1 file changed, 178 insertions, 146 deletions
diff --git a/source/filter.c b/source/filter.c
index f195534..3c0c7e4 100644
--- a/source/filter.c
+++ b/source/filter.c
@@ -1,13 +1,16 @@
-/* filter.c: filter framework functions
- *
- * Copyright (C) 2006-2014 cgit Development Team <cgit@lists.zx2c4.com>
- *
- * Licensed under GNU General Public License v2
- *   (see LICENSE.txt for full license text)
+/*
+ * The two backends behind a cgit filter and the plumbing that hands stdout to
+ * whichever one is open. An exec filter forks a program and feeds it the page
+ * through a pipe, while a Lua filter runs a script inside cgit and feeds it
+ * the page through a write that has been interposed in front of libc's. A
+ * cgitrc command picks its backend with an exec or lua prefix, and a command
+ * with no prefix is taken as a program to run.
  */
 
 #include "cgit.h"
+#include "filter.h"
 #include "html.h"
+#include "shared.h"
 #ifndef NO_LUA
 #include <dlfcn.h>
 #include <lua.h>
@@ -15,32 +18,10 @@
 #include <lauxlib.h>
 #endif
 
-static inline void reap_filter(struct cgit_filter *filter)
-{
-	if (filter && filter->cleanup)
-		filter->cleanup(filter);
-}
-
-void cgit_cleanup_filters(void)
-{
-	int i;
-	reap_filter(ctx.cfg.about_filter);
-	reap_filter(ctx.cfg.commit_filter);
-	reap_filter(ctx.cfg.source_filter);
-	reap_filter(ctx.cfg.email_filter);
-	reap_filter(ctx.cfg.auth_filter);
-	for (i = 0; i < cgit_repolist.count; ++i) {
-		reap_filter(cgit_repolist.repos[i].about_filter);
-		reap_filter(cgit_repolist.repos[i].commit_filter);
-		reap_filter(cgit_repolist.repos[i].source_filter);
-		reap_filter(cgit_repolist.repos[i].email_filter);
-	}
-}
-
 static int open_exec_filter(struct cgit_filter *base, va_list ap)
 {
 	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
-	int pipe_fh[2];
+	int pipefd[2];
 	int i;
 
 	for (i = 0; i < filter->base.argument_count; i++)
@@ -48,19 +29,21 @@ static int open_exec_filter(struct cgit_filter *base, va_list ap)
 
 	filter->old_stdout = cgit_die_unless_positive(dup(STDOUT_FILENO),
 		"Unable to duplicate STDOUT");
-	cgit_die_unless_zero(pipe(pipe_fh), "Unable to create pipe to subprocess");
-	filter->pid = cgit_die_unless_non_negative(fork(), "Unable to create subprocess");
+	cgit_die_unless_zero(pipe(pipefd),
+		"Unable to create pipe to subprocess");
+	filter->pid = cgit_die_unless_non_negative(fork(),
+		"Unable to create subprocess");
 	if (filter->pid == 0) {
-		close(pipe_fh[1]);
-		cgit_die_unless_non_negative(dup2(pipe_fh[0], STDIN_FILENO),
+		close(pipefd[1]);
+		cgit_die_unless_non_negative(dup2(pipefd[0], STDIN_FILENO),
 			"Unable to use pipe as STDIN");
 		execvp(filter->cmd, filter->argv);
 		die_errno("Unable to exec subprocess %s", filter->cmd);
 	}
-	close(pipe_fh[0]);
-	cgit_die_unless_non_negative(dup2(pipe_fh[1], STDOUT_FILENO),
+	close(pipefd[0]);
+	cgit_die_unless_non_negative(dup2(pipefd[1], STDOUT_FILENO),
 		"Unable to use pipe as STDOUT");
-	close(pipe_fh[1]);
+	close(pipefd[1]);
 	return 0;
 }
 
@@ -83,10 +66,10 @@ done:
 	for (i = 0; i < filter->base.argument_count; i++)
 		filter->argv[i + 1] = NULL;
 	return WEXITSTATUS(exit_status);
-
 }
 
