1 /*
2  * Copyright (c) 2018, 2019 Ori Bernstein <ori@openbsd.org>
3  * Copyright (c) 2021 Stefan Sperling <stsp@openbsd.org>
4  *
5  * Permission to use, copy, modify, and distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 #include "got_compat.h"
19 
20 #include <sys/queue.h>
21 #include <sys/types.h>
22 #include <sys/socket.h>
23 #include <netdb.h>
24 
25 #include <assert.h>
26 #include <err.h>
27 #include <limits.h>
28 #include <stdio.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include <unistd.h>
32 
33 #include "got_error.h"
34 #include "got_path.h"
35 
36 #include "got_compat.h"
37 
38 #include "got_lib_dial.h"
39 #include "got_dial.h"
40 
41 #ifndef nitems
42 #define nitems(_a) (sizeof((_a)) / sizeof((_a)[0]))
43 #endif
44 
45 #ifndef ssizeof
46 #define ssizeof(_x) ((ssize_t)(sizeof(_x)))
47 #endif
48 
49 #ifndef MIN
50 #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
51 #endif
52 
53 #ifndef GOT_DIAL_PATH_SSH
54 #define GOT_DIAL_PATH_SSH	"/usr/bin/ssh"
55 #endif
56 
57 /* IANA assigned */
58 #define GOT_DEFAULT_GIT_PORT		9418
59 #define GOT_DEFAULT_GIT_PORT_STR	"9418"
60 
61 const struct got_error *
62 got_dial_apply_unveil(const char *proto)
63 {
64 	if (strcmp(proto, "git+ssh") == 0 || strcmp(proto, "ssh") == 0) {
65 		if (unveil(GOT_DIAL_PATH_SSH, "x") != 0) {
66 			return got_error_from_errno2("unveil",
67 			    GOT_DIAL_PATH_SSH);
68 		}
69 	}
70 
71 	return NULL;
72 }
73 
74 static int
75 hassuffix(const char *base, const char *suf)
76 {
77 	int nb, ns;
78 
79 	nb = strlen(base);
80 	ns = strlen(suf);
81 	if (ns <= nb && strcmp(base + (nb - ns), suf) == 0)
82 		return 1;
83 	return 0;
84 }
85 
86 const struct got_error *
87 got_dial_parse_uri(char **proto, char **host, char **port,
88     char **server_path, char **repo_name, const char *uri)
89 {
90 	const struct got_error *err = NULL;
91 	char *s, *p, *q;
92 
93 	*proto = *host = *port = *server_path = *repo_name = NULL;
94 
95 	p = strstr(uri, "://");
96 	if (!p) {
97 		/* Try parsing Git's "scp" style URL syntax. */
98 		*proto = strdup("ssh");
99 		if (*proto == NULL) {
100 			err = got_error_from_errno("strdup");
101 			goto done;
102 		}
103 		s = (char *)uri;
104 		q = strchr(s, ':');
105 		if (q == NULL) {
106 			err = got_error(GOT_ERR_PARSE_URI);
107 			goto done;
108 		}
109 		/* No slashes allowed before first colon. */
110 		p = strchr(s, '/');
111 		if (p && q > p) {
112 			err = got_error(GOT_ERR_PARSE_URI);
113 			goto done;
114 		}
115 		*host = strndup(s, q - s);
116 		if (*host == NULL) {
117 			err = got_error_from_errno("strndup");
118 			goto done;
119 		}
120 		if ((*host)[0] == '\0') {
121 			err = got_error(GOT_ERR_PARSE_URI);
122 			goto done;
123 		}
124 		p = q + 1;
125 	} else {
126 		*proto = strndup(uri, p - uri);
127 		if (*proto == NULL) {
128 			err = got_error_from_errno("strndup");
129 			goto done;
130 		}
131 		s = p + 3;
132 
133 		p = strstr(s, "/");
134 		if (p == NULL || strlen(p) == 1) {
135 			err = got_error(GOT_ERR_PARSE_URI);
136 			goto done;
137 		}
138 
139 		q = memchr(s, ':', p - s);
