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 int check_key_file(const char *file, int private)
  69 {
  70         struct stat st;
  71
  72         if (stat(file, &st) != 0)
  73                 return -ERRNO_TO_PARA_ERROR(errno);
  74         if (private != LOAD_PRIVATE_KEY)
  75                 return 0;
  76         if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0)
  77                 return -E_KEY_PERM;
  78         return 1;
  79 }
  80
  81 static EVP_PKEY *load_key(const char *file, int private)
  82 {
  83         BIO *key;
  84         EVP_PKEY *pkey = NULL;
  85         int ret = check_key_file(file, private);
  86
  87         if (ret < 0) {
  88                 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
  89                 return NULL;
  90         }
  91         key = BIO_new(BIO_s_file());
  92         if (!key)
  93                 return NULL;
  94         if (BIO_read_filename(key, file) > 0) {
  95                 if (private == LOAD_PRIVATE_KEY)
  96                         pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
  97                 else
  98                         pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
  99         }
 100         BIO_free(key);
 101         return pkey;
 102 }
 103
 104 /**
 105  * read an RSA key from a file
 106  *
 107  * \param key_file the file containing the key
 108  * \param rsa RSA structure is returned here
 109  * \param private if non-zero, read the private key, otherwise the public key
 110  *
 111  * \return The size of the RSA key on success, negative on errors.
 112  *
 113  * \sa openssl(1), rsa(1).
 114  */
 115 int get_rsa_key(char *key_file, RSA **rsa, int private)
 116 {
 117         EVP_PKEY *key = load_key(key_file, private);
 118
 119         if (!key)
 120                 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
 121                         : -E_PUBLIC_KEY;
 122         *rsa = EVP_PKEY_get1_RSA(key);
 123         EVP_PKEY_free(key);
 124         if (!*rsa)
 125                 return -E_RSA;
 126         return RSA_size(*rsa);
 127 }
 128
 129 /**
 130  * free an RSA structure
 131  *
 132  * \param rsa pointer to the RSA struct to free
 133  *
 134  * This must be called for any key obtained by get_rsa_key().
 135  */
 136 void rsa_free(RSA *rsa)
 137 {
 138         if (rsa)
 139                 RSA_free(rsa);
 140 }
 141
 142 /**
 143  * decrypt a buffer using an RSA key
 144  *
 145  * \param key_file full path of the rsa key
 146  * \param outbuf the output buffer
 147  * \param inbuf the encrypted input buffer
 148  * \param rsa_inlen the length of \a inbuf
 149  *
 150  * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
 151  *
 152  * \return The size of the recovered plaintext on success, negative on errors.
 153  *
 154  * \sa RSA_private_decrypt(3)
 155  **/
 156 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
 157                         unsigned rsa_inlen)
 158 {
 159         RSA *rsa;
 160         int ret, inlen = rsa_inlen;
 161
 162         if (inlen < 0)
 163                 return -E_RSA;
 164         ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
 165         if (ret < 0)
 166                 return ret;
 167         /*
 168          * RSA is vulnerable to timing attacks. Generate a random blinding
 169          * factor to protect against this kind of attack.
 170          */
 171         ret = -E_BLINDING;
 172         if (RSA_blinding_on(rsa, NULL) == 0)
 173                 goto out;
 174         ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_OAEP_PADDING);
 175         RSA_blinding_off(rsa);
 176         if (ret <= 0)
 177                 ret = -E_DECRYPT;
 178 out:
 179         rsa_free(rsa);
 180         return ret;
 181 }
 182
 183 /**
 184  * encrypt a buffer using an RSA key
 185  *
 186  * \param rsa: public rsa key
 187  * \param inbuf the input buffer
 188  * \param len the length of \a inbuf
 189  * \param outbuf the output buffer
 190  *
 191  * \return The size of the encrypted data on success, negative on errors
 192  *
 193  * \sa RSA_public_encrypt(3)
 194  */
 195 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
 196                 unsigned len, unsigned char *outbuf)
 197 {
 198         int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 199
 200         if (flen < 0)
 201                 return -E_ENCRYPT;
 202         ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_OAEP_PADDING);
 203         return ret < 0? -E_ENCRYPT : ret;
 204 }
 205
 206 /**
 207  * Encrypt and send a buffer.
