summaryrefslogtreecommitdiff
path: root/src/mod_proxy.c
blob: ad9b28b17a678418de8263c809bd6c9bc4bcacf8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
#include "first.h"

#include <string.h>
#include <stdlib.h>

#include "gw_backend.h"
#include "base.h"
#include "array.h"
#include "buffer.h"
#include "http_kv.h"
#include "http_header.h"
#include "log.h"
#include "sock_addr.h"
#include "status_counter.h"

/**
 *
 * HTTP reverse proxy
 *
 * TODO:      - HTTP/1.1
 *            - HTTP/1.1 persistent connection with upstream servers
 */

/* (future: might split struct and move part to http-header-glue.c) */
typedef struct http_header_remap_opts {
    const array *urlpaths;
    const array *hosts_request;
    const array *hosts_response;
    int https_remap;
    int upgrade;
    int connect_method;
    /*(not used in plugin_config, but used in handler_ctx)*/
    const buffer *http_host;
    const buffer *forwarded_host;
    const data_string *forwarded_urlpath;
} http_header_remap_opts;

typedef enum {
	PROXY_FORWARDED_NONE         = 0x00,
	PROXY_FORWARDED_FOR          = 0x01,
	PROXY_FORWARDED_PROTO        = 0x02,
	PROXY_FORWARDED_HOST         = 0x04,
	PROXY_FORWARDED_BY           = 0x08,
	PROXY_FORWARDED_REMOTE_USER  = 0x10
} proxy_forwarded_t;

typedef struct {
	gw_plugin_config gw;
	array *forwarded_params;
	array *header_params;
	unsigned short replace_http_host;
	unsigned int forwarded;

	http_header_remap_opts header;
} plugin_config;

typedef struct {
	PLUGIN_DATA;
	plugin_config **config_storage;

	plugin_config conf;
} plugin_data;

static int proxy_check_extforward;

typedef struct {
	gw_handler_ctx gw;
	http_response_opts opts;
	plugin_config conf;
} handler_ctx;


INIT_FUNC(mod_proxy_init) {
	plugin_data *p;

	p = calloc(1, sizeof(*p));

	return p;
}


FREE_FUNC(mod_proxy_free) {
	plugin_data *p = p_d;

	UNUSED(srv);

	if (p->config_storage) {
		size_t i;
		for (i = 0; i < srv->config_context->used; i++) {
			plugin_config *s = p->config_storage[i];

			if (NULL == s) continue;

			array_free(s->forwarded_params);
			array_free(s->header_params);

			/*assert(0 == offsetof(s->gw));*/
			gw_plugin_config_free(&s->gw);
			/*free(s);*//*free'd by gw_plugin_config_free()*/
		}
		free(p->config_storage);
	}

	free(p);

	return HANDLER_GO_ON;
}

SETDEFAULTS_FUNC(mod_proxy_set_defaults) {
	plugin_data *p = p_d;
	const data_unset *du;
	size_t i = 0;

	config_values_t cv[] = {
		{ "proxy.server",              NULL, T_CONFIG_LOCAL, T_CONFIG_SCOPE_CONNECTION },       /* 0 */
		{ "proxy.debug",               NULL, T_CONFIG_SHORT, T_CONFIG_SCOPE_CONNECTION },       /* 1 */
		{ "proxy.balance",             NULL, T_CONFIG_LOCAL, T_CONFIG_SCOPE_CONNECTION },       /* 2 */
		{ "proxy.replace-http-host",   NULL, T_CONFIG_BOOLEAN, T_CONFIG_SCOPE_CONNECTION },     /* 3 */
		{ "proxy.forwarded",           NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 4 */
		{ "proxy.header",              NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 5 */
		{ "proxy.map-extensions",      NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 6 */
		{ NULL,                        NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET }
	};

	p->config_storage = calloc(srv->config_context->used, sizeof(plugin_config *));

	for (i = 0; i < srv->config_context->used; i++) {
		data_config const* config = (data_config const*)srv->config_context->data[i];
		plugin_config *s;

		s = calloc(1, sizeof(plugin_config));
		s->gw.debug          = 0;
		s->replace_http_host = 0;
		s->forwarded_params  = array_init();
		s->forwarded         = PROXY_FORWARDED_NONE;
		s->header_params     = array_init();
		s->gw.ext_mapping    = array_init();

		cv[0].destination = NULL; /* T_CONFIG_LOCAL */
		cv[1].destination = &(s->gw.debug);
		cv[2].destination = NULL; /* T_CONFIG_LOCAL */
		cv[3].destination = &(s->replace_http_host);
		cv[4].destination = s->forwarded_params;
		cv[5].destination = s->header_params;
		cv[6].destination = s->gw.ext_mapping;

		p->config_storage[i] = s;

		if (0 != config_insert_values_global(srv, config->value, cv, i == 0 ? T_CONFIG_SCOPE_SERVER : T_CONFIG_SCOPE_CONNECTION)) {
			return HANDLER_ERROR;
		}

		du = array_get_element_klen(config->value, CONST_STR_LEN("proxy.server"));
		if (!gw_set_defaults_backend(srv, (gw_plugin_data *)p, du, i, 0)) {
			return HANDLER_ERROR;
		}

		du = array_get_element_klen(config->value, CONST_STR_LEN("proxy.balance"));
		if (!gw_set_defaults_balance(srv, &s->gw, du)) {
			return HANDLER_ERROR;
		}