140 		if (q) {
141 			*host = strndup(s, q - s);
142 			if (*host == NULL) {
143 				err = got_error_from_errno("strndup");
144 				goto done;
145 			}
146 			if ((*host)[0] == '\0') {
147 				err = got_error(GOT_ERR_PARSE_URI);
148 				goto done;
149 			}
150 			*port = strndup(q + 1, p - (q + 1));
151 			if (*port == NULL) {
152 				err = got_error_from_errno("strndup");
153 				goto done;
154 			}
155 			if ((*port)[0] == '\0') {
156 				err = got_error(GOT_ERR_PARSE_URI);
157 				goto done;
158 			}
159 		} else {
160 			*host = strndup(s, p - s);
161 			if (*host == NULL) {
162 				err = got_error_from_errno("strndup");
163 				goto done;
164 			}
165 			if ((*host)[0] == '\0') {
166 				err = got_error(GOT_ERR_PARSE_URI);
167 				goto done;
168 			}
169 		}
170 	}
171 
172 	while (p[0] == '/' && p[1] == '/')
173 		p++;
174 	*server_path = strdup(p);
175 	if (*server_path == NULL) {
176 		err = got_error_from_errno("strdup");
177 		goto done;
178 	}
179 	got_path_strip_trailing_slashes(*server_path);
180 	if ((*server_path)[0] == '\0') {
181 		err = got_error(GOT_ERR_PARSE_URI);
182 		goto done;
183 	}
184 
185 	err = got_path_basename(repo_name, *server_path);
186 	if (err)
187 		goto done;
188 	if (hassuffix(*repo_name, ".git"))
189 		(*repo_name)[strlen(*repo_name) - 4] = '\0';
190 	if ((*repo_name)[0] == '\0')
191 		err = got_error(GOT_ERR_PARSE_URI);
192 done:
193 	if (err) {
194 		free(*proto);
195 		*proto = NULL;
196 		free(*host);
197 		*host = NULL;
198 		free(*port);
199 		*port = NULL;
200 		free(*server_path);
201 		*server_path = NULL;
202 		free(*repo_name);
203 		*repo_name = NULL;
204 	}
205 	return err;
206 }
207 
208 /*
209  * Escape a given path for the shell which will be started by sshd.
210  * In particular, git-shell is known to require single-quote characters
211  * around its repository path argument and will refuse to run otherwise.
212  */
213 static const struct got_error *
214 escape_path(char *buf, size_t bufsize, const char *path)
215 {
216 	const char	*p;
217 	char		*q;
218 
219 	p = path;
220 	q = buf;
221 
222 	if (bufsize > 1)
223 		*q++ = '\'';
224 
225 	while (*p != '\0' && (q - buf < bufsize)) {
226 		/* git escapes ! too */
227 		if (*p != '\'' && *p != '!') {
228 			*q++ = *p++;
229 			continue;
230 		}
231 
232 		if (q - buf + 4 >= bufsize)
233 			break;
234 		*q++ = '\'';
235 		*q++ = '\\';
236 		*q++ = *p++;
237 		*q++ = '\'';
238 	}
239 
240 	if (*p == '\0' && (q - buf + 1 < bufsize)) {
241 		*q++ = '\'';
242 		*q = '\0';
243 		return NULL;
244 	}
245 
246 	return got_error_fmt(GOT_ERR_NO_SPACE, "overlong path: %s", path);
247 }
248 
249 const struct got_error *
250 got_dial_ssh(pid_t *newpid, int *newfd, const char *host,
251     const char *port, const char *path, const char *direction, int verbosity)
252 {
253 	const struct got_error *error = NULL;
254 	int pid, pfd[2];
255 	char cmd[64];
256 	char escaped_path[PATH_MAX];
257 	const char *argv[11];
258 	int i = 0, j;
259 
260 	*newpid = -1;
261 	*newfd = -1;
262 
263 	error = escape_path(escaped_path, sizeof(escaped_path), path);
