crypt.c

   1 /*
   2  * Copyright (C) 2005-2007 Andre Noll <maan@systemlinux.org>
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     This program is distributed in the hope that it will be useful,
  10  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *     GNU General Public License for more details.
  13  *
  14  *     You should have received a copy of the GNU General Public License
  15  *     along with this program; if not, write to the Free Software
  16  *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  17  */
  18
  19 /** \file crypt.c openssl-based RSA encryption/decryption routines */
  20
  21 #include "para.h"
  22 #include "error.h"
  23 #include "string.h"
  24 #include "crypt.h"
  25
  26 static EVP_PKEY *load_key(const char *file, int private)
  27 {
  28         BIO *key;
  29         EVP_PKEY *pkey = NULL;
  30
  31         key = BIO_new(BIO_s_file());
  32         if (!key)
  33                 return NULL;
  34         if (BIO_read_filename(key, file) > 0) {
  35                 if (private == LOAD_PRIVATE_KEY)
  36                         pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
  37                 else
  38                         pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
  39         }
  40         BIO_free(key);
  41         return pkey;
  42 }
  43
  44 /**
  45  * read an RSA key from a file
  46  *
  47  * \param key_file the file containing the key
  48  * \param rsa RSA structure is returned here
  49  * \param private if non-zero, read the private key, otherwise the public key
  50  *
  51  * \return The size of the RSA key on success, negative on errors.
  52  *
  53  * \sa openssl(1), rsa(1).
  54  */
  55 int get_rsa_key(char *key_file, RSA **rsa, int private)
  56 {
  57         EVP_PKEY *key = load_key(key_file, private);
  58
  59         if (!key)
  60                 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
  61                         : -E_PUBLIC_KEY;
  62         *rsa = EVP_PKEY_get1_RSA(key);
  63         EVP_PKEY_free(key);
  64         if (!*rsa)
  65                 return -E_RSA;
  66         return RSA_size(*rsa);
  67 }
  68
  69 /**
  70  * free an RSA structure
  71  *
  72  * \param rsa pointer to the RSA struct to free
  73  *
  74  * This must be called for any key obtained by get_rsa_key().
  75  */
  76 void rsa_free(RSA *rsa)
  77 {
  78         if (rsa)
  79                 RSA_free(rsa);
  80 }
  81
  82 /**
  83  * decrypt a buffer using an RSA key
  84  *
  85  * \param key_file full path of the rsa key
  86  * \param outbuf the output buffer
  87  * \param inbuf the encrypted input buffer
  88  * \param rsa_inlen the length of \a inbuf
  89  *
  90  * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
  91  *
  92  * \return The size of the recovered plaintext on success, negative on errors.
  93  *
  94  * \sa RSA_private_decrypt(3)
  95  **/
  96 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
  97                         unsigned rsa_inlen)
  98 {
  99         RSA *rsa;
 100         int ret, inlen = rsa_inlen;
 101
 102         if (inlen < 0)
 103                 return -E_RSA;
 104         ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
 105         if (ret < 0)
 106                 return ret;
 107         ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
 108         rsa_free(rsa);
 109         return (ret > 0)? ret : -E_DECRYPT;
 110 }
 111
 112 /**
 113  * decrypt the challenge number sent by para_server
 114  *
 115  * \param key_file full path of the rsa key
 116  * \param challenge_nr result is stored here
 117  * \param inbuf the input buffer
 118  * \param rsa_inlen the length of \a inbuf
 119  *
 120  * \return positive on success, negative on errors
 121  *
 122  * \sa para_decrypt_buffer()
 123  */
 124 int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
 125                 unsigned char *inbuf, unsigned rsa_inlen)
 126 {
 127         unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
 128         int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
 129
 130         if (ret >= 0) {
 131                 rsa_out[ret] = '\0';
 132                 ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1?
 133                         1 : -E_CHALLENGE;
 134         }
 135         OPENSSL_free(rsa_out);
 136         return ret;
 137 }
 138
 139 /**
 140  * encrypt a buffer using an RSA key
 141  *
 142  * \param rsa: public rsa key
 143  * \param inbuf the input buffer
 144  * \param len the length of \a inbuf
 145  * \param outbuf the output buffer
 146  *
 147  * \return The size of the encrypted data on success, negative on errors
 148  *
 149  * \sa RSA_public_encrypt(3)
 150  */
 151 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
 152                 unsigned len, unsigned char *outbuf)
 153 {
 154         int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 155
 156         if (flen < 0)
 157                 return -E_ENCRYPT;
 158         ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
 159         return ret < 0?  -E_ENCRYPT : ret;
 160 }
 161
 162 /**
 163  * encrypt the given challenge number
 164  *
 165  * \param rsa: public rsa key
 166  * \param challenge_nr the number to be encrypted
 167  * \param outbuf the output buffer
 168  *
 169  * \a outbuf must be at least 64 bytes long
 170  *
 171  * \return The size of the encrypted data on success, negative on errors
 172  *
 173  * \sa para_encrypt_buffer()
 174  *
 175  */
 176 int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
 177         unsigned char *outbuf)
 178 {
 179         unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr);
 180         int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf);
 181         free(inbuf);
 182         return ret;
 183 }
 184