[Python-checkins] cpython (merge 3.5 -> 3.6): (Merge 3.5) Catch EPERM error in py_getrandom()

Tue Sep 20 16:52:41 EDT 2016

https://hg.python.org/cpython/rev/27d05bb6f832
changeset: 103973:27d05bb6f832
branch: 3.6
parent: 103969:5af24edf402f
parent: 103972:ddc54f08bdfa
user: Victor Stinner <victor.stinner at gmail.com>
date: Tue Sep 20 22:49:52 2016 +0200
summary:
 (Merge 3.5) Catch EPERM error in py_getrandom()
Issue #27955: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.
files:
 Misc/NEWS | 3 +++
 Python/random.c | 19 +++++++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #27955: Fallback on reading /dev/urandom device when the getrandom()
+ syscall fails with EPERM, for example when blocked by SECCOMP.
+
 - Issue #28192: Don't import readline in isolated mode.
 
 - Upgrade internal unicode databases to Unicode version 9.0.0.
diff --git a/Python/random.c b/Python/random.c
--- a/Python/random.c
+++ b/Python/random.c
@@ -121,9 +121,9 @@
 
 /* Call getrandom()
 - Return 1 on success
- - Return 0 if getrandom() syscall is not available (fails with ENOSYS)
- or if getrandom(GRND_NONBLOCK) fails with EAGAIN (blocking=0 and system
- urandom not initialized yet) and raise=0.
+ - Return 0 if getrandom() syscall is not available (failed with ENOSYS or
+ EPERM) or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom
+ not initialized yet) and raise=0.
 - Raise an exception (if raise is non-zero) and return -1 on error:
 getrandom() failed with EINTR and the Python signal handler raised an
 exception, or getrandom() failed with a different error. */
@@ -131,8 +131,8 @@
 py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise)
 {
 /* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
- fails with ENOSYS. Need Linux kernel 3.17 or newer, or Solaris 11.3
- or newer */
+ failed with ENOSYS or EPERM. Need Linux kernel 3.17 or newer, or Solaris
+ 11.3 or newer */
 static int getrandom_works = 1;
 int flags;
 char *dest;
@@ -178,7 +178,10 @@
 #endif
 
 if (n < 0) {
- if (errno == ENOSYS) {
+ /* ENOSYS: getrandom() syscall not supported by the kernel (but
+ * maybe supported by the host which built Python). EPERM:
+ * getrandom() syscall blocked by SECCOMP or something else. */
+ if (errno == ENOSYS || errno == EPERM) {
 getrandom_works = 0;
 return 0;
 }
@@ -246,8 +249,8 @@
 if (res == 1) {
 return 0;
 }
- /* getrandom() is not supported by the running kernel, fall back
- on reading /dev/urandom */
+ /* getrandom() failed with ENOSYS or EPERM,
+ fall back on reading /dev/urandom */
 #endif
 
 
-- 
Repository URL: https://hg.python.org/cpython