		/* disable check-local for all exts (default enabled) */
		if (s->gw.exts) { /*(check after gw_set_defaults_backend())*/
			for (size_t j = 0; j < s->gw.exts->used; ++j) {
				gw_extension *ex = s->gw.exts->exts[j];
				for (size_t n = 0; n < ex->used; ++n) {
					ex->hosts[n]->check_local = 0;
				}
			}
		}

		if (!array_is_kvany(s->forwarded_params)) {
			log_error_write(srv, __FILE__, __LINE__, "s",
					"unexpected value for proxy.forwarded; expected ( \"param\" => \"value\" )");
			return HANDLER_ERROR;
		}
		for (size_t j = 0, used = s->forwarded_params->used; j < used; ++j) {
			proxy_forwarded_t param;
			du = s->forwarded_params->data[j];
			if (buffer_is_equal_string(&du->key, CONST_STR_LEN("by"))) {
				param = PROXY_FORWARDED_BY;
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("for"))) {
				param = PROXY_FORWARDED_FOR;
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("host"))) {
				param = PROXY_FORWARDED_HOST;
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proto"))) {
				param = PROXY_FORWARDED_PROTO;
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("remote_user"))) {
				param = PROXY_FORWARDED_REMOTE_USER;
			} else {
				log_error_write(srv, __FILE__, __LINE__, "sb",
					        "proxy.forwarded keys must be one of: by, for, host, proto, remote_user, but not:", &du->key);
				return HANDLER_ERROR;
			}
			if (du->type == TYPE_STRING) {
				data_string *ds = (data_string *)du;
				if (buffer_is_equal_string(&ds->value, CONST_STR_LEN("enable"))) {
					s->forwarded |= param;
				} else if (!buffer_is_equal_string(&ds->value, CONST_STR_LEN("disable"))) {
					log_error_write(srv, __FILE__, __LINE__, "sb",
						        "proxy.forwarded values must be one of: 0, 1, enable, disable; error for key:", &du->key);
					return HANDLER_ERROR;
				}
			} else if (du->type == TYPE_INTEGER) {
				data_integer *di = (data_integer *)du;
				if (di->value) s->forwarded |= param;
			} else {
				log_error_write(srv, __FILE__, __LINE__, "sb",
					        "proxy.forwarded values must be one of: 0, 1, enable, disable; error for key:", &du->key);
				return HANDLER_ERROR;
			}
		}

		if (!array_is_kvany(s->header_params)) {
			log_error_write(srv, __FILE__, __LINE__, "s",
					"unexpected value for proxy.header; expected ( \"param\" => ( \"key\" => \"value\" ) )");
			return HANDLER_ERROR;
		}
		for (size_t j = 0, used = s->header_params->used; j < used; ++j) {
			data_array *da = (data_array *)s->header_params->data[j];
			if (buffer_is_equal_string(&da->key, CONST_STR_LEN("https-remap"))) {
				data_string *ds = (data_string *)da;
				if (ds->type != TYPE_STRING) {
					log_error_write(srv, __FILE__, __LINE__, "s",
							"unexpected value for proxy.header; expected \"enable\" or \"disable\" for https-remap");
					return HANDLER_ERROR;
				}
				s->header.https_remap = !buffer_is_equal_string(&ds->value, CONST_STR_LEN("disable"))
						     && !buffer_is_equal_string(&ds->value, CONST_STR_LEN("0"));
				continue;
			}
			else if (buffer_is_equal_string(&da->key, CONST_STR_LEN("upgrade"))) {
				data_string *ds = (data_string *)da;
				if (ds->type != TYPE_STRING) {
					log_error_write(srv, __FILE__, __LINE__, "s",
							"unexpected value for proxy.header; expected \"upgrade\" => \"enable\" or \"disable\"");
					return HANDLER_ERROR;
				}
				s->header.upgrade = !buffer_is_equal_string(&ds->value, CONST_STR_LEN("disable"))
						 && !buffer_is_equal_string(&ds->value, CONST_STR_LEN("0"));
				continue;
			}
			else if (buffer_is_equal_string(&da->key, CONST_STR_LEN("connect"))) {
				data_string *ds = (data_string *)da;
				if (ds->type != TYPE_STRING) {
					log_error_write(srv, __FILE__, __LINE__, "s",
							"unexpected value for proxy.header; expected \"connect\" => \"enable\" or \"disable\"");
					return HANDLER_ERROR;
				}
				s->header.connect_method = !buffer_is_equal_string(&ds->value, CONST_STR_LEN("disable"))
							&& !buffer_is_equal_string(&ds->value, CONST_STR_LEN("0"));
				continue;
			}
			if (da->type != TYPE_ARRAY || !array_is_kvstring(&da->value)) {
				log_error_write(srv, __FILE__, __LINE__, "sb",
						"unexpected value for proxy.header; expected ( \"param\" => ( \"key\" => \"value\" ) ) near key", &da->key);
				return HANDLER_ERROR;
			}
			if (buffer_is_equal_string(&da->key, CONST_STR_LEN("map-urlpath"))) {
				s->header.urlpaths = &da->value;
			}
			else if (buffer_is_equal_string(&da->key, CONST_STR_LEN("map-host-request"))) {
				s->header.hosts_request = &da->value;
			}
			else if (buffer_is_equal_string(&da->key, CONST_STR_LEN("map-host-response"))) {
				s->header.hosts_response = &da->value;
			}
			else {
				log_error_write(srv, __FILE__, __LINE__, "sb",
						"unexpected key for proxy.header; expected ( \"param\" => ( \"key\" => \"value\" ) ) near key", &da->key);
				return HANDLER_ERROR;
			}
		}
	}

