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- 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 /*2 * Copyright (c) 2018, 2019, 2020 Stefan Sperling <stsp@openbsd.org>3 *4 * Permission to use, copy, modify, and distribute this software for any5 * purpose with or without fee is hereby granted, provided that the above6 * copyright notice and this permission notice appear in all copies.7 *8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.15 */17 #include <sys/types.h>18 #include <sys/queue.h>19 #include <sys/uio.h>20 #include <sys/time.h>22 #include <stdint.h>23 #include <limits.h>24 #include <signal.h>25 #include <stdio.h>26 #include <stdlib.h>27 #include <string.h>28 #include <unistd.h>29 #include <zlib.h>31 #include "got_compat.h"33 #include "got_error.h"34 #include "got_object.h"35 #include "got_path.h"37 #include "got_lib_delta.h"38 #include "got_lib_inflate.h"39 #include "got_lib_object.h"40 #include "got_lib_object_parse.h"41 #include "got_lib_privsep.h"42 #include "got_lib_sha1.h"44 static volatile sig_atomic_t sigint_received;46 static void47 catch_sigint(int signo)48 {49 sigint_received = 1;50 }52 int53 main(int argc, char *argv[])54 {55 const struct got_error *err = NULL;56 struct imsgbuf ibuf;57 size_t datalen;58 struct got_parsed_tree_entry *entries = NULL;59 size_t nentries = 0, nentries_alloc = 0;61 signal(SIGINT, catch_sigint);63 imsg_init(&ibuf, GOT_IMSG_FD_CHILD);65 #ifndef PROFILE66 /* revoke access to most system calls */67 if (pledge("stdio recvfd", NULL) == -1) {68 err = got_error_from_errno("pledge");69 got_privsep_send_error(&ibuf, err);70 return 1;71 }73 /* revoke fs access */74 if (landlock_no_fs() == -1) {75 err = got_error_from_errno("landlock_no_fs");76 got_privsep_send_error(&ibuf, err);77 return 1;78 }79 if (cap_enter() == -1) {80 err = got_error_from_errno("cap_enter");81 got_privsep_send_error(&ibuf, err);82 return 1;83 }84 #endif86 for (;;) {87 struct imsg imsg;88 uint8_t *buf = NULL;89 struct got_object_id expected_id;91 if (sigint_received) {92 err = got_error(GOT_ERR_CANCELLED);93 break;94 }96 err = got_privsep_recv_imsg(&imsg, &ibuf, 0);97 if (err) {98 if (err->code == GOT_ERR_PRIVSEP_PIPE)99 err = NULL;100 break;101 }103 if (imsg.hdr.type == GOT_IMSG_STOP)104 break;106 if (imsg.hdr.type != GOT_IMSG_TREE_REQUEST) {107 err = got_error(GOT_ERR_PRIVSEP_MSG);108 goto done;109 }111 datalen = imsg.hdr.len - IMSG_HEADER_SIZE;112 if (datalen != sizeof(expected_id)) {113 err = got_error(GOT_ERR_PRIVSEP_LEN);114 goto done;115 }116 memcpy(&expected_id, imsg.data, sizeof(expected_id));118 if (imsg.fd == -1) {119 err = got_error(GOT_ERR_PRIVSEP_NO_FD);120 goto done;121 }123 /* Always assume file offset zero. */124 err = got_object_read_tree(&entries, &nentries, &nentries_alloc,125 &buf, imsg.fd, &expected_id);126 if (err)127 goto done;129 err = got_privsep_send_tree(&ibuf, entries, nentries);130 done:131 free(buf);132 if (imsg.fd != -1 && close(imsg.fd) == -1 && err == NULL)133 err = got_error_from_errno("close");134 imsg_free(&imsg);135 if (err)136 break;137 }139 free(entries);140 imsg_clear(&ibuf);141 if (err) {142 if (!sigint_received && err->code != GOT_ERR_PRIVSEP_PIPE) {143 fprintf(stderr, "%s: %s\n", getprogname(), err->msg);144 got_privsep_send_error(&ibuf, err);145 }146 }147 if (close(GOT_IMSG_FD_CHILD) == -1 && err == NULL)148 err = got_error_from_errno("close");149 return err ? 1 : 0;150 }