From: Arran Cudbard-Bell <a.cudbardb@freeradius.org>
Date: Wed, 18 Sep 2019 16:30:55 +0000 (-0500)
Subject: Move dlopen functionality from rlm_python into dl_open_by_sym in utility library
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=25422caa02f943d418f459f092989fb7e2af8f29;p=thirdparty%2Ffreeradius-server.git

Move dlopen functionality from rlm_python into dl_open_by_sym in utility library
---

diff --git a/src/lib/util/dl.c b/src/lib/util/dl.c
index f73172aaea3..7a1bca92a5f 100644
--- a/src/lib/util/dl.c
+++ b/src/lib/util/dl.c
@@ -160,6 +160,50 @@ static int dl_handle_cmp(void const *one, void const *two)
 	return strcmp(((dl_t const *)one)->name, ((dl_t const *)two)->name);
 }
 
+/** Utility function to dlopen the library containing a particular symbol
+ *
+ * @note Not really part of our 'dl' API, just a convenience function.
+ *
+ * @param[in] sym_name	to resolve.
+ * @param[in] flags	to pass to dlopen.
+ * @return
+ *	- NULL on error.
+ *      - A new handle on success.
+ */
+void *dl_open_by_sym(char const *sym_name, int flags)
+{
+	Dl_info		info;
+	void		*sym;
+	void		*handle;
+
+	/*
+	 *	Resolve the test symbol in our own symbol space by
+	 *	iterating through all the libraries.
+	 *	This might be slow.  Don't do this at runtime!
+	 */
+	sym = dlsym(RTLD_DEFAULT, sym_name);
+	if (!sym) {
+		fr_strerror_printf("Can't resolve symbol %s", sym_name);
+		return NULL;
+	}
+
+	/*
+	 *	Lookup the library the symbol belongs to
+	 */
+	if (dladdr(sym, &info) == 0) {
+		fr_strerror_printf("Failed retrieving info for \"%s\" (%p)", sym_name, sym);
+		return NULL;
+	}
+
+	handle = dlopen(info.dli_fname, flags);
+	if (!handle) {
+		fr_strerror_printf("Failed loading \"%s\": %s", info.dli_fname, dlerror());
+		return NULL;
+	}
+
+	return handle;
+}
+
 /** Walk over the registered init callbacks, searching for the symbols they depend on
  *
  * Allows code outside of the dl API to register initialisation functions that get
diff --git a/src/lib/util/dl.h b/src/lib/util/dl.h
index 11472618e14..2ba8b670557 100644
--- a/src/lib/util/dl.h
+++ b/src/lib/util/dl.h
@@ -86,6 +86,7 @@ typedef void (*dl_unload_t)(dl_t const *module, void *symbol, void *user_ctx);
 /*
  *	Functions
  */
+void			*dl_open_by_sym(char const *sym_name, int flags);
 
 int			dl_symbol_init(dl_loader_t *dl_loader, dl_t const *dl);
 
diff --git a/src/modules/rlm_python/rlm_python.c b/src/modules/rlm_python/rlm_python.c
index fa92a2269c6..3a7c61e6795 100644
--- a/src/modules/rlm_python/rlm_python.c
+++ b/src/modules/rlm_python/rlm_python.c
@@ -1238,10 +1238,6 @@ static int mod_thread_detach(UNUSED fr_event_list_t *el, void *thread)
 
 static int mod_load(void)
 {
-	Dl_info		info;
-	void		*sym;
-
-#define PYTHON_TEST_SYMBOL "Py_IsInitialized"
 #define LOAD_INFO(_fmt, ...) fr_log(LOG_DST, L_INFO, __FILE__, __LINE__, "rlm_python - " _fmt,  ## __VA_ARGS__)
 #define LOAD_WARN(_fmt, ...) fr_log(LOG_DST, L_WARN, __FILE__, __LINE__, "rlm_python - " _fmt,  ## __VA_ARGS__)
 
@@ -1251,37 +1247,12 @@ static int mod_load(void)
 	dependency_version_number_add(NULL, "python", Py_GetVersion());
 
 	/*
-	 *	Resolve the test symbol in our own
-	 *	symbol space.
-	 */
-	sym = dlsym(RTLD_DEFAULT, PYTHON_TEST_SYMBOL);
-	if (!sym) {
-		LOAD_WARN("Can't find %s in symbol table, skipping loading python into global symbol table",
-			  PYTHON_TEST_SYMBOL);
-		goto skip_dlopen;
-	}
-
-	/*
-	 *	It's unclear whether passing function
-	 *	pointers will always "just work",
-	 *	which is why we resolve the symbol
-	 *	at runtime then call dladdr.
+	 *	Load python using RTLD_GLOBAL and dlopen
+	 *	This fixes issues where python C extensions
+	 *	can't find the symbols they need.
 	 */
-	if (dladdr(sym, &info) == 0) {
-		LOAD_WARN("Failed resolving symbol %s (%p) to library path: %s "
-			  ", skipping loading python into global symbol table", PYTHON_TEST_SYMBOL, sym, dlerror());
-		goto skip_dlopen;
-	}
-
-	/*
-	 *	Explicitly load libpython, so symbols will be available to lib-dynload modules
-	 */
-	python_dlhandle = dlopen(info.dli_fname, RTLD_NOW | RTLD_GLOBAL);
-	if (!python_dlhandle) fr_log(LOG_DST, L_WARN, __FILE__, __LINE__,
-				     "Failed loading libpython symbols from \"%s\" into global symbol table: %s",
-				     info.dli_fname, dlerror());
-
-skip_dlopen:
+	python_dlhandle = dl_open_by_sym("Py_IsInitialized", RTLD_NOW | RTLD_GLOBAL);
+	if (!python_dlhandle) LOAD_WARN("Failed loading libpython symbols into global symbol table: %s", fr_strerror());
 
 #if PY_MAJOR_VERSION == 3
 	/*