	for (i = 0; i < srv->srvconf.modules->used; i++) {
		data_string *ds = (data_string *)srv->srvconf.modules->data[i];
		if (buffer_is_equal_string(&ds->value, CONST_STR_LEN("mod_extforward"))) {
			proxy_check_extforward = 1;
			break;
		}
	}

	return HANDLER_GO_ON;
}


/* (future: might move to http-header-glue.c) */
static const buffer * http_header_remap_host_match (buffer *b, size_t off, http_header_remap_opts *remap_hdrs, int is_req, size_t alen)
{
    const array *hosts = is_req
      ? remap_hdrs->hosts_request
      : remap_hdrs->hosts_response;
    if (hosts) {
        const char * const s = b->ptr+off;
        for (size_t i = 0, used = hosts->used; i < used; ++i) {
            const data_string * const ds = (data_string *)hosts->data[i];
            const buffer *k = &ds->key;
            size_t mlen = buffer_string_length(k);
            if (1 == mlen && k->ptr[0] == '-') {
                /* match with authority provided in Host (if is_req)
                 * (If no Host in client request, then matching against empty
                 *  string will probably not match, and no remap will be
                 *  performed) */
                k = is_req
                  ? remap_hdrs->http_host
                  : remap_hdrs->forwarded_host;
                if (NULL == k) continue;
                mlen = buffer_string_length(k);
            }
            if (buffer_eq_icase_ss(s, alen, k->ptr, mlen)) {
                if (buffer_is_equal_string(&ds->value, CONST_STR_LEN("-"))) {
                    return remap_hdrs->http_host;
                }
                else if (!buffer_string_is_empty(&ds->value)) {
                    /*(save first matched request host for response match)*/
                    if (is_req && NULL == remap_hdrs->forwarded_host)
                        remap_hdrs->forwarded_host = &ds->value;
                    return &ds->value;
                } /*(else leave authority as-is and stop matching)*/
                break;
            }
        }
    }
    return NULL;
}


/* (future: might move to http-header-glue.c) */
static size_t http_header_remap_host (buffer *b, size_t off, http_header_remap_opts *remap_hdrs, int is_req, size_t alen)
{
    const buffer * const m =
      http_header_remap_host_match(b, off, remap_hdrs, is_req, alen);
    if (NULL == m) return alen; /*(no match; return original authority length)*/

    buffer_substr_replace(b, off, alen, m);
    return buffer_string_length(m); /*(length of replacement authority)*/
}


/* (future: might move to http-header-glue.c) */
static size_t http_header_remap_urlpath (buffer *b, size_t off, http_header_remap_opts *remap_hdrs, int is_req)
{
    const array *urlpaths = remap_hdrs->urlpaths;
    if (urlpaths) {
        const char * const s = b->ptr+off;
        const size_t plen = buffer_string_length(b) - off; /*(urlpath len)*/
        if (is_req) { /* request */
            for (size_t i = 0, used = urlpaths->used; i < used; ++i) {
                const data_string * const ds = (data_string *)urlpaths->data[i];
                const size_t mlen = buffer_string_length(&ds->key);
                if (mlen <= plen && 0 == memcmp(s, ds->key.ptr, mlen)) {
                    if (NULL == remap_hdrs->forwarded_urlpath)
                        remap_hdrs->forwarded_urlpath = ds;
                    buffer_substr_replace(b, off, mlen, &ds->value);
                    return buffer_string_length(&ds->value);/*(replacement len)*/
                }
            }
        }
        else {        /* response; perform reverse map */
            if (NULL != remap_hdrs->forwarded_urlpath) {
                const data_string * const ds = remap_hdrs->forwarded_urlpath;
                const size_t mlen = buffer_string_length(&ds->value);
                if (mlen <= plen && 0 == memcmp(s, ds->value.ptr, mlen)) {
                    buffer_substr_replace(b, off, mlen, &ds->key);
                    return buffer_string_length(&ds->key); /*(replacement len)*/
                }
            }
            for (size_t i = 0, used = urlpaths->used; i < used; ++i) {
                const data_string * const ds = (data_string *)urlpaths->data[i];
                const size_t mlen = buffer_string_length(&ds->value);
                if (mlen <= plen && 0 == memcmp(s, ds->value.ptr, mlen)) {
                    buffer_substr_replace(b, off, mlen, &ds->key);
                    return buffer_string_length(&ds->key); /*(replacement len)*/
                }
            }
        }
    }
    return 0;
}


