Issue #25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom()

function instead of the getentropy() function. The getentropy() function is
blocking to generate very good quality entropy, os.urandom() doesn't need such
high-quality entropy.

diff --git a/Misc/NEWS b/Misc/NEWS
index 827d788286022d826764e9b00613d4716d660798..77efd05f913ece74b93465a52edca7c36862e021 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,11 @@ Release date: XXXX-XX-XX
 Core and Builtins
 -----------------
 
+- Issue #25003: On Solaris 11.3 or newer, os.urandom() now uses the
+  getrandom() function instead of the getentropy() function. The getentropy()
+  function is blocking to generate very good quality entropy, os.urandom()
+  doesn't need such high-quality entropy.
+
 - Issue #9232: Modify Python's grammar to allow trailing commas in the
   argument list of a function declaration.  For example, "def f(*, a =
   3,): pass" is now legal. Patch from Mark Dickinson.

diff --git a/Python/random.c b/Python/random.c
index ea09e84a7b0d73e5160ee865c8831c9fdc7e9c1e..8f3e6d60219dadb87fdcf0ab6aecd249c636a383 100644 (file)
--- a/Python/random.c
+++ b/Python/random.c
@@ -6,7 +6,9 @@
 #  ifdef HAVE_SYS_STAT_H
 #    include <sys/stat.h>
 #  endif
-#  ifdef HAVE_GETRANDOM_SYSCALL
+#  ifdef HAVE_GETRANDOM
+#    include <sys/random.h>
+#  elif defined(HAVE_GETRANDOM_SYSCALL)
 #    include <sys/syscall.h>
 #  endif
 #endif
@@ -70,7 +72,9 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
     return 0;
 }
 
-#elif HAVE_GETENTROPY
+#elif defined(HAVE_GETENTROPY) && !defined(sun)
+#define PY_GETENTROPY
+
 /* Fill buffer with size pseudo-random bytes generated by getentropy().
    Return 0 on success, or raise an exception and return -1 on error.
 
@@ -105,16 +109,19 @@ py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal)
     return 0;
 }
 
-#else   /* !HAVE_GETENTROPY */
+#else
+
+#if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
+#define PY_GETRANDOM
 
-#ifdef HAVE_GETRANDOM_SYSCALL
 static int
 py_getrandom(void *buffer, Py_ssize_t size, int raise)
 {
-    /* is getrandom() supported by the running kernel?
-     * need Linux kernel 3.17 or later */
+    /* Is getrandom() supported by the running kernel?
+     * Need Linux kernel 3.17 or newer, or Solaris 11.3 or newer */
     static int getrandom_works = 1;
-    /* Use /dev/urandom, block if the kernel has no entropy */
+    /* Use non-blocking /dev/urandom device. On Linux at boot, the getrandom()
+     * syscall blocks until /dev/urandom is initialized with enough entropy. */
     const int flags = 0;
     int n;
 
@@ -124,7 +131,18 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
     while (0 < size) {
         errno = 0;
 
-        /* Use syscall() because the libc doesn't expose getrandom() yet, see:
+#ifdef HAVE_GETRANDOM
+        if (raise) {
+            Py_BEGIN_ALLOW_THREADS
+            n = getrandom(buffer, size, flags);
+            Py_END_ALLOW_THREADS
+        }
+        else {
+            n = getrandom(buffer, size, flags);
+        }
+#else
+        /* On Linux, use the syscall() function because the GNU libc doesn't
+         * expose the Linux getrandom() syscall yet. See:
          * https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
         if (raise) {
             Py_BEGIN_ALLOW_THREADS
@@ -134,6 +152,7 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
         else {
             n = syscall(SYS_getrandom, buffer, size, flags);
         }
+#endif
 
         if (n < 0) {
             if (errno == ENOSYS) {
@@ -182,7 +201,7 @@ dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
 
     assert (0 < size);
 
-#ifdef HAVE_GETRANDOM_SYSCALL
+#ifdef PY_GETRANDOM
     if (py_getrandom(buffer, size, 0) == 1)
         return;
     /* getrandom() is not supported by the running kernel, fall back
@@ -218,14 +237,14 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
     int fd;
     Py_ssize_t n;
     struct _Py_stat_struct st;
-#ifdef HAVE_GETRANDOM_SYSCALL
+#ifdef PY_GETRANDOM
     int res;
 #endif
 
     if (size <= 0)
         return 0;
 
-#ifdef HAVE_GETRANDOM_SYSCALL
+#ifdef PY_GETRANDOM
     res = py_getrandom(buffer, size, 1);
     if (res < 0)
         return -1;
@@ -304,7 +323,7 @@ dev_urandom_close(void)
     }
 }
 
-#endif /* HAVE_GETENTROPY */
+#endif
 
 /* Fill buffer with pseudo-random bytes generated by a linear congruent
    generator (LCG):
@@ -345,7 +364,7 @@ _PyOS_URandom(void *buffer, Py_ssize_t size)
 
