347 lines
9.5 KiB
C
347 lines
9.5 KiB
C
/*
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*
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* authfile.c
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*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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*
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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*
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* Created: Mon Mar 27 03:52:05 1995 ylo
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*
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* This file contains functions for reading and writing identity files, and
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* for reading the passphrase from the user.
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*
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* $FreeBSD$
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*/
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#include "includes.h"
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RCSID("$Id: authfile.c,v 1.11 1999/12/06 19:11:15 deraadt Exp $");
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#include <openssl/bn.h>
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#include "xmalloc.h"
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#include "buffer.h"
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#include "bufaux.h"
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#include "cipher.h"
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#include "ssh.h"
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/* Version identification string for identity files. */
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#define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
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/*
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* Saves the authentication (private) key in a file, encrypting it with
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* passphrase. The identification of the file (lowest 64 bits of n) will
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* precede the key to provide identification of the key without needing a
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* passphrase.
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*/
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int
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save_private_key(const char *filename, const char *passphrase,
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RSA *key, const char *comment)
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{
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Buffer buffer, encrypted;
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char buf[100], *cp;
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int fd, i;
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CipherContext cipher;
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int cipher_type;
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u_int32_t rand;
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/*
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* If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
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* to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
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*/
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if (strcmp(passphrase, "") == 0)
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cipher_type = SSH_CIPHER_NONE;
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else
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cipher_type = SSH_AUTHFILE_CIPHER;
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/* This buffer is used to built the secret part of the private key. */
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buffer_init(&buffer);
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/* Put checkbytes for checking passphrase validity. */
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rand = arc4random();
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buf[0] = rand & 0xff;
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buf[1] = (rand >> 8) & 0xff;
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buf[2] = buf[0];
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buf[3] = buf[1];
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buffer_append(&buffer, buf, 4);
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/*
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* Store the private key (n and e will not be stored because they
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* will be stored in plain text, and storing them also in encrypted
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* format would just give known plaintext).
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*/
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buffer_put_bignum(&buffer, key->d);
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buffer_put_bignum(&buffer, key->iqmp);
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buffer_put_bignum(&buffer, key->q); /* reverse from SSL p */
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buffer_put_bignum(&buffer, key->p); /* reverse from SSL q */
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/* Pad the part to be encrypted until its size is a multiple of 8. */
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while (buffer_len(&buffer) % 8 != 0)
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buffer_put_char(&buffer, 0);
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/* This buffer will be used to contain the data in the file. */
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buffer_init(&encrypted);
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/* First store keyfile id string. */
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cp = AUTHFILE_ID_STRING;
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for (i = 0; cp[i]; i++)
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buffer_put_char(&encrypted, cp[i]);
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buffer_put_char(&encrypted, 0);
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/* Store cipher type. */
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buffer_put_char(&encrypted, cipher_type);
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buffer_put_int(&encrypted, 0); /* For future extension */
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/* Store public key. This will be in plain text. */
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buffer_put_int(&encrypted, BN_num_bits(key->n));
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buffer_put_bignum(&encrypted, key->n);
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buffer_put_bignum(&encrypted, key->e);
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buffer_put_string(&encrypted, comment, strlen(comment));
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/* Allocate space for the private part of the key in the buffer. */
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buffer_append_space(&encrypted, &cp, buffer_len(&buffer));
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cipher_set_key_string(&cipher, cipher_type, passphrase, 1);
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cipher_encrypt(&cipher, (unsigned char *) cp,
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(unsigned char *) buffer_ptr(&buffer),
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buffer_len(&buffer));
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memset(&cipher, 0, sizeof(cipher));
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/* Destroy temporary data. */
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memset(buf, 0, sizeof(buf));
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buffer_free(&buffer);
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fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
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if (fd < 0)
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return 0;
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if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) !=
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buffer_len(&encrypted)) {
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debug("Write to key file %.200s failed: %.100s", filename,
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strerror(errno));
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buffer_free(&encrypted);
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close(fd);
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remove(filename);
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return 0;
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}
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close(fd);
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buffer_free(&encrypted);
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return 1;
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}
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/*
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* Loads the public part of the key file. Returns 0 if an error was
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* encountered (the file does not exist or is not readable), and non-zero
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* otherwise.
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*/
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int
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load_public_key(const char *filename, RSA * pub,
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char **comment_return)
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{
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int fd, i;
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off_t len;
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Buffer buffer;
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char *cp;
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fd = open(filename, O_RDONLY);
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if (fd < 0)
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return 0;
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len = lseek(fd, (off_t) 0, SEEK_END);
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lseek(fd, (off_t) 0, SEEK_SET);
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buffer_init(&buffer);
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buffer_append_space(&buffer, &cp, len);
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if (read(fd, cp, (size_t) len) != (size_t) len) {
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debug("Read from key file %.200s failed: %.100s", filename,
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strerror(errno));
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buffer_free(&buffer);
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close(fd);
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return 0;
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}
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close(fd);
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/* Check that it is at least big enought to contain the ID string. */
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if (len < strlen(AUTHFILE_ID_STRING) + 1) {
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debug("Bad key file %.200s.", filename);
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buffer_free(&buffer);
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return 0;
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}
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/*
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* Make sure it begins with the id string. Consume the id string
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* from the buffer.