/* (future: might move to http-header-glue.c) */
static void http_header_remap_uri (buffer *b, size_t off, http_header_remap_opts *remap_hdrs, int is_req)
{
    /* find beginning of URL-path (might be preceded by scheme://authority
     * (caller should make sure any leading whitespace is prior to offset) */
    if (b->ptr[off] != '/') {
        char *s = b->ptr+off;
        size_t alen; /*(authority len (host len))*/
        size_t slen; /*(scheme len)*/
        const buffer *m;
        /* skip over scheme and authority of URI to find beginning of URL-path
         * (value might conceivably be relative URL-path instead of URI) */
        if (NULL == (s = strchr(s, ':')) || s[1] != '/' || s[2] != '/') return;
        slen = s - (b->ptr+off);
        s += 3;
        off = (size_t)(s - b->ptr);
        if (NULL != (s = strchr(s, '/'))) {
            alen = (size_t)(s - b->ptr) - off;
            if (0 == alen) return; /*(empty authority, e.g. "http:///")*/
        }
        else {
            alen = buffer_string_length(b) - off;
            if (0 == alen) return; /*(empty authority, e.g. "http:///")*/
            buffer_append_string_len(b, CONST_STR_LEN("/"));
        }

        /* remap authority (if configured) and set offset to url-path */
        m = http_header_remap_host_match(b, off, remap_hdrs, is_req, alen);
        if (NULL != m) {
            if (remap_hdrs->https_remap
                && (is_req ? 5==slen && 0==memcmp(b->ptr+off-slen-3,"https",5)
                           : 4==slen && 0==memcmp(b->ptr+off-slen-3,"http",4))){
                if (is_req) {
                    memcpy(b->ptr+off-slen-3+4,"://",3);  /*("https"=>"http")*/
                    --off;
                    ++alen;
                }
                else {/*(!is_req)*/
                    memcpy(b->ptr+off-slen-3+4,"s://",4); /*("http" =>"https")*/
                    ++off;
                    --alen;
                }
            }
            buffer_substr_replace(b, off, alen, m);
            alen = buffer_string_length(m);/*(length of replacement authority)*/
        }
        off += alen;
    }

    /* remap URLs (if configured) */
    http_header_remap_urlpath(b, off, remap_hdrs, is_req);
}


/* (future: might move to http-header-glue.c) */
static void http_header_remap_setcookie (buffer *b, size_t off, http_header_remap_opts *remap_hdrs)
{
    /* Given the special-case of Set-Cookie and the (too) loosely restricted
     * characters allowed, for best results, the Set-Cookie value should be the
     * entire string in b from offset to end of string.  In response headers,
     * lighttpd may concatenate multiple Set-Cookie headers into single entry
     * in con->response.headers, separated by "\r\nSet-Cookie: " */
    for (char *s = b->ptr+off, *e; *s; s = e) {
        size_t len;
        {
            while (*s != ';' && *s != '\n' && *s != '\0') ++s;
            if (*s == '\n') {
                /*(include +1 for '\n', but leave ' ' for ++s below)*/
                s += sizeof("Set-Cookie:");
            }
            if ('\0' == *s) return;
            do { ++s; } while (*s == ' ' || *s == '\t');
            if ('\0' == *s) return;
            e = s+1;
            if ('=' == *s) continue;
            /*(interested only in Domain and Path attributes)*/
            while (*e != '=' && *e != '\0') ++e;
            if ('\0' == *e) return;
            ++e;
            switch ((int)(e - s - 1)) {
              case 4:
                if (buffer_eq_icase_ssn(s, "path", 4)) {
                    if (*e == '"') ++e;
                    if (*e != '/') continue;
                    off = (size_t)(e - b->ptr);
                    len = http_header_remap_urlpath(b, off, remap_hdrs, 0);
                    e = b->ptr+off+len; /*(b may have been reallocated)*/
                    continue;
                }
                break;
              case 6:
                if (buffer_eq_icase_ssn(s, "domain", 6)) {
                    size_t alen = 0;
                    if (*e == '"') ++e;
                    if (*e == '.') ++e;
                    if (*e == ';') continue;
                    off = (size_t)(e - b->ptr);
                    for (char c; (c = e[alen]) != ';' && c != ' ' && c != '\t'
                                          && c != '\r' && c != '\0'; ++alen);
                    len = http_header_remap_host(b, off, remap_hdrs, 0, alen);
                    e = b->ptr+off+len; /*(b may have been reallocated)*/
                    continue;
                }
                break;
              default:
                break;
            }
        }
    }
}


static void buffer_append_string_backslash_escaped(buffer *b, const char *s, size_t len) {
    /* (future: might move to buffer.c) */
    size_t j = 0;
    char *p;

    buffer_string_prepare_append(b, len*2 + 4);
    p = b->ptr + buffer_string_length(b);

    for (size_t i = 0; i < len; ++i) {
        int c = s[i];
        if (c == '"' || c == '\\' || c == 0x7F || (c < 0x20 && c != '\t'))
            p[j++] = '\\';
        p[j++] = c;
    }

    buffer_commit(b, j);
}

static void proxy_set_Forwarded(connection *con, const unsigned int flags) {
    buffer *b = NULL, *efor = NULL, *eproto = NULL, *ehost = NULL;
    int semicolon = 0;

    if (proxy_check_extforward) {
        efor   =
          http_header_env_get(con, CONST_STR_LEN("_L_EXTFORWARD_ACTUAL_FOR"));
        eproto =
          http_header_env_get(con, CONST_STR_LEN("_L_EXTFORWARD_ACTUAL_PROTO"));
        ehost  =
          http_header_env_get(con, CONST_STR_LEN("_L_EXTFORWARD_ACTUAL_HOST"));
    }

