_number(cipher_type);
if (cipher == NULL) {
debug("Unsupported cipher %d used in key file %.200s.",
cipher_type, filename);
buffer_free(&buffer);
goto fail;
}
/* Initialize space for decrypted data. */
buffer_init(&decrypted);
cp = buffer_append_space(&decrypted, buffer_len(&buffer));

/* Rest of the buffer is encrypted. Decrypt it using the passphrase. */
cipher_set_key_string(&ciphercontext, cipher, passphrase,
CIPHER_DECRYPT);
cipher_crypt(&ciphercontext, cp,
buffer_ptr(&buffer), buffer_len(&buffer));
cipher_cleanup(&ciphercontext);
memset(&ciphercontext, 0, sizeof(ciphercontext));
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);
goto fail;
}
/* Read the rest of the private key. */
buffer_get_bignum(&decrypted, prv->rsa->d);
buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */
/* in SSL and SSH v1 p and q are exchanged */
buffer_get_bignum(&decrypted, prv->rsa->q); /* p */
buffer_get_bignum(&decrypted, prv->rsa->p); /* q */

/* calculate p-1 and q-1 */
rsa_generate_additional_parameters(prv->rsa);

buffer_free(&decrypted);

/* enable blinding */
if (RSA_blinding_on(prv->rsa, NULL) != 1) {
error("key_load_private_rsa1: RSA_blinding_on failed");
goto fail;
}
close(fd);
return prv;

fail:
if (commentp)
xfree(*commentp);
close(fd);
key_free(prv);
return NULL;
}

Key *
key_load_private_pem(int fd, int type, const char *passphrase,
    char **commentp)
{
FILE *fp;
EVP_PKEY *pk = NULL;
Key *prv = NULL;
char *name = "<no key>";

fp = fdopen(fd, "r");
if (fp == NULL) {
error("fdopen failed: %s", strerror(errno));
close(fd);
return NULL;
}
pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase);
if (pk == NULL) {
debug("PEM_read_PrivateKey failed");
(void)ERR_get_error();
} else if (pk->type == EVP_PKEY_RSA &&
(type == KEY_UNSPEC||type==KEY_RSA)) {
prv = key_new(KEY_UNSPEC);
prv->rsa = EVP_PKEY_get1_RSA(pk);
prv->type = KEY_RSA;
name = "rsa w/o comment";
#ifdef DEBUG_PK
RSA_print_fp(stderr, prv->rsa, 8);
#endif
if (RSA_blinding_on(prv->rsa, NULL) != 1) {
error("key_load_private_pem: RSA_blinding_on failed");
key_free(prv);
prv = NULL;
}
} else if (pk->type == EVP_PKEY_DSA &&
(type == KEY_UNSPEC||type==KEY_DSA)) {
prv = key_new(KEY_UNSPEC);
prv->dsa = EVP_PKEY_get1_DSA(pk);
prv->type = KEY_DSA;
name = "dsa w/o comment";
#ifdef DEBUG_PK
DSA_print_fp(stderr, prv->dsa, 8);
#endif
} else {
error("PEM_read_PrivateKey: mismatch or "
"unknown EVP_PKEY save_type %d", pk->save_type);
}
fclose(fp);
if (pk != NULL)
EVP_PKEY_free(pk);
if (prv != NULL && commentp)
*commentp = xstrdup(name);
debug("read PEM private key done: type %s",
prv ? key_type(prv) : "<unknown>");
return prv;
}

static int
key_perm_ok(int fd, const char *filename)
{
struct stat st;

if (fstat(fd, &st) < 0)
return 0;
/*
* if a key owned by the user is accessed, then we check the
* permissions of the file. if the key owned by a different user,
* then we don't care.
*/
#ifdef HAVE_CYGWIN
if (check_ntsec(filename))
#endif
if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @");
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("Permissions 0%3.3o for '%s' are too open.",
(u_int)st.st_mode & 0777, filename);
error("It is recommended that your private key files are NOT accessible by others.");
error("This private key will be ignored.");
return 0;
}
return 1;
}

Key *
key_load_private_type(int type, const char *filename, const char *passphrase,
    char **commentp)
{
int fd;

fd = open(filename, O_RDONLY);
if (fd < 0)
return NULL;
if (!key_perm_ok(fd, filename)) {
error("bad permissions: ignore key: %s", filename);
close(fd);
return NULL;
}
switch (type) {
case KEY_RSA1:
return key_load_private_rsa1(fd, filename, passphrase,
commentp);
/* closes fd */
break;
case KEY_DSA:
case KEY_RSA:
case KEY_UNSPEC:
return key_load_private_pem(fd, type, passphrase, commentp);
/* closes fd */
break;
default:
close(fd);
break;
}
return NULL;
}

Key *
key_load_private(const char *filename, const char *passphrase,
    char **commentp)
{
Key *pub, *prv;
int fd;

fd = open(filename, O_RDONLY);
if (fd < 0)
return NULL;
if (!key_perm_ok(fd, filename)) {
error("bad permissions: ignore key: %s", filename);
close(fd);
return NULL;
}
pub = key_load_public_rsa1(fd, filename, commentp);
lseek(fd, (off_t) 0, SEEK_SET); /* rewind */
if (pub == NULL) {
/* closes fd */
prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL);
/* use the filename as a comment for PEM */
if (commentp && prv)
*commentp = xstrdup(filename);
} else {
/* it's a SSH v1 key if the public key part is readable */
key_free(pub);
/* closes fd */
prv = key_load_private_rsa1(fd, filename, passphrase, NULL);
}
return prv;
}
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