filter.c

/* filter.c: filter framework functions
 *
 * Copyright (C) 2006-2014 cgit Development Team <cgit@lists.zx2c4.com>
 *
 * Licensed under GNU General Public License v2
 *   (see COPYING for full license text)
 */

#include "cgit.h"
#include "html.h"
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <errno.h>
#ifndef NO_LUA
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
#endif

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 struct cgit_filter *current_write_filter = NULL;

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.owner_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);
		reap_filter(cgit_repolist.repos[i].owner_filter);
	}
}

void cgit_init_filters(void)
{
	libc_write = dlsym(RTLD_NEXT, "write");
	if (!libc_write)
		die("Could not locate libc's write function");
}

ssize_t write(int fd, const void *buf, size_t count)
{
	if (fd != STDOUT_FILENO || !filter_write)
		return libc_write(fd, buf, 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))
{
	/* We want to avoid buggy nested patterns. */
	assert(filter_write == NULL);
	assert(current_write_filter == NULL);
	current_write_filter = filter;
	filter_write = new_write;
}

static inline void unhook_write()
{
	assert(filter_write != NULL);
	assert(current_write_filter != NULL);
	filter_write = NULL;
	current_write_filter = NULL;
}

static int open_exec_filter(struct cgit_filter *base, va_list ap)
{
	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
	int i;

	for (i = 0; i < filter->base.argument_count; i++)
		filter->argv[i + 1] = va_arg(ap, char *);

	filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
		"Unable to duplicate STDOUT");
	chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
	filter->pid = chk_non_negative(fork(), "Unable to create subprocess");
	if (filter->pid == 0) {
		close(filter->pipe_fh[1]);
		chk_non_negative(dup2(filter->pipe_fh[0], STDIN_FILENO),
			"Unable to use pipe as STDIN");
		execvp(filter->cmd, filter->argv);
		die_errno("Unable to exec subprocess %s", filter->cmd);
	}
	close(filter->pipe_fh[0]);
	chk_non_negative(dup2(filter->pipe_fh[1], STDOUT_FILENO),
		"Unable to use pipe as STDOUT");
	close(filter->pipe_fh[1]);
	return 0;
}

static int close_exec_filter(struct cgit_filter *base)
{
	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
	int i, exit_status = 0;

	chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
		"Unable to restore STDOUT");
	close(filter->old_stdout);
	if (filter->pid < 0)
		goto done;
	waitpid(filter->pid, &exit_status, 0);
	if (WIFEXITED(exit_status))
		goto done;
	die("Subprocess %s exited abnormally", filter->cmd);

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)
{
	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
	fprintf(f, "%sexec:%s\n", prefix, filter->cmd);
}

static void cleanup_exec_filter(struct cgit_filter *base)
{
	struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
	if (filter->argv) {
		free(filter->argv);
		filter->argv = NULL;
	}
	if (filter->cmd) {
		free(filter->cmd);
		filter->cmd = NULL;
	}
}

static struct cgit_filter *new_exec_filter(const char *cmd, int argument_count)
{
	struct cgit_exec_filter *f;
	int args_size = 0;

	f = xmalloc(sizeof(*f));
	/* We leave argv for now and assign it below. */
	cgit_exec_filter_init(f, xstrdup(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;
}

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;
	filter->base.close = close_exec_filter;
	filter->base.fprintf = fprintf_exec_filter;
	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;
}

