[libcxx] r231764 - Add support for arc4random() to random_device.
Ed Schouten
ed at 80386.nl
Tue Mar 10 00:46:06 PDT 2015
Author: ed
Date: Tue Mar 10 02:46:06 2015
New Revision: 231764
URL: http://llvm.org/viewvc/llvm-project?rev=231764&view=rev
Log:
Add support for arc4random() to random_device.
Nuxi CloudABI (https://github.com/NuxiNL/cloudlibc) does not allow
processes to access the global filesystem namespace. This breaks
random_device, as it attempts to use /dev/{u,}random. This change adds
support for arc4random(), which is present on CloudABI.
In my opinion it would also make sense to use arc4random() on other
operating systems, such as *BSD and Mac OS X, but I'd rather leave that
to the maintainers of the respective platforms. Switching to
arc4random() does change the ABI.
This change also attempts to make some cleanups to the code. It adds a
single #define for every random interface, instead of testing against
operating systems explicitly.
As discussed, also validate the token argument to be equal to
"/dev/urandom" on all systems that only provide pseudo-random numbers.
This should cause little to no breakage, as "/dev/urandom" is also the
default argument value.
Reviewed by: jfb
Differential Revision: http://reviews.llvm.org/D8134
Modified:
libcxx/trunk/include/__config
libcxx/trunk/include/random
libcxx/trunk/src/random.cpp
libcxx/trunk/test/std/numerics/rand/rand.device/ctor.pass.cpp
Modified: libcxx/trunk/include/__config
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__config?rev=231764&r1=231763&r2=231764&view=diff
==============================================================================
--- libcxx/trunk/include/__config (original)
+++ libcxx/trunk/include/__config Tue Mar 10 02:46:06 2015
@@ -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>
Modified: libcxx/trunk/include/random
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/random?rev=231764&r1=231763&r2=231764&view=diff
==============================================================================
--- libcxx/trunk/include/random (original)
+++ libcxx/trunk/include/random Tue Mar 10 02:46:06 2015
@@ -3475,9 +3475,9 @@ typedef shuffle_order_engine<minstd_rand
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;
Modified: libcxx/trunk/src/random.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/random.cpp?rev=231764&r1=231763&r2=231764&view=diff
==============================================================================
--- libcxx/trunk/src/random.cpp (original)
+++ libcxx/trunk/src/random.cpp Tue Mar 10 02:46:06 2015
@@ -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&)
+random_device::random_device(const string& __token)
{
+ if (__token != "/dev/urandom")
+ __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
}
random_device::~random_device()
@@ -43,10 +48,43 @@ random_device::~random_device()
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;
}
@@ -79,44 +117,31 @@ random_device::operator()()
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))
{
- 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
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
Modified: libcxx/trunk/test/std/numerics/rand/rand.device/ctor.pass.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/numerics/rand/rand.device/ctor.pass.cpp?rev=231764&r1=231763&r2=231764&view=diff
==============================================================================
--- libcxx/trunk/test/std/numerics/rand/rand.device/ctor.pass.cpp (original)
+++ libcxx/trunk/test/std/numerics/rand/rand.device/ctor.pass.cpp Tue Mar 10 02:46:06 2015
@@ -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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