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Date:: Sun Oct 23 00:37:19 2022 UTC
Message:: introduce gotd(8), a Git repository server reachable via ssh(1) This is an initial barebones implementation which provides the absolute minimum of functionality required to serve got(1) and git(1) clients. Basic fetch/send functionality has been tested and seems to work here, but this server is not yet expected to be stable. More testing is welcome. See the man pages for setup instructions. The current design uses one reader and one writer process per repository, which will have to be extended to N readers and N writers in the future. At startup, each process will chroot(2) into its assigned repository. This works because gotd(8) can only be started as root, and will then fork+exec, chroot, and privdrop. At present the parent process runs with the following pledge(2) promises: "stdio rpath wpath cpath proc getpw sendfd recvfd fattr flock unix unveil" The parent is the only process able to modify the repository in a way that becomes visible to Git clients. The parent uses unveil(2) to restrict its view of the filesystem to /tmp and the repositories listed in the configuration file gotd.conf(5). Per-repository chroot(2) processes use "stdio rpath sendfd recvfd". The writer defers to the parent for modifying references in the repository to point at newly uploaded commits. The reader is fine without such help, because Git repositories can be read without having to create any lock-files. gotd(8) requires a dedicated user ID, which should own repositories on the filesystem, and a separate secondary group, which should not have filesystem-level repository access, and must be allowed access to the gotd(8) socket. To obtain Git repository access, users must be members of this secondary group, and must have their login shell set to gotsh(1). gotsh(1) connects to the gotd(8) socket and speaks Git-protocol towards the client on the other end of the SSH connection. gotsh(1) is not an interactive command shell. At present, authenticated clients are granted read/write access to all repositories and all references (except for the "refs/got/" and the "refs/remotes/" namespaces, which are already being protected from modification). While complicated access control mechanism are not a design goal, making it possible to safely offer anonymous Git repository access over ssh(1) is on the road map.
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  1 13b2bc37 2022-10-23 stsp /*
  2 13b2bc37 2022-10-23 stsp  * Copyright (c) 2022 Stefan Sperling <stsp@openbsd.org>
  3 13b2bc37 2022-10-23 stsp  *
  4 13b2bc37 2022-10-23 stsp  * Permission to use, copy, modify, and distribute this software for any
  5 13b2bc37 2022-10-23 stsp  * purpose with or without fee is hereby granted, provided that the above
  6 13b2bc37 2022-10-23 stsp  * copyright notice and this permission notice appear in all copies.
  7 13b2bc37 2022-10-23 stsp  *
