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authorLennart Poettering <lennart@poettering.net>2014-10-30 15:27:53 +0100
committerLennart Poettering <lennart@poettering.net>2014-10-30 15:27:53 +0100
commit97768fc5746ea97cb2d3ac6854b4fc7ce1c14f24 (patch)
tree38fc777e924deba4030a40d1ad8c1c5e22ea83e6 /src/shared/util.c
parente3c72c21d62aadabf4df436c3e2c7219eeeccc1c (diff)
util: don't block on getrandom()
Diffstat (limited to 'src/shared/util.c')
-rw-r--r--src/shared/util.c24
1 files changed, 20 insertions, 4 deletions
diff --git a/src/shared/util.c b/src/shared/util.c
index ceafba86af..1d67abe58f 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2470,10 +2470,17 @@ int dev_urandom(void *p, size_t n) {
int r, fd;
ssize_t k;
- /* Use the syscall unless we know we don't have it, or when
- * the requested size is too large for it. */
+ /* Gathers some randomness from the kernel. This call will
+ * never block, and will always return some data from the
+ * kernel, regardless if the random pool is fully initialized
+ * or not. It thus makes no guarantee for the quality of the
+ * returned entropy, but is good enough for or usual usecases
+ * of seeding the hash functions for hashtable */
+
+ /* Use the getrandom() syscall unless we know we don't have
+ * it, or when the requested size is too large for it. */
if (have_syscall != 0 || (size_t) (int) n != n) {
- r = getrandom(p, n, 0);
+ r = getrandom(p, n, GRND_NONBLOCK);
if (r == (int) n) {
have_syscall = true;
return 0;
@@ -2481,8 +2488,17 @@ int dev_urandom(void *p, size_t n) {
if (r < 0) {
if (errno == ENOSYS)
- /* we lack the syscall, continue with reading from /dev/urandom */
+ /* we lack the syscall, continue with
+ * reading from /dev/urandom */
have_syscall = false;
+ else if (errno == EAGAIN)
+ /* not enough entropy for now. Let's
+ * remember to use the syscall the
+ * next time, again, but also read
+ * from /dev/urandom for now, which
+ * doesn't care about the current
+ * amount of entropy. */
+ have_syscall = true;
else
return -errno;
} else