#ifndef NO_LUA
struct lua_filter {
	struct cgit_filter base;
	char *script_file;
	lua_State *lua_state;
};

static void error_lua_filter(struct lua_filter *filter)
{
	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)
{
	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);
		errno = EIO;
		return -1;
	}
	return count;
}

static inline int hook_lua_filter(lua_State *lua_state, void (*fn)(const char *txt))
{
	const char *str;
	ssize_t (*save_filter_write)(struct cgit_filter *base, const void *buf, size_t count);
	struct cgit_filter *save_filter;

	str = lua_tostring(lua_state, 1);
	if (!str)
		return 0;

	save_filter_write = filter_write;
	save_filter = current_write_filter;
	unhook_write();
	fn(str);
	hook_write(save_filter, save_filter_write);

	return 0;
}

static int html_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, html);
}

static int html_txt_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, html_txt);
}

static int html_attr_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, html_attr);
}

static int html_url_path_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, html_url_path);
}

static int html_url_arg_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, html_url_arg);
}

static int html_include_lua_filter(lua_State *lua_state)
{
	return hook_lua_filter(lua_state, (void (*)(const char *))html_include);
}

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 int init_lua_filter(struct lua_filter *filter)
{
	if (filter->lua_state)
		return 0;

	if (!(filter->lua_state = luaL_newstate()))
		return 1;

	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");

	if (luaL_dofile(filter->lua_state, filter->script_file)) {
		error_lua_filter(filter);
		lua_close(filter->lua_state);
		filter->lua_state = NULL;
		return 1;
	}
	return 0;
}

static int open_lua_filter(struct cgit_filter *base, va_list ap)
{
	struct lua_filter *filter = (struct lua_filter *)base;
	int i;

	if (init_lua_filter(filter))
		return 1;

	hook_write(base, write_lua_filter);

	lua_getglobal(filter->lua_state, "filter_open");
	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);
		return 1;
	}
	return 0;
}

static int close_lua_filter(struct cgit_filter *base)
{
	struct lua_filter *filter = (struct lua_filter *)base;
	int ret = 0;

	lua_getglobal(filter->lua_state, "filter_close");
	if (lua_pcall(filter->lua_state, 0, 1, 0)) {
		error_lua_filter(filter);
		ret = -1;
	} else {
		ret = lua_tonumber(filter->lua_state, -1);
		lua_pop(filter->lua_state, 1);
	}

	unhook_write();
	return ret;
}

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 struct cgit_filter *new_lua_filter(const char *cmd, int argument_count)
{
	struct lua_filter *filter;

	filter = xmalloc(sizeof(*filter));
	memset(filter, 0, sizeof(*filter));
	filter->base.open = open_lua_filter;
	filter->base.close = close_lua_filter;
	filter->base.fprintf = fprintf_lua_filter;
	filter->base.cleanup = cleanup_lua_filter;
	filter->base.argument_count = argument_count;
	filter->script_file = xstrdup(cmd);

	return &filter->base;
}

#endif


int cgit_open_filter(struct cgit_filter *filter, ...)
{
	int result;
	va_list ap;
	if (!filter)
		return 0;
	va_start(ap, filter);
	result = filter->open(filter, ap);
	va_end(ap);
	return result;
}

int cgit_close_filter(struct cgit_filter *filter)
{
	if (!filter)
		return 0;
	return filter->close(filter);
}

void cgit_fprintf_filter(struct cgit_filter *filter, FILE *f, const char *prefix)
{
	filter->fprintf(filter, f, prefix);
}



static const struct {
	const char *prefix;
	struct cgit_filter *(*ctor)(const char *cmd, int argument_count);
} filter_specs[] = {
	{ "exec", new_exec_filter },
#ifndef NO_LUA
	{ "lua", new_lua_filter },
#endif
};

struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
{
	char *colon;
	int i;
	size_t len;
	int argument_count;

	if (!cmd || !cmd[0])
		return NULL;

	colon = strchr(cmd, ':');
	len = colon - cmd;
	/*
	 * In case we're running on Windows, don't allow a single letter before
	 * the colon.
	 */
	if (len == 1)
		colon = NULL;

	switch (filtertype) {
		case AUTH:
			argument_count = 12;
			break;

		case EMAIL:
			argument_count = 2;
			break;

		case OWNER:
			argument_count = 0;
			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);
	}

	die("Invalid filter type: %.*s", (int) len, cmd);
}