    /* note: set "Forwarded" prior to updating X-Forwarded-For (below) */

    if (flags)
        b = http_header_request_get(con, HTTP_HEADER_FORWARDED, CONST_STR_LEN("Forwarded"));

    if (flags && NULL == b) {
        const buffer *xff =
          http_header_request_get(con, HTTP_HEADER_X_FORWARDED_FOR, CONST_STR_LEN("X-Forwarded-For"));
        http_header_request_set(con, HTTP_HEADER_FORWARDED,
                                CONST_STR_LEN("Forwarded"),
                                CONST_STR_LEN("x")); /*(must not be blank for _get below)*/
      #ifdef __COVERITY__
        force_assert(NULL != b); /*(not NULL because created directly above)*/
      #endif
        b = http_header_request_get(con, HTTP_HEADER_FORWARDED, CONST_STR_LEN("Forwarded"));
        buffer_clear(b);
        if (NULL != xff) {
            /* use X-Forwarded-For contents to seed Forwarded */
            char *s = xff->ptr;
            size_t used = buffer_string_length(xff);
            for (size_t i=0, j, ipv6; i < used; ++i) {
                while (s[i] == ' ' || s[i] == '\t' || s[i] == ',') ++i;
                if (s[i] == '\0') break;
                j = i;
                do {
                    ++i;
                } while (s[i]!=' ' && s[i]!='\t' && s[i]!=',' && s[i]!='\0');
                buffer_append_string_len(b, CONST_STR_LEN("for="));
                /* over-simplified test expecting only IPv4 or IPv6 addresses,
                 * (not expecting :port, so treat existence of colon as IPv6,
                 *  and not expecting unix paths, especially not containing ':')
                 * quote all strings, backslash-escape since IPs not validated*/
                ipv6 = (NULL != memchr(s+j, ':', i-j)); /*(over-simplified) */
                buffer_append_string_len(b, CONST_STR_LEN("\""));
                if (ipv6)
                    buffer_append_string_len(b, CONST_STR_LEN("["));
                buffer_append_string_backslash_escaped(b, s+j, i-j);
                if (ipv6)
                    buffer_append_string_len(b, CONST_STR_LEN("]"));
                buffer_append_string_len(b, CONST_STR_LEN("\""));
                buffer_append_string_len(b, CONST_STR_LEN(", "));
            }
        }
    } else if (flags) { /*(NULL != b)*/
        buffer_append_string_len(b, CONST_STR_LEN(", "));
    }

    if (flags & PROXY_FORWARDED_FOR) {
        int family = sock_addr_get_family(&con->dst_addr);
        buffer_append_string_len(b, CONST_STR_LEN("for="));
        if (NULL != efor) {
            /* over-simplified test expecting only IPv4 or IPv6 addresses,
             * (not expecting :port, so treat existence of colon as IPv6,
             *  and not expecting unix paths, especially not containing ':')
             * quote all strings and backslash-escape since IPs not validated
             * (should be IP from original con->dst_addr_buf,
             *  so trustable and without :port) */
            int ipv6 = (NULL != strchr(efor->ptr, ':'));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
            if (ipv6) buffer_append_string_len(b, CONST_STR_LEN("["));
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(efor));
            if (ipv6) buffer_append_string_len(b, CONST_STR_LEN("]"));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
        } else if (family == AF_INET) {
            /*(Note: if :port is added, then must be quoted-string:
             * e.g. for="...:port")*/
            buffer_append_string_buffer(b, con->dst_addr_buf);
        } else if (family == AF_INET6) {
            buffer_append_string_len(b, CONST_STR_LEN("\"["));
            buffer_append_string_buffer(b, con->dst_addr_buf);
            buffer_append_string_len(b, CONST_STR_LEN("]\""));
        } else {
            buffer_append_string_len(b, CONST_STR_LEN("\""));
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(con->dst_addr_buf));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
        }
        semicolon = 1;
    }

    if (flags & PROXY_FORWARDED_BY) {
        int family = sock_addr_get_family(&con->srv_socket->addr);
        /* Note: getsockname() and inet_ntop() are expensive operations.
         * (recommendation: do not to enable by=... unless required)
         * future: might use con->srv_socket->srv_token if addr is not
         *   INADDR_ANY or in6addr_any, but must omit optional :port
         *   from con->srv_socket->srv_token for consistency */

        if (semicolon) buffer_append_string_len(b, CONST_STR_LEN(";"));
        buffer_append_string_len(b, CONST_STR_LEN("by="));
        buffer_append_string_len(b, CONST_STR_LEN("\""));
      #ifdef HAVE_SYS_UN_H
        /* special-case: might need to encode unix domain socket path */
        if (family == AF_UNIX) {
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(con->srv_socket->srv_token));
        }
        else
      #endif
        {
            sock_addr addr;
            socklen_t addrlen = sizeof(addr);
            if (0 == getsockname(con->fd,(struct sockaddr *)&addr, &addrlen)) {
                sock_addr_stringify_append_buffer(b, &addr);
            }
        }
        buffer_append_string_len(b, CONST_STR_LEN("\""));
        semicolon = 1;
    }

    if (flags & PROXY_FORWARDED_PROTO) {
        /* expecting "http" or "https"
         * (not checking if quoted-string and encoding needed) */
        if (semicolon) buffer_append_string_len(b, CONST_STR_LEN(";"));
        buffer_append_string_len(b, CONST_STR_LEN("proto="));
        if (NULL != eproto) {
            buffer_append_string_buffer(b, eproto);
        } else if (con->srv_socket->is_ssl) {
            buffer_append_string_len(b, CONST_STR_LEN("https"));
        } else {
            buffer_append_string_len(b, CONST_STR_LEN("http"));
        }
        semicolon = 1;
    }

