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Merge branch 'better-entropy' (pull request #30)
This commit is contained in:
Sebastian Pipping
commit
64f3cf982a
4 changed files with 184 additions and 17 deletions
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@ -2,6 +2,13 @@ Release ??????????
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Security fixes:
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CVE-2016-9063 -- Detect integer overflow
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#25 More integer overflow detection (function poolGrow)
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Use high quality entropy for hash initialization:
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* arc4random_buf on BSD, systems with libbsd
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(when configured with --with-libbsd), CloudABI
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* RtlGenRandom on Windows XP / Server 2003 and later
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* getrandom on Linux 3.17+
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In a way, that's still part of CVE-2016-5300.
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For run-time debug output, EXPAT_ENTROPY_DEBUG=1 can be used.
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Bug fixes:
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#539 Fix regression from fix to CVE-2016-0718 cutting off
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@ -124,7 +124,7 @@ LTFLAGS = --verbose
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COMPILE = $(CC) $(INCLUDES) $(CFLAGS) $(DEFS) $(CPPFLAGS)
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CXXCOMPILE = $(CXX) $(INCLUDES) $(CXXFLAGS) $(DEFS) $(CPPFLAGS)
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LTCOMPILE = $(LIBTOOL) $(LTFLAGS) --mode=compile $(COMPILE)
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LINK_LIB = $(LIBTOOL) $(LTFLAGS) --mode=link $(COMPILE) -no-undefined $(VSNFLAG) -rpath $(libdir) $(LDFLAGS) -o $@
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LINK_LIB = $(LIBTOOL) $(LTFLAGS) --mode=link $(COMPILE) -no-undefined $(VSNFLAG) -rpath $(libdir) $(LDFLAGS) @LIBS@ -o $@
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LINK_EXE = $(LIBTOOL) $(LTFLAGS) --mode=link $(COMPILE) $(LDFLAGS) -o $@
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LINK_CXX_EXE = $(LIBTOOL) $(LTFLAGS) --mode=link $(CXXCOMPILE) $(LDFLAGS) -o $@
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@ -99,6 +99,69 @@ AC_C_CONST
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AC_TYPE_SIZE_T
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AC_CHECK_FUNCS(memmove bcopy)
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AC_ARG_WITH([libbsd], [
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AS_HELP_STRING([--with-libbsd], [utilize libbsd (for arc4random_buf)])
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], [], [with_libbsd=no])
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AS_IF([test "x${with_libbsd}" != xno], [
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AC_CHECK_LIB([bsd], [arc4random_buf], [], [
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AS_IF([test "x${with_libbsd}" = xyes], [
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AC_MSG_ERROR([Enforced use of libbsd cannot be satisfied.])
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])
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])
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])
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AC_MSG_CHECKING([for arc4random_buf (BSD or libbsd)])
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AC_LINK_IFELSE([AC_LANG_SOURCE([
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#include <stdlib.h> /* for arc4random_buf on BSD, for NULL */
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#if defined(HAVE_LIBBSD)
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# include <bsd/stdlib.h>
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#endif
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int main() {
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arc4random_buf(NULL, 0U);
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return 0;
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}
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])], [
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AC_DEFINE([HAVE_ARC4RANDOM_BUF], [1],
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[Define to 1 if you have the `arc4random_buf' function.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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])
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AC_MSG_CHECKING([for getrandom (Linux 3.17+, glibc 2.25+)])
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([
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#include <stdlib.h> /* for NULL */
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#include <sys/random.h>
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int main() {
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return getrandom(NULL, 0U, 0U);
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}
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])], [
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AC_DEFINE([HAVE_GETRANDOM], [1],
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[Define to 1 if you have the `getrandom' function.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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AC_MSG_CHECKING([for syscall SYS_getrandom (Linux 3.17+)])
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AC_LINK_IFELSE([AC_LANG_SOURCE([
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#include <stdlib.h> /* for NULL */
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#include <unistd.h> /* for syscall */
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#include <sys/syscall.h> /* for SYS_getrandom */
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int main() {
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syscall(SYS_getrandom, NULL, 0, 0);
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return 0;
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}
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])], [
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AC_DEFINE([HAVE_SYSCALL_GETRANDOM], [1],
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[Define to 1 if you have `syscall' and `SYS_getrandom'.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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])
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])
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dnl Only needed for xmlwf:
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AC_CHECK_HEADERS(fcntl.h unistd.h)
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AC_TYPE_OFF_T
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@ -2,10 +2,14 @@
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See the file COPYING for copying permission.
