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