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 : -E_PUBLIC_KEY;
  61         *rsa = EVP_PKEY_get1_RSA(key);
  62         EVP_PKEY_free(key);
  63         if (!*rsa)
  64                 return -E_RSA;
  65         return RSA_size(*rsa);
  66 }
  67
  68 /**
  69  * free an RSA structure
  70  *
  71  * \param rsa pointer to the RSA struct to free
  72  *
  73  * This must be called for any key obtained by get_rsa_key().
  74  */
  75 void rsa_free(RSA *rsa)
  76 {
  77         if (rsa)
  78                 RSA_free(rsa);
  79 }
  80
  81 /**
  82  * decrypt a buffer using an RSA key
  83  *
  84  * \param key_file full path of the rsa key
  85  * \param outbuf the output buffer
  86  * \param inbuf the encrypted input buffer
  87  * \param rsa_inlen the length of \a inbuf
  88  *
  89  * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
  90  *
  91  * \return The size of the recovered plaintext on success, negative on errors.
  92  *
  93  * \sa RSA_private_decrypt(3)
  94  **/
  95 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
  96                         unsigned rsa_inlen)
  97 {
  98         RSA *rsa;
  99         int ret, inlen = rsa_inlen;
 100
 101         if (inlen < 0)
 102                 return -E_RSA;
 103         ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
 104         if (ret < 0)
 105                 return ret;
 106         ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
 107         rsa_free(rsa);
 108         return (ret > 0)? ret : -E_DECRYPT;
 109 }
 110
 111 /**
 112  * decrypt the challenge number sent by para_server
 113  *
 114  * \param key_file full path of the rsa key
 115  * \param challenge_nr result is stored here
 116  * \param inbuf the input buffer
 117  * \param rsa_inlen the length of \a inbuf
 118  *
 119  * \return positive on success, negative on errors
 120  *
 121  * \sa para_decrypt_buffer()
 122  */
 123 int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
 124                 unsigned char *inbuf, unsigned rsa_inlen)
 125 {
 126         unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
 127         int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
 128
 129         if (ret >= 0) {
 130                 rsa_out[ret] = '\0';
 131                 ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1?
 132                         1 : -E_CHALLENGE;
 133         }
 134         OPENSSL_free(rsa_out);
 135         return ret;
 136 }
 137
 138 /**
 139  * encrypt a buffer using an RSA key
 140  *
 141  * \param rsa: public rsa key
 142  * \param inbuf the input buffer
 143  * \param len the length of \a inbuf
 144  * \param outbuf the output buffer
 145  *
 146  * \return The size of the encrypted data on success, negative on errors
 147  *
 148  * \sa RSA_public_encrypt(3)
 149  */
 150 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
 151                 unsigned len, unsigned char *outbuf)
 152 {
 153         int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 154
 155         if (flen < 0)
 156                 return -E_ENCRYPT;
 157         ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
 158         return ret < 0?  -E_ENCRYPT : ret;
 159 }
 160
 161 /**
 162  * encrypt the given challenge number
 163  *
 164  * \param rsa: public rsa key
 165  * \param challenge_nr the number to be encrypted
 166  * \param outbuf the output buffer
 167  *
 168  * \a outbuf must be at least 64 bytes long
 169  *
 170  * \return The size of the encrypted data on success, negative on errors
 171  *
 172  * \sa para_encrypt_buffer()
 173  *
 174  */
 175 int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
 176         unsigned char *outbuf)
 177 {
 178         unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr);
 179         int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf);
 180         free(inbuf);
 181         return ret;
 182 }
 183