From 54b80263a2363436c7d5cd3f173f6750ad8a3b03 Mon Sep 17 00:00:00 2001 From: Jonas 'Sortie' Termansen Date: Wed, 1 Apr 2015 00:23:28 +0200 Subject: [PATCH] Add -d option to chroot(1). --- utils/chroot.cpp | 129 ++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 106 insertions(+), 23 deletions(-) diff --git a/utils/chroot.cpp b/utils/chroot.cpp index 5438cf72..9218cb88 100644 --- a/utils/chroot.cpp +++ b/utils/chroot.cpp @@ -1,6 +1,6 @@ /******************************************************************************* - Copyright(C) Jonas 'Sortie' Termansen 2013. + Copyright(C) Jonas 'Sortie' Termansen 2013, 2015. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free @@ -20,34 +20,39 @@ *******************************************************************************/ +#include +#include +#include + #include #include +#include +#include +#include #include #include #include #include -#if !defined(VERSIONSTR) -#define VERSIONSTR "unknown version" -#endif - -void CompactArguments(int* argc, char*** argv) +static void compact_arguments(int* argc, char*** argv) { for ( int i = 0; i < *argc; i++ ) - while ( i < *argc && !(*argv)[i] ) { - for ( int n = i; n < *argc; n++ ) - (*argv)[n] = (*argv)[n+1]; - (*argc)--; + while ( i < *argc && !(*argv)[i] ) + { + for ( int n = i; n < *argc; n++ ) + (*argv)[n] = (*argv)[n+1]; + (*argc)--; + } } } -void Help(FILE* fp, const char* argv0) +static void help(FILE* fp, const char* argv0) { fprintf(fp, "Usage: %s [OPTION]... ROOT [CMD] [ARGUMENT...]\n", argv0); } -void Version(FILE* fp, const char* argv0) +static void version(FILE* fp, const char* argv0) { fprintf(fp, "%s (Sortix) %s\n", argv0, VERSIONSTR); fprintf(fp, "License GPLv3+: GNU GPL version 3 or later .\n"); @@ -55,14 +60,28 @@ void Version(FILE* fp, const char* argv0) fprintf(fp, "There is NO WARRANTY, to the extent permitted by law.\n"); } +static char* mount_point_dev; + +static void unmount_handler(int signum) +{ + (void) signum; + if ( mount_point_dev ) + { + unmount(mount_point_dev, 0); + mount_point_dev = NULL; + } + raise(signum); +} + int main(int argc, char* argv[]) { + bool devices = false; const char* argv0 = argv[0]; for ( int i = 1; i < argc; i++ ) { const char* arg = argv[i]; - if ( arg[0] != '-' ) - continue; + if ( arg[0] != '-' || !arg[1] ) + break; // Intentionally not continue. argv[i] = NULL; if ( !strcmp(arg, "--") ) break; @@ -70,31 +89,94 @@ int main(int argc, char* argv[]) { while ( char c = *++arg ) switch ( c ) { + case 'd': devices = true; break; default: fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c); - Help(stderr, argv0); + help(stderr, argv0); exit(1); } } - else if ( !strcmp(arg, "--help") ) { Help(stdout, argv0); exit(0); } - else if ( !strcmp(arg, "--version") ) { Version(stdout, argv0); exit(0); } + else if ( !strcmp(arg, "--help") ) + help(stdout, argv0), exit(0); + else if ( !strcmp(arg, "--version") ) + version(stdout, argv0), exit(0); else { fprintf(stderr, "%s: unknown option: %s\n", argv0, arg); - Help(stderr, argv0); + help(stderr, argv0); exit(1); } } - CompactArguments(&argc, &argv); + compact_arguments(&argc, &argv); if ( argc < 2 ) + error(1, 0, "missing operand, expected new root directory"); + + if ( devices ) { - error(0, 0, "missing operand, expected new root directory"); - Help(stdout, argv0); - exit(0); + if ( asprintf(&mount_point_dev, "%s/dev", argv[1]) < 0 ) + error(1, errno, "asprintf: `%s/dev'", argv[1]); + + // Create a device directory in the root filesystem. + mkdir(mount_point_dev, 0755); + + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_handler = unmount_handler; + sa.sa_flags = SA_RESETHAND; + sigaction(SIGHUP, &sa, NULL); + sigaction(SIGINT, &sa, NULL); + sigaction(SIGQUIT, &sa, NULL); + + // Mount the current device directory inside the new root filesystem. + int old_dev_fd = open("/dev", O_DIRECTORY | O_RDONLY); + int new_dev_fd = open(mount_point_dev, O_DIRECTORY | O_RDONLY); + fsm_fsbind(old_dev_fd, new_dev_fd, 0); + close(new_dev_fd); + close(old_dev_fd); + + sigset_t oldset, sigs; + sigemptyset(&sigs); + sigaddset(&sigs, SIGHUP); + sigaddset(&sigs, SIGINT); + sigaddset(&sigs, SIGQUIT); + sigprocmask(SIG_BLOCK, &sigs, &oldset); + pid_t child_pid = fork(); + if ( child_pid < 0 ) + { + int errnum = errno; + unmount(mount_point_dev, 0); + mount_point_dev = NULL; + sigprocmask(SIG_SETMASK, &oldset, NULL); + error(1, errnum, "fork"); + } + if ( child_pid != 0 ) + { + sigprocmask(SIG_SETMASK, &oldset, NULL); + int code; + waitpid(child_pid, &code, 0); + sigprocmask(SIG_BLOCK, &sigs, &oldset); + unmount(mount_point_dev, 0); + sigprocmask(SIG_SETMASK, &oldset, NULL); + mount_point_dev = NULL; + if ( WIFEXITED(code) ) + return WEXITSTATUS(code); + raise(WTERMSIG(code)); + return 128 + WTERMSIG(code); + } + signal(SIGHUP, SIG_DFL); + signal(SIGINT, SIG_DFL); + signal(SIGQUIT, SIG_DFL); + sigprocmask(SIG_SETMASK, &oldset, NULL); } + pid_t child_pid = 0; + if ( devices ) + child_pid = fork(); + if ( child_pid < 0 ) + error(1, errno, "fork"); + if ( chroot(argv[1]) != 0 ) error(1, errno, "`%s'", argv[1]); @@ -106,5 +188,6 @@ int main(int argc, char* argv[]) char** exec_argv = 3 <= argc ? argv + 2 : default_argv; execvp(exec_argv[0], exec_argv); - error(127, errno, "`%s'", exec_argv[0]); + error(0, errno, "`%s'", exec_argv[0]); + _exit(127); }