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authorLennart Poettering <lennart@poettering.net>2014-01-28 13:07:28 +0100
committerLennart Poettering <lennart@poettering.net>2014-01-28 13:07:28 +0100
commitb89446bb33fbe6b9820efdbea62433657757a03f (patch)
treeb4c738ece8e391c0bfff729bd2094d9634238ed2 /src
parent7d5dd5e0cf2f0f2af39d72b1ee65651731bf0129 (diff)
util: introduce new dev_urandom() call that is like random_bytes() but doesn't fall back to PRNG
Diffstat (limited to 'src')
-rw-r--r--src/shared/util.c38
-rw-r--r--src/shared/util.h1
2 files changed, 26 insertions, 13 deletions
diff --git a/src/shared/util.c b/src/shared/util.c
index 945f1525a2..f452431c67 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2255,25 +2255,37 @@ char* dirname_malloc(const char *path) {
return dir;
}
-void random_bytes(void *p, size_t n) {
- static bool srand_called = false;
+int dev_urandom(void *p, size_t n) {
_cleanup_close_ int fd;
ssize_t k;
- uint8_t *q;
fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0)
- goto fallback;
+ return errno == ENOENT ? -ENOSYS : -errno;
k = loop_read(fd, p, n, true);
- if (k < 0 || (size_t) k != n)
- goto fallback;
+ if (k < 0)
+ return (int) k;
+ if ((size_t) k != n)
+ return -EIO;
- return;
+ return 0;
+}
-fallback:
+void random_bytes(void *p, size_t n) {
+ static bool srand_called = false;
+ uint8_t *q;
+ int r;
+
+ r = dev_urandom(p, n);
+ if (r >= 0)
+ return;
+
+ /* If some idiot made /dev/urandom unavailable to us, he'll
+ * get a PRNG instead. */
if (!srand_called) {
+ unsigned x = 0;
#ifdef HAVE_SYS_AUXV_H
/* The kernel provides us with a bit of entropy in
@@ -2285,16 +2297,16 @@ fallback:
auxv = (void*) getauxval(AT_RANDOM);
if (auxv)
- srand(*(unsigned*) auxv);
- else
+ x ^= *(unsigned*) auxv;
#endif
- srand(time(NULL) + gettid());
+ x ^= (unsigned) now(CLOCK_REALTIME);
+ x ^= (unsigned) gettid();
+
+ srand(x);
srand_called = true;
}
- /* If some idiot made /dev/urandom unavailable to us, he'll
- * get a PRNG instead. */
for (q = p; q < (uint8_t*) p + n; q ++)
*q = rand();
}
diff --git a/src/shared/util.h b/src/shared/util.h
index 1169864c3a..117855de81 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -272,6 +272,7 @@ int make_stdio(int fd);
int make_null_stdio(void);
int make_console_stdio(void);
+int dev_urandom(void *p, size_t n);
void random_bytes(void *p, size_t n);
static inline uint64_t random_u64(void) {