added fork_rand test to check for PID wraparound

ok beck@

2 files changed, 91 insertions, 0 deletions

diff --git a/tests/fork_rand.c b/tests/fork_rand.c
new file mode 100644
index 0000000..75f2cc2
--- /dev/null
+++ b/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;
+}
+
diff --git a/tests/fork_rand.sh b/tests/fork_rand.sh
new file mode 100755
index 0000000..333516e
--- /dev/null
+++ b/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