/*

*** mod_proxy_uwsgi ***

To build:

apxs2 -i -c mod_proxy_uwsgi.c

To use:

LoadModule proxy_uwsgi_module /usr/lib/apache2/modules/mod_proxy_uwsgi.so
ProxyPass / uwsgi://127.0.0.1:3031/

Docs:

https://uwsgi-docs.readthedocs.io/en/latest/Apache.html#mod-proxy-uwsgi

*/
#define APR_WANT_MEMFUNC
#define APR_WANT_STRFUNC
#include "apr_strings.h"
#include "apr_hooks.h"
#include "apr_optional_hooks.h"
#include "apr_buckets.h"

#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
#include "http_protocol.h"
#include "http_request.h"
#include "util_script.h"

#include "mod_proxy.h"


#define UWSGI_SCHEME "uwsgi"
#define UWSGI_DEFAULT_PORT 3031

module AP_MODULE_DECLARE_DATA proxy_uwsgi_module;


static int uwsgi_canon(request_rec *r, char *url)
{
    char *host, sport[sizeof(":65535")];
    const char *err, *path;
    apr_port_t port = UWSGI_DEFAULT_PORT;

    if (strncasecmp(url, UWSGI_SCHEME "://", sizeof(UWSGI_SCHEME) + 2)) {
        return DECLINED;
    }
    url += sizeof(UWSGI_SCHEME); /* Keep slashes */

    err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
    if (err) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                    "error parsing URL %s: %s", url, err);
        return HTTP_BAD_REQUEST;
    }

    if (port != UWSGI_DEFAULT_PORT)
        apr_snprintf(sport, sizeof(sport), ":%u", port);
    else
        sport[0] = '\0';

    if (ap_strchr(host, ':')) { /* if literal IPv6 address */
        host = apr_pstrcat(r->pool, "[", host, "]", NULL);
    }

    path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0,
                             r->proxyreq);
    if (!path) {
        return HTTP_BAD_REQUEST;
    }

    r->filename = apr_pstrcat(r->pool, "proxy:" UWSGI_SCHEME "://", host, sport, "/",
                              path, NULL);

    return OK;
}


static int uwsgi_send(proxy_conn_rec *conn, const char *buf, apr_size_t length,
                   request_rec *r)
{
    apr_status_t rv;
    apr_size_t written;

    while (length > 0) {
        written = length;
        if ((rv = apr_socket_send(conn->sock, buf, &written)) != APR_SUCCESS) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r,
                          "sending data to %s:%u failed",
                          conn->hostname, conn->port);
            return HTTP_SERVICE_UNAVAILABLE;
        }

        /* count for stats */
        conn->worker->s->transferred += written;
        buf += written;
        length -= written;
    }

    return OK;
}


/*
 * Send uwsgi header block
 */
static int uwsgi_send_headers(request_rec *r, proxy_conn_rec *conn)
{
    char *buf, *ptr;

    const apr_array_header_t *env_table;
    const apr_table_entry_t *env;

    int j;

    apr_size_t headerlen = 4;
    uint16_t pktsize, keylen, vallen;

    ap_add_common_vars(r);
    ap_add_cgi_vars(r);

    // this is not a security problem (in Linux) as uWSGI destroy the env memory area readable in /proc
    // and generally if you host untrusted apps in your server and allows them to read others uid /proc/<pid>
    // files you have higher problems...
    const char *auth = apr_table_get(r->headers_in, "Authorization");
    if (auth) {
        apr_table_setn(r->subprocess_env, "HTTP_AUTHORIZATION", auth); 
    }

    const char *script_name = apr_table_get(r->subprocess_env, "SCRIPT_NAME");
    const char *path_info = apr_table_get(r->subprocess_env, "PATH_INFO");

    if (script_name && path_info) {
        if (strcmp(path_info, "/")) {
            apr_table_set(r->subprocess_env, "SCRIPT_NAME", apr_pstrndup(r->pool, script_name, strlen(script_name)-strlen(path_info)));
	}
        else {
            if (!strcmp(script_name, "/")) {
                apr_table_set(r->subprocess_env, "SCRIPT_NAME", "");
            }
        }
    }

    env_table = apr_table_elts(r->subprocess_env);
    env = (apr_table_entry_t *)env_table->elts;

    for (j = 0; j < env_table->nelts; ++j) {
        headerlen += 2 + strlen(env[j].key) + 2 + strlen(env[j].val) ;
    }

    ptr = buf = apr_palloc(r->pool, headerlen);

    ptr+=4;

