Merge pull request #6207 from libgit2/ethomson/prng mktmp: improve our temp file creation
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diff --git a/COPYING b/COPYING
index efeff14..ccfb7db 100644
--- a/COPYING
+++ b/COPYING
@@ -1132,3 +1132,15 @@ STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
OF THE POSSIBILITY OF SUCH DAMAGE.
+----------------------------------------------------------------------
+
+The xoroshiro256** implementation is licensed in the public domain:
+
+Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
+
+To the extent possible under law, the author has dedicated all copyright
+and related and neighboring rights to this software to the public domain
+worldwide. This software is distributed without any warranty.
+
+See <http://creativecommons.org/publicdomain/zero/1.0/>.
+
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e2da4bc..e7b54d0 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -55,6 +55,8 @@ check_prototype_definition(qsort_r
check_function_exists(qsort_s GIT_QSORT_S)
+check_function_exists(getentropy GIT_RAND_GETENTROPY)
+
# Find required dependencies
if(WIN32)
diff --git a/src/features.h.in b/src/features.h.in
index 81a8ae0..f920135 100644
--- a/src/features.h.in
+++ b/src/features.h.in
@@ -48,4 +48,6 @@
#cmakedefine GIT_SHA1_OPENSSL 1
#cmakedefine GIT_SHA1_MBEDTLS 1
+#cmakedefine GIT_RAND_GETENTROPY 1
+
#endif
diff --git a/src/fs_path.c b/src/fs_path.c
index f9da304..7a65777 100644
--- a/src/fs_path.c
+++ b/src/fs_path.c
@@ -1040,8 +1040,8 @@ fail:
return -1;
}
-static const char *nfc_file = "\xC3\x85\x73\x74\x72\xC3\xB6\x6D.XXXXXX";
-static const char *nfd_file = "\x41\xCC\x8A\x73\x74\x72\x6F\xCC\x88\x6D.XXXXXX";
+static const char *nfc_file = "\xC3\x85\x73\x74\x72\xC3\xB6\x6D";
+static const char *nfd_file = "\x41\xCC\x8A\x73\x74\x72\x6F\xCC\x88\x6D";
/* Check if the platform is decomposing unicode data for us. We will
* emulate core Git and prefer to use precomposed unicode data internally
@@ -1054,39 +1054,42 @@ static const char *nfd_file = "\x41\xCC\x8A\x73\x74\x72\x6F\xCC\x88\x6D.XXXXXX";
*/
bool git_fs_path_does_decompose_unicode(const char *root)
{
- git_str path = GIT_STR_INIT;
+ git_str nfc_path = GIT_STR_INIT;
+ git_str nfd_path = GIT_STR_INIT;
int fd;
bool found_decomposed = false;
- char tmp[6];
+ size_t orig_len;
+ const char *trailer;
/* Create a file using a precomposed path and then try to find it
* using the decomposed name. If the lookup fails, then we will mark
* that we should precompose unicode for this repository.
