Hi jfb, majnemer,
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.
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.
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"
@@ -19,18 +18,22 @@
#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&)
{
@@ -43,10 +46,43 @@
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 +115,14 @@
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());
}
random_device::~random_device()
{
- close(__f_);
}
unsigned
@@ -97,26 +129,15 @@
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 +23,14 @@
#include <unistd.h>
bool is_valid_random_device(const std::string &token) {
-#if defined(_WIN32)
- return true;
+#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";
#elif defined(_LIBCPP_USING_NACL_RANDOM)
return token == "/dev/urandom";
-#else // !defined(_WIN32) && !defined(_LIBCPP_USING_NACL_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 true;
+#endif
}
void check_random_device_valid(const std::string &token) {
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