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 <sys/queue.h>
19 #include <sys/types.h>
20 #include <sys/socket.h>
21 #include <netdb.h>
22 
23 #include <assert.h>
24 #include <err.h>
25 #include <limits.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <unistd.h>
30 
31 #include "got_error.h"
32 #include "got_path.h"
33 
34 #include "got_lib_dial.h"
35 #include "got_dial.h"
36 
37 #ifndef nitems
38 #define nitems(_a) (sizeof((_a)) / sizeof((_a)[0]))
39 #endif
40 
41 #ifndef ssizeof
42 #define ssizeof(_x) ((ssize_t)(sizeof(_x)))
43 #endif
44 
45 #ifndef MIN
46 #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
47 #endif
48 
49 #ifndef GOT_DIAL_PATH_SSH
50 #define GOT_DIAL_PATH_SSH	"/usr/bin/ssh"
51 #endif
52 
53 /* IANA assigned */
54 #define GOT_DEFAULT_GIT_PORT		9418
55 #define GOT_DEFAULT_GIT_PORT_STR	"9418"
56 
57 const struct got_error *
58 got_dial_apply_unveil(const char *proto)
59 {
60 	if (strcmp(proto, "git+ssh") == 0 || strcmp(proto, "ssh") == 0) {
61 		if (unveil(GOT_DIAL_PATH_SSH, "x") != 0) {
62 			return got_error_from_errno2("unveil",
63 			    GOT_DIAL_PATH_SSH);
64 		}
65 	}
66 
67 	return NULL;
68 }
69 
70 static int
71 hassuffix(const char *base, const char *suf)
72 {
73 	int nb, ns;
74 
75 	nb = strlen(base);
76 	ns = strlen(suf);
77 	if (ns <= nb && strcmp(base + (nb - ns), suf) == 0)
78 		return 1;
79 	return 0;
80 }
81 
82 const struct got_error *
83 got_dial_parse_uri(char **proto, char **host, char **port,
84     char **server_path, char **repo_name, const char *uri)
85 {
86 	const struct got_error *err = NULL;
87 	char *s, *p, *q;
88 
89 	*proto = *host = *port = *server_path = *repo_name = NULL;
90 
91 	p = strstr(uri, "://");
92 	if (!p) {
93 		/* Try parsing Git's "scp" style URL syntax. */
94 		*proto = strdup("ssh");
95 		if (*proto == NULL) {
96 			err = got_error_from_errno("strdup");
97 			goto done;
98 		}
99 		s = (char *)uri;
100 		q = strchr(s, ':');
101 		if (q == NULL) {
102 			err = got_error(GOT_ERR_PARSE_URI);
103 			goto done;
104 		}
105 		/* No slashes allowed before first colon. */
106 		p = strchr(s, '/');
107 		if (p && q > p) {
108 			err = got_error(GOT_ERR_PARSE_URI);
109 			goto done;
110 		}
111 		*host = strndup(s, q - s);
112 		if (*host == NULL) {
113 			err = got_error_from_errno("strndup");
114 			goto done;
115 		}
116 		if ((*host)[0] == '\0') {
117 			err = got_error(GOT_ERR_PARSE_URI);
118 			goto done;
119 		}
120 		p = q + 1;
121 	} else {
122 		*proto = strndup(uri, p - uri);
123 		if (*proto == NULL) {
124 			err = got_error_from_errno("strndup");
125 			goto done;
126 		}
127 		s = p + 3;
128 
129 		p = strstr(s, "/");
130 		if (p == NULL || strlen(p) == 1) {
131 			err = got_error(GOT_ERR_PARSE_URI);
132 			goto done;
133 		}
134 
135 		q = memchr(s, ':', p - s);
136 		if (q) {
137 			*host = strndup(s, q - s);
138 			if (*host == NULL) {
139 				err = got_error_from_errno("strndup");