-static void fprintf_exec_filter(struct cgit_filter *base, FILE *f, const char *prefix)
+static void fprintf_exec_filter(struct cgit_filter *base, FILE *f,
+				const char *prefix)
 {
 	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
 	fprintf(f, "%sexec:%s\n", prefix, filter->cmd);
@@ -107,21 +90,23 @@ static void cleanup_exec_filter(struct cgit_filter *base)
 
 static struct cgit_filter *new_exec_filter(const char *cmd, int argument_count)
 {
-	struct cgit_exec_filter *f;
-	int args_size = 0;
+	struct cgit_exec_filter *filter;
+	int argv_size;
 
-	f = xmalloc(sizeof(*f));
-	/* We leave argv for now and assign it below. */
-	cgit_exec_filter_init(f, cgit_strdup_first_line(cmd), NULL);
-	f->base.argument_count = argument_count;
-	args_size = (2 + argument_count) * sizeof(char *);
-	f->argv = xmalloc(args_size);
-	memset(f->argv, 0, args_size);
-	f->argv[0] = f->cmd;
-	return &f->base;
+	filter = xmalloc(sizeof(*filter));
+	cgit_exec_filter_init(filter, cgit_strdup_first_line(cmd), NULL);
+	filter->base.argument_count = argument_count;
+	// argv is the command, then a slot per argument, then the NULL that
+	// execvp needs to find the end.
+	argv_size = (2 + argument_count) * sizeof(char *);
+	filter->argv = xmalloc(argv_size);
+	memset(filter->argv, 0, argv_size);
+	filter->argv[0] = filter->cmd;
+	return &filter->base;
 }
 
-void cgit_exec_filter_init(struct cgit_exec_filter *filter, char *cmd, char **argv)
+void cgit_exec_filter_init(struct cgit_exec_filter *filter, char *cmd,
+			   char **argv)
 {
 	memset(filter, 0, sizeof(*filter));
 	filter->base.open = open_exec_filter;
@@ -130,7 +115,6 @@ void cgit_exec_filter_init(struct cgit_exec_filter *filter, char *cmd, char **ar
 	filter->base.cleanup = cleanup_exec_filter;
 	filter->cmd = cmd;
 	filter->argv = argv;
-	/* The argument count for open_filter is zero by default, unless called from new_filter, above. */
 	filter->base.argument_count = 0;
 }
 
@@ -141,8 +125,17 @@ void cgit_init_filters(void)
 #endif
 
 #ifndef NO_LUA
+struct lua_filter {
+	struct cgit_filter base;
+	char *script_file;
+	lua_State *lua_state;
+};
+
+typedef ssize_t (*filter_write_fn)(struct cgit_filter *base, const void *buf,
+				   size_t count);
+
 static ssize_t (*libc_write)(int fd, const void *buf, size_t count);
-static ssize_t (*filter_write)(struct cgit_filter *base, const void *buf, size_t count) = NULL;
+static filter_write_fn filter_write = NULL;
 static struct cgit_filter *current_write_filter = NULL;
 
 void cgit_init_filters(void)
@@ -152,6 +145,10 @@ void cgit_init_filters(void)
 		die("Could not locate libc's write function");
 }
 
+/*
+ * Interposing on write is what lets a Lua filter see output produced by code
+ * that has no idea a filter is running.
+ */
 ssize_t write(int fd, const void *buf, size_t count)
 {
 	if (fd != STDOUT_FILENO || !filter_write)
@@ -159,13 +156,15 @@ ssize_t write(int fd, const void *buf, size_t count)
 	return filter_write(current_write_filter, buf, count);
 }
 
-static inline void hook_write(struct cgit_filter *filter, ssize_t (*new_write)(struct cgit_filter *base, const void *buf, size_t count))
+static inline void hook_write(struct cgit_filter *filter,
+			      filter_write_fn write_fn)
 {
-	/* We want to avoid buggy nested patterns. */
+	// Filters cannot nest, because there is one stdout and one hook, so a
+	// second one would strand the first.
 	assert(filter_write == NULL);
 	assert(current_write_filter == NULL);
 	current_write_filter = filter;
-	filter_write = new_write;
+	filter_write = write_fn;
 }
 
 static inline void unhook_write(void)
@@ -176,102 +175,113 @@ static inline void unhook_write(void)
 	current_write_filter = NULL;
 }
 
