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