140 				goto done;
141 			}
142 			if ((*host)[0] == '\0') {
143 				err = got_error(GOT_ERR_PARSE_URI);
144 				goto done;
145 			}
146 			*port = strndup(q + 1, p - (q + 1));
147 			if (*port == NULL) {
148 				err = got_error_from_errno("strndup");
149 				goto done;
150 			}
151 			if ((*port)[0] == '\0') {
152 				err = got_error(GOT_ERR_PARSE_URI);
153 				goto done;
154 			}
155 		} else {
156 			*host = strndup(s, p - s);
157 			if (*host == NULL) {
158 				err = got_error_from_errno("strndup");
159 				goto done;
160 			}
161 			if ((*host)[0] == '\0') {
162 				err = got_error(GOT_ERR_PARSE_URI);
163 				goto done;
164 			}
165 		}
166 	}
167 
168 	while (p[0] == '/' && p[1] == '/')
169 		p++;
170 	*server_path = strdup(p);
171 	if (*server_path == NULL) {
172 		err = got_error_from_errno("strdup");
173 		goto done;
174 	}
175 	got_path_strip_trailing_slashes(*server_path);
176 	if ((*server_path)[0] == '\0') {
177 		err = got_error(GOT_ERR_PARSE_URI);
178 		goto done;
179 	}
180 
181 	err = got_path_basename(repo_name, *server_path);
182 	if (err)
183 		goto done;
184 	if (hassuffix(*repo_name, ".git"))
185 		(*repo_name)[strlen(*repo_name) - 4] = '\0';
186 	if ((*repo_name)[0] == '\0')
187 		err = got_error(GOT_ERR_PARSE_URI);
188 done:
189 	if (err) {
190 		free(*proto);
191 		*proto = NULL;
192 		free(*host);
193 		*host = NULL;
194 		free(*port);
195 		*port = NULL;
196 		free(*server_path);
197 		*server_path = NULL;
198 		free(*repo_name);
199 		*repo_name = NULL;
200 	}
201 	return err;
202 }
203 
204 /*
205  * Escape a given path for the shell which will be started by sshd.
206  * In particular, git-shell is known to require single-quote characters
207  * around its repository path argument and will refuse to run otherwise.
208  */
209 static const struct got_error *
210 escape_path(char *buf, size_t bufsize, const char *path)
211 {
212 	const char	*p;
213 	char		*q;
214 
215 	p = path;
216 	q = buf;
217 
218 	if (bufsize > 1)
219 		*q++ = '\'';
220 
221 	while (*p != '\0' && (q - buf < bufsize)) {
222 		/* git escapes ! too */
223 		if (*p != '\'' && *p != '!') {
224 			*q++ = *p++;
225 			continue;
226 		}
227 
228 		if (q - buf + 4 >= bufsize)
229 			break;
230 		*q++ = '\'';
231 		*q++ = '\\';
232 		*q++ = *p++;
233 		*q++ = '\'';
234 	}
235 
236 	if (*p == '\0' && (q - buf + 1 < bufsize)) {
237 		*q++ = '\'';
238 		*q = '\0';
239 		return NULL;
240 	}
241 
242 	return got_error_fmt(GOT_ERR_NO_SPACE, "overlong path: %s", path);
243 }
244 
245 const struct got_error *
246 got_dial_ssh(pid_t *newpid, int *newfd, const char *host,
247     const char *port, const char *path, const char *command, int verbosity)
248 {
249 	const struct got_error *error = NULL;
250 	int pid, pfd[2];
251 	char cmd[64];
252 	char escaped_path[PATH_MAX];
253 	const char *argv[11];
254 	int i = 0, j;
255 
256 	*newpid = -1;
257 	*newfd = -1;
258 
