added fork_rand test to check for PID wraparound

ok beck@

tests/fork_rand.c

@@ -0,0 +1,81 @@
+/*
+ * Checks if LibreSSL's PRNG is fork-safe on Linux.
+ * From https://www.agwa.name/blog/post/libressls_prng_is_unsafe_on_linux
+ */
+
+#include <openssl/rand.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static void random_bytes (unsigned char* p, size_t len)
+{
+	if (RAND_bytes(p, len) != 1) {
+		fprintf(stderr, "RAND_bytes failed\n");
+		abort();
+	}
+}
+
+static void random_stir (void)
+{
+	if (RAND_poll() != 1) {
+		fprintf(stderr, "RAND_poll failed\n");
+		abort();
+	}
+}
+
+static void print_buffer (unsigned char* p, size_t len)
+{
+	while (len--) {
+		printf("%02x", (unsigned int)*p++);
+	}
+}
+
+int main ()
+{
+	char c = 0;
+	int	pipefd[2];
+	pipe(pipefd);
+	setbuf(stdout, NULL);
+
+	if (fork() == 0) {
+		unsigned char buffer[32];
+		pid_t grandparent_pid = getpid();
+
+		random_bytes(buffer, sizeof(buffer));
+
+		if (fork() == 0) {
+			random_stir();
+			setsid();
+			while (1) {
+				pid_t	grandchild_pid = fork();
+				if (grandchild_pid == 0) {
+					random_stir();
+					if (getpid() == grandparent_pid) {
+						random_bytes(buffer, sizeof(buffer));
+						print_buffer(buffer, sizeof(buffer));
+						printf("\n");
+					}
+					_exit(0);
+				}
+				wait(NULL);
+				if (grandchild_pid == grandparent_pid) {
+					break;
+				}
+			}
+			write(pipefd[1], &c, 1);
+			_exit(0);
+		}
+
+		random_bytes(buffer, sizeof(buffer));
+		print_buffer(buffer, sizeof(buffer));
+		printf(" ");
+		_exit(0);
+	}
+	wait(NULL);
+	close(pipefd[1]);
+	read(pipefd[0], &c, 1);
+	return 0;
+}
+

tests/fork_rand.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+./fork_rand > fork_rand.txt
+while read -r a b;
+do
+	if [ "$a" = "$b" ]; then
+		echo "FAIL: $a = $b"
+	else
+		echo "PASS: $a != $b"
+	fi
+done < fork_rand.txt

update.sh

@@ -273,7 +273,7 @@ copy_src apps "apps.c apps.h asn1pars.c ca.c ciphers.c cms.c crl.c crl2p7.c
 	s_server.c s_socket.c s_time.c sess_id.c smime.c speed.c spkac.c
 	testdsa.h testrsa.h timeouts.h ts.c verify.c version.c x509.c"
 
-rm -f tests/*.c
+rm -f tests/*test.c
 for i in aead/aeadtest.c aeswrap/aes_wrap.c base64/base64test.c bf/bftest.c \
 	bio/biotest.c bn/general/bntest.c bn/mont/mont.c \
 	cast/casttest.c chacha/chachatest.c cts128/cts128test.c \
@@ -295,7 +295,7 @@ for i in asn1/asn1test.c ssl/ssltest.c ssl/testssl certs/ca.pem certs/server.pem
 done
 
 # do not directly run all test programs
-test_excludes=(biotest aeadtest evptest pq_test ssltest arc4randomforktest)
+test_excludes=(biotest aeadtest evptest pq_test ssltest arc4randomforktest fork_rand)
 (cd tests
 	cp Makefile.am.tpl Makefile.am