*/
- if (git_str_joinpath(&path, root, nfc_file) < 0 ||
- (fd = p_mkstemp(path.ptr)) < 0)
+ if (git_str_joinpath(&nfc_path, root, nfc_file) < 0)
+ goto done;
+
+ /* record original path length before trailer */
+ orig_len = nfc_path.size;
+
+ if ((fd = git_futils_mktmp(&nfc_path, nfc_path.ptr, 0666)) < 0)
goto done;
p_close(fd);
- /* record trailing digits generated by mkstemp */
- memcpy(tmp, path.ptr + path.size - sizeof(tmp), sizeof(tmp));
+ trailer = nfc_path.ptr + orig_len;
/* try to look up as NFD path */
- if (git_str_joinpath(&path, root, nfd_file) < 0)
+ if (git_str_joinpath(&nfd_path, root, nfd_file) < 0 ||
+ git_str_puts(&nfd_path, trailer) < 0)
goto done;
- memcpy(path.ptr + path.size - sizeof(tmp), tmp, sizeof(tmp));
- found_decomposed = git_fs_path_exists(path.ptr);
+ found_decomposed = git_fs_path_exists(nfd_path.ptr);
/* remove temporary file (using original precomposed path) */
- if (git_str_joinpath(&path, root, nfc_file) < 0)
- goto done;
- memcpy(path.ptr + path.size - sizeof(tmp), tmp, sizeof(tmp));
-
- (void)p_unlink(path.ptr);
+ (void)p_unlink(nfc_path.ptr);
done:
- git_str_dispose(&path);
+ git_str_dispose(&nfc_path);
+ git_str_dispose(&nfd_path);
return found_decomposed;
}
diff --git a/src/futils.c b/src/futils.c
index 318e878..42c3595 100644
--- a/src/futils.c
+++ b/src/futils.c
@@ -10,6 +10,8 @@
#include "runtime.h"
#include "strmap.h"
#include "hash.h"
+#include "rand.h"
+
#include <ctype.h>
#if GIT_WIN32
#include "win32/findfile.h"
@@ -27,23 +29,20 @@ int git_futils_mkpath2file(const char *file_path, const mode_t mode)
int git_futils_mktmp(git_str *path_out, const char *filename, mode_t mode)
{
const int open_flags = O_RDWR | O_CREAT | O_EXCL | O_BINARY | O_CLOEXEC;
- /* TMP_MAX is unrelated to mktemp but should provide a reasonable amount */
- unsigned int tries = TMP_MAX;
+ unsigned int tries = 32;
int fd;
while (tries--) {
+ uint64_t rand = git_rand_next();
+
git_str_sets(path_out, filename);
- git_str_puts(path_out, "_git2_XXXXXX");
+ git_str_puts(path_out, "_git2_");
+ git_str_encode_hexstr(path_out, (void *)&rand, sizeof(uint64_t));
if (git_str_oom(path_out))
return -1;
- /* Using mktemp is safe when we open with O_CREAT | O_EXCL */
- p_mktemp(path_out->ptr);
- /* mktemp sets template to empty string on failure */
- if (path_out->ptr[0] == '\0')
- break;
-
+ /* Note that we open with O_CREAT | O_EXCL */
if ((fd = p_open(path_out->ptr, open_flags, mode)) >= 0)
return fd;
}
diff --git a/src/futils.h b/src/futils.h
index 1827cba..a82ec41 100644
--- a/src/futils.h
+++ b/src/futils.h
@@ -177,11 +177,12 @@ extern int git_futils_rmdir_r(const char *path, const char *base, uint32_t flags
* protected directory; the file created will created will honor
* the current `umask`. Writes the filename into path_out.
*
- * This function is *NOT* suitable for use in temporary directories
- * that are world writable. It uses `mktemp` (for portability) and
- * many `mktemp` implementations use weak random characters. It
- * should only be assumed to be suitable for atomically writing
- * a new file in a directory that you control.
+ * This function uses a high-quality PRNG seeded by the system's
+ * entropy pool _where available_ and falls back to a simple seed
+ * (time plus system information) when not. This is suitable for
+ * writing within a protected directory, but the system's safe
+ * temporary file creation functions should be preferred where
+ * available when writing into world-writable (temp) directories.
*
* @return On success, an open file descriptor, else an error code < 0.
*/
diff --git a/src/libgit2.c b/src/libgit2.c
index b3a72de..b17485d 100644
--- a/src/libgit2.c
+++ b/src/libgit2.c
@@ -20,6 +20,7 @@
#include "mwindow.h"
#include "object.h"
#include "odb.h"
+#include "rand.h"
#include "refs.h"
#include "runtime.h"
#include "sysdir.h"
@@ -70,6 +71,7 @@ int git_libgit2_init(void)
git_allocator_global_init,
git_threadstate_global_init,
git_threads_global_init,
+ git_rand_global_init,
git_hash_global_init,
git_sysdir_global_init,
git_filter_global_init,
diff --git a/src/posix.h b/src/posix.h
index 1757764..e6f6030 100644
--- a/src/posix.h
+++ b/src/posix.h
@@ -131,7 +131,6 @@ extern ssize_t p_pwrite(int fd, const void *data, size_t size, off64_t offset);
#define p_close(fd) close(fd)
#define p_umask(m) umask(m)
-#define p_mktemp(p) mktemp(p)
extern int p_open(const char *path, int flags, ...);
extern int p_creat(const char *path, mode_t mode);
diff --git a/src/rand.c b/src/rand.c
new file mode 100644
index 0000000..0a20813
--- /dev/null
+++ b/src/rand.c
@@ -0,0 +1,226 @@
+/* Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
+
+To the extent possible under law, the author has dedicated all copyright
+and related and neighboring rights to this software to the public domain
+worldwide. This software is distributed without any warranty.