259 	error = escape_path(escaped_path, sizeof(escaped_path), path);
260 	if (error)
261 		return error;
262 
263 	argv[i++] = GOT_DIAL_PATH_SSH;
264 	if (port != NULL) {
265 		argv[i++] = "-p";
266 		argv[i++] = (char *)port;
267 	}
268 	if (verbosity == -1) {
269 		argv[i++] = "-q";
270 	} else {
271 		/* ssh(1) allows up to 3 "-v" options. */
272 		for (j = 0; j < MIN(3, verbosity); j++)
273 			argv[i++] = "-v";
274 	}
275 	argv[i++] = "--";
276 	argv[i++] = (char *)host;
277 	argv[i++] = (char *)cmd;
278 	argv[i++] = (char *)escaped_path;
279 	argv[i++] = NULL;
280 	assert(i <= nitems(argv));
281 
282 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pfd) == -1)
283 		return got_error_from_errno("socketpair");
284 
285 	pid = fork();
286 	if (pid == -1) {
287 		error = got_error_from_errno("fork");
288 		close(pfd[0]);
289 		close(pfd[1]);
290 		return error;
291 	} else if (pid == 0) {
292 		if (close(pfd[1]) == -1)
293 			err(1, "close");
294 		if (dup2(pfd[0], 0) == -1)
295 			err(1, "dup2");
296 		if (dup2(pfd[0], 1) == -1)
297 			err(1, "dup2");
298 		if (strlcpy(cmd, command, sizeof(cmd)) >= sizeof(cmd))
299 			err(1, "snprintf");
300 		if (execv(GOT_DIAL_PATH_SSH, (char *const *)argv) == -1)
301 			err(1, "execv");
302 		abort(); /* not reached */
303 	} else {
304 		if (close(pfd[0]) == -1)
305 			return got_error_from_errno("close");
306 		*newpid = pid;
307 		*newfd = pfd[1];
308 		return NULL;
309 	}
310 }
311 
312 const struct got_error *
313 got_dial_git(int *newfd, const char *host, const char *port,
314     const char *path, const char *command)
315 {
316 	const struct got_error *err = NULL;
317 	struct addrinfo hints, *servinfo, *p;
318 	char *cmd = NULL;
319 	int fd = -1, len, r, eaicode;
320 
321 	*newfd = -1;
322 
323 	if (port == NULL)
324 		port = GOT_DEFAULT_GIT_PORT_STR;
325 
326 	memset(&hints, 0, sizeof hints);
327 	hints.ai_family = AF_UNSPEC;
328 	hints.ai_socktype = SOCK_STREAM;
329 	eaicode = getaddrinfo(host, port, &hints, &servinfo);
330 	if (eaicode) {
331 		char msg[512];
332 		snprintf(msg, sizeof(msg), "%s: %s", host,
333 		    gai_strerror(eaicode));
334 		return got_error_msg(GOT_ERR_ADDRINFO, msg);
335 	}
336 
337 	for (p = servinfo; p != NULL; p = p->ai_next) {
338 		if ((fd = socket(p->ai_family, p->ai_socktype,
339 		    p->ai_protocol)) == -1)
340 			continue;
341 		if (connect(fd, p->ai_addr, p->ai_addrlen) == 0) {
342 			err = NULL;
343 			break;
344 		}
345 		err = got_error_from_errno("connect");
346 		close(fd);
347 	}
348 	freeaddrinfo(servinfo);
349 	if (p == NULL)
350 		goto done;
351 
352 	if (asprintf(&cmd, "%s %s", command, path) == -1) {
353 		err = got_error_from_errno("asprintf");
354 		goto done;
355 	}
356 	len = 4 + strlen(cmd) + 1 + strlen("host=") + strlen(host) + 1;
357 	r = dprintf(fd, "%04x%s%chost=%s%c", len, cmd, '\0', host, '\0');
358 	if (r < 0)
359 		err = got_error_from_errno("dprintf");
360 done:
