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