  8 13b2bc37 2022-10-23 stsp  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9 13b2bc37 2022-10-23 stsp  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10 13b2bc37 2022-10-23 stsp  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11 13b2bc37 2022-10-23 stsp  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12 13b2bc37 2022-10-23 stsp  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13 13b2bc37 2022-10-23 stsp  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14 13b2bc37 2022-10-23 stsp  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15 13b2bc37 2022-10-23 stsp  */
 16 13b2bc37 2022-10-23 stsp 
 17 13b2bc37 2022-10-23 stsp #include <sys/queue.h>
 18 13b2bc37 2022-10-23 stsp #include <sys/socket.h>
 19 13b2bc37 2022-10-23 stsp #include <sys/un.h>
 20 13b2bc37 2022-10-23 stsp 
 21 13b2bc37 2022-10-23 stsp #include <err.h>
 22 13b2bc37 2022-10-23 stsp #include <event.h>
 23 13b2bc37 2022-10-23 stsp #include <imsg.h>
 24 13b2bc37 2022-10-23 stsp #include <limits.h>
 25 13b2bc37 2022-10-23 stsp #include <sha1.h>
 26 13b2bc37 2022-10-23 stsp #include <stdio.h>
 27 13b2bc37 2022-10-23 stsp #include <stdlib.h>
 28 13b2bc37 2022-10-23 stsp #include <string.h>
 29 13b2bc37 2022-10-23 stsp #include <unistd.h>
 30 13b2bc37 2022-10-23 stsp 
 31 13b2bc37 2022-10-23 stsp #include "got_error.h"
 32 13b2bc37 2022-10-23 stsp #include "got_serve.h"
 33 13b2bc37 2022-10-23 stsp 
 34 13b2bc37 2022-10-23 stsp #include "gotd.h"
 35 13b2bc37 2022-10-23 stsp 
 36 13b2bc37 2022-10-23 stsp static int chattygot;
 37 13b2bc37 2022-10-23 stsp 
 38 13b2bc37 2022-10-23 stsp __dead static void
 39 13b2bc37 2022-10-23 stsp usage()
 40 13b2bc37 2022-10-23 stsp {
 41 13b2bc37 2022-10-23 stsp 	fprintf(stderr, "usage: %s -c '%s|%s repository-path'\n",
 42 13b2bc37 2022-10-23 stsp 	    getprogname(), GOT_SERVE_CMD_SEND, GOT_SERVE_CMD_FETCH);
 43 13b2bc37 2022-10-23 stsp 	exit(1);
 44 13b2bc37 2022-10-23 stsp }
 45 13b2bc37 2022-10-23 stsp 
 46 13b2bc37 2022-10-23 stsp static const struct got_error *
 47 13b2bc37 2022-10-23 stsp apply_unveil(const char *unix_socket_path)
 48 13b2bc37 2022-10-23 stsp {
 49 13b2bc37 2022-10-23 stsp #ifdef PROFILE
 50 13b2bc37 2022-10-23 stsp 	if (unveil("gmon.out", "rwc") != 0)
 51 13b2bc37 2022-10-23 stsp 		return got_error_from_errno2("unveil", "gmon.out");
 52 13b2bc37 2022-10-23 stsp #endif
 53 13b2bc37 2022-10-23 stsp 	if (unveil(unix_socket_path, "w") != 0)
 54 13b2bc37 2022-10-23 stsp 		return got_error_from_errno2("unveil", unix_socket_path);
 55 13b2bc37 2022-10-23 stsp 
 56 13b2bc37 2022-10-23 stsp 	if (unveil(NULL, NULL) != 0)
 57 13b2bc37 2022-10-23 stsp 		return got_error_from_errno("unveil");
 58 13b2bc37 2022-10-23 stsp 
 59 13b2bc37 2022-10-23 stsp 	return NULL;
 60 13b2bc37 2022-10-23 stsp }
 61 13b2bc37 2022-10-23 stsp 
 62 13b2bc37 2022-10-23 stsp int
 63 13b2bc37 2022-10-23 stsp main(int argc, char *argv[])
 64 13b2bc37 2022-10-23 stsp {
 65 13b2bc37 2022-10-23 stsp 	const struct got_error *error;
 66 13b2bc37 2022-10-23 stsp 	char unix_socket_path[PATH_MAX];
 67 13b2bc37 2022-10-23 stsp 	char *unix_socket_path_env = getenv("GOTD_UNIX_SOCKET");
 68 13b2bc37 2022-10-23 stsp 	int gotd_sock = -1;
 69 13b2bc37 2022-10-23 stsp 	struct sockaddr_un	 sun;
 70 13b2bc37 2022-10-23 stsp 
