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Use arc4random for non-blocking prng on FreeBSD (GH #1098)

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Jeffrey Walton 2021-12-29 04:45:53 -05:00
parent 66e18a2b6f
commit d994989cda
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GPG Key ID: B36AB348921B1838
1 changed files with 26 additions and 5 deletions
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31
osrng.cpp
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@ -21,6 +21,17 @@
#include "osrng.h"
#include "rng.h"
// FreeBSD links /dev/urandom -> /dev/random. It showed up when we added
// O_NOFOLLOW to harden the non-blocking generator. Use Arc4Random instead
// for a non-blocking generator. Arc4Random is cryptograhic quality prng
// based on ChaCha20. The ChaCha20 generator is seeded from /dev/random,
// so we can't completely avoid the blocking.
// https://www.freebsd.org/cgi/man.cgi?query=arc4random_buf.
#ifdef __FreeBSD__
# define USE_FREEBSD_ARC4RANDOM 1
# include <stdlib.h>
#endif
#ifdef CRYPTOPP_WIN32_AVAILABLE
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
@ -134,24 +145,27 @@ MicrosoftCryptoProvider::~MicrosoftCryptoProvider()
NonblockingRng::NonblockingRng()
{
#ifndef CRYPTOPP_WIN32_AVAILABLE
# ifdef O_NOFOLLOW
# ifndef USE_FREEBSD_ARC4RANDOM
# ifdef O_NOFOLLOW
const int flags = O_RDONLY|O_NOFOLLOW;
# else
# else
const int flags = O_RDONLY;
# endif
# endif
m_fd = open("/dev/urandom", flags);
if (m_fd == -1)
throw OS_RNG_Err("open /dev/urandom");
# endif
#endif
}
NonblockingRng::~NonblockingRng()
{
#ifndef CRYPTOPP_WIN32_AVAILABLE
# ifndef USE_FREEBSD_ARC4RANDOM
close(m_fd);
# endif
#endif
}
@ -194,6 +208,12 @@ void NonblockingRng::GenerateBlock(byte *output, size_t size)
}
# endif
#else
# if defined(USE_FREEBSD_ARC4RANDOM)
// Cryptographic quality prng based on ChaCha20,
// https://www.freebsd.org/cgi/man.cgi?query=arc4random_buf
arc4random_buf(output, size);
# else
while (size)
{
ssize_t len = read(m_fd, output, size);
@ -205,10 +225,11 @@ void NonblockingRng::GenerateBlock(byte *output, size_t size)
continue;
}
output += len;
size -= len;
}
# endif // USE_FREEBSD_ARC4RANDOM
#endif // CRYPTOPP_WIN32_AVAILABLE
}