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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 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  */

17 #include <sys/types.h>

18 #include <sys/queue.h>

20 #include <ctype.h>

21 #include <string.h>

23 #include "got_reference.h"

25 #include "got_lib_lockfile.h"

27 #ifndef nitems

28 #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))

29 #endif

31 int

32 got_ref_name_is_valid(const char *name)

33 {

34 	const char *s, *seg;

35 	const char forbidden[] = { ' ', '~', '^', ':', '?', '*', '[' , '\\' };

36 	const char *forbidden_seq[] = { "//", "..", "@{" };

37 	const char *lfs = GOT_LOCKFILE_SUFFIX;

38 	const size_t lfs_len = sizeof(GOT_LOCKFILE_SUFFIX) - 1;

39 	size_t i;

41 	if (name[0] == '@' && name[1] == '\0')

42 		return 0;

44 	s = name;

45 	seg = s;

46 	if (seg[0] == '\0' || seg[0] == '.' || seg[0] == '/')

47 		return 0;

48 	while (*s) {

49 		for (i = 0; i < nitems(forbidden); i++) {

50 			if (*s == forbidden[i])

51 				return 0;

52 		}

53 		for (i = 0; i < nitems(forbidden_seq); i++) {

54 			if (s[0] == forbidden_seq[i][0] &&

55 			    s[1] == forbidden_seq[i][1])

56 				return 0;

57 		}

58 		if (iscntrl((unsigned char)s[0]))

59 			return 0;

60 		if (s[0] == '.' && s[1] == '\0')

61 			return 0;

62 		if (*s == '/') {

63 			const char *nextseg = s + 1;

64 			if (nextseg[0] == '\0' || nextseg[0] == '.' ||

65 			    nextseg[0] == '/')

66 				return 0;

67 			if (seg <= s - lfs_len &&

68 			    strncmp(s - lfs_len, lfs, lfs_len) == 0)

69 				return 0;

70 			seg = nextseg;

71 		}

72 		s++;

73 	}

75 	if (seg <= s - lfs_len &&

76 	    strncmp(s - lfs_len, lfs, lfs_len) == 0)

77 		return 0;

79 	return 1;

80 }