curl.rs

use std::ffi::{c_char, c_void};

use ngx::core;
use ngx::ffi::{
    ngx_array_push, ngx_command_t, ngx_conf_t, ngx_http_handler_pt, ngx_http_module_t,
    ngx_http_phases_NGX_HTTP_ACCESS_PHASE, ngx_int_t, ngx_module_t, ngx_str_t, ngx_uint_t, NGX_CONF_TAKE1,
    NGX_HTTP_LOC_CONF, NGX_HTTP_LOC_CONF_OFFSET, NGX_HTTP_MODULE,
};
use ngx::http::{self, HttpModule, MergeConfigError};
use ngx::http::{HttpModuleLocationConf, HttpModuleMainConf, NgxHttpCoreModule};
use ngx::{http_request_handler, ngx_log_debug_http, ngx_string};

struct Module;

impl http::HttpModule for Module {
    fn module() -> &'static ngx_module_t {
        unsafe { &*::core::ptr::addr_of!(ngx_http_curl_module) }
    }

    unsafe extern "C" fn postconfiguration(cf: *mut ngx_conf_t) -> ngx_int_t {
        // SAFETY: this function is called with non-NULL cf always
        let cf = &mut *cf;
        let cmcf = NgxHttpCoreModule::main_conf_mut(cf).expect("http core main conf");

        let h = ngx_array_push(&mut cmcf.phases[ngx_http_phases_NGX_HTTP_ACCESS_PHASE as usize].handlers)
            as *mut ngx_http_handler_pt;
        if h.is_null() {
            return core::Status::NGX_ERROR.into();
        }
        // set an Access phase handler
        *h = Some(curl_access_handler);
        core::Status::NGX_OK.into()
    }
}

#[derive(Debug, Default)]
struct ModuleConfig {
    enable: bool,
}

unsafe impl HttpModuleLocationConf for Module {
    type LocationConf = ModuleConfig;
}

static mut NGX_HTTP_CURL_COMMANDS: [ngx_command_t; 2] = [
    ngx_command_t {
        name: ngx_string!("curl"),
        type_: (NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1) as ngx_uint_t,
        set: Some(ngx_http_curl_commands_set_enable),
        conf: NGX_HTTP_LOC_CONF_OFFSET,
        offset: 0,
        post: std::ptr::null_mut(),
    },
    ngx_command_t::empty(),
];

static NGX_HTTP_CURL_MODULE_CTX: ngx_http_module_t = ngx_http_module_t {
    preconfiguration: Some(Module::preconfiguration),
    postconfiguration: Some(Module::postconfiguration),
    create_main_conf: None,
    init_main_conf: None,
    create_srv_conf: None,
    merge_srv_conf: None,
    create_loc_conf: Some(Module::create_loc_conf),
    merge_loc_conf: Some(Module::merge_loc_conf),
};

// Generate the `ngx_modules` table with exported modules.
// This feature is required to build a 'cdylib' dynamic module outside of the NGINX buildsystem.
#[cfg(feature = "export-modules")]
ngx::ngx_modules!(ngx_http_curl_module);

#[used]
#[allow(non_upper_case_globals)]
#[cfg_attr(not(feature = "export-modules"), no_mangle)]
pub static mut ngx_http_curl_module: ngx_module_t = ngx_module_t {
    ctx: std::ptr::addr_of!(NGX_HTTP_CURL_MODULE_CTX) as _,
    commands: unsafe { &NGX_HTTP_CURL_COMMANDS[0] as *const _ as *mut _ },
    type_: NGX_HTTP_MODULE as _,
    ..ngx_module_t::default()
};

impl http::Merge for ModuleConfig {
    fn merge(&mut self, prev: &ModuleConfig) -> Result<(), MergeConfigError> {
        if prev.enable {
            self.enable = true;
        };
        Ok(())
    }
}

http_request_handler!(curl_access_handler, |request: &mut http::Request| {
    let co = Module::location_conf(request).expect("module config is none");

    ngx_log_debug_http!(request, "curl module enabled: {}", co.enable);

    match co.enable {
        true => {
            if request
                .user_agent()
                .is_some_and(|ua| ua.as_bytes().starts_with(b"curl"))
            {
                http::HTTPStatus::FORBIDDEN.into()
            } else {
                core::Status::NGX_DECLINED
            }
        }
        false => core::Status::NGX_DECLINED,
    }
});

extern "C" fn ngx_http_curl_commands_set_enable(
    cf: *mut ngx_conf_t,
    _cmd: *mut ngx_command_t,
    conf: *mut c_void,
) -> *mut c_char {
    unsafe {
        let conf = &mut *(conf as *mut ModuleConfig);
        let args = (*(*cf).args).elts as *mut ngx_str_t;

        let val = (*args.add(1)).to_str();

        // set default value optionally
        conf.enable = false;

        if val.len() == 2 && val.eq_ignore_ascii_case("on") {
            conf.enable = true;
        } else if val.len() == 3 && val.eq_ignore_ascii_case("off") {
            conf.enable = false;
        }
    };

    std::ptr::null_mut()
}