    for (j = 0; j < env_table->nelts; ++j) {
	keylen = strlen(env[j].key);
	*ptr++= (uint8_t) (keylen & 0xff);
	*ptr++= (uint8_t) ((keylen >> 8)  & 0xff);
	memcpy(ptr, env[j].key, keylen) ; ptr+=keylen;

	vallen = strlen(env[j].val);
	*ptr++= (uint8_t) (vallen & 0xff);
	*ptr++= (uint8_t) ((vallen >> 8)  & 0xff);
	memcpy(ptr, env[j].val, vallen) ; ptr+=vallen;
    }

    pktsize = headerlen-4;

    buf[0] = 0;
    buf[1] = (uint8_t) (pktsize & 0xff);
    buf[2] = (uint8_t) ((pktsize >> 8) & 0xff);
    buf[3] = 0;

    return uwsgi_send(conn, buf, headerlen, r);
}


static int uwsgi_send_body(request_rec *r, proxy_conn_rec *conn)
{
    if (ap_should_client_block(r)) {
        char *buf = apr_palloc(r->pool, AP_IOBUFSIZE);
        int status;
        apr_size_t readlen;

        readlen = ap_get_client_block(r, buf, AP_IOBUFSIZE);
        while (readlen > 0) {
            status = uwsgi_send(conn, buf, readlen, r);
            if (status != OK) {
                return HTTP_SERVICE_UNAVAILABLE;
            }
            readlen = ap_get_client_block(r, buf, AP_IOBUFSIZE);
        }
        if (readlen == -1) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                          "receiving request body failed");
            return HTTP_INTERNAL_SERVER_ERROR;
        }
    }

    return OK;
}

#if AP_MODULE_MAGIC_AT_LEAST(20111130,0)
static request_rec *ap_proxy_make_fake_req(conn_rec *c, request_rec *r)
{
    apr_pool_t *pool;
    request_rec *rp;

    apr_pool_create(&pool, c->pool);

    rp = apr_pcalloc(pool, sizeof(*r));

    rp->pool            = pool;
    rp->status          = HTTP_OK;

    rp->headers_in      = apr_table_make(pool, 50);
    rp->subprocess_env  = apr_table_make(pool, 50);
    rp->headers_out     = apr_table_make(pool, 12);
    rp->err_headers_out = apr_table_make(pool, 5);
    rp->notes           = apr_table_make(pool, 5);

    rp->server = r->server;
    rp->log = r->log;
    rp->proxyreq = r->proxyreq;
    rp->request_time = r->request_time;
    rp->connection      = c;
    rp->output_filters  = c->output_filters;
    rp->input_filters   = c->input_filters;
    rp->proto_output_filters  = c->output_filters;
    rp->proto_input_filters   = c->input_filters;
    rp->useragent_ip = c->client_ip;
    rp->useragent_addr = c->client_addr;

    rp->request_config  = ap_create_request_config(pool);
    proxy_run_create_req(r, rp);

    return rp;
}

apr_status_t ap_proxy_buckets_lifetime_transform(request_rec *r,
        apr_bucket_brigade *from, apr_bucket_brigade *to)
{
    apr_bucket *e;
    apr_bucket *new;
    const char *data;
    apr_size_t bytes;
    apr_status_t rv = APR_SUCCESS;

    apr_brigade_cleanup(to);
    for (e = APR_BRIGADE_FIRST(from);
         e != APR_BRIGADE_SENTINEL(from);
         e = APR_BUCKET_NEXT(e)) {
        if (!APR_BUCKET_IS_METADATA(e)) {
            apr_bucket_read(e, &data, &bytes, APR_BLOCK_READ);
            new = apr_bucket_transient_create(data, bytes, r->connection->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(to, new);
        }
        else if (APR_BUCKET_IS_FLUSH(e)) {
            new = apr_bucket_flush_create(r->connection->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(to, new);
        }
        else if (APR_BUCKET_IS_EOS(e)) {
            new = apr_bucket_eos_create(r->connection->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(to, new);
        }
        else {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00964)
                          "Unhandled bucket type of type %s in"
                          " proxy_buckets_lifetime_transform", e->type->name);
            apr_bucket_delete(e);
            rv = APR_EGENERAL;
        }
    }
    return rv;
}
#endif


static int uwsgi_response(request_rec *r, proxy_conn_rec *backend, proxy_server_conf *conf)
{

	char buffer[HUGE_STRING_LEN];
	const char *buf;
	char *value, *end;
	int len;
	int backend_broke = 0;
	apr_status_t rc;
	conn_rec *c = r->connection;
	apr_off_t readbytes;
	apr_status_t rv;
	apr_bucket *e;
	apr_read_type_e mode = APR_NONBLOCK_READ;