-struct lua_filter {
-	struct cgit_filter base;
-	char *script_file;
-	lua_State *lua_state;
-};
-
-static void error_lua_filter(struct lua_filter *filter)
+static void die_lua_error(struct lua_filter *filter)
 {
-	die("Lua error in %s: %s", filter->script_file, lua_tostring(filter->lua_state, -1));
+	die("Lua error in %s: %s", filter->script_file,
+	    lua_tostring(filter->lua_state, -1));
 	lua_pop(filter->lua_state, 1);
 }
 
-static ssize_t write_lua_filter(struct cgit_filter *base, const void *buf, size_t count)
+static ssize_t write_lua_filter(struct cgit_filter *base, const void *buf,
+				size_t count)
 {
 	struct lua_filter *filter = (struct lua_filter *)base;
 
 	lua_getglobal(filter->lua_state, "filter_write");
 	lua_pushlstring(filter->lua_state, buf, count);
 	if (lua_pcall(filter->lua_state, 1, 0, 0)) {
-		error_lua_filter(filter);
+		die_lua_error(filter);
 		errno = EIO;
 		return -1;
 	}
 	return count;
 }
 
-static inline int hook_lua_filter(lua_State *lua_state, void (*fn)(const char *txt))
+/*
+ * Output a script asks for belongs on the page and not back in its own filter,
+ * so the hook comes off around the call. The zero returned is Lua's count of
+ * values pushed for the script, not a success code.
+ */
+static inline int emit_unfiltered(lua_State *lua_state,
+				  void (*emit)(const char *text))
 {
-	const char *str;
-	ssize_t (*save_filter_write)(struct cgit_filter *base, const void *buf, size_t count);
-	struct cgit_filter *save_filter;
+	const char *text;
+	filter_write_fn saved_write;
+	struct cgit_filter *saved_filter;
 
-	str = lua_tostring(lua_state, 1);
-	if (!str)
+	text = lua_tostring(lua_state, 1);
+	if (!text)
 		return 0;
 
-	save_filter_write = filter_write;
-	save_filter = current_write_filter;
+	saved_write = filter_write;
+	saved_filter = current_write_filter;
 	unhook_write();
-	fn(str);
-	// fn buffers, so empty it while the hook is still off. Re-hooking first
-	// would send the page's own bytes back into the filter that asked for
-	// them to be written.
+	emit(text);
+	// emit leaves bytes in the html buffer, so empty it while the hook is
+	// still off. Re-hooking first would send the page's own bytes back into
+	// the filter.
 	html_flush();
-	hook_write(save_filter, save_filter_write);
+	hook_write(saved_filter, saved_write);
 
 	return 0;
 }
 
-static int html_lua_filter(lua_State *lua_state)
+static int script_html(lua_State *lua_state)
 {
-	return hook_lua_filter(lua_state, html);
+	return emit_unfiltered(lua_state, html);
 }
 
-static int html_txt_lua_filter(lua_State *lua_state)
+static int script_html_txt(lua_State *lua_state)
 {
-	return hook_lua_filter(lua_state, html_txt);
+	return emit_unfiltered(lua_state, html_txt);
 }
 
-static int html_attr_lua_filter(lua_State *lua_state)
+static int script_html_attr(lua_State *lua_state)
 {
-	return hook_lua_filter(lua_state, html_attr);
+	return emit_unfiltered(lua_state, html_attr);
 }
 
-static int html_url_path_lua_filter(lua_State *lua_state)
+static int script_html_url_path(lua_State *lua_state)
 {
-	return hook_lua_filter(lua_state, html_url_path);
+	return emit_unfiltered(lua_state, html_url_path);
 }
 
-static int html_url_arg_lua_filter(lua_State *lua_state)
+static int script_html_url_arg(lua_State *lua_state)
 {
-	return hook_lua_filter(lua_state, html_url_arg);
+	return emit_unfiltered(lua_state, html_url_arg);
 }
 