+
+See <http://creativecommons.org/publicdomain/zero/1.0/>. */
+
+#include "common.h"
+#include "rand.h"
+#include "runtime.h"
+
+#if defined(GIT_RAND_GETENTROPY)
+# include <sys/random.h>
+#endif
+
+static uint64_t state[4];
+static git_mutex state_lock;
+
+typedef union {
+ double f;
+ uint64_t d;
+} bits;
+
+#if defined(GIT_WIN32)
+GIT_INLINE(int) getseed(uint64_t *seed)
+{
+ HCRYPTPROV provider;
+ SYSTEMTIME systemtime;
+ FILETIME filetime, idletime, kerneltime, usertime;
+ bits convert;
+
+ if (CryptAcquireContext(&provider, 0, 0, PROV_RSA_FULL,
+ CRYPT_VERIFYCONTEXT|CRYPT_SILENT)) {
+ BOOL success = CryptGenRandom(provider, sizeof(uint64_t), (void *)seed);
+ CryptReleaseContext(provider, 0);
+
+ if (success)
+ return 0;
+ }
+
+ GetSystemTime(&systemtime);
+ if (!SystemTimeToFileTime(&systemtime, &filetime)) {
+ git_error_set(GIT_ERROR_OS, "could not get time for random seed");
+ return -1;
+ }
+
+ /* Fall-through: generate a seed from the time and system state */
+ *seed = 0;
+ *seed |= ((uint64_t)filetime.dwLowDateTime << 32);
+ *seed |= ((uint64_t)filetime.dwHighDateTime);
+
+ GetSystemTimes(&idletime, &kerneltime, &usertime);
+
+ *seed ^= ((uint64_t)idletime.dwLowDateTime << 32);
+ *seed ^= ((uint64_t)kerneltime.dwLowDateTime);
+ *seed ^= ((uint64_t)usertime.dwLowDateTime << 32);
+
+ *seed ^= ((uint64_t)idletime.dwHighDateTime);
+ *seed ^= ((uint64_t)kerneltime.dwHighDateTime << 12);
+ *seed ^= ((uint64_t)usertime.dwHighDateTime << 24);
+
+ *seed ^= ((uint64_t)GetCurrentProcessId() << 32);
+ *seed ^= ((uint64_t)GetCurrentThreadId() << 48);
+
+ convert.f = git__timer(); *seed ^= (convert.d);
+
+ /* Mix in the addresses of some functions and variables */
+ *seed ^= (((uint64_t)((uintptr_t)seed) << 32));
+ *seed ^= (((uint64_t)((uintptr_t)&errno)));
+
+ return 0;
+}
+
+#else
+
+GIT_INLINE(int) getseed(uint64_t *seed)
+{
+ struct timeval tv;
+ double loadavg[3];
+ bits convert;
+ int fd;
+
+# if defined(GIT_RAND_GETENTROPY)
+ GIT_UNUSED((fd = 0));
+
+ if (getentropy(seed, sizeof(uint64_t)) == 0)
+ return 0;
+# else
+ /*
+ * Try to read from /dev/urandom; most modern systems will have
+ * this, but we may be chrooted, etc, so it's not a fatal error
+ */
+ if ((fd = open("/dev/urandom", O_RDONLY)) >= 0) {
+ ssize_t ret = read(fd, seed, sizeof(uint64_t));
+ close(fd);
+
+ if (ret == (ssize_t)sizeof(uint64_t))
+ return 0;
+ }
+# endif
+
+ /* Fall-through: generate a seed from the time and system state */
+ if (gettimeofday(&tv, NULL) < 0) {
+ git_error_set(GIT_ERROR_OS, "could get time for random seed");
+ return -1;
+ }
+
+ getloadavg(loadavg, 3);
+
+ *seed = 0;
+ *seed |= ((uint64_t)tv.tv_usec << 40);
+ *seed |= ((uint64_t)tv.tv_sec);
+
+ *seed ^= ((uint64_t)getpid() << 48);
+ *seed ^= ((uint64_t)getppid() << 32);
+ *seed ^= ((uint64_t)getpgid(0) << 28);
+ *seed ^= ((uint64_t)getsid(0) << 16);
+ *seed ^= ((uint64_t)getuid() << 8);
+ *seed ^= ((uint64_t)getgid());
