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Use getrandom rather than getentropy on Linux for random_get. #151

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Merged
sunfishcode merged 1 commit into from
May 15, 2019
Merged

Use getrandom rather than getentropy on Linux for random_get. #151

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6 changes: 3 additions & 3 deletions wasmtime-wasi/sandboxed-system-primitives/src/config.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,15 +20,15 @@
#define CONFIG_HAS_ARC4RANDOM_BUF 0
#endif

// On Linux, prefer to use getentropy, though it isn't available in
// On Linux, prefer to use getrandom, though it isn't available in
// GLIBC before 2.25.
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@bjorn3 bjorn3 May 15, 2019

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Is this still the correct version?

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@sunfishcode sunfishcode May 15, 2019

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yes

#if defined(__linux__) && \
(!defined(__GLIBC__) || \
__GLIBC__ > 2 || \
(__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25))
#define CONFIG_HAS_GETENTROPY 1
#define CONFIG_HAS_GETRANDOM 1
#else
#define CONFIG_HAS_GETENTROPY 0
#define CONFIG_HAS_GETRANDOM 0
#endif

#if defined(__CloudABI__)
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20 changes: 18 additions & 2 deletions wasmtime-wasi/sandboxed-system-primitives/src/random.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

#include "random.h"
Expand All @@ -25,10 +27,24 @@ void random_buf(void *buf, size_t len) {
arc4random_buf(buf, len);
}

#elif CONFIG_HAS_GETENTROPY
#elif CONFIG_HAS_GETRANDOM

#include <sys/random.h>

void random_buf(void *buf, size_t len) {
getentropy(buf, len);
for (;;) {
ssize_t x = getrandom(buf, len, 0);
if (x < 0) {
if (errno == EINTR)
continue;
fprintf(stderr, "getrandom failed: %s", strerror(errno));
abort();
}
if (x == len)
return;
buf = (void *)((unsigned char *)buf + x);
len -= x;
}
}

#else
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