Log dangerous registration of signal handlers

[vlc] / bin / override.c

diff --git a/bin/override.c b/bin/override.c
index 048c8fe1ca50d5f810951b228f26db19485521d0..1eabda0135b5efa9edec3a727d3f349f68993794 100644 (file)
--- a/bin/override.c
+++ b/bin/override.c
@@ -41,6 +41,7 @@ void vlc_enable_override (void)
 #include <stdio.h>
 #include <stdlib.h>
 #include <dlfcn.h>
+#include <pthread.h>
 
 static void vlogbug (const char *level, const char *func, const char *fmt,
                      va_list ap)
@@ -77,4 +78,99 @@ static void *getsym (const char *name)
     ({ typeof (func) *sym = getsym ( # func); sym (__VA_ARGS__); })
 
 
+/*** Environment ***
+ *
+ * "Conforming multi-threaded applications shall not use the environ variable
+ *  to access or modify any environment variable while any other thread is
+ *  concurrently modifying any environment variable." -- POSIX.
+ *
+ * Some evil libraries modify the environment. We currently ignore the calls as
+ * they could crash the process. This may cause funny behaviour though. */
+int putenv (char *str)
+{
+    if (override)
+    {
+        LOG("Blocked", "\"%s\"", str);
+        return 0;
+    }
+    return CALL(putenv, str);
+}
+
+int setenv (const char *name, const char *value, int overwrite)
+{
+    if (override)
+    {
+        LOG("Blocked", "\"%s\", \"%s\", %d", name, value, overwrite);
+        return 0;
+    }
+    return CALL(setenv, name, value, overwrite);
+}
+
+int unsetenv (const char *name)
+{
+    if (override)
+    {
+        LOG("Blocked", "\"%s\"", name);
+        return 0;
+    }
+    return CALL(unsetenv, name);
+}
+
+
+/*** Pseudo random numbers ***
+ *
+ * The C PRNG is not thread-safe (and generally sucks, the POSIX 48-bits PRNG
+ * is much better as a reproducible non-secure PRNG). To work around this, we
+ * force evil callers to serialize. This makes the call safe, but fails to
+ * preserve reproducibility of the number sequence (which usually does not
+ * matter).
+ **/
+static pthread_mutex_t prng_lock = PTHREAD_MUTEX_INITIALIZER;
+
+void srand (unsigned int seed)
+{
+    pthread_mutex_lock (&prng_lock);
+    LOG("Warning", "%d", seed);
+    CALL(srand, seed);
+    pthread_mutex_unlock (&prng_lock);
+}
+
+int rand (void)
+{
+    int ret;
+
+    pthread_mutex_lock (&prng_lock);
+    LOG("Warning", "");
+    ret = CALL(rand);
+    pthread_mutex_unlock (&prng_lock);
+    return ret;
+}
+
+
+/** Signals **/
+#include <signal.h>
+
+void (*signal (int signum, void (*handler) (int))) (int)
+{
+    if (override)
+    {
+        const char *msg = "Error";
+
+        if ((signum == SIGPIPE && handler == SIG_IGN)
+         || (signum != SIGPIPE && handler == SIG_DFL))
+            /* Same settings we already use */
+            msg = "Warning";
+        LOG(msg, "%d, %p", signum, handler);
+    }
+    return CALL(signal, signum, handler);
+}
+
+int sigaction (int signum, const struct sigaction *act, struct sigaction *old)
+{
+    if (act != NULL)
+        LOG("Error", "%d, %p, %p", signum, act, old);
+    return CALL(sigaction, signum, act, old);
+}
+
+
 #endif /* __ELF__ */