	request_rec *rp = ap_proxy_make_fake_req(backend->connection, r);
	rp->proxyreq = PROXYREQ_RESPONSE;

	apr_bucket_brigade *bb = apr_brigade_create(r->pool, c->bucket_alloc);
	apr_bucket_brigade *pass_bb = apr_brigade_create(r->pool, c->bucket_alloc);

	len = ap_getline(buffer, sizeof(buffer), rp, 1);
	if (len <= 0) {
		/* invalid or empty */
		return HTTP_INTERNAL_SERVER_ERROR;
	}
	backend->worker->s->read += len;
	if ((apr_size_t)len >= sizeof(buffer)) {
	        /* too long */
		return HTTP_INTERNAL_SERVER_ERROR;
	}

	/* Position of http status code */
	int status_start;
	if (apr_date_checkmask(buffer, "HTTP/#.# ###*")) {
		status_start = 9;
	} else if (apr_date_checkmask(buffer, "HTTP/# ###*")) {
		status_start = 7;
	} else {
	        /* not HTTP */
	        return HTTP_BAD_GATEWAY;
	}
	int status_end = status_start + 3;

	char keepchar = buffer[status_end];
	buffer[status_end] = '\0';
	r->status = atoi(&buffer[status_start]);

	if (keepchar != '\0') {
		buffer[status_end] = keepchar;
	} else {
		/* 2616 requires the space in Status-Line; the origin
		* server may have sent one but ap_rgetline_core will
		* have stripped it. */
		buffer[status_end] = ' ';
		buffer[status_end+1] = '\0';
	}
	r->status_line = apr_pstrdup(r->pool, &buffer[status_start]);

	/* parse headers */
	while ((len = ap_getline(buffer, sizeof(buffer), rp, 1)) > 0) {
	        if ((apr_size_t)len >= sizeof(buffer)) {
		  /* too long */
		  len = -1;
		  break;
		}
		value = strchr(buffer, ':');
		if (!value) {
		  /* invalid header */
		  len = -1;
		  break;
		}
		*value++ = '\0';
		if (*ap_scan_http_token(buffer)) {
		  /* invalid name */
		  len = -1;
		  break;
		}
		while (apr_isspace(*value)) ++value; 
		for (end = &value[strlen(value)-1]; end > value && apr_isspace(*end); --end) *end = '\0';
		if (*ap_scan_http_field_content(value)) {
		  /* invalid value */
		  len = -1;
		  break;
		}
		apr_table_add(r->headers_out, buffer, value);
	}
	if (len < 0) {
	  /* Reset headers, but not to NULL because things below the chain expect
	   * this to be non NULL e.g. the ap_content_length_filter.
	   */
	  r->headers_out = apr_table_make(r->pool, 1);
	  return HTTP_BAD_GATEWAY;
	}

	if ((buf = apr_table_get(r->headers_out, "Content-Type"))) {
		ap_set_content_type(r, apr_pstrdup(r->pool, buf));
	}

    // honor ProxyErrorOverride and ErrorDocument
#if AP_MODULE_MAGIC_AT_LEAST(20101106,0)
    proxy_dir_conf *dconf = ap_get_module_config(r->per_dir_config, &proxy_module);
    if (dconf->error_override && ap_is_HTTP_ERROR(r->status)) {
#else
    if (conf->error_override && ap_is_HTTP_ERROR(r->status)) {
#endif
        int status = r->status;
        r->status = HTTP_OK;
        r->status_line = NULL;

        apr_brigade_cleanup(bb);
               apr_brigade_cleanup(pass_bb);

        return status;
    }

	int finish = 0;
	while(!finish) {
		rv = ap_get_brigade(rp->input_filters, bb,
                                        AP_MODE_READBYTES, mode,
                                        conf->io_buffer_size);
		if (APR_STATUS_IS_EAGAIN(rv)
                        || (rv == APR_SUCCESS && APR_BRIGADE_EMPTY(bb)) ) {
			e = apr_bucket_flush_create(c->bucket_alloc);
			APR_BRIGADE_INSERT_TAIL(bb, e);
			if (ap_pass_brigade(r->output_filters, bb) || c->aborted) {
				break;
			}
			apr_brigade_cleanup(bb);
			mode = APR_BLOCK_READ;
			continue;
		}
		else if (rv == APR_EOF) {
			break;
		}
		else if (rv != APR_SUCCESS) {
			ap_proxy_backend_broke(r, bb);
			ap_pass_brigade(r->output_filters, bb);
			backend_broke = 1;
			break;
		}

		mode = APR_NONBLOCK_READ;
		apr_brigade_length(bb, 0, &readbytes);
		backend->worker->s->read += readbytes;

		if (APR_BRIGADE_EMPTY(bb)) {
                        apr_brigade_cleanup(bb);
                        break;
                }

		ap_proxy_buckets_lifetime_transform(r, bb, pass_bb);

