shell.c

   1 #include "cache.h"
   2 #include "quote.h"
   3 #include "exec-cmd.h"
   4 #include "strbuf.h"
   5 #include "run-command.h"
   6 #include "alias.h"
   7 #include "prompt.h"
   8
   9 #define COMMAND_DIR "git-shell-commands"
  10 #define HELP_COMMAND COMMAND_DIR "/help"
  11 #define NOLOGIN_COMMAND COMMAND_DIR "/no-interactive-login"
  12
  13 static int do_generic_cmd(const char *me, char *arg)
  14 {
  15         const char *my_argv[4];
  16
  17         setup_path();
  18         if (!arg || !(arg = sq_dequote(arg)) || *arg == '-')
  19                 die("bad argument");
  20         if (!skip_prefix(me, "git-", &me))
  21                 die("bad command");
  22
  23         my_argv[0] = me;
  24         my_argv[1] = arg;
  25         my_argv[2] = NULL;
  26
  27         return execv_git_cmd(my_argv);
  28 }
  29
  30 static int is_valid_cmd_name(const char *cmd)
  31 {
  32         /* Test command contains no . or / characters */
  33         return cmd[strcspn(cmd, "./")] == '\0';
  34 }
  35
  36 static char *make_cmd(const char *prog)
  37 {
  38         return xstrfmt("%s/%s", COMMAND_DIR, prog);
  39 }
  40
  41 static void cd_to_homedir(void)
  42 {
  43         const char *home = getenv("HOME");
  44         if (!home)
  45                 die("could not determine user's home directory; HOME is unset");
  46         if (chdir(home) == -1)
  47                 die("could not chdir to user's home directory");
  48 }
  49
  50 #define MAX_INTERACTIVE_COMMAND (4*1024*1024)
  51
  52 static void run_shell(void)
  53 {
  54         int done = 0;
  55         static const char *help_argv[] = { HELP_COMMAND, NULL };
  56
  57         if (!access(NOLOGIN_COMMAND, F_OK)) {
  58                 /* Interactive login disabled. */
  59                 const char *argv[] = { NOLOGIN_COMMAND, NULL };
  60                 int status;
  61
  62                 status = run_command_v_opt(argv, 0);
  63                 if (status < 0)
  64                         exit(127);
  65                 exit(status);
  66         }
  67
  68         /* Print help if enabled */
  69         run_command_v_opt(help_argv, RUN_SILENT_EXEC_FAILURE);
  70
  71         do {
  72                 const char *prog;
  73                 char *full_cmd;
  74                 char *rawargs;
  75                 size_t len;
  76                 char *split_args;
  77                 const char **argv;
  78                 int code;
  79                 int count;
  80
  81                 fprintf(stderr, "git> ");
  82
  83                 /*
  84                  * Avoid using a strbuf or git_read_line_interactively() here.
  85                  * We don't want to allocate arbitrary amounts of memory on
  86                  * behalf of a possibly untrusted client, and we're subject to
  87                  * OS limits on command length anyway.
  88                  */
  89                 fflush(stdout);
  90                 rawargs = xmalloc(MAX_INTERACTIVE_COMMAND);
  91                 if (!fgets(rawargs, MAX_INTERACTIVE_COMMAND, stdin)) {
  92                         fprintf(stderr, "\n");
  93                         free(rawargs);
  94                         break;
  95                 }
  96                 len = strlen(rawargs);
  97
  98                 /*
  99                  * If we truncated due to our input buffer size, reject the
 100                  * command. That's better than running bogus input, and
 101                  * there's a good chance it's just malicious garbage anyway.
