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 <errno.h>
20 #include <string.h>
21 
22 #include "gmid.h"
23 
24 static inline void
25 safe_setenv(const char *name, const char *val)
26 {
27 	if (val == NULL)
28 		val = "";
29 	setenv(name, val, 1);
30 }
31 
32 /*
33  * the inverse of this algorithm, i.e. starting from the start of the
34  * path + strlen(cgi), and checking if each component, should be
35  * faster.  But it's tedious to write.  This does the opposite: starts
36  * from the end and strip one component at a time, until either an
37  * executable is found or we emptied the path.
38  */
39 int
40 check_for_cgi(char *path, char *query, struct pollfd *fds, struct client *c)
41 {
42 	char *end;
43 	end = strchr(path, '\0');
44 
45 	/* NB: assume CGI is enabled and path matches cgi */
46 
47 	while (end > path) {
48 		/* go up one level.  UNIX paths are simple and POSIX
49 		 * dirname, with its ambiguities on if the given path
50 		 * is changed or not, gives me headaches. */
51 		while (*end != '/')
52 			end--;
53 		*end = '\0';
54 
55 		switch (check_path(c, path, &c->fd)) {
56 		case FILE_EXECUTABLE:
57 			return start_cgi(path, end+1, query, fds,c);
58 		case FILE_MISSING:
59 			break;
60 		default:
61 			goto err;
62 		}
63 
64 		*end = '/';
65 		end--;
66 	}
67 
68 err:
69 	if (!start_reply(fds, c, NOT_FOUND, "not found"))
70 		return 0;
71 	goodbye(fds, c);
72 	return 0;
73 }
74 
75 int
76 start_cgi(const char *spath, const char *relpath, const char *query,
77     struct pollfd *fds, struct client *c)
78 {
79 	pid_t pid;
80 	int p[2];		/* read end, write end */
81 
82 	if (pipe(p) == -1)
83 		goto err;
84 
85 	switch (pid = fork()) {
86 	case -1:
87 		goto err;
88 
89 	case 0: {		/* child */
90 		char *ex, *requri, *portno;
91 		char addr[NI_MAXHOST];
92 		char *argv[] = { NULL, NULL, NULL };
93 		int ec;
94 
95 		close(p[0]);
96 		if (dup2(p[1], 1) == -1)
97 			goto childerr;
98 
99 		ec = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
100 		    addr, sizeof(addr),
101 		    NULL, 0,
102 		    NI_NUMERICHOST | NI_NUMERICSERV);
103 		if (ec != 0)
104 			goto childerr;
105 
106 		if (asprintf(&portno, "%d", conf.port) == -1)
107 			goto childerr;
108 
109 		if (asprintf(&ex, "%s/%s", c->host->dir, spath) == -1)
110 			goto childerr;
111 
112 		if (asprintf(&requri, "%s%s%s", spath,
113 		    *relpath == '\0' ? "" : "/", relpath) == -1)
114 			goto childerr;
115 
116 		argv[0] = argv[1] = ex;
117 
118 		/* fix the env */
119 		safe_setenv("GATEWAY_INTERFACE", "CGI/1.1");
120 		safe_setenv("SERVER_SOFTWARE", "gmid");
121 		safe_setenv("SERVER_PORT", portno);
122 
123 		if (!strcmp(c->host->domain, "*"))
124 			safe_setenv("SERVER_NAME", c->host->domain)
125 
126 		safe_setenv("SCRIPT_NAME", spath);
127 		safe_setenv("SCRIPT_EXECUTABLE", ex);
128 		safe_setenv("REQUEST_URI", requri);
129 		safe_setenv("REQUEST_RELATIVE", relpath);
130 		safe_setenv("QUERY_STRING", query);
131 		safe_setenv("REMOTE_HOST", addr);
132 		safe_setenv("REMOTE_ADDR", addr);
133 		safe_setenv("DOCUMENT_ROOT", c->host->dir);
134 
135 		if (tls_peer_cert_provided(c->ctx)) {
136 			safe_setenv("AUTH_TYPE", "Certificate");
137 			safe_setenv("REMOTE_USER", tls_peer_cert_subject(c->ctx));
138 			safe_setenv("TLS_CLIENT_ISSUER", tls_peer_cert_issuer(c->ctx));
139 			safe_setenv("TLS_CLIENT_HASH", tls_peer_cert_hash(c->ctx));
140 		}
141 
142 		execvp(ex, argv);
143 		goto childerr;
144 	}
145 
146 	default:		/* parent */
147 		close(p[1]);
148 		close(c->fd);
149 		c->fd = p[0];
150 		c->child = pid;
151 		mark_nonblock(c->fd);
152 		c->state = S_SENDING;
153 		handle_cgi(fds, c);
154 		return 0;
155 	}
156 
157 err:
158 	if (!start_reply(fds, c, TEMP_FAILURE, "internal server error"))
159 		return 0;
160 	goodbye(fds, c);
161 	return 0;
162 
163 childerr:
164 	dprintf(p[1], "%d internal server error\r\n", TEMP_FAILURE);
165 	close(p[1]);
166 	_exit(1);
167 }
168 
169 void
170 cgi_poll_on_child(struct pollfd *fds, struct client *c)
171 {
172 	int fd;
173 
174 	if (c->waiting_on_child)
175 		return;
176 	c->waiting_on_child = 1;
177 
178 	fds->events = POLLIN;
179 
180 	fd = fds->fd;
181 	fds->fd = c->fd;
182 	c->fd = fd;
183 }
184 
185 void
186 cgi_poll_on_client(struct pollfd *fds, struct client *c)
187 {
188 	int fd;
189 
190 	if (!c->waiting_on_child)
191 		return;
192 	c->waiting_on_child = 0;
193 
194 	fd = fds->fd;
195 	fds->fd = c->fd;
196 	c->fd = fd;
197 }
198 
199 void
200 handle_cgi(struct pollfd *fds, struct client *c)
201 {
202 	ssize_t r;
203 
204 	/* ensure c->fd is the child and fds->fd the client */
205 	cgi_poll_on_client(fds, c);
206 
207 	while (1) {
208 		if (c->len == 0) {
209 			if ((r = read(c->fd, c->sbuf, sizeof(c->sbuf))) == 0)
210 				goto end;
211 			if (r == -1) {
212 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
213 					cgi_poll_on_child(fds, c);
214 					return;
215 				}
216                                 goto end;
217 			}
218 			c->len = r;
219 			c->off = 0;
220 		}
221 
222 		while (c->len > 0) {
223 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
224 			case -1:
225 				goto end;
226 
227 			case TLS_WANT_POLLOUT:
228 				fds->events = POLLOUT;
229 				return;
230 
231 			case TLS_WANT_POLLIN:
232 				fds->events = POLLIN;
233 				return;
234 
235 			default:
236                                 c->off += r;
237 				c->len -= r;
238 				break;
239 			}
240 		}
241 	}
242 
243 end:
244 	goodbye(fds, c);
245 }