    if (flags & PROXY_FORWARDED_HOST) {
        if (NULL != ehost) {
            if (semicolon)
                buffer_append_string_len(b, CONST_STR_LEN(";"));
            buffer_append_string_len(b, CONST_STR_LEN("host=\""));
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(ehost));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
            semicolon = 1;
        } else if (!buffer_string_is_empty(con->request.http_host)) {
            if (semicolon)
                buffer_append_string_len(b, CONST_STR_LEN(";"));
            buffer_append_string_len(b, CONST_STR_LEN("host=\""));
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(con->request.http_host));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
            semicolon = 1;
        }
    }

    if (flags & PROXY_FORWARDED_REMOTE_USER) {
        const buffer *remote_user =
          http_header_env_get(con, CONST_STR_LEN("REMOTE_USER"));
        if (NULL != remote_user) {
            if (semicolon)
                buffer_append_string_len(b, CONST_STR_LEN(";"));
            buffer_append_string_len(b, CONST_STR_LEN("remote_user=\""));
            buffer_append_string_backslash_escaped(
              b, CONST_BUF_LEN(remote_user));
            buffer_append_string_len(b, CONST_STR_LEN("\""));
            semicolon = 1;
        }
    }

    /* legacy X-* headers, including X-Forwarded-For */

    b = (NULL != efor) ? efor : con->dst_addr_buf;
    http_header_request_set(con, HTTP_HEADER_X_FORWARDED_FOR,
                            CONST_STR_LEN("X-Forwarded-For"),
                            CONST_BUF_LEN(b));

    b = (NULL != ehost) ? ehost : con->request.http_host;
    if (!buffer_string_is_empty(b)) {
        http_header_request_set(con, HTTP_HEADER_OTHER,
                                CONST_STR_LEN("X-Host"),
                                CONST_BUF_LEN(b));
        http_header_request_set(con, HTTP_HEADER_OTHER,
                                CONST_STR_LEN("X-Forwarded-Host"),
                                CONST_BUF_LEN(b));
    }

    b = (NULL != eproto) ? eproto : con->uri.scheme;
    http_header_request_set(con, HTTP_HEADER_X_FORWARDED_PROTO,
                            CONST_STR_LEN("X-Forwarded-Proto"),
                            CONST_BUF_LEN(b));
}


static handler_t proxy_create_env(server *srv, gw_handler_ctx *gwhctx) {
	handler_ctx *hctx = (handler_ctx *)gwhctx;
	connection *con = hctx->gw.remote_conn;
	const int remap_headers = (NULL != hctx->conf.header.urlpaths
				   || NULL != hctx->conf.header.hosts_request);
	const int upgrade = hctx->conf.header.upgrade
	    && (NULL != http_header_request_get(con, HTTP_HEADER_UPGRADE, CONST_STR_LEN("Upgrade")));
	size_t rsz = (size_t)(con->read_queue->bytes_out - hctx->gw.wb->bytes_in);
	buffer * const b = chunkqueue_prepend_buffer_open_sz(hctx->gw.wb, rsz < 65536 ? rsz : con->header_len);

	/* build header */

	/* request line */
	http_method_append(b, con->request.http_method);
	buffer_append_string_len(b, CONST_STR_LEN(" "));
	buffer_append_string_buffer(b, con->request.uri);
	if (remap_headers)
		http_header_remap_uri(b, buffer_string_length(b) - buffer_string_length(con->request.uri), &hctx->conf.header, 1);
	if (!upgrade)
		buffer_append_string_len(b, CONST_STR_LEN(" HTTP/1.0\r\n"));
	else
		buffer_append_string_len(b, CONST_STR_LEN(" HTTP/1.1\r\n"));

	if (hctx->conf.replace_http_host && !buffer_string_is_empty(hctx->gw.host->id)) {
		if (hctx->gw.conf.debug > 1) {
			log_error_write(srv, __FILE__, __LINE__,  "SBS",
					"proxy - using \"", hctx->gw.host->id, "\" as HTTP Host");
		}
		buffer_append_string_len(b, CONST_STR_LEN("Host: "));
		buffer_append_string_buffer(b, hctx->gw.host->id);
		buffer_append_string_len(b, CONST_STR_LEN("\r\n"));
	} else if (!buffer_string_is_empty(con->request.http_host)) {
		buffer_append_string_len(b, CONST_STR_LEN("Host: "));
		buffer_append_string_buffer(b, con->request.http_host);
		if (remap_headers) {
			size_t alen = buffer_string_length(con->request.http_host);
			http_header_remap_host(b, buffer_string_length(b) - alen, &hctx->conf.header, 1, alen);
		}
		buffer_append_string_len(b, CONST_STR_LEN("\r\n"));
	}

	/* "Forwarded" and legacy X- headers */
	proxy_set_Forwarded(con, hctx->conf.forwarded);

	if (con->request.content_length > 0
	    || (0 == con->request.content_length
		&& HTTP_METHOD_GET != con->request.http_method
		&& HTTP_METHOD_HEAD != con->request.http_method)) {
		/* set Content-Length if client sent Transfer-Encoding: chunked
		 * and not streaming to backend (request body has been fully received) */
		const buffer *vb = http_header_request_get(con, HTTP_HEADER_CONTENT_LENGTH, CONST_STR_LEN("Content-Length"));
		if (NULL == vb) {
			char buf[LI_ITOSTRING_LENGTH];
			li_itostrn(buf, sizeof(buf), con->request.content_length);
			http_header_request_set(con, HTTP_HEADER_CONTENT_LENGTH, CONST_STR_LEN("Content-Length"), buf, strlen(buf));
		}
	}