+
+ convert.f = loadavg[0]; *seed ^= (convert.d >> 36);
+ convert.f = loadavg[1]; *seed ^= (convert.d);
+ convert.f = loadavg[2]; *seed ^= (convert.d >> 16);
+
+ convert.f = git__timer(); *seed ^= (convert.d);
+
+ /* Mix in the addresses of some variables */
+ *seed ^= ((uint64_t)((size_t)((void *)seed)) << 32);
+ *seed ^= ((uint64_t)((size_t)((void *)&errno)));
+
+ return 0;
+}
+#endif
+
+static void git_rand_global_shutdown(void)
+{
+ git_mutex_free(&state_lock);
+}
+
+int git_rand_global_init(void)
+{
+ uint64_t seed = 0;
+
+ if (git_mutex_init(&state_lock) < 0 || getseed(&seed) < 0)
+ return -1;
+
+ if (!seed) {
+ git_error_set(GIT_ERROR_INTERNAL, "failed to generate random seed");
+ return -1;
+ }
+
+ git_rand_seed(seed);
+ git_runtime_shutdown_register(git_rand_global_shutdown);
+
+ return 0;
+}
+
+/*
+ * This is splitmix64. xoroshiro256** uses 256 bit seed; this is used
+ * to generate 256 bits of seed from the given 64, per the author's
+ * recommendation.
+ */
+GIT_INLINE(uint64_t) splitmix64(uint64_t *in)
+{
+ uint64_t z;
+
+ *in += 0x9e3779b97f4a7c15;
+
+ z = *in;
+ z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
+ z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
+ return z ^ (z >> 31);
+}
+
+void git_rand_seed(uint64_t seed)
+{
+ uint64_t mixer;
+
+ mixer = seed;
+
+ git_mutex_lock(&state_lock);
+ state[0] = splitmix64(&mixer);
+ state[1] = splitmix64(&mixer);
+ state[2] = splitmix64(&mixer);
+ state[3] = splitmix64(&mixer);
+ git_mutex_unlock(&state_lock);
+}
+
+/* This is xoshiro256** 1.0, one of our all-purpose, rock-solid
+ generators. It has excellent (sub-ns) speed, a state (256 bits) that is
+ large enough for any parallel application, and it passes all tests we
+ are aware of.
+
+ For generating just floating-point numbers, xoshiro256+ is even faster.
+
+ The state must be seeded so that it is not everywhere zero. If you have
+ a 64-bit seed, we suggest to seed a splitmix64 generator and use its
+ output to fill s. */
+
+GIT_INLINE(uint64_t) rotl(const uint64_t x, int k) {
+ return (x << k) | (x >> (64 - k));
+}
+
+uint64_t git_rand_next(void) {
+ uint64_t t, result;
+
+ git_mutex_lock(&state_lock);
+
+ result = rotl(state[1] * 5, 7) * 9;
+
+ t = state[1] << 17;
+
+ state[2] ^= state[0];
+ state[3] ^= state[1];
+ state[1] ^= state[2];
+ state[0] ^= state[3];
+
+ state[2] ^= t;
+
+ state[3] = rotl(state[3], 45);
+
+ git_mutex_unlock(&state_lock);
+
+ return result;
+}
diff --git a/src/rand.h b/src/rand.h
new file mode 100644
index 0000000..2e60561
--- /dev/null
+++ b/src/rand.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_rand_h__
+#define INCLUDE_rand_h__
+
+#include "common.h"
+
+/**
+ * Initialize the random number generation subsystem. This will
+ * seed the random number generator with the system's entropy pool,
+ * if available, and will fall back to the current time and
+ * system information if not.
