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 <sys/queue.h>
22 #include <sys/types.h>
23 #include <sys/uio.h>
24 
25 #include <err.h>
26 #include <errno.h>
27 #include <event.h>
28 #include <imsg.h>
29 #include <limits.h>
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 #include <sha1.h>
34 #include <sha2.h>
35 #include <syslog.h>
36 #include <util.h>
37 #include <unistd.h>
38 
39 #include "got_error.h"
40 #include "got_object.h"
41 #include "got_path.h"
42 
43 #include "got_lib_dial.h"
44 
45 #include "gotd.h"
46 #include "log.h"
47 
48 #ifndef GITWRAPPER_GIT_LIBEXEC_DIR
49 #define GITWRAPPER_GIT_LIBEXEC_DIR "/usr/local/libexec/git"
50 #endif
51 
52 #ifndef GITWRAPPER_MY_SERVER_PROG
53 #define GITWRAPPER_MY_SERVER_PROG "gotsh"
54 #endif
55 
56 
57 __dead static void
58 usage(void)
59 {
60 	fprintf(stderr, "usage: %s -c '%s|%s repository-path'\n",
61 	    getprogname(), GOT_DIAL_CMD_SEND, GOT_DIAL_CMD_FETCH);
62 	exit(1);
63 }
64 
65 /*
66  * Unveil the specific programs we want to start and hide everything else.
67  * This is important to limit the impact of our "exec" pledge.
68  */
69 static const struct got_error *
70 apply_unveil(const char *myserver)
71 {
72 	const char *fetchcmd = GITWRAPPER_GIT_LIBEXEC_DIR "/" \
73 		GOT_DIAL_CMD_FETCH;
74 	const char *sendcmd = GITWRAPPER_GIT_LIBEXEC_DIR "/" \
75 		GOT_DIAL_CMD_SEND;
76 
77 #ifdef PROFILE
78 	if (unveil("gmon.out", "rwc") != 0)
79 		return got_error_from_errno2("unveil", "gmon.out");
80 #endif
81 	if (unveil(fetchcmd, "x") != 0 && errno != ENOENT)
82 		return got_error_from_errno2("unveil", fetchcmd);
83 
84 	if (unveil(sendcmd, "x") != 0 && errno != ENOENT)
85 		return got_error_from_errno2("unveil", sendcmd);
86 
87 	if (myserver && unveil(myserver, "x") != 0 && errno != ENOENT)
88 		return got_error_from_errno2("unveil", myserver);
89 
90 	if (unveil(NULL, NULL) != 0)
91 		return got_error_from_errno("unveil");
92 
93 	return NULL;
94 }
95 
96 int
97 main(int argc, char *argv[])
98 {
99 	const struct got_error *error;
100 	const char *confpath = NULL;
101 	char *command = NULL, *repo_name = NULL; /* for matching gotd.conf */
102 	char *myserver = NULL;
103 	const char *repo_path = NULL; /* as passed on the command line */
104 	const char *relpath;
105 	char *gitcommand = NULL;
106 	struct gotd gotd;
107 	struct gotd_repo *repo = NULL;
108 
109 	log_init(1, LOG_USER); /* Log to stderr. */
110 
111 #ifndef PROFILE
112 	if (pledge("stdio rpath exec unveil", NULL) == -1)
113 		err(1, "pledge");
114 #endif
115 
116 	/*
117 	 * Look up our own server program in PATH so we can unveil(2) it.
118 	 * This call only errors out upon memory allocation failure.
119 	 * If the program cannot be found then myserver will be set to NULL.
120 	 */
121 	error = got_path_find_prog(&myserver, GITWRAPPER_MY_SERVER_PROG);
122 	if (error)
123 		goto done;
124 
125 	/*
126 	 * Run parse_config() before unveil(2) because parse_config()
127 	 * checks whether repository paths exist on disk.
128 	 * Parsing errors and warnings will be logged to stderr.
129 	 * Upon failure we will run Git's native tooling so do not
130 	 * bother checking for errors here.
131 	 */
132 	confpath = getenv("GOTD_CONF_PATH");
133 	if (confpath == NULL)
134 		confpath = GOTD_CONF_PATH;
135 	parse_config(confpath, PROC_GITWRAPPER, &gotd);
136 
137 	error = apply_unveil(myserver);
138 	if (error)
139 		goto done;
140 
141 #ifndef PROFILE
142 	if (pledge("stdio exec", NULL) == -1)
143 		err(1, "pledge");
144 #endif
145 
146 	if (strcmp(getprogname(), GOT_DIAL_CMD_SEND) == 0 ||
147 	    strcmp(getprogname(), GOT_DIAL_CMD_FETCH) == 0) {
148 		if (argc != 2)
149 			usage();
150 		command = strdup(getprogname());
151 		if (command == NULL) {
152 			error = got_error_from_errno("strdup");
153 			goto done;
154 		}
155 		repo_path = argv[1];
156 		relpath = argv[1];
157 		while (relpath[0] == '/')
158 			relpath++;
159 		repo_name = strdup(relpath);
160 		if (repo_name == NULL) {
161 			error = got_error_from_errno("strdup");
162 			goto done;
163 		}
164 	} else {
165 		if (argc != 3 || strcmp(argv[1], "-c") != 0)
166 			usage();
167 		repo_path = argv[2];
168 		error = got_dial_parse_command(&command, &repo_name,
169 		    repo_path);
170 		if (error && error->code == GOT_ERR_BAD_PACKET)
171 			usage();
172 		if (error)
173 			goto done;
174 	}
175 
176 	repo = gotd_find_repo_by_name(repo_name, &gotd.repos);
177 
178 	/*
179 	 * Invoke our custom Git server if the repository was found
180 	 * in gotd.conf. Otherwise invoke native git(1) tooling.
181 	 */
182 	if (repo) {
183 		if (myserver == NULL) {
184 			error = got_error_fmt(GOT_ERR_NO_PROG,
185 			    "cannot run '%s'",
186 			    GITWRAPPER_MY_SERVER_PROG);
187 			goto done;
188 		}
189 		execl(myserver, command, repo_name, (char *)NULL);
190 		error = got_error_from_errno2("execl", myserver);
191 	} else {
192 		if (asprintf(&gitcommand, "%s/%s",
193 		    GITWRAPPER_GIT_LIBEXEC_DIR, command) == -1) {
194 			error = got_error_from_errno("asprintf");
195 			goto done;
196 		}
197 		execl(gitcommand, gitcommand, repo_path, (char *)NULL);
198 		error = got_error_from_errno2("execl", gitcommand);
199 	}
200 
201 done:
202 	free(command);
203 	free(repo_name);
204 	free(myserver);
205 	free(gitcommand);
206 	if (error) {
207 		fprintf(stderr, "%s: %s\n", getprogname(), error->msg);
208 		return 1;
209 	}
210 
211 	return 0;
212 }