NAME
----
-git-shell - Restricted login shell for GIT-only SSH access
+git-shell - Restricted login shell for Git-only SSH access
SYNOPSIS
--------
-'$(git --exec-path)/git-shell' -c <command> <argument>
+'git shell' [-c <command> <argument>]
DESCRIPTION
-----------
-This is meant to be used as a login shell for SSH accounts you want
-to restrict to GIT pull/push access only. It permits execution only
-of server-side GIT commands implementing the pull/push functionality.
-The commands can be executed only by the '-c' option; the shell is not
-interactive.
-
-Currently, only four commands are permitted to be called, 'git-receive-pack'
-'git-upload-pack' and 'git-upload-archive' with a single required argument, or
-'cvs server' (to invoke 'git-cvsserver').
+
+A login shell for SSH accounts to provide restricted Git access. When
+'-c' is given, the program executes <command> non-interactively;
+<command> can be one of 'git receive-pack', 'git upload-pack', 'git
+upload-archive', 'cvs server', or a command in COMMAND_DIR. The shell
+is started in interactive mode when no arguments are given; in this
+case, COMMAND_DIR must exist, and any of the executables in it can be
+invoked.
+
+'cvs server' is a special command which executes git-cvsserver.
+
+COMMAND_DIR is the path "$HOME/git-shell-commands". The user must have
+read and execute permissions to the directory in order to execute the
+programs in it. The programs are executed with a cwd of $HOME, and
+<argument> is parsed as a command-line string.
Author
------
#include "quote.h"
#include "exec_cmd.h"
#include "strbuf.h"
+#include "run-command.h"
+
+#define COMMAND_DIR "git-shell-commands"
+#define HELP_COMMAND COMMAND_DIR "/help"
static int do_generic_cmd(const char *me, char *arg)
{
return execv_git_cmd(cvsserver_argv);
}
+static int is_valid_cmd_name(const char *cmd)
+{
+ /* Test command contains no . or / characters */
+ return cmd[strcspn(cmd, "./")] == '\0';
+}
+
+static char *make_cmd(const char *prog)
+{
+ char *prefix = xmalloc((strlen(prog) + strlen(COMMAND_DIR) + 2));
+ strcpy(prefix, COMMAND_DIR);
+ strcat(prefix, "/");
+ strcat(prefix, prog);
+ return prefix;
+}
+
+static void cd_to_homedir(void)
+{
+ const char *home = getenv("HOME");
+ if (!home)
+ die("could not determine user's home directory; HOME is unset");
+ if (chdir(home) == -1)
+ die("could not chdir to user's home directory");
+}
+
+static void run_shell(void)
+{
+ int done = 0;
+ static const char *help_argv[] = { HELP_COMMAND, NULL };
+ /* Print help if enabled */
+ run_command_v_opt(help_argv, RUN_SILENT_EXEC_FAILURE);
+
+ do {
+ struct strbuf line = STRBUF_INIT;
+ const char *prog;
+ char *full_cmd;
+ char *rawargs;
+ char *split_args;
+ const char **argv;
+ int code;
+ int count;
+
+ fprintf(stderr, "git> ");
+ if (strbuf_getline(&line, stdin, '\n') == EOF) {
+ fprintf(stderr, "\n");
+ strbuf_release(&line);
+ break;
+ }
+ strbuf_trim(&line);
+ rawargs = strbuf_detach(&line, NULL);
+ split_args = xstrdup(rawargs);
+ count = split_cmdline(split_args, &argv);
+ if (count < 0) {
+ fprintf(stderr, "invalid command format '%s': %s\n", rawargs,
+ split_cmdline_strerror(count));
+ free(split_args);
+ free(rawargs);
+ continue;
+ }
+
+ prog = argv[0];
+ if (!strcmp(prog, "")) {
+ } else if (!strcmp(prog, "quit") || !strcmp(prog, "logout") ||
+ !strcmp(prog, "exit") || !strcmp(prog, "bye")) {
+ done = 1;
+ } else if (is_valid_cmd_name(prog)) {
+ full_cmd = make_cmd(prog);
+ argv[0] = full_cmd;
+ code = run_command_v_opt(argv, RUN_SILENT_EXEC_FAILURE);
+ if (code == -1 && errno == ENOENT) {
+ fprintf(stderr, "unrecognized command '%s'\n", prog);
+ }
+ free(full_cmd);
+ } else {
+ fprintf(stderr, "invalid command format '%s'\n", prog);
+ }
+
+ free(argv);
+ free(rawargs);
+ } while (!done);
+}
static struct commands {
const char *name;
int main(int argc, char **argv)
{
char *prog;
+ const char **user_argv;
struct commands *cmd;
int devnull_fd;
+ int count;
/*
* Always open file descriptors 0/1/2 to avoid clobbering files
/*
* Special hack to pretend to be a CVS server
*/
- if (argc == 2 && !strcmp(argv[1], "cvs server"))
+ if (argc == 2 && !strcmp(argv[1], "cvs server")) {
argv--;
+ } else if (argc == 1) {
+ /* Allow the user to run an interactive shell */
+ cd_to_homedir();
+ if (access(COMMAND_DIR, R_OK | X_OK) == -1) {
+ die("Interactive git shell is not enabled.\n"
+ "hint: ~/" COMMAND_DIR " should exist "
+ "and have read and execute access.");
+ }
+ run_shell();
+ exit(0);
+ } else if (argc != 3 || strcmp(argv[1], "-c")) {
+ /*
+ * We do not accept any other modes except "-c" followed by
+ * "cmd arg", where "cmd" is a very limited subset of git
+ * commands or a command in the COMMAND_DIR
+ */
+ die("Run with no arguments or with -c cmd");
+ }
- /*
- * We do not accept anything but "-c" followed by "cmd arg",
- * where "cmd" is a very limited subset of git commands.
- */
- else if (argc != 3 || strcmp(argv[1], "-c"))
- die("What do you think I am? A shell?");
-
- prog = argv[2];
+ prog = xstrdup(argv[2]);
if (!strncmp(prog, "git", 3) && isspace(prog[3]))
/* Accept "git foo" as if the caller said "git-foo". */
prog[3] = '-';
}
exit(cmd->exec(cmd->name, arg));
}
- die("unrecognized command '%s'", prog);
+
+ cd_to_homedir();
+ count = split_cmdline(prog, &user_argv);
+ if (count >= 0) {
+ if (is_valid_cmd_name(user_argv[0])) {
+ prog = make_cmd(user_argv[0]);
+ user_argv[0] = prog;
+ execv(user_argv[0], (char *const *) user_argv);
+ }
+ free(prog);
+ free(user_argv);
+ die("unrecognized command '%s'", argv[2]);
+ } else {
+ free(prog);
+ die("invalid command format '%s': %s", argv[2],
+ split_cmdline_strerror(count));
+ }
}
projects / git.git / commitdiff