filter: add lua support

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

4 files changed, 235 insertions, 3 deletions

diff --git a/README b/README
index e1d5262..d79cd43 100644
--- a/README
+++ b/README
@@ -38,6 +38,7 @@ Dependencies
 * libzip
 * libcrypto (OpenSSL)
 * libssl (OpenSSL)
+* optional: luajit or lua
 
 Apache configuration
 --------------------
diff --git a/cgit.mk b/cgit.mk
index 9d6dea8..25f2eab 100644
--- a/cgit.mk
+++ b/cgit.mk
@@ -25,6 +25,25 @@ ifdef NO_C99_FORMAT
         CFLAGS += -DNO_C99_FORMAT
 endif
 
+ifdef NO_LUA
+        CFLAGS += -DNO_LUA
+else
+
+ifeq (VANILLA,$(LUA_IMPLEMENTATION))
+        CFLAGS += -llua
+else
+        LUAJIT_LIBS := $(shell pkg-config --libs luajit)
+        LUAJIT_CFLAGS := $(shell pkg-config --cflags luajit)
+        CGIT_LIBS += $(LUAJIT_LIBS)
+        CFLAGS += $(LUAJIT_CFLAGS)
+endif
+
+endif
+
+CGIT_LIBS += -ldl
+
+
+
 CGIT_OBJ_NAMES += cgit.o
 CGIT_OBJ_NAMES += cache.o
 CGIT_OBJ_NAMES += cmd.o
@@ -61,9 +80,6 @@ $(CGIT_VERSION_OBJS): $(CGIT_PREFIX)VERSION
 $(CGIT_VERSION_OBJS): EXTRA_CPPFLAGS = \
         -DCGIT_VERSION='"$(CGIT_VERSION)"'
 
-CGIT_LIBS += -ldl
-
-
 # Git handles dependencies using ":=" so dependencies in CGIT_OBJ are not
 # handled by that and we must handle them ourselves.
 cgit_dep_files := $(foreach f,$(CGIT_OBJS),$(dir $f).depend/$(notdir $f).d)
diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index 60159f6..78f33c8 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -564,6 +564,35 @@ specification with the relevant string; available values are:
 'exec:'::
         The default "one process per filter" mode.
 
+'lua:'::
+        Executes the script using a built-in Lua interpreter. The script is
+        loaded once per execution of cgit, and may be called multiple times
+        during cgit's lifetime, making it a good choice for repeated filters
+        such as the 'email filter'. It responds to three functions:
+
+        'filter_open(argument1, argument2, argument3, ...)'::
+                This is called upon activation of the filter for a particular
+                set of data.
+        'filter_write(buffer)'::
+                This is called whenever cgit writes data to the webpage.
+        'filter_close()'::
+                This is called when the current filtering operation is
+                completed.
+        
+        Additionally, cgit exposes to the Lua the following built-in functions:
+
+        'html(str)'::
+                Writes 'str' to the webpage.
+        'html_txt(str)'::
+                HTML escapes and writes 'str' to the webpage.
+        'html_attr(str)'::
+                HTML escapes for an attribute and writes "str' to the webpage.
+        'html_url_path(str)'::
+                URL escapes for a path and writes 'str' to the webpage.
+        'html_url_arg(str)'::
+                URL escapes for an argument and writes 'str' to the webpage.
+
+
 Parameters are provided to filters as follows.
 
 about filter::
diff --git a/filter.c b/filter.c
index f5a5992..3702585 100644
--- a/filter.c
+++ b/filter.c
@@ -7,12 +7,19 @@
  */
 
 #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;
@@ -164,6 +171,182 @@ void cgit_exec_filter_init(struct cgit_exec_filter *filter, char *cmd, char **ar
         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 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");
+
+        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, 0, 0)) {
+                error_lua_filter(filter);
+                ret = 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;
@@ -191,6 +374,9 @@ static const struct {
         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)