Use openssl's RAND_load_file() and RAND_bytes() to get randomness.

[paraslash.git] / crypt.c

diff --git a/crypt.c b/crypt.c
index 46a90533489696df9c3fb2eff665535b3bf2e0bf..580974d7d74a6b97d1f4b2d6a436adc98ba7408b 100644 (file)
--- a/crypt.c
+++ b/crypt.c
@@ -1,19 +1,7 @@
 /*
- * Copyright (C) 2005-2007 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
  *
- *     This program is free software; you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation; either version 2 of the License, or
- *     (at your option) any later version.
- *
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- *
- *     You should have received a copy of the GNU General Public License
- *     along with this program; if not, write to the Free Software
- *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
+ * Licensed under the GPL v2. For licencing details see COPYING.
  */
 
 /** \file crypt.c openssl-based RSA encryption/decryption routines */
@@ -22,6 +10,54 @@
 #include "error.h"
 #include "string.h"
 #include "crypt.h"
+#include <openssl/rand.h>
+#include <openssl/err.h>
+
+/**
+ * Fill a buffer with random content.
+ *
+ * \param buf The buffer to fill.
+ * \param num The size of \a buf in bytes.
+ *
+ * This function puts \a num cryptographically strong pseudo-random bytes into
+ * buf. If libssl can not guarantee an unpredictable byte sequence (for example
+ * because the PRNG has not been seeded with enough randomness) the function
+ * logs an error message and calls exit().
+ */
+void get_random_bytes_or_die(unsigned char *buf, int num)
+{
+       unsigned long err;
+
+       /* RAND_bytes() returns 1 on success, 0 otherwise. */
+       if (RAND_bytes(buf, num) == 1)
+               return;
+       err = ERR_get_error();
+       PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
+       exit(EXIT_FAILURE);
+}
+
+/**
+ * Seed pseudo random number generators.
+ *
+ * This function reads 64 bytes from /dev/urandom and adds them to the SSL
+ * PRNG. It also seeds the PRNG used by random() with a random seed obtained
+ * from SSL. If /dev/random could not be read, an error message is logged and
+ * the function calls exit().
+ *
+ * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
+ * random(3), \ref para_random().
+ */
+void init_random_seed_or_die(void)
+{
+       int seed, ret = RAND_load_file("/dev/urandom", 64);
+
+       if (ret != 64) {
+               PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
+               exit(EXIT_FAILURE);
+       }
+       get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
+       srandom(seed);
+}
 
 static EVP_PKEY *load_key(const char *file, int private)
 {
@@ -57,7 +93,8 @@ int get_rsa_key(char *key_file, RSA **rsa, int private)
        EVP_PKEY *key = load_key(key_file, private);
 
        if (!key)
-               return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY : -E_PUBLIC_KEY;
+               return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
+                       : -E_PUBLIC_KEY;
        *rsa = EVP_PKEY_get1_RSA(key);
        EVP_PKEY_free(key);
        if (!*rsa)
@@ -93,14 +130,18 @@ void rsa_free(RSA *rsa)
  * \sa RSA_private_decrypt(3)
  **/
 int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
-                       int rsa_inlen)
+                       unsigned rsa_inlen)
 {
        RSA *rsa;
-       int ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
+       int ret, inlen = rsa_inlen;
 
+       if (inlen < 0)
+               return -E_RSA;
+       ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
        if (ret < 0)
                return ret;
-       ret = RSA_private_decrypt(rsa_inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
+       ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
+       rsa_free(rsa);
        return (ret > 0)? ret : -E_DECRYPT;
 }
 
@@ -117,7 +158,7 @@ int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *in
  * \sa para_decrypt_buffer()
  */
 int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
-               unsigned char *inbuf, int rsa_inlen)
+               unsigned char *inbuf, unsigned rsa_inlen)
 {
        unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
        int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
@@ -144,10 +185,13 @@ int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
  * \sa RSA_public_encrypt(3)
  */
 int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
-               const unsigned len, unsigned char *outbuf)
+               unsigned len, unsigned char *outbuf)
 {
-       int ret = RSA_public_encrypt(len, inbuf, outbuf, rsa,
-               RSA_PKCS1_PADDING);
+       int ret, flen = len; /* RSA_public_encrypt expects a signed int */
+
+       if (flen < 0)
+               return -E_ENCRYPT;
+       ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
        return ret < 0?  -E_ENCRYPT : ret;
 }