 #ifdef MS_WINDOWS
     return win32_urandom((unsigned char *)buffer, size, 1);
-#elif HAVE_GETENTROPY
+#elif PY_GETENTROPY
     return py_getentropy(buffer, size, 0);
 #else
     return dev_urandom_python((char*)buffer, size);
@@ -392,7 +411,7 @@ _PyRandom_Init(void)
     else {
 #ifdef MS_WINDOWS
         (void)win32_urandom(secret, secret_size, 0);
-#elif HAVE_GETENTROPY
+#elif PY_GETENTROPY
         (void)py_getentropy(secret, secret_size, 1);
 #else
         dev_urandom_noraise(secret, secret_size);
@@ -408,7 +427,7 @@ _PyRandom_Fini(void)
         CryptReleaseContext(hCryptProv, 0);
         hCryptProv = 0;
     }
-#elif HAVE_GETENTROPY
+#elif PY_GETENTROPY
     /* nothing to clean */
 #else
     dev_urandom_close();

diff --git a/configure b/configure
index 95d953ac3dab74378378471b3b6e25f5d1a9b6b4..f7b1839c1937c4881787275b96ed797b259e4bb7 100755 (executable)
--- a/configure
+++ b/configure
@@ -16005,11 +16005,11 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
     #include <sys/syscall.h>
 
     int main() {
-        const int flags = 0;
         char buffer[1];
-        int n;
+        const size_t buflen = sizeof(buffer);
+        const int flags = 0;
         /* ignore the result, Python checks for ENOSYS at runtime */
-        (void)syscall(SYS_getrandom, buffer, sizeof(buffer), flags);
+        (void)syscall(SYS_getrandom, buffer, buflen, flags);
         return 0;
     }
 
@@ -16031,6 +16031,43 @@ $as_echo "#define HAVE_GETRANDOM_SYSCALL 1" >>confdefs.h
 
 fi
 
+# check if the getrandom() function is available
+# the test was written for the Solaris function of <sys/random.h>
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for the getrandom() function" >&5
+$as_echo_n "checking for the getrandom() function... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+
+    #include <sys/random.h>
+
+    int main() {
+        char buffer[1];
+        const size_t buflen = sizeof(buffer);
+        const int flags = 0;
+        /* ignore the result, Python checks for ENOSYS at runtime */
+        (void)getrandom(buffer, buflen, flags);
+        return 0;
+    }
+
+
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  have_getrandom=yes
+else
+  have_getrandom=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_getrandom" >&5
+$as_echo "$have_getrandom" >&6; }
+
+if test "$have_getrandom" = yes; then
+
+$as_echo "#define HAVE_GETRANDOM 1" >>confdefs.h
+
+fi
+
 # generate output files
 ac_config_files="$ac_config_files Makefile.pre Modules/Setup.config Misc/python.pc Misc/python-config.sh"
 

diff --git a/configure.ac b/configure.ac
index 668234d7e2ecf366f5c061b76329039901c462ad..180a421f707fd250b66da1def1450ce809bea47f 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -5111,11 +5111,11 @@ AC_LINK_IFELSE(
     #include <sys/syscall.h>
 
     int main() {
-        const int flags = 0;
         char buffer[1];
-        int n;
+        const size_t buflen = sizeof(buffer);
+        const int flags = 0;
         /* ignore the result, Python checks for ENOSYS at runtime */
-        (void)syscall(SYS_getrandom, buffer, sizeof(buffer), flags);
+        (void)syscall(SYS_getrandom, buffer, buflen, flags);
         return 0;
     }
   ]])
@@ -5127,6 +5127,31 @@ if test "$have_getrandom_syscall" = yes; then
               [Define to 1 if the Linux getrandom() syscall is available])
 fi
 
+# check if the getrandom() function is available
+# the test was written for the Solaris function of <sys/random.h>
+AC_MSG_CHECKING(for the getrandom() function)
+AC_LINK_IFELSE(
+[
+  AC_LANG_SOURCE([[
+    #include <sys/random.h>
+
+    int main() {
+        char buffer[1];
+        const size_t buflen = sizeof(buffer);
+        const int flags = 0;
+        /* ignore the result, Python checks for ENOSYS at runtime */
+        (void)getrandom(buffer, buflen, flags);
+        return 0;
+    }
+  ]])
+],[have_getrandom=yes],[have_getrandom=no])
+AC_MSG_RESULT($have_getrandom)
+
+if test "$have_getrandom" = yes; then
+    AC_DEFINE(HAVE_GETRANDOM, 1,
+              [Define to 1 if the getrandom() function is available])
+fi
+
 # generate output files
 AC_CONFIG_FILES(Makefile.pre Modules/Setup.config Misc/python.pc Misc/python-config.sh)
 AC_CONFIG_FILES([Modules/ld_so_aix], [chmod +x Modules/ld_so_aix])

diff --git a/pyconfig.h.in b/pyconfig.h.in
index 0d40c94cd4c0a36057ef6658e00bb3ae0a5acafa..b0cafb318574c9ddf2ff1e296fbeabde90e76353 100644 (file)
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -395,6 +395,9 @@
 /* Define to 1 if you have the `getpwent' function. */
 #undef HAVE_GETPWENT
 
+/* Define to 1 if the getrandom() function is available */
+#undef HAVE_GETRANDOM
+
 /* Define to 1 if the Linux getrandom() syscall is available */
 #undef HAVE_GETRANDOM_SYSCALL