	/* request header */
	for (size_t i = 0, used = con->request.headers.used; i < used; ++i) {
		data_string *ds = (data_string *)con->request.headers.data[i];
		const size_t klen = buffer_string_length(&ds->key);
		size_t vlen;
		switch (klen) {
		default:
			break;
		case 4:
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Host"))) continue; /*(handled further above)*/
			break;
		case 10:
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Connection"))) continue;
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Set-Cookie"))) continue; /*(response header only; avoid accidental reflection)*/
			break;
		case 16:
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Proxy-Connection"))) continue;
			break;
		case 5:
			/* Do not emit HTTP_PROXY in environment.
			 * Some executables use HTTP_PROXY to configure
			 * outgoing proxy.  See also https://httpoxy.org/ */
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Proxy"))) continue;
			break;
		case 0:
			continue;
		}

		vlen = buffer_string_length(&ds->value);
		if (0 == vlen) continue;

		if (buffer_string_space(b) < klen + vlen + 4) {
			size_t extend = b->size * 2 - buffer_string_length(b);
			extend = extend > klen + vlen + 4 ? extend : klen + vlen + 4 + 4095;
			buffer_string_prepare_append(b, extend);
		}

		buffer_append_string_len(b, ds->key.ptr, klen);
		buffer_append_string_len(b, CONST_STR_LEN(": "));
		buffer_append_string_len(b, ds->value.ptr, vlen);
		buffer_append_string_len(b, CONST_STR_LEN("\r\n"));

		if (!remap_headers) continue;

		/* check for hdrs for which to remap URIs in-place after append to b */

		switch (klen) {
		default:
			continue;
	      #if 0 /* "URI" is HTTP response header (non-standard; historical in Apache) */
		case 3:
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("URI"))) break;
			continue;
	      #endif
	      #if 0 /* "Location" is HTTP response header */
		case 8:
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Location"))) break;
			continue;
	      #endif
		case 11: /* "Destination" is WebDAV request header */
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Destination"))) break;
			continue;
		case 16: /* "Content-Location" may be HTTP request or response header */
			if (buffer_is_equal_caseless_string(&ds->key, CONST_STR_LEN("Content-Location"))) break;
			continue;
		}

		http_header_remap_uri(b, buffer_string_length(b) - vlen - 2, &hctx->conf.header, 1);
	}

	if (!upgrade)
		buffer_append_string_len(b, CONST_STR_LEN("Connection: close\r\n\r\n"));
	else
		buffer_append_string_len(b, CONST_STR_LEN("Connection: close, upgrade\r\n\r\n"));

	hctx->gw.wb_reqlen = buffer_string_length(b);
	chunkqueue_prepend_buffer_commit(hctx->gw.wb);

	if (con->request.content_length) {
		chunkqueue_append_chunkqueue(hctx->gw.wb, con->request_content_queue);
		if (con->request.content_length > 0)
			hctx->gw.wb_reqlen += con->request.content_length; /* total req size */
		else /* as-yet-unknown total request size (Transfer-Encoding: chunked)*/
			hctx->gw.wb_reqlen = -hctx->gw.wb_reqlen;
	}

	status_counter_inc(srv, CONST_STR_LEN("proxy.requests"));
	return HANDLER_GO_ON;
}


static handler_t proxy_create_env_connect(server *srv, gw_handler_ctx *gwhctx) {
	handler_ctx *hctx = (handler_ctx *)gwhctx;
	connection *con = hctx->gw.remote_conn;
	con->http_status = 200; /* OK */
	con->file_started = 1;
	gw_set_transparent(srv, &hctx->gw);
	http_response_upgrade_read_body_unknown(srv, con);

	status_counter_inc(srv, CONST_STR_LEN("proxy.requests"));
	return HANDLER_GO_ON;
}


#define PATCH(x) \
	p->conf.x = s->x;
#define PATCH_GW(x) \
	p->conf.gw.x = s->gw.x;
static int mod_proxy_patch_connection(server *srv, connection *con, plugin_data *p) {
	size_t i, j;
	plugin_config *s = p->config_storage[0];

	PATCH_GW(exts);
	PATCH_GW(exts_auth);
	PATCH_GW(exts_resp);
	PATCH_GW(debug);
	PATCH_GW(ext_mapping);
	PATCH_GW(balance);
	PATCH(replace_http_host);
	PATCH(forwarded);
	PATCH(header); /*(copies struct)*/

	/* skip the first, the global context */
	for (i = 1; i < srv->config_context->used; i++) {
		data_config *dc = (data_config *)srv->config_context->data[i];
		s = p->config_storage[i];

		/* condition didn't match */
		if (!config_check_cond(srv, con, dc)) continue;