264 	if (error)
265 		return error;
266 
267 	argv[i++] = GOT_DIAL_PATH_SSH;
268 	if (port != NULL) {
269 		argv[i++] = "-p";
270 		argv[i++] = (char *)port;
271 	}
272 	if (verbosity == -1) {
273 		argv[i++] = "-q";
274 	} else {
275 		/* ssh(1) allows up to 3 "-v" options. */
276 		for (j = 0; j < MIN(3, verbosity); j++)
277 			argv[i++] = "-v";
278 	}
279 	argv[i++] = "--";
280 	argv[i++] = (char *)host;
281 	argv[i++] = (char *)cmd;
282 	argv[i++] = (char *)escaped_path;
283 	argv[i++] = NULL;
284 	assert(i <= nitems(argv));
285 
286 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pfd) == -1)
287 		return got_error_from_errno("socketpair");
288 
289 	pid = fork();
290 	if (pid == -1) {
291 		error = got_error_from_errno("fork");
292 		close(pfd[0]);
293 		close(pfd[1]);
294 		return error;
295 	} else if (pid == 0) {
296 		int n;
297 		if (close(pfd[1]) == -1)
298 			err(1, "close");
299 		if (dup2(pfd[0], 0) == -1)
300 			err(1, "dup2");
301 		if (dup2(pfd[0], 1) == -1)
302 			err(1, "dup2");
303 		n = snprintf(cmd, sizeof(cmd), "git-%s-pack", direction);
304 		if (n < 0 || n >= ssizeof(cmd))
305 			err(1, "snprintf");
306 		if (execv(GOT_DIAL_PATH_SSH, (char *const *)argv) == -1)
307 			err(1, "execv");
308 		abort(); /* not reached */
309 	} else {
310 		if (close(pfd[0]) == -1)
311 			return got_error_from_errno("close");
312 		*newpid = pid;
313 		*newfd = pfd[1];
314 		return NULL;
315 	}
316 }
317 
318 const struct got_error *
319 got_dial_git(int *newfd, const char *host, const char *port,
320     const char *path, const char *direction)
321 {
322 	const struct got_error *err = NULL;
323 	struct addrinfo hints, *servinfo, *p;
324 	char *cmd = NULL;
325 	int fd = -1, len, r, eaicode;
326 
327 	*newfd = -1;
328 
329 	if (port == NULL)
330 		port = GOT_DEFAULT_GIT_PORT_STR;
331 
332 	memset(&hints, 0, sizeof hints);
333 	hints.ai_family = AF_UNSPEC;
334 	hints.ai_socktype = SOCK_STREAM;
335 	eaicode = getaddrinfo(host, port, &hints, &servinfo);
336 	if (eaicode) {
337 		char msg[512];
338 		snprintf(msg, sizeof(msg), "%s: %s", host,
339 		    gai_strerror(eaicode));
340 		return got_error_msg(GOT_ERR_ADDRINFO, msg);
341 	}
342 
343 	for (p = servinfo; p != NULL; p = p->ai_next) {
344 		if ((fd = socket(p->ai_family, p->ai_socktype,
345 		    p->ai_protocol)) == -1)
346 			continue;
347 		if (connect(fd, p->ai_addr, p->ai_addrlen) == 0) {
348 			err = NULL;
349 			break;
350 		}
351 		err = got_error_from_errno("connect");
352 		close(fd);
353 	}
354 	freeaddrinfo(servinfo);
355 	if (p == NULL)
356 		goto done;
357 
358 	if (asprintf(&cmd, "git-%s-pack %s", direction, path) == -1) {
359 		err = got_error_from_errno("asprintf");
360 		goto done;
361 	}
362 	len = 4 + strlen(cmd) + 1 + strlen("host=") + strlen(host) + 1;
363 	r = dprintf(fd, "%04x%s%chost=%s%c", len, cmd, '\0', host, '\0');
364 	if (r < 0)
365 		err = got_error_from_errno("dprintf");
366 done:
367 	free(cmd);
368 	if (err) {
369 		if (fd != -1)
370 			close(fd);
371 	} else
372 		*newfd = fd;
373 	return err;
374 }