crypt.c

   1 /*
   2  * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file crypt.c openssl-based RSA encryption/decryption routines */
   8
   9 #include <regex.h>
  10 #include <dirent.h>
  11 #include <sys/types.h>
  12 #include <sys/socket.h>
  13 #include <openssl/rand.h>
  14 #include <openssl/err.h>
  15 #include <openssl/rc4.h>
  16
  17 #include "para.h"
  18 #include "error.h"
  19 #include "string.h"
  20 #include "crypt.h"
  21 #include "fd.h"
  22 /**
  23  * Fill a buffer with random content.
  24  *
  25  * \param buf The buffer to fill.
  26  * \param num The size of \a buf in bytes.
  27  *
  28  * This function puts \a num cryptographically strong pseudo-random bytes into
  29  * buf. If libssl can not guarantee an unpredictable byte sequence (for example
  30  * because the PRNG has not been seeded with enough randomness) the function
  31  * logs an error message and calls exit().
  32  */
  33 void get_random_bytes_or_die(unsigned char *buf, int num)
  34 {
  35         unsigned long err;
  36
  37         /* RAND_bytes() returns 1 on success, 0 otherwise. */
  38         if (RAND_bytes(buf, num) == 1)
  39                 return;
  40         err = ERR_get_error();
  41         PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
  42         exit(EXIT_FAILURE);
  43 }
  44
  45 /**
  46  * Seed pseudo random number generators.
  47  *
  48  * This function reads 64 bytes from /dev/urandom and adds them to the SSL
  49  * PRNG. It also seeds the PRNG used by random() with a random seed obtained
  50  * from SSL. If /dev/random could not be read, an error message is logged and
  51  * the function calls exit().
  52  *
  53  * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
  54  * random(3), \ref para_random().
  55  */
  56 void init_random_seed_or_die(void)
  57 {
  58         int seed, ret = RAND_load_file("/dev/urandom", 64);
  59
  60         if (ret != 64) {
  61                 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
  62                 exit(EXIT_FAILURE);
  63         }
  64         get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
  65         srandom(seed);
  66 }
  67
  68 static EVP_PKEY *load_key(const char *file, int private)
  69 {
  70         BIO *key;
  71         EVP_PKEY *pkey = NULL;
  72
  73         key = BIO_new(BIO_s_file());
  74         if (!key)
  75                 return NULL;
  76         if (BIO_read_filename(key, file) > 0) {
  77                 if (private == LOAD_PRIVATE_KEY)
  78                         pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
  79                 else
  80                         pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
  81         }
  82         BIO_free(key);
  83         return pkey;
  84 }
  85
  86 /**
  87  * read an RSA key from a file
  88  *
  89  * \param key_file the file containing the key
  90  * \param rsa RSA structure is returned here
  91  * \param private if non-zero, read the private key, otherwise the public key
  92  *
  93  * \return The size of the RSA key on success, negative on errors.
  94  *
  95  * \sa openssl(1), rsa(1).
  96  */
  97 int get_rsa_key(char *key_file, RSA **rsa, int private)
  98 {
  99         EVP_PKEY *key = load_key(key_file, private);
 100
 101         if (!key)
 102                 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
 103                         : -E_PUBLIC_KEY;
 104         *rsa = EVP_PKEY_get1_RSA(key);
 105         EVP_PKEY_free(key);
 106         if (!*rsa)
 107                 return -E_RSA;
 108         return RSA_size(*rsa);
 109 }
 110
 111 /**
 112  * free an RSA structure
 113  *
 114  * \param rsa pointer to the RSA struct to free
 115  *
 116  * This must be called for any key obtained by get_rsa_key().
 117  */
 118 void rsa_free(RSA *rsa)
 119 {
 120         if (rsa)
 121                 RSA_free(rsa);
 122 }
 123
 124 /**
 125  * decrypt a buffer using an RSA key
 126  *
 127  * \param key_file full path of the rsa key
 128  * \param outbuf the output buffer
 129  * \param inbuf the encrypted input buffer
 130  * \param rsa_inlen the length of \a inbuf
 131  *
 132  * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
 133  *
 134  * \return The size of the recovered plaintext on success, negative on errors.
