openlog(): keep the ident string in a safe place

Notes from the openlog(3) man page:

"The argument ident in the call of openlog() is probably stored as-is.
Thus, if the string it points to is changed, syslog() may start prepending
the changed string, and if the string it points to ceases to exist, the
results are undefined. Most portable is to use a string constant."

.npmignore

@@ -13,3 +13,5 @@ node_modules/
 lib/posix/*~
 test/unit/*~
 .*~
+.*
+*.gz

README.md

@@ -22,6 +22,7 @@ Other extension modules that provide POSIX/Unix/Linux/BSD functionality:
 * chroot(), daemonization http://search.npmjs.org/#/daemon-tools
 * iconv() http://search.npmjs.org/#/iconv
 * mmap() http://search.npmjs.org/#/mmap
+* PAM authentication, flock() and mkstemp() http://search.npmjs.org/#/unixlib
 
 ## Roadmap
 

src/posix.cc

@@ -365,6 +365,11 @@ static Handle<Value> node_setreuid(const Arguments& args) {
     return Undefined();
 }
 
+// openlog() first argument (const char* ident) is not guaranteed to be
+// copied within the openlog() call so we need to keep it in a safe location
+static const size_t MAX_SYSLOG_IDENT=100;
+static char syslog_ident[MAX_SYSLOG_IDENT+1] = {0};
+
 static Handle<Value> node_openlog(const Arguments& args) {
     HandleScope scope;
 
@@ -373,11 +378,13 @@ static Handle<Value> node_openlog(const Arguments& args) {
     }
 
     String::Utf8Value ident(args[0]->ToString());
+    strncpy(syslog_ident, *ident, MAX_SYSLOG_IDENT);
+    syslog_ident[MAX_SYSLOG_IDENT] = 0;
     if(!args[1]->IsNumber() || !args[2]->IsNumber()) {
         return EXCEPTION("openlog: invalid argument values");
     }
     // note: openlog does not ever fail, no return value
-    openlog(*ident, args[1]->Int32Value(), args[2]->Int32Value());
+    openlog(syslog_ident, args[1]->Int32Value(), args[2]->Int32Value());
 
     return Undefined();
 }