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authorGravatar Abseil Team <absl-team@google.com>2021-06-01 18:32:49 -0700
committerGravatar Derek Mauro <dmauro@google.com>2021-06-01 21:35:59 -0400
commit702cae1e762dc6f2f9d31777db04e1adbdb36697 (patch)
treec53a37262658d44629c6ef8ddfcdfd42cb80195c /absl
parent0d5156018dd3d0d075cc14a0aa6078979c7a85d3 (diff)
Export of internal Abseil changes
-- 2c81c02d2b68303134e777f31921679ab87a2639 by Derek Mauro <dmauro@google.com>: Use getentropy() to get seed material when using glibc >= 2.25 getentropy() uses the getrandom syscall on Linux to avoid file descriptors. It is never interputed (EINTR) and uses the same source as /dev/urandom. https://man7.org/linux/man-pages/man3/getentropy.3.html getrandom has been in the Linux since kernel 3.17 When unavailable (ENOSYS), fallback to /dev/urandom. PiperOrigin-RevId: 376962620 -- 81cd41372a04eda400a2e3be53c239c0dac6bdf3 by Abseil Team <absl-team@google.com>: Make FunctionRef no longer have -Wdeprecated-copy warnings from Clang by defaulting the copy constructor. This is needed because the assignment operator is deleted. Fixes #948 PiperOrigin-RevId: 376928548 GitOrigin-RevId: 2c81c02d2b68303134e777f31921679ab87a2639 Change-Id: I0abb18052ffff5dd1448f0b68edbb668045335f0
Diffstat (limited to 'absl')
-rw-r--r--absl/functional/function_ref.h1
-rw-r--r--absl/random/internal/seed_material.cc40
2 files changed, 40 insertions, 1 deletions
diff --git a/absl/functional/function_ref.h b/absl/functional/function_ref.h
index 6e03ac2e..5790a652 100644
--- a/absl/functional/function_ref.h
+++ b/absl/functional/function_ref.h
@@ -122,6 +122,7 @@ class FunctionRef<R(Args...)> {
// To help prevent subtle lifetime bugs, FunctionRef is not assignable.
// Typically, it should only be used as an argument type.
FunctionRef& operator=(const FunctionRef& rhs) = delete;
+ FunctionRef(const FunctionRef& rhs) = default;
// Call the underlying object.
R operator()(Args... args) const {
diff --git a/absl/random/internal/seed_material.cc b/absl/random/internal/seed_material.cc
index 4d38a574..0fcba509 100644
--- a/absl/random/internal/seed_material.cc
+++ b/absl/random/internal/seed_material.cc
@@ -50,6 +50,12 @@
#endif
+#if defined(__GLIBC__) && \
+ (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25))
+// glibc >= 2.25 has getentropy()
+#define ABSL_RANDOM_USE_GET_ENTROPY 1
+#endif
+
#if defined(ABSL_RANDOM_USE_BCRYPT)
#include <bcrypt.h>
@@ -122,8 +128,29 @@ bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
#else
+#if defined(ABSL_RANDOM_USE_GET_ENTROPY)
+// On *nix, use getentropy() if supported. Note that libc may support
+// getentropy(), but the kernel may not, in which case this function will return
+// false.
+bool ReadSeedMaterialFromGetEntropy(absl::Span<uint32_t> values) {
+ auto buffer = reinterpret_cast<uint8_t*>(values.data());
+ size_t buffer_size = sizeof(uint32_t) * values.size();
+ while (buffer_size > 0) {
+ // getentropy() has a maximum permitted length of 256.
+ size_t to_read = std::min<size_t>(buffer_size, 256);
+ int result = getentropy(buffer, to_read);
+ if (result < 0) {
+ return false;
+ }
+ buffer += to_read;
+ buffer_size -= to_read;
+ }
+ return true;
+}
+#endif // defined(ABSL_RANDOM_GETENTROPY)
+
// On *nix, read entropy from /dev/urandom.
-bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
+bool ReadSeedMaterialFromDevURandom(absl::Span<uint32_t> values) {
const char kEntropyFile[] = "/dev/urandom";
auto buffer = reinterpret_cast<uint8_t*>(values.data());
@@ -150,6 +177,17 @@ bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
return success;
}
+bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
+#if defined(ABSL_RANDOM_USE_GET_ENTROPY)
+ if (ReadSeedMaterialFromGetEntropy(values)) {
+ return true;
+ }
+#endif
+ // Libc may support getentropy, but the kernel may not, so we still have
+ // to fallback to ReadSeedMaterialFromDevURandom().
+ return ReadSeedMaterialFromDevURandom(values);
+}
+
#endif
} // namespace