		// found the last brigade?
		if (APR_BUCKET_IS_EOS(APR_BRIGADE_LAST(bb))) finish = 1;

		// do not pass chunk if it is zero_sized
		apr_brigade_length(pass_bb, 0, &readbytes);

		if ((readbytes > 0 && ap_pass_brigade(r->output_filters, pass_bb) != APR_SUCCESS) || c->aborted) {
			finish = 1;
		}

		apr_brigade_cleanup(bb);
		apr_brigade_cleanup(pass_bb);
	}

	e = apr_bucket_eos_create(c->bucket_alloc);
	APR_BRIGADE_INSERT_TAIL(bb, e);
        ap_pass_brigade(r->output_filters, bb);

	apr_brigade_cleanup(bb);

	if (c->aborted || backend_broke) {
        	return DONE;
        }

	return OK;
}

static int uwsgi_handler(request_rec *r, proxy_worker *worker,
                        proxy_server_conf *conf, char *url,
                        const char *proxyname, apr_port_t proxyport)
{
    int status;
    proxy_conn_rec *backend = NULL;
    apr_pool_t *p = r->pool;
    apr_uri_t *uri = apr_palloc(r->pool, sizeof(*uri));
    char server_portstr[32];

    if (strncasecmp(url, UWSGI_SCHEME "://", sizeof(UWSGI_SCHEME) + 2)) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                      "declining URL %s", url);
        return DECLINED;
    }

    // ADD PATH_INFO
#if AP_MODULE_MAGIC_AT_LEAST(20111130,0)
    size_t w_len = strlen(worker->s->name);
#else
    size_t w_len = strlen(worker->name);
#endif
    char *u_path_info = r->filename + 6 + w_len;
    int delta = 0;
    if (u_path_info[0] != '/') {
        delta = 1;
    }
    int decode_status = ap_unescape_url(url+w_len-delta);
    if (decode_status) {
       ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                      "unable to decode uri: %s",
                      url+w_len-delta);
        return HTTP_INTERNAL_SERVER_ERROR;
    }
    apr_table_add(r->subprocess_env, "PATH_INFO", url+w_len-delta);


    /* Create space for state information */
    status = ap_proxy_acquire_connection(UWSGI_SCHEME, &backend, worker,
                                         r->server);
    if (status != OK) {
        goto cleanup;
    }
    backend->is_ssl = 0;

    /* Step One: Determine Who To Connect To */
    status = ap_proxy_determine_connection(p, r, conf, worker, backend,
                                           uri, &url, proxyname, proxyport,
                                           server_portstr, sizeof(server_portstr));
    if (status != OK) {
        goto cleanup;
    }


    /* Step Two: Make the Connection */
    if (ap_proxy_connect_backend(UWSGI_SCHEME, backend, worker, r->server)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                      "failed to make connection to backend: %s:%u",
                      backend->hostname, backend->port);
        status = HTTP_SERVICE_UNAVAILABLE;
        goto cleanup;
    }

    /* Step Three: Create conn_rec */
    if (!backend->connection) {
	if ((status = ap_proxy_connection_create(UWSGI_SCHEME, backend,
						r->connection, r->server)) != OK)
		goto cleanup;
    }

    /* Step Four: Process the Request */
    if (   ((status = ap_setup_client_block(r, REQUEST_CHUNKED_ERROR)) != OK)
        || ((status = uwsgi_send_headers(r, backend)) != OK)
        || ((status = uwsgi_send_body(r, backend)) != OK)
        || ((status = uwsgi_response(r, backend, conf)) != OK)) {
        goto cleanup;
    }

cleanup:
    if (backend) {
        backend->close = 1; /* always close the socket */
        ap_proxy_release_connection(UWSGI_SCHEME, backend, r->server);
    }
    return status;
}


static void register_hooks(apr_pool_t *p)
{
    proxy_hook_scheme_handler(uwsgi_handler, NULL, NULL, APR_HOOK_FIRST);
    proxy_hook_canon_handler(uwsgi_canon, NULL, NULL, APR_HOOK_FIRST);
}


module AP_MODULE_DECLARE_DATA proxy_uwsgi_module = {
    STANDARD20_MODULE_STUFF,
    NULL,		/* create per-directory config structure */
    NULL,		/* merge per-directory config structures */
    NULL,		/* create per-server config structure */
    NULL,		/* merge per-server config structures */
    NULL,		/* command table */
    register_hooks	/* register hooks */
};