 102                  */
 103                 if (len >= MAX_INTERACTIVE_COMMAND - 1)
 104                         die("invalid command format: input too long");
 105
 106                 if (len > 0 && rawargs[len - 1] == '\n') {
 107                         if (--len > 0 && rawargs[len - 1] == '\r')
 108                                 --len;
 109                         rawargs[len] = '\0';
 110                 }
 111
 112                 split_args = xstrdup(rawargs);
 113                 count = split_cmdline(split_args, &argv);
 114                 if (count < 0) {
 115                         fprintf(stderr, "invalid command format '%s': %s\n", rawargs,
 116                                 split_cmdline_strerror(count));
 117                         free(split_args);
 118                         free(rawargs);
 119                         continue;
 120                 }
 121
 122                 prog = argv[0];
 123                 if (!strcmp(prog, "")) {
 124                 } else if (!strcmp(prog, "quit") || !strcmp(prog, "logout") ||
 125                            !strcmp(prog, "exit") || !strcmp(prog, "bye")) {
 126                         done = 1;
 127                 } else if (is_valid_cmd_name(prog)) {
 128                         full_cmd = make_cmd(prog);
 129                         argv[0] = full_cmd;
 130                         code = run_command_v_opt(argv, RUN_SILENT_EXEC_FAILURE);
 131                         if (code == -1 && errno == ENOENT) {
 132                                 fprintf(stderr, "unrecognized command '%s'\n", prog);
 133                         }
 134                         free(full_cmd);
 135                 } else {
 136                         fprintf(stderr, "invalid command format '%s'\n", prog);
 137                 }
 138
 139                 free(argv);
 140                 free(rawargs);
 141         } while (!done);
 142 }
 143
 144 static struct commands {
 145         const char *name;
 146         int (*exec)(const char *me, char *arg);
 147 } cmd_list[] = {
 148         { "git-receive-pack", do_generic_cmd },
 149         { "git-upload-pack", do_generic_cmd },
 150         { "git-upload-archive", do_generic_cmd },
 151         { NULL },
 152 };
 153
 154 int cmd_main(int argc, const char **argv)
 155 {
 156         char *prog;
 157         const char **user_argv;
 158         struct commands *cmd;
 159         int count;
 160
 161         /*
 162          * Special hack to pretend to be a CVS server
 163          */
 164         if (argc == 2 && !strcmp(argv[1], "cvs server")) {
 165                 argv--;
 166         } else if (argc == 1) {
 167                 /* Allow the user to run an interactive shell */
 168                 cd_to_homedir();
 169                 if (access(COMMAND_DIR, R_OK | X_OK) == -1) {
 170                         die("Interactive git shell is not enabled.\n"
 171                             "hint: ~/" COMMAND_DIR " should exist "
 172                             "and have read and execute access.");
 173                 }
 174                 run_shell();
 175                 exit(0);
 176         } else if (argc != 3 || strcmp(argv[1], "-c")) {
 177                 /*
 178                  * We do not accept any other modes except "-c" followed by
 179                  * "cmd arg", where "cmd" is a very limited subset of git
 180                  * commands or a command in the COMMAND_DIR
 181                  */
 182                 die("Run with no arguments or with -c cmd");
 183         }
 184
 185         prog = xstrdup(argv[2]);
 186         if (!strncmp(prog, "git", 3) && isspace(prog[3]))
 187                 /* Accept "git foo" as if the caller said "git-foo". */
 188                 prog[3] = '-';
 189
 190         for (cmd = cmd_list ; cmd->name ; cmd++) {
 191                 int len = strlen(cmd->name);
 192                 char *arg;
 193                 if (strncmp(cmd->name, prog, len))
 194                         continue;
 195                 arg = NULL;
 196                 switch (prog[len]) {
 197                 case '\0':
 198                         arg = NULL;
 199                         break;
 200                 case ' ':
 201                         arg = prog + len + 1;
 202                         break;
 203                 default:
 204                         continue;
 205                 }
 206                 exit(cmd->exec(cmd->name, arg));
 207         }
 208
 209         cd_to_homedir();
 210         count = split_cmdline(prog, &user_argv);
 211         if (count >= 0) {
 212                 if (is_valid_cmd_name(user_argv[0])) {
 213                         prog = make_cmd(user_argv[0]);
 214                         user_argv[0] = prog;
 215                         execv(user_argv[0], (char *const *) user_argv);
 216                 }
 217                 free(prog);
 218                 free(user_argv);
 219                 die("unrecognized command '%s'", argv[2]);
 220         } else {
 221                 free(prog);
 222                 die("invalid command format '%s': %s", argv[2],
 223                     split_cmdline_strerror(count));
 224         }
 225 }