361 	free(cmd);
362 	if (err) {
363 		if (fd != -1)
364 			close(fd);
365 	} else
366 		*newfd = fd;
367 	return err;
368 }
369 
370 const struct got_error *
371 got_dial_parse_command(char **command, char **repo_path, const char *gitcmd)
372 {
373 	const struct got_error *err = NULL;
374 	size_t len, cmdlen, pathlen;
375 	char *path0 = NULL, *path, *abspath = NULL, *canonpath = NULL;
376 	const char *relpath;
377 
378 	*command = NULL;
379 	*repo_path = NULL;
380 
381 	len = strlen(gitcmd);
382 
383 	if (len >= strlen(GOT_DIAL_CMD_SEND) &&
384 	    strncmp(gitcmd, GOT_DIAL_CMD_SEND,
385 	    strlen(GOT_DIAL_CMD_SEND)) == 0)
386 		cmdlen = strlen(GOT_DIAL_CMD_SEND);
387 	else if (len >= strlen(GOT_DIAL_CMD_FETCH) &&
388 	    strncmp(gitcmd, GOT_DIAL_CMD_FETCH,
389 	    strlen(GOT_DIAL_CMD_FETCH)) == 0)
390 		cmdlen = strlen(GOT_DIAL_CMD_FETCH);
391 	else
392 		return got_error(GOT_ERR_BAD_PACKET);
393 
394 	if (len <= cmdlen + 1 || gitcmd[cmdlen] != ' ')
395 		return got_error(GOT_ERR_BAD_PACKET);
396 
397 	if (memchr(&gitcmd[cmdlen + 1], '\0', len - cmdlen) == NULL)
398 		return got_error(GOT_ERR_BAD_PATH);
399 
400 	/* Forbid linefeeds in paths, like Git does. */
401 	if (memchr(&gitcmd[cmdlen + 1], '\n', len - cmdlen) != NULL)
402 		return got_error(GOT_ERR_BAD_PATH);
403 
404 	path0 = strdup(&gitcmd[cmdlen + 1]);
405 	if (path0 == NULL)
406 		return got_error_from_errno("strdup");
407 	path = path0;
408 	pathlen = strlen(path);
409 
410 	/*
411 	 * Git clients send a shell command.
412 	 * Trim spaces and quotes around the path.
413 	 */
414 	while (path[0] == '\'' || path[0] == '\"' || path[0] == ' ') {
415 		path++;
416 		pathlen--;
417 	}
418 	while (pathlen > 0 &&
419 	    (path[pathlen - 1] == '\'' || path[pathlen - 1] == '\"' ||
420 	    path[pathlen - 1] == ' ')) {
421 		path[pathlen - 1] = '\0';
422 		pathlen--;
423 	}
424 
425 	/* Deny an empty repository path. */
426 	if (path[0] == '\0' || got_path_is_root_dir(path)) {
427 		err = got_error(GOT_ERR_NOT_GIT_REPO);
428 		goto done;
429 	}
430 
431 	if (asprintf(&abspath, "/%s", path) == -1) {
432 		err = got_error_from_errno("asprintf");
433 		goto done;
434 	}
435 	pathlen = strlen(abspath);
436 	canonpath = malloc(pathlen + 1);
437 	if (canonpath == NULL) {
438 		err = got_error_from_errno("malloc");
439 		goto done;
440 	}
441 	err = got_canonpath(abspath, canonpath, pathlen + 1);
442 	if (err)
443 		goto done;
444 
445 	relpath = canonpath;
446 	while (relpath[0] == '/')
447 		relpath++;
448 	*repo_path = strdup(relpath);
449 	if (*repo_path == NULL) {
450 		err = got_error_from_errno("strdup");
451 		goto done;
452 	}
453 	*command = strndup(gitcmd, cmdlen);
454 	if (*command == NULL)
455 		err = got_error_from_errno("strndup");
456 done:
457 	free(path0);
458 	free(abspath);
459 	free(canonpath);
460 	if (err) {
461 		free(*repo_path);
462 		*repo_path = NULL;
463 	}
464 	return err;
465 }