 208  *
 209  * \param rc4c The rc4 crypt context.
 210  * \param buf The buffer to send.
 211  * \param len The size of \a buf in bytes.
 212  *
 213  * \return The return value of the underyling call to write_all().
 214  *
 215  * \sa \ref write_all(), RC4(3).
 216  */
 217 int rc4_send_bin_buffer(struct rc4_context *rc4c, const char *buf, size_t len)
 218 {
 219         int ret;
 220         unsigned char *tmp;
 221
 222         assert(len);
 223         tmp = para_malloc(len);
 224         RC4(&rc4c->send_key, len, (const unsigned char *)buf, tmp);
 225         ret = write_all(rc4c->fd, (char *)tmp, &len);
 226         free(tmp);
 227         return ret;
 228 }
 229
 230 /**
 231  * Encrypt and send a \p NULL-terminated buffer.
 232  *
 233  * \param rc4c The rc4 crypt context.
 234  * \param buf The buffer to send.
 235  *
 236  * \return The return value of the underyling call to rc4_send_bin_buffer().
 237  */
 238 int rc4_send_buffer(struct rc4_context *rc4c, const char *buf)
 239 {
 240         return rc4_send_bin_buffer(rc4c, buf, strlen(buf));
 241 }
 242
 243 /**
 244  * Format, encrypt and send a buffer.
 245  *
 246  * \param rc4c The rc4 crypt context.
 247  * \param fmt A format string.
 248  *
 249  * \return The return value of the underyling call to rc4_send_buffer().
 250  */
 251 __printf_2_3 int rc4_send_va_buffer(struct rc4_context *rc4c, const char *fmt, ...)
 252 {
 253         char *msg;
 254         int ret;
 255
 256         PARA_VSPRINTF(fmt, msg);
 257         ret = rc4_send_buffer(rc4c, msg);
 258         free(msg);
 259         return ret;
 260 }
 261
 262 /**
 263  * Receive a buffer and decrypt it.
 264  *
 265  * \param rc4c The rc4 crypt context.
 266  * \param buf The buffer to write the decrypted data to.
 267  * \param size The size of \a buf.
 268  *
 269  * \return The number of bytes received on success, negative on errors, zero if
 270  * the peer has performed an orderly shutdown.
 271  *
 272  * \sa recv(2), RC4(3).
 273  */
 274 int rc4_recv_bin_buffer(struct rc4_context *rc4c, char *buf, size_t size)
 275 {
 276         unsigned char *tmp = para_malloc(size);
 277         ssize_t ret = recv(rc4c->fd, tmp, size, 0);
 278
 279         if (ret > 0)
 280                 RC4(&rc4c->recv_key, ret, tmp, (unsigned char *)buf);
 281         else if (ret < 0)
 282                 ret = -ERRNO_TO_PARA_ERROR(errno);
 283         free(tmp);
 284         return ret;
 285 }
 286
 287 /**
 288  * Receive a buffer, decrypt it and write terminating NULL byte.
 289  *
 290  * \param rc4c The rc4 crypt context.
 291  * \param buf The buffer to write the decrypted data to.
 292  * \param size The size of \a buf.
 293  *
 294  * Read at most \a size - 1 bytes from file descriptor given by \a rc4c,
 295  * decrypt the received data and write a NULL byte at the end of the decrypted
 296  * data.
 297  *
 298  * \return The return value of the underlying call to \ref
 299  * rc4_recv_bin_buffer().
 300  */
 301 int rc4_recv_buffer(struct rc4_context *rc4c, char *buf, size_t size)
 302 {
 303         int n;
 304
 305         assert(size);
 306         n = rc4_recv_bin_buffer(rc4c, buf, size - 1);
 307         if (n >= 0)
 308                 buf[n] = '\0';
 309         else
 310                 *buf = '\0';
 311         return n;
 312 }