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Allow creation of arbitrary git-shell commands

This provides a mechanism for the server to expose custom
functionality to clients.  My particular use case is that I would like
a way of discovering all repositories available for cloning.  A
client that clones via

  git clone user@example.com

can invoke a command by

  ssh user@example.com $command

Signed-off-by: Greg Brockman <gdb@mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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1 parent 64fdc08 commit 2dbc887eaa6fbd787edfc9472b86b0faeb54e2ae Greg Brockman committed with gitster Jul 29, 2010
Showing with 42 additions and 2 deletions.
  1. +42 −2 shell.c
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@@ -3,6 +3,8 @@
#include "exec_cmd.h"
#include "strbuf.h"
+#define COMMAND_DIR "git-shell-commands"
+
static int do_generic_cmd(const char *me, char *arg)
{
const char *my_argv[4];
@@ -33,6 +35,29 @@ static int do_cvs_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 struct commands {
const char *name;
@@ -48,6 +73,7 @@ static struct commands {
int main(int argc, char **argv)
{
char *prog;
+ const char **user_argv;
struct commands *cmd;
int devnull_fd;
@@ -76,7 +102,7 @@ int main(int argc, char **argv)
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] = '-';
@@ -99,5 +125,19 @@ int main(int argc, char **argv)
}
exit(cmd->exec(cmd->name, arg));
}
- die("unrecognized command '%s'", prog);
+
+ cd_to_homedir();
+ if (split_cmdline(prog, &user_argv) != -1) {
+ 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'", argv[2]);
+ }
}

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