Hi JF,
In http://reviews.llvm.org/D8134#136002, @jfb wrote:
> arc4random was broken for a short while on FreeBSD:
> http://lwn.net/Articles/633805/rss
> Not much can be done from libc++, but I'd avoid using it for a while on that
> platform so we can be reasonably certain they're fixed.
Just for the record, as Ed Maste ([email protected]) reported, arc4random()
was only broken in the development track of FreeBSD. There shouldn't be any
reason to not use it on supported versions of FreeBSD. For now I'll only enable
this on CloudABI (because it's needed to make libc++ build).
I've updated the patch to check for /dev/urandom on all architectures now. Be
sure to let me know what you think.
Thanks,
Ed
REPOSITORY
rL LLVM
http://reviews.llvm.org/D8134
Files:
include/__config
include/random
src/random.cpp
test/std/numerics/rand/rand.device/ctor.pass.cpp
EMAIL PREFERENCES
http://reviews.llvm.org/settings/panel/emailpreferences/
Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -110,12 +110,22 @@
# endif
#endif // __sun__
-#if defined(__native_client__)
+#if defined(__CloudABI__)
+ // Certain architectures provide arc4random(). Prefer using
+ // arc4random() over /dev/{u,}random to make it possible to obtain
+ // random data even when using sandboxing mechanisms such as chroots,
+ // Capsicum, etc.
+# define _LIBCPP_USING_ARC4_RANDOM
+#elif defined(__native_client__)
// NaCl's sandbox (which PNaCl also runs in) doesn't allow filesystem access,
// including accesses to the special files under /dev. C++11's
// std::random_device is instead exposed through a NaCl syscall.
# define _LIBCPP_USING_NACL_RANDOM
-#endif // defined(__native_client__)
+#elif defined(_WIN32)
+# define _LIBCPP_USING_WIN32_RANDOM
+#else
+# define _LIBCPP_USING_DEV_RANDOM
+#endif
#if !defined(_LIBCPP_LITTLE_ENDIAN) || !defined(_LIBCPP_BIG_ENDIAN)
# include <endian.h>
Index: include/random
===================================================================
--- include/random
+++ include/random
@@ -3475,9 +3475,9 @@
class _LIBCPP_TYPE_VIS random_device
{
-#if !(defined(_WIN32) || defined(_LIBCPP_USING_NACL_RANDOM))
+#ifdef _LIBCPP_USING_DEV_RANDOM
int __f_;
-#endif // !(defined(_WIN32) || defined(_LIBCPP_USING_NACL_RANDOM))
+#endif // defined(_LIBCPP_USING_DEV_RANDOM)
public:
// types
typedef unsigned result_type;
Index: src/random.cpp
===================================================================
--- src/random.cpp
+++ src/random.cpp
@@ -7,11 +7,10 @@
//
//===----------------------------------------------------------------------===//
-#if defined(_WIN32)
+#if defined(_LIBCPP_USING_WIN32_RANDOM)
// Must be defined before including stdlib.h to enable rand_s().