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*/
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#define _GNU_SOURCE /* syscall prototype */
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#include <stddef.h>
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#include <string.h> /* memset(), memcpy() */
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#include <assert.h>
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#include <limits.h> /* UINT_MAX */
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#include <stdio.h> /* fprintf */
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#include <stdlib.h> /* getenv */
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#ifdef _WIN32
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#define getpid GetCurrentProcessId
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@ -697,6 +701,80 @@ static const XML_Char implicitContext[] = {
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ASCII_s, ASCII_p, ASCII_a, ASCII_c, ASCII_e, '\0'
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};
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#if defined(HAVE_GETRANDOM) || defined(HAVE_SYSCALL_GETRANDOM)
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# include <errno.h>
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# if defined(HAVE_GETRANDOM)
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# include <sys/random.h> /* getrandom */
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# else
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# include <unistd.h> /* syscall */
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# include <sys/syscall.h> /* SYS_getrandom */
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# endif
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/* Obtain entropy on Linux 3.17+ */
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static int
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writeRandomBytes_getrandom(void * target, size_t count) {
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int success = 0; /* full count bytes written? */
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size_t bytesWrittenTotal = 0;
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const unsigned int getrandomFlags = 0;
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do {
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void * const currentTarget = (void*)((char*)target + bytesWrittenTotal);
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const size_t bytesToWrite = count - bytesWrittenTotal;
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const int bytesWrittenMore =
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#if defined(HAVE_GETRANDOM)
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getrandom(currentTarget, bytesToWrite, getrandomFlags);
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#else
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syscall(SYS_getrandom, currentTarget, bytesToWrite, getrandomFlags);
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#endif
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if (bytesWrittenMore > 0) {
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bytesWrittenTotal += bytesWrittenMore;
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if (bytesWrittenTotal >= count)
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success = 1;
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}
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} while (! success && (errno == EINTR || errno == EAGAIN));
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return success;
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}
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#endif /* defined(HAVE_GETRANDOM) || defined(HAVE_SYSCALL_GETRANDOM) */
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#ifdef _WIN32
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typedef BOOLEAN (APIENTRY *RTLGENRANDOM_FUNC)(PVOID, ULONG);
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/* Obtain entropy on Windows XP / Windows Server 2003 and later.
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* Hint on RtlGenRandom and the following article from libsodioum.
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*
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* Michael Howard: Cryptographically Secure Random number on Windows without using CryptoAPI
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* https://blogs.msdn.microsoft.com/michael_howard/2005/01/14/cryptographically-secure-random-number-on-windows-without-using-cryptoapi/
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*/
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static int
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writeRandomBytes_RtlGenRandom(void * target, size_t count) {
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int success = 0; /* full count bytes written? */
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const HMODULE advapi32 = LoadLibrary("ADVAPI32.DLL");
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if (advapi32) {
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const RTLGENRANDOM_FUNC RtlGenRandom
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= (RTLGENRANDOM_FUNC)GetProcAddress(advapi32, "SystemFunction036");
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if (RtlGenRandom) {
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if (RtlGenRandom((PVOID)target, (ULONG)count) == TRUE) {
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success = 1;
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}
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}
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FreeLibrary(advapi32);
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}
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return success;
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}
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#endif /* _WIN32 */
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static unsigned long
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gather_time_entropy(void)
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{
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@ -716,34 +794,53 @@ gather_time_entropy(void)
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#endif
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}
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#if defined(HAVE_ARC4RANDOM_BUF) && defined(HAVE_LIBBSD)
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# include <bsd/stdlib.h>
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#endif
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static unsigned long
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ENTROPY_DEBUG(const char * label, unsigned long entropy) {
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const char * const EXPAT_ENTROPY_DEBUG = getenv("EXPAT_ENTROPY_DEBUG");
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if (EXPAT_ENTROPY_DEBUG && ! strcmp(EXPAT_ENTROPY_DEBUG, "1")) {
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fprintf(stderr, "Entropy: %s --> 0x%0*lx (%lu bytes)\n",
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label,
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(int)sizeof(unsigned long) * 2, entropy,
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sizeof(unsigned long));
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}
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return entropy;
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}
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static unsigned long
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generate_hash_secret_salt(XML_Parser parser)
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{
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#if defined(__UINTPTR_TYPE__)
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# define PARSER_CAST(p) (__UINTPTR_TYPE__)(p)
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#elif defined(_WIN64) && defined(_MSC_VER)
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# define PARSER_CAST(p) (unsigned __int64)(p)
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#else
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# define PARSER_CAST(p) (p)
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#endif
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#ifdef __CloudABI__
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unsigned long entropy;
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(void)parser;
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#if defined(HAVE_ARC4RANDOM_BUF) || defined(__CloudABI__)
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(void)gather_time_entropy;
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arc4random_buf(&entropy, sizeof(entropy));
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return entropy;
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return ENTROPY_DEBUG("arc4random_buf", entropy);
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#else
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/* Process ID is 0 bits entropy if attacker has local access
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* XML_Parser address is few bits of entropy if attacker has local access */
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const unsigned long entropy =
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gather_time_entropy() ^ getpid() ^ (unsigned long)PARSER_CAST(parser);
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/* Try high quality providers first .. */
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#ifdef _WIN32
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if (writeRandomBytes_RtlGenRandom((void *)&entropy, sizeof(entropy))) {
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return ENTROPY_DEBUG("RtlGenRandom", entropy);
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}
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#elif defined(HAVE_GETRANDOM) || defined(HAVE_SYSCALL_GETRANDOM)
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if (writeRandomBytes_getrandom((void *)&entropy, sizeof(entropy))) {
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return ENTROPY_DEBUG("getrandom", entropy);
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}
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#endif
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/* .. and self-made low quality for backup: */
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/* Process ID is 0 bits entropy if attacker has local access */
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entropy = gather_time_entropy() ^ getpid();
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/* Factors are 2^31-1 and 2^61-1 (Mersenne primes M31 and M61) */
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if (sizeof(unsigned long) == 4) {
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return entropy * 2147483647;
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return ENTROPY_DEBUG("fallback(4)", entropy * 2147483647);
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} else {
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return entropy * (unsigned long)2305843009213693951;
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return ENTROPY_DEBUG("fallback(8)",
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entropy * (unsigned long)2305843009213693951);
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}
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#endif
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}
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