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*/
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for (i = 0; i < (unsigned int) strlen(AUTHFILE_ID_STRING) + 1; i++)
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if (buffer_get_char(&buffer) != (u_char) AUTHFILE_ID_STRING[i]) {
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debug("Bad key file %.200s.", filename);
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buffer_free(&buffer);
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return 0;
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}
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/* Skip cipher type and reserved data. */
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(void) buffer_get_char(&buffer); /* cipher type */
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(void) buffer_get_int(&buffer); /* reserved */
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/* Read the public key from the buffer. */
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buffer_get_int(&buffer);
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pub->n = BN_new();
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buffer_get_bignum(&buffer, pub->n);
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pub->e = BN_new();
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buffer_get_bignum(&buffer, pub->e);
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if (comment_return)
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*comment_return = buffer_get_string(&buffer, NULL);
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/* The encrypted private part is not parsed by this function. */
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buffer_free(&buffer);
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return 1;
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}
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/*
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* Loads the private key from the file. Returns 0 if an error is encountered
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* (file does not exist or is not readable, or passphrase is bad). This
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* initializes the private key.
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* Assumes we are called under uid of the owner of the file.
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*/
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int
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load_private_key(const char *filename, const char *passphrase,
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RSA * prv, char **comment_return)
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{
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int fd, i, check1, check2, cipher_type;
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off_t len;
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Buffer buffer, decrypted;
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char *cp;
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CipherContext cipher;
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BN_CTX *ctx;
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BIGNUM *aux;
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struct stat st;
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fd = open(filename, O_RDONLY);
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if (fd < 0)
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return 0;
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/* check owner and modes */
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if (fstat(fd, &st) < 0 ||
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(st.st_uid != 0 && st.st_uid != getuid()) ||
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(st.st_mode & 077) != 0) {
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close(fd);
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error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
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error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @");
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error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
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error("Bad ownership or mode(0%3.3o) for '%s'.",
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st.st_mode & 0777, filename);
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error("It is recommended that your private key files are NOT accessible by others.");
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return 0;
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}
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len = lseek(fd, (off_t) 0, SEEK_END);
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lseek(fd, (off_t) 0, SEEK_SET);
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buffer_init(&buffer);
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buffer_append_space(&buffer, &cp, len);
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if (read(fd, cp, (size_t) len) != (size_t) len) {
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debug("Read from key file %.200s failed: %.100s", filename,
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strerror(errno));
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buffer_free(&buffer);
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close(fd);
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return 0;
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}
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close(fd);
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/* Check that it is at least big enought to contain the ID string. */
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if (len < strlen(AUTHFILE_ID_STRING) + 1) {
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debug("Bad key file %.200s.", filename);
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buffer_free(&buffer);
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return 0;
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}
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/*
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* Make sure it begins with the id string. Consume the id string
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* from the buffer.
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*/
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for (i = 0; i < (unsigned int) strlen(AUTHFILE_ID_STRING) + 1; i++)
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if (buffer_get_char(&buffer) != (unsigned char) AUTHFILE_ID_STRING[i]) {
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debug("Bad key file %.200s.", filename);
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buffer_free(&buffer);
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return 0;
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}
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/* Read cipher type. */
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cipher_type = buffer_get_char(&buffer);
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(void) buffer_get_int(&buffer); /* Reserved data. */
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/* Read the public key from the buffer. */
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buffer_get_int(&buffer);
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prv->n = BN_new();
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buffer_get_bignum(&buffer, prv->n);
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prv->e = BN_new();
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buffer_get_bignum(&buffer, prv->e);
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if (comment_return)
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*comment_return = buffer_get_string(&buffer, NULL);
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else
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xfree(buffer_get_string(&buffer, NULL));
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/* Check that it is a supported cipher. */
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if (((cipher_mask() | SSH_CIPHER_NONE | SSH_AUTHFILE_CIPHER) &
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(1 << cipher_type)) == 0) {
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debug("Unsupported cipher %.100s used in key file %.200s.",
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cipher_name(cipher_type), filename);
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buffer_free(&buffer);
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goto fail;
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}
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/* Initialize space for decrypted data. */
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buffer_init(&decrypted);
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buffer_append_space(&decrypted, &cp, buffer_len(&buffer));
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/* Rest of the buffer is encrypted. Decrypt it using the passphrase. */
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cipher_set_key_string(&cipher, cipher_type, passphrase, 0);
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cipher_decrypt(&cipher, (unsigned char *) cp,
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(unsigned char *) buffer_ptr(&buffer),
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buffer_len(&buffer));
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buffer_free(&buffer);
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check1 = buffer_get_char(&decrypted);
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check2 = buffer_get_char(&decrypted);
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if (check1 != buffer_get_char(&decrypted) ||
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check2 != buffer_get_char(&decrypted)) {
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if (strcmp(passphrase, "") != 0)
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debug("Bad passphrase supplied for key file %.200s.", filename);
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/* Bad passphrase. */
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buffer_free(&decrypted);
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fail:
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BN_clear_free(prv->n);
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BN_clear_free(prv->e);
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if (comment_return)
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xfree(*comment_return);
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return 0;
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}
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/* Read the rest of the private key. */
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prv->d = BN_new();
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buffer_get_bignum(&decrypted, prv->d);
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prv->iqmp = BN_new();
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buffer_get_bignum(&decrypted, prv->iqmp); /* u */
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/* in SSL and SSH p and q are exchanged */
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prv->q = BN_new();
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buffer_get_bignum(&decrypted, prv->q); /* p */
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prv->p = BN_new();
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buffer_get_bignum(&decrypted, prv->p); /* q */
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ctx = BN_CTX_new();
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aux = BN_new();
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BN_sub(aux, prv->q, BN_value_one());
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prv->dmq1 = BN_new();
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BN_mod(prv->dmq1, prv->d, aux, ctx);
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BN_sub(aux, prv->p, BN_value_one());
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prv->dmp1 = BN_new();
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BN_mod(prv->dmp1, prv->d, aux, ctx);
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BN_clear_free(aux);
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BN_CTX_free(ctx);
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buffer_free(&decrypted);
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return 1;
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}
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