#define _CRT_RAND_S
-#include <stdio.h>
-#endif // defined(_WIN32)
+#endif // defined(_LIBCPP_USING_WIN32_RANDOM)
#include "random"
#include "system_error"
@@ -19,21 +18,27 @@
#if defined(__sun__)
#define rename solaris_headers_are_broken
#endif // defined(__sun__)
-#if !defined(_WIN32)
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#if defined(_LIBCPP_USING_DEV_RANDOM)
#include <fcntl.h>
#include <unistd.h>
-#endif // !defined(_WIN32)
-#include <errno.h>
-#if defined(_LIBCPP_USING_NACL_RANDOM)
+#elif defined(_LIBCPP_USING_NACL_RANDOM)
#include <nacl/nacl_random.h>
-#endif // defined(_LIBCPP_USING_NACL_RANDOM)
+#endif
+
_LIBCPP_BEGIN_NAMESPACE_STD
-#if defined(_WIN32)
+#if defined(_LIBCPP_USING_ARC4_RANDOM)
random_device::random_device(const string&)
{
+ if (__token != "/dev/urandom")
+ __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
}
random_device::~random_device()
@@ -43,10 +48,43 @@
unsigned
random_device::operator()()
{
+ return arc4random();
+}
+
+#elif defined(_LIBCPP_USING_DEV_RANDOM)
+
+random_device::random_device(const string& __token)
+ : __f_(open(__token.c_str(), O_RDONLY))
+{
+ if (__f_ < 0)
+ __throw_system_error(errno, ("random_device failed to open " + __token).c_str());
+}
+
+random_device::~random_device()
+{
+ close(__f_);
+}
+
+unsigned
+random_device::operator()()
+{
unsigned r;
- errno_t err = rand_s(&r);
- if (err)
- __throw_system_error(err, "random_device rand_s failed.");
+ size_t n = sizeof(r);
+ char* p = reinterpret_cast<char*>(&r);
+ while (n > 0)
+ {
+ ssize_t s = read(__f_, p, n);
+ if (s == 0)
+ __throw_system_error(ENODATA, "random_device got EOF");
+ if (s == -1)
+ {
+ if (errno != EINTR)
+ __throw_system_error(errno, "random_device got an unexpected error");
+ continue;
+ }
+ n -= static_cast<size_t>(s);
+ p += static_cast<size_t>(s);
+ }
return r;
}
@@ -79,18 +117,16 @@
return r;
}
-#else // !defined(_WIN32) && !defined(_LIBCPP_USING_NACL_RANDOM)
+#elif defined(_LIBCPP_USING_WIN32_RANDOM)
-random_device::random_device(const string& __token)
- : __f_(open(__token.c_str(), O_RDONLY))
+random_device::random_device(const string&)
{
- if (__f_ < 0)
- __throw_system_error(errno, ("random_device failed to open " + __token).c_str());
+ if (__token != "/dev/urandom")
+ __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
}
random_device::~random_device()
{
- close(__f_);
}
unsigned
@@ -97,26 +133,15 @@
random_device::operator()()
{
unsigned r;
- size_t n = sizeof(r);
- char* p = reinterpret_cast<char*>(&r);
- while (n > 0)
- {
- ssize_t s = read(__f_, p, n);
- if (s == 0)
- __throw_system_error(ENODATA, "random_device got EOF");
- if (s == -1)
- {
- if (errno != EINTR)
- __throw_system_error(errno, "random_device got an unexpected error");
- continue;
- }
- n -= static_cast<size_t>(s);
- p += static_cast<size_t>(s);
- }
+ errno_t err = rand_s(&r);
+ if (err)
+ __throw_system_error(err, "random_device rand_s failed.");
return r;
}
-#endif // defined(_WIN32) || defined(_LIBCPP_USING_NACL_RANDOM)
+#else
+#error "Random device not implemented for this architecture"
+#endif
double
random_device::entropy() const _NOEXCEPT
Index: test/std/numerics/rand/rand.device/ctor.pass.cpp
===================================================================
--- test/std/numerics/rand/rand.device/ctor.pass.cpp
+++ test/std/numerics/rand/rand.device/ctor.pass.cpp
@@ -23,14 +23,12 @@
#include <unistd.h>
bool is_valid_random_device(const std::string &token) {
-#if defined(_WIN32)
- return true;
-#elif defined(_LIBCPP_USING_NACL_RANDOM)
- return token == "/dev/urandom";
-#else // !defined(_WIN32) && !defined(_LIBCPP_USING_NACL_RANDOM)
+#if defined(_LIBCPP_USING_DEV_RANDOM)
// Not an exhaustive list: they're the only tokens that are tested below.
return token == "/dev/urandom" || token == "/dev/random";
-#endif // defined(_WIN32) || defined(_LIBCPP_USING_NACL_RANDOM)
+#else
+ return token == "/dev/urandom";
+#endif
}
void check_random_device_valid(const std::string &token) {
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