OpenBSD-4.6/usr.bin/ssh/authfile.c
/* $OpenBSD: authfile.c,v 1.76 2006/08/03 03:34:41 deraadt Exp $ */
/*
* 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/types.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "xmalloc.h"
#include "cipher.h"
#include "buffer.h"
#include "key.h"
#include "ssh.h"
#include "log.h"
#include "authfile.h"
#include "rsa.h"
#include "misc.h"
#include "atomicio.h"
/* Version identification string for SSH v1 identity files. */
static const char 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.
*/
static int
key_save_private_rsa1(Key *key, const char *filename, const char *passphrase,
const char *comment)
{
Buffer buffer, encrypted;
u_char buf[100], *cp;
int fd, i, cipher_num;
CipherContext ciphercontext;
Cipher *cipher;
u_int32_t rnd;
/*
* If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
* to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
*/
cipher_num = (strcmp(passphrase, "") == 0) ?
SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER;
if ((cipher = cipher_by_number(cipher_num)) == NULL)
fatal("save_private_key_rsa: bad cipher");
/* This buffer is used to built the secret part of the private key. */
buffer_init(&buffer);
/* Put checkbytes for checking passphrase validity. */
rnd = arc4random();
buf[0] = rnd & 0xff;
buf[1] = (rnd >> 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->rsa->d);
buffer_put_bignum(&buffer, key->rsa->iqmp);
buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */
buffer_put_bignum(&buffer, key->rsa->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. */
for (i = 0; authfile_id_string[i]; i++)
buffer_put_char(&encrypted, authfile_id_string[i]);
buffer_put_char(&encrypted, 0);
/* Store cipher type. */
buffer_put_char(&encrypted, cipher_num);
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->rsa->n));
buffer_put_bignum(&encrypted, key->rsa->n);
buffer_put_bignum(&encrypted, key->rsa->e);
buffer_put_cstring(&encrypted, comment);
/* Allocate space for the private part of the key in the buffer. */
cp = buffer_append_space(&encrypted, buffer_len(&buffer));
cipher_set_key_string(&ciphercontext, cipher, passphrase,
CIPHER_ENCRYPT);
cipher_crypt(&ciphercontext, cp,
buffer_ptr(&buffer), buffer_len(&buffer));
cipher_cleanup(&ciphercontext);
memset(&ciphercontext, 0, sizeof(ciphercontext));
/* Destroy temporary data. */
memset(buf, 0, sizeof(buf));
buffer_free(&buffer);
fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
if (fd < 0) {
error("open %s failed: %s.", filename, strerror(errno));
buffer_free(&encrypted);
return 0;
}
if (atomicio(vwrite, fd, buffer_ptr(&encrypted),
buffer_len(&encrypted)) != buffer_len(&encrypted)) {
error("write to key file %s failed: %s", filename,
strerror(errno));
buffer_free(&encrypted);
close(fd);
unlink(filename);
return 0;
}
close(fd);
buffer_free(&encrypted);
return 1;
}
/* save SSH v2 key in OpenSSL PEM format */
static int
key_save_private_pem(Key *key, const char *filename, const char *_passphrase,
const char *comment)
{
FILE *fp;
int fd;
int success = 0;
int len = strlen(_passphrase);
u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL;
const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL;
if (len > 0 && len <= 4) {
error("passphrase too short: have %d bytes, need > 4", len);
return 0;
}
fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
if (fd < 0) {
error("open %s failed: %s.", filename, strerror(errno));
return 0;
}
fp = fdopen(fd, "w");
if (fp == NULL) {
error("fdopen %s failed: %s.", filename, strerror(errno));
close(fd);
return 0;
}
switch (key->type) {
case KEY_DSA:
success = PEM_write_DSAPrivateKey(fp, key->dsa,
cipher, passphrase, len, NULL, NULL);
break;
case KEY_RSA:
success = PEM_write_RSAPrivateKey(fp, key->rsa,
cipher, passphrase, len, NULL, NULL);
break;
}
fclose(fp);
return success;
}
int
key_save_private(Key *key, const char *filename, const char *passphrase,
const char *comment)
{
switch (key->type) {
case KEY_RSA1:
return key_save_private_rsa1(key, filename, passphrase,
comment);
case KEY_DSA:
case KEY_RSA:
return key_save_private_pem(key, filename, passphrase,
comment);
default:
break;
}
error("key_save_private: cannot save key type %d", key->type);
return 0;
}
/*
* 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;
u_int i;
size_t len;
if (fstat(fd, &st) < 0) {
error("fstat for key file %.200s failed: %.100s",
filename, strerror(errno));
return NULL;
}
if (st.st_size > 1*1024*1024) {
error("key file %.200s too large", filename);
return NULL;
}
len = (size_t)st.st_size; /* truncated */
buffer_init(&buffer);
cp = buffer_append_space(&buffer, len);
if (atomicio(read, fd, cp, len) != 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;
}
/*
* 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)
{
u_int i;
int check1, check2, cipher_type;
size_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;
}
if (st.st_size > 1*1024*1024) {
error("key file %.200s too large", filename);
close(fd);
return (NULL);
}
len = (size_t)st.st_size; /* truncated */
buffer_init(&buffer);
cp = buffer_append_space(&buffer, len);
if (atomicio(read, fd, cp, len) != 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;
}
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.
*/
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 *perm_ok)
{
int fd;
fd = open(filename, O_RDONLY);
if (fd < 0)
return NULL;
if (!key_perm_ok(fd, filename)) {
if (perm_ok != NULL)
*perm_ok = 0;
error("bad permissions: ignore key: %s", filename);
close(fd);
return NULL;
}
if (perm_ok != NULL)
*perm_ok = 1;
switch (type) {
case KEY_RSA1:
return key_load_private_rsa1(fd, filename, passphrase,
commentp);
/* closes fd */
case KEY_DSA:
case KEY_RSA:
case KEY_UNSPEC:
return key_load_private_pem(fd, type, passphrase, commentp);
/* closes fd */
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;
}
static int
key_try_load_public(Key *k, const char *filename, char **commentp)
{
FILE *f;
char line[SSH_MAX_PUBKEY_BYTES];
char *cp;
u_long linenum = 0;
f = fopen(filename, "r");
if (f != NULL) {
while (read_keyfile_line(f, filename, line, sizeof(line),
&linenum) != -1) {
cp = line;
switch (*cp) {
case '#':
case '\n':
case '\0':
continue;
}
/* Skip leading whitespace. */
for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
;
if (*cp) {
if (key_read(k, &cp) == 1) {
if (commentp)
*commentp=xstrdup(filename);
fclose(f);
return 1;
}
}
}
fclose(f);
}
return 0;
}
/* load public key from ssh v1 private or any pubkey file */
Key *
key_load_public(const char *filename, char **commentp)
{
Key *pub;
char file[MAXPATHLEN];
/* try rsa1 private key */
pub = key_load_public_type(KEY_RSA1, filename, commentp);
if (pub != NULL)
return pub;
/* try rsa1 public key */
pub = key_new(KEY_RSA1);
if (key_try_load_public(pub, filename, commentp) == 1)
return pub;
key_free(pub);
/* try ssh2 public key */
pub = key_new(KEY_UNSPEC);
if (key_try_load_public(pub, filename, commentp) == 1)
return pub;
if ((strlcpy(file, filename, sizeof file) < sizeof(file)) &&
(strlcat(file, ".pub", sizeof file) < sizeof(file)) &&
(key_try_load_public(pub, file, commentp) == 1))
return pub;
key_free(pub);
return NULL;
}