From 21e00e905037cf604ad8bfd83a32e6aaa4a84598 Mon Sep 17 00:00:00 2001 From: "Wladimir J. van der Laan" Date: Wed, 1 Mar 2017 12:40:06 +0100 Subject: [PATCH] Merge #9821: util: Specific GetOSRandom for Linux/FreeBSD/OpenBSD 7e6dcd9 random: Add fallback if getrandom syscall not available (Wladimir J. van der Laan) 7cad849 sanity: Move OS random to sanity check function (Wladimir J. van der Laan) aa09ccb squashme: comment that NUM_OS_RANDOM_BYTES should not be changed lightly (Wladimir J. van der Laan) 224e6eb util: Specific GetOSRandom for Linux/FreeBSD/OpenBSD (Wladimir J. van der Laan) Tree-SHA512: 9fd408b1316c69de86674f342339b2f89192fd317c8c036b5df4320f828fa263c7966146bfc1904c51137ee4a26e4cb0f560b2cd05e18cde4d808b9b92ad15c4 --- configure.ac | 27 ++++++++ src/Makefile.test.include | 1 + src/init.cpp | 6 ++ src/random.cpp | 128 +++++++++++++++++++++++++++++++++----- src/random.h | 17 +++++ src/test/random_tests.cpp | 19 ++++++ 6 files changed, 181 insertions(+), 17 deletions(-) create mode 100644 src/test/random_tests.cpp diff --git a/configure.ac b/configure.ac index 0e75c13802..e7e9a62b4b 100644 --- a/configure.ac +++ b/configure.ac @@ -583,6 +583,33 @@ AC_LINK_IFELSE([AC_LANG_SOURCE([ ] ) +# Check for different ways of gathering OS randomness +AC_MSG_CHECKING(for Linux getrandom syscall) +AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include + #include + #include ]], + [[ syscall(SYS_getrandom, nullptr, 32, 0); ]])], + [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_SYS_GETRANDOM, 1,[Define this symbol if the Linux getrandom system call is available]) ], + [ AC_MSG_RESULT(no)] +) + +AC_MSG_CHECKING(for getentropy) +AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include ]], + [[ getentropy(nullptr, 32) ]])], + [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_GETENTROPY, 1,[Define this symbol if the BSD getentropy system call is available]) ], + [ AC_MSG_RESULT(no)] +) + +AC_MSG_CHECKING(for sysctl KERN_ARND) +AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include + #include ]], + [[ static const int name[2] = {CTL_KERN, KERN_ARND}; + sysctl(name, 2, nullptr, nullptr, nullptr, 0); ]])], + [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_SYSCTL_ARND, 1,[Define this symbol if the BSD sysctl(KERN_ARND) is available]) ], + [ AC_MSG_RESULT(no)] +) + +# Check for reduced exports if test x$use_reduce_exports = xyes; then AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],[RE_CXXFLAGS="-fvisibility=hidden"], [AC_MSG_ERROR([Cannot set default symbol visibility. Use --disable-reduce-exports.])]) diff --git a/src/Makefile.test.include b/src/Makefile.test.include index b30a02c1d1..be0ed5302e 100644 --- a/src/Makefile.test.include +++ b/src/Makefile.test.include @@ -108,6 +108,7 @@ BITCOIN_TESTS =\ test/policyestimator_tests.cpp \ test/pow_tests.cpp \ test/prevector_tests.cpp \ + test/random_tests.cpp \ test/raii_event_tests.cpp \ test/ratecheck_tests.cpp \ test/reverselock_tests.cpp \ diff --git a/src/init.cpp b/src/init.cpp index deadc606e3..764cbe9649 100644 --- a/src/init.cpp +++ b/src/init.cpp @@ -846,6 +846,7 @@ bool InitSanityCheck(void) InitError("Elliptic curve cryptography sanity check failure. Aborting."); return false; } + if (!glibc_sanity_test() || !glibcxx_sanity_test()) return false; @@ -853,6 +854,11 @@ bool InitSanityCheck(void) return false; } + if (!Random_SanityCheck()) { + InitError("OS cryptographic RNG sanity check failure. Aborting."); + return false; + } + return true; } diff --git a/src/random.cpp b/src/random.cpp index 27516d164b..8db22a5980 100644 --- a/src/random.cpp +++ b/src/random.cpp @@ -21,6 +21,17 @@ #include #endif +#ifdef HAVE_SYS_GETRANDOM +#include +#include +#endif +#ifdef HAVE_GETENTROPY +#include +#endif +#ifdef HAVE_SYSCTL_ARND +#include +#endif + #include #include @@ -91,34 +102,86 @@ static void RandAddSeedPerfmon() #endif } -/** Get 32 bytes of system entropy. */ -static void GetOSRand(unsigned char *ent32) +#ifndef WIN32 +/** Fallback: get 32 bytes of system entropy from /dev/urandom. The most + * compatible way to get cryptographic randomness on UNIX-ish platforms. + */ +void GetDevURandom(unsigned char *ent32) { -#ifdef WIN32 - HCRYPTPROV hProvider; - int ret = CryptAcquireContextW(&hProvider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT); - if (!ret) { - RandFailure(); - } - ret = CryptGenRandom(hProvider, 32, ent32); - if (!ret) { - RandFailure(); - } - CryptReleaseContext(hProvider, 0); -#else int f = open("/dev/urandom", O_RDONLY); if (f == -1) { RandFailure(); } int