 71 13b2bc37 2022-10-23 stsp #ifndef PROFILE
 72 13b2bc37 2022-10-23 stsp 	if (pledge("stdio recvfd unix unveil", NULL) == -1)
 73 13b2bc37 2022-10-23 stsp 		err(1, "pledge");
 74 13b2bc37 2022-10-23 stsp #endif
 75 13b2bc37 2022-10-23 stsp 	if (argc != 3 ||
 76 13b2bc37 2022-10-23 stsp 	    strcmp(argv[1], "-c") != 0 ||
 77 13b2bc37 2022-10-23 stsp 	    (strncmp(argv[2], GOT_SERVE_CMD_SEND,
 78 13b2bc37 2022-10-23 stsp 	    strlen(GOT_SERVE_CMD_SEND)) != 0 &&
 79 13b2bc37 2022-10-23 stsp 	    (strncmp(argv[2], GOT_SERVE_CMD_FETCH,
 80 13b2bc37 2022-10-23 stsp 	    strlen(GOT_SERVE_CMD_FETCH)) != 0)))
 81 13b2bc37 2022-10-23 stsp 		usage();
 82 13b2bc37 2022-10-23 stsp 
 83 13b2bc37 2022-10-23 stsp 	if (unix_socket_path_env) {
 84 13b2bc37 2022-10-23 stsp 		if (strlcpy(unix_socket_path, unix_socket_path_env,
 85 13b2bc37 2022-10-23 stsp 		    sizeof(unix_socket_path)) >= sizeof(unix_socket_path)) 
 86 13b2bc37 2022-10-23 stsp 			errx(1, "gotd socket path too long");
 87 13b2bc37 2022-10-23 stsp 	} else {
 88 13b2bc37 2022-10-23 stsp 		strlcpy(unix_socket_path, GOTD_UNIX_SOCKET,
 89 13b2bc37 2022-10-23 stsp 		    sizeof(unix_socket_path));
 90 13b2bc37 2022-10-23 stsp 	}
 91 13b2bc37 2022-10-23 stsp 
 92 13b2bc37 2022-10-23 stsp 	error = apply_unveil(unix_socket_path);
 93 13b2bc37 2022-10-23 stsp 	if (error)
 94 13b2bc37 2022-10-23 stsp 		goto done;
 95 13b2bc37 2022-10-23 stsp 
 96 13b2bc37 2022-10-23 stsp #ifndef PROFILE
 97 13b2bc37 2022-10-23 stsp 	if (pledge("stdio recvfd unix", NULL) == -1)
 98 13b2bc37 2022-10-23 stsp 		err(1, "pledge");
 99 13b2bc37 2022-10-23 stsp #endif
100 13b2bc37 2022-10-23 stsp 	if ((gotd_sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
101 13b2bc37 2022-10-23 stsp 		err(1, "socket");
102 13b2bc37 2022-10-23 stsp 
103 13b2bc37 2022-10-23 stsp 	memset(&sun, 0, sizeof(sun));
104 13b2bc37 2022-10-23 stsp 	sun.sun_family = AF_UNIX;
105 13b2bc37 2022-10-23 stsp 	if (strlcpy(sun.sun_path, unix_socket_path,
106 13b2bc37 2022-10-23 stsp 	    sizeof(sun.sun_path)) >= sizeof(sun.sun_path))
107 13b2bc37 2022-10-23 stsp 		errx(1, "gotd socket path too long");
108 13b2bc37 2022-10-23 stsp 	if (connect(gotd_sock, (struct sockaddr *)&sun, sizeof(sun)) == -1)
109 13b2bc37 2022-10-23 stsp 		err(1, "connect: %s", unix_socket_path);
110 13b2bc37 2022-10-23 stsp 
111 13b2bc37 2022-10-23 stsp #ifndef PROFILE
112 13b2bc37 2022-10-23 stsp 	if (pledge("stdio recvfd", NULL) == -1)
113 13b2bc37 2022-10-23 stsp 		err(1, "pledge");
114 13b2bc37 2022-10-23 stsp #endif
115 13b2bc37 2022-10-23 stsp 	error = got_serve(STDIN_FILENO, STDOUT_FILENO, argv[2], gotd_sock,
116 13b2bc37 2022-10-23 stsp 	    chattygot);
117 13b2bc37 2022-10-23 stsp done:
118 13b2bc37 2022-10-23 stsp 	if (gotd_sock != -1)
119 13b2bc37 2022-10-23 stsp 		close(gotd_sock);
120 13b2bc37 2022-10-23 stsp 	if (error) {
121 13b2bc37 2022-10-23 stsp 		fprintf(stderr, "%s: %s\n", getprogname(), error->msg);
122 13b2bc37 2022-10-23 stsp 		return 1;
123 13b2bc37 2022-10-23 stsp 	}
124 13b2bc37 2022-10-23 stsp 
125 13b2bc37 2022-10-23 stsp 	return 0;
126 13b2bc37 2022-10-23 stsp }