-static int html_include_lua_filter(lua_State *lua_state)
+/*
+ * html_include returns whether it found the file, and calling it through a
+ * pointer that claims it returns nothing would be undefined, so the result is
+ * dropped in a wrapper of the right shape.
+ */
+static void include_and_discard_result(const char *filename)
 {
-	return hook_lua_filter(lua_state, (void (*)(const char *))html_include);
+	html_include(filename);
 }
 
-static void cleanup_lua_filter(struct cgit_filter *base)
+static int script_html_include(lua_State *lua_state)
 {
-	struct lua_filter *filter = (struct lua_filter *)base;
-
-	if (!filter->lua_state)
-		return;
-
-	lua_close(filter->lua_state);
-	filter->lua_state = NULL;
-	if (filter->script_file) {
-		free(filter->script_file);
-		filter->script_file = NULL;
-	}
+	return emit_unfiltered(lua_state, include_and_discard_result);
 }
 
+static const struct {
+	const char *name;
+	lua_CFunction fn;
+} script_globals[] = {
+	{ "html", script_html },
+	{ "html_txt", script_html_txt },
+	{ "html_attr", script_html_attr },
+	{ "html_url_path", script_html_url_path },
+	{ "html_url_arg", script_html_url_arg },
+	{ "html_include", script_html_include },
+};
+
 static int init_lua_filter(struct lua_filter *filter)
 {
+	size_t i;
+
 	if (filter->lua_state)
 		return 0;
 
@@ -280,21 +290,13 @@ static int init_lua_filter(struct lua_filter *filter)
 
 	luaL_openlibs(filter->lua_state);
 
-	lua_pushcfunction(filter->lua_state, html_lua_filter);
-	lua_setglobal(filter->lua_state, "html");
-	lua_pushcfunction(filter->lua_state, html_txt_lua_filter);
-	lua_setglobal(filter->lua_state, "html_txt");
-	lua_pushcfunction(filter->lua_state, html_attr_lua_filter);
-	lua_setglobal(filter->lua_state, "html_attr");
-	lua_pushcfunction(filter->lua_state, html_url_path_lua_filter);
-	lua_setglobal(filter->lua_state, "html_url_path");
-	lua_pushcfunction(filter->lua_state, html_url_arg_lua_filter);
-	lua_setglobal(filter->lua_state, "html_url_arg");
-	lua_pushcfunction(filter->lua_state, html_include_lua_filter);
-	lua_setglobal(filter->lua_state, "html_include");
+	for (i = 0; i < ARRAY_SIZE(script_globals); i++) {
+		lua_pushcfunction(filter->lua_state, script_globals[i].fn);
+		lua_setglobal(filter->lua_state, script_globals[i].name);
+	}
 
 	if (luaL_dofile(filter->lua_state, filter->script_file)) {
-		error_lua_filter(filter);
+		die_lua_error(filter);
 		lua_close(filter->lua_state);
 		filter->lua_state = NULL;
 		return 1;
@@ -316,7 +318,7 @@ static int open_lua_filter(struct cgit_filter *base, va_list ap)
 	for (i = 0; i < filter->base.argument_count; ++i)
 		lua_pushstring(filter->lua_state, va_arg(ap, char *));
 	if (lua_pcall(filter->lua_state, filter->base.argument_count, 0, 0)) {
-		error_lua_filter(filter);
+		die_lua_error(filter);
 		return 1;
 	}
 	return 0;
@@ -329,7 +331,7 @@ static int close_lua_filter(struct cgit_filter *base)
 
 	lua_getglobal(filter->lua_state, "filter_close");
 	if (lua_pcall(filter->lua_state, 0, 1, 0)) {
-		error_lua_filter(filter);
+		die_lua_error(filter);
 		ret = -1;
 	} else {
 		ret = lua_tonumber(filter->lua_state, -1);
@@ -340,12 +342,27 @@ static int close_lua_filter(struct cgit_filter *base)
 	return ret;
 }
 
-static void fprintf_lua_filter(struct cgit_filter *base, FILE *f, const char *prefix)
+static void fprintf_lua_filter(struct cgit_filter *base, FILE *f,
+			       const char *prefix)
 {
 	struct lua_filter *filter = (struct lua_filter *)base;
 	fprintf(f, "%slua:%s\n", prefix, filter->script_file);
 }
 