have = 0; do { - ssize_t n = read(f, ent32 + have, 32 - have); - if (n <= 0 || n + have > 32) { + ssize_t n = read(f, ent32 + have, NUM_OS_RANDOM_BYTES - have); + if (n <= 0 || n + have > NUM_OS_RANDOM_BYTES) { RandFailure(); } have += n; - } while (have < 32); + } while (have < NUM_OS_RANDOM_BYTES); close(f); +} +#endif + +/** Get 32 bytes of system entropy. */ +void GetOSRand(unsigned char *ent32) +{ +#if defined(WIN32) + HCRYPTPROV hProvider; + int ret = CryptAcquireContextW(&hProvider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT); + if (!ret) { + RandFailure(); + } + ret = CryptGenRandom(hProvider, NUM_OS_RANDOM_BYTES, ent32); + if (!ret) { + RandFailure(); + } + CryptReleaseContext(hProvider, 0); +#elif defined(HAVE_SYS_GETRANDOM) + /* Linux. From the getrandom(2) man page: + * "If the urandom source has been initialized, reads of up to 256 bytes + * will always return as many bytes as requested and will not be + * interrupted by signals." + */ + int rv = syscall(SYS_getrandom, ent32, NUM_OS_RANDOM_BYTES, 0); + if (rv != NUM_OS_RANDOM_BYTES) { + if (rv < 0 && errno == ENOSYS) { + /* Fallback for kernel <3.17: the return value will be -1 and errno + * ENOSYS if the syscall is not available, in that case fall back + * to /dev/urandom. + */ + GetDevURandom(ent32); + } else { + RandFailure(); + } + } +#elif defined(HAVE_GETENTROPY) + /* On OpenBSD this can return up to 256 bytes of entropy, will return an + * error if more are requested. + * The call cannot return less than the requested number of bytes. + */ + if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) { + RandFailure(); + } +#elif defined(HAVE_SYSCTL_ARND) + /* FreeBSD and similar. It is possible for the call to return less + * bytes than requested, so need to read in a loop. + */ + static const int name[2] = {CTL_KERN, KERN_ARND}; + int have = 0; + do { + size_t len = NUM_OS_RANDOM_BYTES - have; + if (sysctl(name, ARRAYLEN(name), ent32 + have, &len, NULL, 0) != 0) { + RandFailure(); + } + have += len; + } while (have < NUM_OS_RANDOM_BYTES); +#else + /* Fall back to /dev/urandom if there is no specific method implemented to + * get system entropy for this OS. + */ + GetDevURandom(ent32); #endif } @@ -205,3 +268,34 @@ FastRandomContext::FastRandomContext(bool fDeterministic) Rw = tmp; } } + +bool Random_SanityCheck() +{ + /* This does not measure the quality of randomness, but it does test that + * OSRandom() overwrites all 32 bytes of the output given a maximum + * number of tries. + */ + static const ssize_t MAX_TRIES = 1024; + uint8_t data[NUM_OS_RANDOM_BYTES]; + bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */ + int num_overwritten; + int tries = 0; + /* Loop until all bytes have been overwritten at least once, or max number tries reached */ + do { + memset(data, 0, NUM_OS_RANDOM_BYTES); + GetOSRand(data); + for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) { + overwritten[x] |= (data[x] != 0); + } + + num_overwritten = 0; + for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) { + if (overwritten[x]) { + num_overwritten += 1; + } + } + + tries += 1; + } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES); + return (num_overwritten == NUM_OS_RANDOM_BYTES); /* If this failed, bailed out after too many tries */ +} diff --git a/src/random.h b/src/random.h index 83464794d6..888ca35b00 100644 --- a/src/random.h +++ b/src/random.h @@ -56,4 +56,21 @@ public: uint32_t Rw; }; +/* Number of random bytes returned by GetOSRand. + * When changing this constant make sure to change all call sites, and make + * sure that the underlying OS APIs for all platforms support the number. + * (many cap out at 256 bytes). + */ +static const ssize_t NUM_OS_RANDOM_BYTES = 32; + +/** Get 32 bytes of system entropy. Do not use this in application code: use + * GetStrongRandBytes instead. + */ +void GetOSRand(unsigned char *ent32); + +/** Check that OS randomness is available and returning the requested number + * of bytes. + */ +bool Random_SanityCheck(); + #endif // BITCOIN_RANDOM_H diff --git a/src/test/random_tests.cpp b/src/test/random_tests.cpp new file mode 100644 index 0000000000..d2c46c0daa --- /dev/null +++ b/src/test/random_tests.cpp @@ -0,0 +1,19 @@ +// Copyright (c) 2017 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#include "random.h" + +#include "test/test_bitcoin.h" + +#include + +BOOST_FIXTURE_TEST_SUITE(random_tests, BasicTestingSetup) + +BOOST_AUTO_TEST_CASE(osrandom_tests) +{ + BOOST_CHECK(Random_SanityCheck()); +} + +BOOST_AUTO_TEST_SUITE_END() +