Make rc4 encryption/decryption more explicit.

[paraslash.git] / crypt.c

diff --git a/crypt.c b/crypt.c
index 6d394530ffe19a5ab9294fb6f6021d0bf0490410..679ba35dd07d59ec184942524f8a1bb0be786939 100644 (file)
--- a/crypt.c
+++ b/crypt.c
@@ -1,15 +1,68 @@
 /*
- * Copyright (C) 2005-2007 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
 
 /** \file crypt.c openssl-based RSA encryption/decryption routines */
 
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <openssl/rand.h>
+#include <openssl/err.h>
+#include <openssl/rc4.h>
+
 #include "para.h"
 #include "error.h"
 #include "string.h"
 #include "crypt.h"
+#include "fd.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)
 {
@@ -170,3 +223,110 @@ int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
        return ret;
 }
 
+/**
+ * Encrypt and send a buffer.
+ *
+ * \param rc4c The rc4 crypt context.
+ * \param buf The buffer to send.
+ * \param len The size of \a buf in bytes.
+ *
+ * \return The return value of the underyling call to write_all().
+ *
+ * \sa \ref write_all(), RC4(3).
+ */
+int rc4_send_bin_buffer(struct rc4_context *rc4c, const char *buf, size_t len)
+{
+       int ret;
+       unsigned char *tmp;
+
+       assert(len);
+       tmp = para_malloc(len);
+       RC4(&rc4c->send_key, len, (const unsigned char *)buf, tmp);
+       ret = write_all(rc4c->fd, (char *)tmp, &len);
+       free(tmp);
+       return ret;
+}
+
+/**
+ * Encrypt and send a \p NULL-terminated buffer.
+ *
+ * \param rc4c The rc4 crypt context.
+ * \param buf The buffer to send.
+ *
+ * \return The return value of the underyling call to rc4_send_bin_buffer().
+ */
+int rc4_send_buffer(struct rc4_context *rc4c, const char *buf)
+{
+       return rc4_send_bin_buffer(rc4c, buf, strlen(buf));
+}
+
+/**
+ * Format, encrypt and send a buffer.
+ *
+ * \param rc4c The rc4 crypt context.
+ * \param fmt A format string.
+ *
+ * \return The return value of the underyling call to rc4_send_buffer().
+ */
+__printf_2_3 int rc4_send_va_buffer(struct rc4_context *rc4c, const char *fmt, ...)
+{
+       char *msg;
+       int ret;
+
+       PARA_VSPRINTF(fmt, msg);
+       ret = rc4_send_buffer(rc4c, msg);
+       free(msg);
+       return ret;
+}
+
+/**
+ * Receive a buffer and decrypt it.
+ *
+ * \param rc4c The rc4 crypt context.
+ * \param buf The buffer to write the decrypted data to.
+ * \param size The size of \a buf.
+ *
+ * \return The number of bytes received on success, negative on errors, zero if
+ * the peer has performed an orderly shutdown.
+ *
+ * \sa recv(2), RC4(3).
+ */
+int rc4_recv_bin_buffer(struct rc4_context *rc4c, char *buf, size_t size)
+{
+       unsigned char *tmp = para_malloc(size);
+       ssize_t ret = recv(rc4c->fd, tmp, size, 0);
+
+       if (ret > 0)
+               RC4(&rc4c->recv_key, ret, tmp, (unsigned char *)buf);
+       else if (ret < 0)
+               ret = -ERRNO_TO_PARA_ERROR(errno);
+       free(tmp);
+       return ret;
+}
+
+/**
+ * Receive a buffer, decrypt it and write terminating NULL byte.
+ *
+ * \param rc4c The rc4 crypt context.
+ * \param buf The buffer to write the decrypted data to.
+ * \param size The size of \a buf.
+ *
+ * Read at most \a size - 1 bytes from file descriptor given by \a rc4c,
+ * decrypt the received data and write a NULL byte at the end of the decrypted
+ * data.
+ *
+ * \return The return value of the underlying call to \ref
+ * rc4_recv_bin_buffer().
+ */
+int rc4_recv_buffer(struct rc4_context *rc4c, char *buf, size_t size)
+{
+       int n;
+
+       assert(size);
+       n = rc4_recv_bin_buffer(rc4c, buf, size - 1);
+       if (n >= 0)
+               buf[n] = '\0';
+       else
+               *buf = '\0';
+       return n;
+}