 135  *
 136  * \sa RSA_private_decrypt(3)
 137  **/
 138 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
 139                         unsigned rsa_inlen)
 140 {
 141         RSA *rsa;
 142         int ret, inlen = rsa_inlen;
 143
 144         if (inlen < 0)
 145                 return -E_RSA;
 146         ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
 147         if (ret < 0)
 148                 return ret;
 149         ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_OAEP_PADDING);
 150         rsa_free(rsa);
 151         return (ret > 0)? ret : -E_DECRYPT;
 152 }
 153
 154 /**
 155  * encrypt a buffer using an RSA key
 156  *
 157  * \param rsa: public rsa key
 158  * \param inbuf the input buffer
 159  * \param len the length of \a inbuf
 160  * \param outbuf the output buffer
 161  *
 162  * \return The size of the encrypted data on success, negative on errors
 163  *
 164  * \sa RSA_public_encrypt(3)
 165  */
 166 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
 167                 unsigned len, unsigned char *outbuf)
 168 {
 169         int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 170
 171         if (flen < 0)
 172                 return -E_ENCRYPT;
 173         ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_OAEP_PADDING);
 174         return ret < 0? -E_ENCRYPT : ret;
 175 }
 176
 177 /**
 178  * Encrypt and send a buffer.
 179  *
 180  * \param rc4c The rc4 crypt context.
 181  * \param buf The buffer to send.
 182  * \param len The size of \a buf in bytes.
 183  *
 184  * \return The return value of the underyling call to write_all().
 185  *
 186  * \sa \ref write_all(), RC4(3).
 187  */
 188 int rc4_send_bin_buffer(struct rc4_context *rc4c, const char *buf, size_t len)
 189 {
 190         int ret;
 191         unsigned char *tmp;
 192
 193         assert(len);
 194         tmp = para_malloc(len);
 195         RC4(&rc4c->send_key, len, (const unsigned char *)buf, tmp);
 196         ret = write_all(rc4c->fd, (char *)tmp, &len);
 197         free(tmp);
 198         return ret;
 199 }
 200
 201 /**
 202  * Encrypt and send a \p NULL-terminated buffer.
 203  *
 204  * \param rc4c The rc4 crypt context.
 205  * \param buf The buffer to send.
 206  *
 207  * \return The return value of the underyling call to rc4_send_bin_buffer().
 208  */
 209 int rc4_send_buffer(struct rc4_context *rc4c, const char *buf)
 210 {
 211         return rc4_send_bin_buffer(rc4c, buf, strlen(buf));
 212 }
 213
 214 /**
 215  * Format, encrypt and send a buffer.
 216  *
 217  * \param rc4c The rc4 crypt context.
 218  * \param fmt A format string.
 219  *
 220  * \return The return value of the underyling call to rc4_send_buffer().
 221  */
 222 __printf_2_3 int rc4_send_va_buffer(struct rc4_context *rc4c, const char *fmt, ...)
 223 {
 224         char *msg;
 225         int ret;
 226
 227         PARA_VSPRINTF(fmt, msg);
 228         ret = rc4_send_buffer(rc4c, msg);
 229         free(msg);
 230         return ret;
 231 }
 232
 233 /**
 234  * Receive a buffer and decrypt it.
 235  *
 236  * \param rc4c The rc4 crypt context.
 237  * \param buf The buffer to write the decrypted data to.
 238  * \param size The size of \a buf.
 239  *
 240  * \return The number of bytes received on success, negative on errors, zero if
 241  * the peer has performed an orderly shutdown.
 242  *
 243  * \sa recv(2), RC4(3).
 244  */
 245 int rc4_recv_bin_buffer(struct rc4_context *rc4c, char *buf, size_t size)
 246 {
 247         unsigned char *tmp = para_malloc(size);
 248         ssize_t ret = recv(rc4c->fd, tmp, size, 0);
 249
 250         if (ret > 0)
 251                 RC4(&rc4c->recv_key, ret, tmp, (unsigned char *)buf);
 252         else if (ret < 0)
 253                 ret = -ERRNO_TO_PARA_ERROR(errno);
 254         free(tmp);
 255         return ret;
 256 }
 257
 258 /**
 259  * Receive a buffer, decrypt it and write terminating NULL byte.
 260  *
 261  * \param rc4c The rc4 crypt context.
 262  * \param buf The buffer to write the decrypted data to.
 263  * \param size The size of \a buf.
 264  *
 265  * Read at most \a size - 1 bytes from file descriptor given by \a rc4c,
 266  * decrypt the received data and write a NULL byte at the end of the decrypted
 267  * data.
 268  *
 269  * \return The return value of the underlying call to \ref
 270  * rc4_recv_bin_buffer().
 271  */
 272 int rc4_recv_buffer(struct rc4_context *rc4c, char *buf, size_t size)
 273 {
 274         int n;
 275
 276         assert(size);
 277         n = rc4_recv_bin_buffer(rc4c, buf, size - 1);
 278         if (n >= 0)
 279                 buf[n] = '\0';
 280         else
 281                 *buf = '\0';
 282         return n;
 283 }