1 /*
2  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <netdb.h>
18 
19 #include <err.h>
20 #include <errno.h>
21 #include <string.h>
22 
23 #include "gmid.h"
24 
25 /*
26  * the inverse of this algorithm, i.e. starting from the start of the
27  * path + strlen(cgi), and checking if each component, should be
28  * faster.  But it's tedious to write.  This does the opposite: starts
29  * from the end and strip one component at a time, until either an
30  * executable is found or we emptied the path.
31  */
32 int
33 check_for_cgi(char *path, char *query, struct pollfd *fds, struct client *c)
34 {
35 	char *end;
36 	end = strchr(path, '\0');
37 
38 	/* NB: assume CGI is enabled and path matches cgi */
39 
40 	while (end > path) {
41 		/* go up one level.  UNIX paths are simple and POSIX
42 		 * dirname, with its ambiguities on if the given path
43 		 * is changed or not, gives me headaches. */
44 		while (*end != '/')
45 			end--;
46 		*end = '\0';
47 
48 		switch (check_path(c, path, &c->fd)) {
49 		case FILE_EXECUTABLE:
50 			return start_cgi(path, end+1, query, fds,c);
51 		case FILE_MISSING:
52 			break;
53 		default:
54 			goto err;
55 		}
56 
57 		*end = '/';
58 		end--;
59 	}
60 
61 err:
62 	if (!start_reply(fds, c, NOT_FOUND, "not found"))
63 		return 0;
64 	goodbye(fds, c);
65 	return 0;
66 }
67 
68 int
69 start_cgi(const char *spath, const char *relpath, const char *query,
70     struct pollfd *fds, struct client *c)
71 {
72 	char addr[NI_MAXHOST];
73 	const char *ruser, *cissuer, *chash;
74 	int e;
75 
76 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
77 	    addr, sizeof(addr),
78 	    NULL, 0,
79 	    NI_NUMERICHOST);
80 	if (e != 0)
81 		goto err;
82 
83 	if (tls_peer_cert_provided(c->ctx)) {
84 		ruser = tls_peer_cert_subject(c->ctx);
85 		cissuer = tls_peer_cert_issuer(c->ctx);
86 		chash = tls_peer_cert_hash(c->ctx);
87 	} else {
88 		ruser = NULL;
89 		cissuer = NULL;
90 		chash = NULL;
91 	}
92 
93 	if (!send_string(exfd, spath)
94 	    || !send_string(exfd, relpath)
95 	    || !send_string(exfd, query)
96 	    || !send_string(exfd, addr)
97 	    || !send_string(exfd, ruser)
98 	    || !send_string(exfd, cissuer)
99 	    || !send_string(exfd, chash)
100 	    || !send_vhost(exfd, c->host))
101 		goto err;
102 
103 	close(c->fd);
104 	if ((c->fd = recv_fd(exfd)) == -1) {
105 		if (!start_reply(fds, c, TEMP_FAILURE, "internal server error"))
106 			return 0;
107 		goodbye(fds, c);
108 		return 0;
109 	}
110 	c->child = 1;
111 	c->state = S_SENDING;
112 	cgi_poll_on_child(fds, c);
113 	/* handle_cgi(fds, c); */
114 	return 0;
115 
116 err:
117 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
118 	err(1, "cannot talk to the executor process");
119 }
120 
121 void
122 cgi_poll_on_child(struct pollfd *fds, struct client *c)
123 {
124 	int fd;
125 
126 	if (c->waiting_on_child)
127 		return;
128 	c->waiting_on_child = 1;
129 
130 	fds->events = POLLIN;
131 
132 	fd = fds->fd;
133 	fds->fd = c->fd;
134 	c->fd = fd;
135 }
136 
137 void
138 cgi_poll_on_client(struct pollfd *fds, struct client *c)
139 {
140 	int fd;
141 
142 	if (!c->waiting_on_child)
143 		return;
144 	c->waiting_on_child = 0;
145 
146 	fd = fds->fd;
147 	fds->fd = c->fd;
148 	c->fd = fd;
149 }
150 
151 void
152 handle_cgi(struct pollfd *fds, struct client *c)
153 {
154 	ssize_t r;
155 
156 	/* ensure c->fd is the child and fds->fd the client */
157 	cgi_poll_on_client(fds, c);
158 
159 	while (1) {
160 		if (c->len == 0) {
161 			if ((r = read(c->fd, c->sbuf, sizeof(c->sbuf))) == 0)
162 				goto end;
163 			if (r == -1) {
164 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
165 					cgi_poll_on_child(fds, c);
166 					return;
167 				}
168                                 goto end;
169 			}
170 			c->len = r;
171 			c->off = 0;
172 		}
173 
174 		while (c->len > 0) {
175 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
176 			case -1:
177 				goto end;
178 
179 			case TLS_WANT_POLLOUT:
180 				fds->events = POLLOUT;
181 				return;
182 
183 			case TLS_WANT_POLLIN:
184 				fds->events = POLLIN;
185 				return;
186 
187 			default:
188                                 c->off += r;
189 				c->len -= r;
190 				break;
191 			}
192 		}
193 	}
194 
195 end:
196 	goodbye(fds, c);
197 }