		/* merge config */
		for (j = 0; j < dc->value->used; j++) {
			data_unset *du = dc->value->data[j];

			if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.server"))) {
				PATCH_GW(exts);
				PATCH_GW(exts_auth);
				PATCH_GW(exts_resp);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.debug"))) {
				PATCH_GW(debug);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.balance"))) {
				PATCH_GW(balance);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.map-extensions"))) {
				PATCH_GW(ext_mapping);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.replace-http-host"))) {
				PATCH(replace_http_host);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.forwarded"))) {
				PATCH(forwarded);
			} else if (buffer_is_equal_string(&du->key, CONST_STR_LEN("proxy.header"))) {
				PATCH(header); /*(copies struct)*/
			}
		}
	}

	return 0;
}
#undef PATCH_GW
#undef PATCH

static handler_t proxy_response_headers(server *srv, connection *con, struct http_response_opts_t *opts) {
    /* response headers just completed */
    handler_ctx *hctx = (handler_ctx *)opts->pdata;

    if (con->response.htags & HTTP_HEADER_UPGRADE) {
        if (hctx->conf.header.upgrade && con->http_status == 101) {
            /* 101 Switching Protocols; transition to transparent proxy */
            gw_set_transparent(srv, &hctx->gw);
            http_response_upgrade_read_body_unknown(srv, con);
        }
        else {
            con->response.htags &= ~HTTP_HEADER_UPGRADE;
          #if 0
            /* preserve prior questionable behavior; likely broken behavior
             * anyway if backend thinks connection is being upgraded but client
             * does not receive Connection: upgrade */
            http_header_response_unset(con, HTTP_HEADER_UPGRADE,
                                       CONST_STR_LEN("Upgrade"))
          #endif
        }
    }

    /* rewrite paths, if needed */

    if (NULL == hctx->conf.header.urlpaths
        && NULL == hctx->conf.header.hosts_response)
        return HANDLER_GO_ON;

    if (con->response.htags & HTTP_HEADER_LOCATION) {
        buffer *vb = http_header_response_get(con, HTTP_HEADER_LOCATION, CONST_STR_LEN("Location"));
        if (vb) http_header_remap_uri(vb, 0, &hctx->conf.header, 0);
    }
    if (con->response.htags & HTTP_HEADER_CONTENT_LOCATION) {
        buffer *vb = http_header_response_get(con, HTTP_HEADER_CONTENT_LOCATION, CONST_STR_LEN("Content-Location"));
        if (vb) http_header_remap_uri(vb, 0, &hctx->conf.header, 0);
    }
    if (con->response.htags & HTTP_HEADER_SET_COOKIE) {
        buffer *vb = http_header_response_get(con, HTTP_HEADER_SET_COOKIE, CONST_STR_LEN("Set-Cookie"));
        if (vb) http_header_remap_setcookie(vb, 0, &hctx->conf.header);
    }

    return HANDLER_GO_ON;
}

static handler_t mod_proxy_check_extension(server *srv, connection *con, void *p_d) {
	plugin_data *p = p_d;
	handler_t rc;

	if (con->mode != DIRECT) return HANDLER_GO_ON;

	mod_proxy_patch_connection(srv, con, p);
	if (NULL == p->conf.gw.exts) return HANDLER_GO_ON;

	rc = gw_check_extension(srv, con, (gw_plugin_data *)p, 1, sizeof(handler_ctx));
	if (HANDLER_GO_ON != rc) return rc;

	if (con->mode == p->id) {
		handler_ctx *hctx = con->plugin_ctx[p->id];
		hctx->gw.create_env = proxy_create_env;
		hctx->gw.response = chunk_buffer_acquire();
		hctx->gw.opts.backend = BACKEND_PROXY;
		hctx->gw.opts.pdata = hctx;
		hctx->gw.opts.headers = proxy_response_headers;

		hctx->conf = p->conf; /*(copies struct)*/
		hctx->conf.header.http_host = con->request.http_host;
		hctx->conf.header.upgrade  &= (con->request.http_version == HTTP_VERSION_1_1);
		/* mod_proxy currently sends all backend requests as http.
		 * https-remap is a flag since it might not be needed if backend
		 * honors Forwarded or X-Forwarded-Proto headers, e.g. by using
		 * lighttpd mod_extforward or similar functionality in backend*/
		if (hctx->conf.header.https_remap) {
			hctx->conf.header.https_remap =
			  buffer_is_equal_string(con->uri.scheme, CONST_STR_LEN("https"));
		}

		if (con->request.http_method == HTTP_METHOD_CONNECT) {
			/*(note: not requiring HTTP/1.1 due to too many non-compliant
			 * clients such as 'openssl s_client')*/
			if (hctx->conf.header.connect_method) {
				hctx->gw.create_env = proxy_create_env_connect;
			}
			else {
				con->http_status = 405; /* Method Not Allowed */
				con->mode = DIRECT;
				return HANDLER_FINISHED;
			}
		}
	}

	return HANDLER_GO_ON;
}


int mod_proxy_plugin_init(plugin *p);
int mod_proxy_plugin_init(plugin *p) {
	p->version      = LIGHTTPD_VERSION_ID;
	p->name         = buffer_init_string("proxy");

	p->init         = mod_proxy_init;
	p->cleanup      = mod_proxy_free;
	p->set_defaults = mod_proxy_set_defaults;
	p->connection_reset        = gw_connection_reset;
	p->handle_uri_clean        = mod_proxy_check_extension;
	p->handle_subrequest       = gw_handle_subrequest;
	p->handle_trigger          = gw_handle_trigger;
	p->handle_waitpid          = gw_handle_waitpid_cb;

	p->data         = NULL;

	return 0;
}