+ */
+int git_rand_global_init(void);
+
+/**
+ * Seed the pseudo-random number generator. This is not needed to be
+ * called; the PRNG is seeded by `git_rand_global_init`, but it may
+ * be useful for testing. When the same seed is specified, the same
+ * sequence of random numbers from `git_rand_next` is emitted.
+ *
+ * @param seed the seed to use
+ */
+void git_rand_seed(uint64_t seed);
+
+/**
+ * Get the next pseudo-random number in the sequence.
+ *
+ * @return a 64-bit pseudo-random number
+ */
+uint64_t git_rand_next(void);
+
+#endif
diff --git a/src/str.c b/src/str.c
index 9d579f1..0d405bf 100644
--- a/src/str.c
+++ b/src/str.c
@@ -217,6 +217,32 @@ int git_str_puts(git_str *buf, const char *string)
return git_str_put(buf, string, strlen(string));
}
+static char hex_encode[] = "0123456789abcdef";
+
+int git_str_encode_hexstr(git_str *str, const char *data, size_t len)
+{
+ size_t new_size, i;
+ char *s;
+
+ GIT_ERROR_CHECK_ALLOC_MULTIPLY(&new_size, len, 2);
+ GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
+
+ if (git_str_grow_by(str, new_size) < 0)
+ return -1;
+
+ s = str->ptr + str->size;
+
+ for (i = 0; i < len; i++) {
+ *s++ = hex_encode[(data[i] & 0xf0) >> 4];
+ *s++ = hex_encode[(data[i] & 0x0f)];
+ }
+
+ str->size += (len * 2);
+ str->ptr[str->size] = '\0';
+
+ return 0;
+}
+
static const char base64_encode[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
diff --git a/src/str.h b/src/str.h
index af7acc2..ef769ce 100644
--- a/src/str.h
+++ b/src/str.h
@@ -217,6 +217,9 @@ int git_str_cmp(const git_str *a, const git_str *b);
int git_str_quote(git_str *str);
int git_str_unquote(git_str *str);
+/* Write data as a hex string */
+int git_str_encode_hexstr(git_str *str, const char *data, size_t len);
+
/* Write data as base64 encoded in string buffer */
int git_str_encode_base64(git_str *str, const char *data, size_t len);
/* Decode the given bas64 and write the result to the string buffer */
diff --git a/src/unix/posix.h b/src/unix/posix.h
index 27a8fec..49065e5 100644
--- a/src/unix/posix.h
+++ b/src/unix/posix.h
@@ -58,7 +58,6 @@ GIT_INLINE(int) p_fsync(int fd)
#define p_strncasecmp(s1, s2, c) strncasecmp(s1, s2, c)
#define p_vsnprintf(b, c, f, a) vsnprintf(b, c, f, a)
#define p_snprintf snprintf
-#define p_mkstemp(p) mkstemp(p)
#define p_chdir(p) chdir(p)
#define p_rmdir(p) rmdir(p)
#define p_access(p,m) access(p,m)
diff --git a/src/win32/posix.h b/src/win32/posix.h
index 87c6b43..578347f 100644
--- a/src/win32/posix.h
+++ b/src/win32/posix.h
@@ -42,7 +42,6 @@ extern int p_inet_pton(int af, const char *src, void* dst);
extern int p_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr);
extern int p_snprintf(char *buffer, size_t count, const char *format, ...) GIT_FORMAT_PRINTF(3, 4);
-extern int p_mkstemp(char *tmp_path);
extern int p_chdir(const char *path);
extern int p_chmod(const char *path, mode_t mode);
extern int p_rmdir(const char *path);
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index b607241..5f7cd0c 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -860,20 +860,6 @@ int p_snprintf(char *buffer, size_t count, const char *format, ...)
return r;
}
-/* TODO: wut? */
-int p_mkstemp(char *tmp_path)
-{
-#if defined(_MSC_VER) && _MSC_VER >= 1500
- if (_mktemp_s(tmp_path, strlen(tmp_path) + 1) != 0)
- return -1;
-#else
- if (_mktemp(tmp_path) == NULL)
- return -1;
-#endif
-
- return p_open(tmp_path, O_RDWR | O_CREAT | O_EXCL, 0744); /* -V536 */
-}
-
int p_access(const char *path, mode_t mode)
{
git_win32_path buf;