1 /*
2  * Copyright (c) 2023 Stefan Sperling <stsp@openbsd.org>
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 /*
18  * Resolve path namespace conflicts for git-upload-pack and git-receive-pack.
19  */
20 
21 #include "got_compat.h"
22 
23 #include <sys/queue.h>
24 #include <sys/types.h>
25 #include <sys/uio.h>
26 
27 #include <err.h>
28 #include <errno.h>
29 #include <event.h>
30 #include <limits.h>
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <syslog.h>
35 #include <unistd.h>
36 
37 #include "got_error.h"
38 #include "got_path.h"
39 
40 #include "got_lib_dial.h"
41 
42 #include "gotd.h"
43 #include "log.h"
44 
45 #ifndef GITWRAPPER_GIT_LIBEXEC_DIR
46 #define GITWRAPPER_GIT_LIBEXEC_DIR "/usr/local/libexec/git"
47 #endif
48 
49 #ifndef GITWRAPPER_MY_SERVER_PROG
50 #define GITWRAPPER_MY_SERVER_PROG "gotsh"
51 #endif
52 
53 
54 __dead static void
55 usage(void)
56 {
57 	fprintf(stderr, "usage: %s -c '%s|%s repository-path'\n",
58 	    getprogname(), GOT_DIAL_CMD_SEND, GOT_DIAL_CMD_FETCH);
59 	exit(1);
60 }
61 
62 /*
63  * Unveil the specific programs we want to start and hide everything else.
64  * This is important to limit the impact of our "exec" pledge.
65  */
66 static const struct got_error *
67 apply_unveil(const char *myserver)
68 {
69 	const char *fetchcmd = GITWRAPPER_GIT_LIBEXEC_DIR "/" \
70 		GOT_DIAL_CMD_FETCH;
71 	const char *sendcmd = GITWRAPPER_GIT_LIBEXEC_DIR "/" \
72 		GOT_DIAL_CMD_SEND;
73 
74 #ifdef PROFILE
75 	if (unveil("gmon.out", "rwc") != 0)
76 		return got_error_from_errno2("unveil", "gmon.out");
77 #endif
78 	if (unveil(fetchcmd, "x") != 0 && errno != ENOENT)
79 		return got_error_from_errno2("unveil", fetchcmd);
80 
81 	if (unveil(sendcmd, "x") != 0 && errno != ENOENT)
82 		return got_error_from_errno2("unveil", sendcmd);
83 
84 	if (myserver && unveil(myserver, "x") != 0 && errno != ENOENT)
85 		return got_error_from_errno2("unveil", myserver);
86 
87 	if (unveil(NULL, NULL) != 0)
88 		return got_error_from_errno("unveil");
89 
90 	return NULL;
91 }
92 
93 int
94 main(int argc, char *argv[])
95 {
96 	const struct got_error *error;
97 	const char *confpath = NULL;
98 	char *command = NULL, *repo_name = NULL; /* for matching gotd.conf */
99 	char *myserver = NULL;
100 	const char *repo_path = NULL; /* as passed on the command line */
101 	const char *relpath;
102 	char *gitcommand = NULL;
103 	struct gotd gotd;
104 	struct gotd_repo *repo = NULL;
105 
106 	log_init(1, LOG_USER); /* Log to stderr. */
107 
108 #ifndef PROFILE
109 	if (pledge("stdio rpath exec unveil", NULL) == -1)
110 		err(1, "pledge");
111 #endif
112 
113 	/*
114 	 * Look up our own server program in PATH so we can unveil(2) it.
115 	 * This call only errors out upon memory allocation failure.
116 	 * If the program cannot be found then myserver will be set to NULL.
117 	 */
118 	error = got_path_find_prog(&myserver, GITWRAPPER_MY_SERVER_PROG);
119 	if (error)
120 		goto done;
121 
122 	/*
123 	 * Run parse_config() before unveil(2) because parse_config()
124 	 * checks whether repository paths exist on disk.
125 	 * Parsing errors and warnings will be logged to stderr.
126 	 * Upon failure we will run Git's native tooling so do not
127 	 * bother checking for errors here.
128 	 */
129 	confpath = getenv("GOTD_CONF_PATH");
130 	if (confpath == NULL)
131 		confpath = GOTD_CONF_PATH;
132 	parse_config(confpath, PROC_GITWRAPPER, &gotd);
133 
134 	error = apply_unveil(myserver);
135 	if (error)
136 		goto done;
137 
138 #ifndef PROFILE
139 	if (pledge("stdio exec", NULL) == -1)
140 		err(1, "pledge");
141 #endif
142 
143 	if (strcmp(getprogname(), GOT_DIAL_CMD_SEND) == 0 ||
144 	    strcmp(getprogname(), GOT_DIAL_CMD_FETCH) == 0) {
145 		if (argc != 2)
146 			usage();
147 		command = strdup(getprogname());
148 		if (command == NULL) {
149 			error = got_error_from_errno("strdup");
150 			goto done;
151 		}
152 		repo_path = argv[1];
153 		relpath = argv[1];
154 		while (relpath[0] == '/')
155 			relpath++;
156 		repo_name = strdup(relpath);
157 		if (repo_name == NULL) {
158 			error = got_error_from_errno("strdup");
159 			goto done;
160 		}
161 	} else {
162 		if (argc != 3 || strcmp(argv[1], "-c") != 0)
163 			usage();
164 		repo_path = argv[2];
165 		error = got_dial_parse_command(&command, &repo_name,
166 		    repo_path);
167 		if (error && error->code == GOT_ERR_BAD_PACKET)
168 			usage();
169 		if (error)
170 			goto done;
171 	}
172 
173 	repo = gotd_find_repo_by_name(repo_name, &gotd.repos);
174 
175 	/*
176 	 * Invoke our custom Git server if the repository was found
177 	 * in gotd.conf. Otherwise invoke native git(1) tooling.
178 	 */
179 	if (repo) {
180 		if (myserver == NULL) {
181 			error = got_error_fmt(GOT_ERR_NO_PROG,
182 			    "cannot run '%s'",
183 			    GITWRAPPER_MY_SERVER_PROG);
184 			goto done;
185 		}
186 		execl(myserver, command, repo_name, (char *)NULL);
187 		error = got_error_from_errno2("execl", myserver);
188 	} else {
189 		if (asprintf(&gitcommand, "%s/%s",
190 		    GITWRAPPER_GIT_LIBEXEC_DIR, command) == -1) {
191 			error = got_error_from_errno("asprintf");
192 			goto done;
193 		}
194 		execl(gitcommand, gitcommand, repo_path, (char *)NULL);
195 		error = got_error_from_errno2("execl", gitcommand);
196 	}
197 
198 done:
199 	free(command);
200 	free(repo_name);
201 	free(myserver);
202 	free(gitcommand);
203 	if (error) {
204 		fprintf(stderr, "%s: %s\n", getprogname(), error->msg);
205 		return 1;
206 	}
207 
208 	return 0;
209 }