build: Support for CentOS7

CMakeLists.txt

@@ -83,6 +83,14 @@ if (UNIX)
         string(APPEND COMPILER_FLAGS " -D__RTP_NO_CRYPTO__")
     endif(DISABLE_CRYPTO)
 
+    # Check the getrandom() function exists
+    include(CheckCXXSymbolExists)
+    check_cxx_symbol_exists(getrandom sys/random.h HAVE_GETRANDOM)
+
+    if(HAVE_GETRANDOM)
+        add_compile_definitions(HAVE_GETRANDOM=1)
+    endif()
+
     # if (NOT "${LIBRARY_PATHS}" STREQUAL "")
     #     add_custom_command(TARGET uvgrtp POST_BUILD
     #         COMMAND ar crsT ARGS libuvgrtp_thin.a libuvgrtp.a ${LIBRARY_PATHS}

include/crypto.hh

@@ -1,5 +1,6 @@
 #pragma once
 
+#if __cplusplus >= 201703L
 #if __has_include(<cryptopp/aes.h>) && \
     __has_include(<cryptopp/base32.h>) && \
     __has_include(<cryptopp/cryptlib.h>) && \
@@ -24,6 +25,22 @@
 #include <cryptopp/crc.h>
 
 #endif
+#else // __cplusplus
+#ifndef __RTP_NO_CRYPTO__
+#define __RTP_CRYPTO__
+
+#include <cryptopp/aes.h>
+#include <cryptopp/base32.h>
+#include <cryptopp/cryptlib.h>
+#include <cryptopp/dh.h>
+#include <cryptopp/hmac.h>
+#include <cryptopp/modes.h>
+#include <cryptopp/osrng.h>
+#include <cryptopp/sha.h>
+#include <cryptopp/crc.h>
+
+#endif
+#endif // __cplusplus
 
 namespace uvgrtp {
 

src/random.cc

@@ -2,9 +2,14 @@
 #include <winsock2.h>
 #include <windows.h>
 #include <wincrypt.h>
-#else
+#else // _WIN32
+#ifdef HAVE_GETRANDOM
 #include <sys/random.h>
-#endif
+#else // HAVE_GETRANDOM
+#include <unistd.h>
+#include <sys/syscall.h>
+#endif // HAVE_GETRANDOM
+#endif // _WIN32
 
 #include <cstdlib>
 #include <ctime>
@@ -25,8 +30,27 @@ rtp_error_t uvgrtp::random::init()
 int uvgrtp::random::generate(void *buf, size_t n)
 {
 #ifdef __linux__
+#ifdef HAVE_GETRANDOM
     return getrandom(buf, n, 0);
-#else
+#else // HAVE_GETRANDOM
+
+    // Replace with the syscall
+    int read = syscall(SYS_getrandom, buf, n, 0);
+
+    // On error, return the same value as getrandom()
+    if (read == -EINTR || read == -ERESTART) {
+        errno = EINTR;
+        read = -1;
+    }
+
+    if (read < -1) {
+        errno = -read;
+        read = -1;
+    }
+
+    return read;
+#endif // HAVE_GETRANDOM
+#else // __linux__
     HCRYPTPROV hCryptProv;
     if (CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL, 0) == TRUE) {
         bool res = CryptGenRandom(hCryptProv, n, (BYTE *)buf);