+static void cleanup_lua_filter(struct cgit_filter *base)
+{
+	struct lua_filter *filter = (struct lua_filter *)base;
+
+	if (!filter->lua_state)
+		return;
+
+	lua_close(filter->lua_state);
+	filter->lua_state = NULL;
+	if (filter->script_file) {
+		free(filter->script_file);
+		filter->script_file = NULL;
+	}
+}
 
 static struct cgit_filter *new_lua_filter(const char *cmd, int argument_count)
 {
@@ -362,10 +379,8 @@ static struct cgit_filter *new_lua_filter(const char *cmd, int argument_count)
 
 	return &filter->base;
 }
-
 #endif
 
-
 int cgit_open_filter(struct cgit_filter *filter, ...)
 {
 	int result;
@@ -391,16 +406,37 @@ int cgit_close_filter(struct cgit_filter *filter)
 	return filter->close(filter);
 }
 
-void cgit_fprintf_filter(struct cgit_filter *filter, FILE *f, const char *prefix)
+void cgit_fprintf_filter(struct cgit_filter *filter, FILE *f,
+			 const char *prefix)
 {
 	filter->fprintfp(filter, f, prefix);
 }
 
+static inline void cleanup_filter(struct cgit_filter *filter)
+{
+	if (filter && filter->cleanup)
+		filter->cleanup(filter);
+}
 
+void cgit_cleanup_filters(void)
+{
+	int i;
+	cleanup_filter(ctx.cfg.about_filter);
+	cleanup_filter(ctx.cfg.commit_filter);
+	cleanup_filter(ctx.cfg.source_filter);
+	cleanup_filter(ctx.cfg.email_filter);
+	cleanup_filter(ctx.cfg.auth_filter);
+	for (i = 0; i < cgit_repolist.count; ++i) {
+		cleanup_filter(cgit_repolist.repos[i].about_filter);
+		cleanup_filter(cgit_repolist.repos[i].commit_filter);
+		cleanup_filter(cgit_repolist.repos[i].source_filter);
+		cleanup_filter(cgit_repolist.repos[i].email_filter);
+	}
+}
 
 static const struct {
 	const char *prefix;
-	struct cgit_filter *(*ctor)(const char *cmd, int argument_count);
+	struct cgit_filter *(*create)(const char *cmd, int argument_count);
 } filter_specs[] = {
 	{ "exec", new_exec_filter },
 #ifndef NO_LUA
@@ -419,42 +455,38 @@ struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
 		return NULL;
 
 	colon = strchr(cmd, ':');
-	len = colon - cmd;
-	/*
-	 * In case we're running on Windows, don't allow a single letter before
-	 * the colon.
-	 */
+	// Measured only once there is a colon to measure against, because
+	// subtracting from a null pointer is not something C defines.
+	len = colon ? (size_t)(colon - cmd) : 0;
+	// A single letter before the colon is a Windows drive letter, not a
+	// filter prefix.
 	if (len == 1)
 		colon = NULL;
 
 	switch (filtertype) {
-		case AUTH:
-			argument_count = 12;
-			break;
-
-		case EMAIL:
-			argument_count = 2;
-			break;
-
-		case SOURCE:
-		case ABOUT:
-			argument_count = 1;
-			break;
-
-		case COMMIT:
-		default:
-			argument_count = 0;
-			break;
+	case AUTH:
+		argument_count = 12;
+		break;
+	case EMAIL:
+		argument_count = 2;
+		break;
+	case SOURCE:
+	case ABOUT:
+		argument_count = 1;
+		break;
+	case COMMIT:
+	default:
+		argument_count = 0;
+		break;
 	}
 
-	/* If no prefix is given, exec filter is the default. */
 	if (!colon)
 		return new_exec_filter(cmd, argument_count);
 
 	for (i = 0; i < ARRAY_SIZE(filter_specs); i++) {
 		if (len == strlen(filter_specs[i].prefix) &&
 		    !strncmp(filter_specs[i].prefix, cmd, len))
-			return filter_specs[i].ctor(colon + 1, argument_count);
+			return filter_specs[i].create(colon + 1, argument_count);
 	}
 
 	die("Invalid filter type: %.*s", (int) len, cmd);