/* Copyright (c) 2001 Matej Pfajfar. * Copyright (c) 2001-2004, Roger Dingledine. * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. * Copyright (c) 2007-2013, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file sandbox.c * \brief Code to enable sandboxing. **/ /** * Temporarily required for O_LARGEFILE flag. Needs to be removed * with the libevent fix. */ #define _LARGEFILE64_SOURCE #include #include #include #include "sandbox.h" #include "torlog.h" #include "orconfig.h" #include "torint.h" #include "util.h" #if defined(HAVE_SECCOMP_H) && defined(__linux__) #define USE_LIBSECCOMP #endif #define DEBUGGING_CLOSE #if defined(USE_LIBSECCOMP) #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static sandbox_cfg_t *filter_dynamic = NULL; /** Variable used for storing all syscall numbers that will be allowed with the * stage 1 general Tor sandbox. */ static int filter_nopar_gen[] = { SCMP_SYS(access), SCMP_SYS(brk), SCMP_SYS(clock_gettime), SCMP_SYS(close), SCMP_SYS(clone), SCMP_SYS(epoll_create), SCMP_SYS(epoll_wait), SCMP_SYS(fcntl), SCMP_SYS(fstat), #ifdef __NR_fstat64 SCMP_SYS(fstat64), #endif SCMP_SYS(getdents64), SCMP_SYS(getegid), #ifdef __NR_getegid32 SCMP_SYS(getegid32), #endif SCMP_SYS(geteuid), #ifdef __NR_geteuid32 SCMP_SYS(geteuid32), #endif SCMP_SYS(getgid), #ifdef __NR_getgid32 SCMP_SYS(getgid32), #endif SCMP_SYS(getrlimit), SCMP_SYS(gettimeofday), SCMP_SYS(getuid), #ifdef __NR_getuid32 SCMP_SYS(getuid32), #endif SCMP_SYS(lseek), #ifdef __NR__llseek SCMP_SYS(_llseek), #endif SCMP_SYS(mkdir), SCMP_SYS(mlockall), SCMP_SYS(mmap), SCMP_SYS(munmap), SCMP_SYS(read), SCMP_SYS(rename), SCMP_SYS(rt_sigreturn), SCMP_SYS(set_robust_list), #ifdef __NR_sigreturn SCMP_SYS(sigreturn), #endif SCMP_SYS(stat), SCMP_SYS(uname), SCMP_SYS(write), SCMP_SYS(exit_group), SCMP_SYS(exit), SCMP_SYS(madvise), // getaddrinfo uses this.. SCMP_SYS(stat64), // socket syscalls SCMP_SYS(bind), SCMP_SYS(connect), SCMP_SYS(getsockname), SCMP_SYS(recv), SCMP_SYS(recvmsg), SCMP_SYS(recvfrom), SCMP_SYS(sendto), SCMP_SYS(send), SCMP_SYS(unlink) // ? }; static int sb_rt_sigaction(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int i, rc; int param[] = { SIGINT, SIGTERM, SIGPIPE, SIGUSR1, SIGUSR2, SIGHUP, SIGCHLD, #ifdef SIGXFSZ SIGXFSZ #endif }; for (i = 0; i < ARRAY_LENGTH(param); i++) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigaction), 1, SCMP_CMP(0, SCMP_CMP_EQ, param[i])); if (rc) break; } return rc; } static int sb_execve(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc; sandbox_cfg_t *elem = NULL; // for each dynamic parameter filters for (elem = filter; elem != NULL; elem = elem->next) { if (elem->prot == 1 && elem->syscall == SCMP_SYS(execve)) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(execve), 1, SCMP_CMP(0, SCMP_CMP_EQ, elem->param)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add execve syscall, received libseccomp " "error %d", rc); return rc; } } } return 0; } static int sb_time(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { return seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(time), 1, SCMP_CMP(0, SCMP_CMP_EQ, 0)); } static int sb_accept4(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { return seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketcall), 1, SCMP_CMP(0, SCMP_CMP_EQ, 18)); } #ifdef __NR_mmap2 static int sb_mmap2(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_NONE), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE|MAP_ANONYMOUS)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE), SCMP_CMP(3, SCMP_CMP_EQ,MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS)); if (rc) { return rc; } rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 2, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_EXEC), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE|MAP_DENYWRITE)); if (rc) { return rc; } return 0; } #endif static int sb_open(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc; sandbox_cfg_t *elem = NULL; // for each dynamic parameter filters for (elem = filter; elem != NULL; elem = elem->next) { if (elem->prot == 1 && elem->syscall == SCMP_SYS(open)) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1, SCMP_CMP(0, SCMP_CMP_EQ, elem->param)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add open syscall, received libseccomp " "error %d", rc); return rc; } } } // problem: required by getaddrinfo rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1, SCMP_CMP(1, SCMP_CMP_EQ, O_RDONLY|O_CLOEXEC)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add open syscall, received libseccomp " "error %d", rc); return rc; } return 0; } static int sb_openat(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc; sandbox_cfg_t *elem = NULL; // for each dynamic parameter filters for (elem = filter; elem != NULL; elem = elem->next) { if (elem->prot == 1 && elem->syscall == SCMP_SYS(openat)) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), 1, SCMP_CMP(0, SCMP_CMP_EQ, AT_FDCWD), SCMP_CMP(1, SCMP_CMP_EQ, elem->param), SCMP_CMP(2, SCMP_CMP_EQ, O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY| O_CLOEXEC)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add openat syscall, received libseccomp " "error %d", rc); return rc; } } } return 0; } static int sb_socket(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; #ifdef __i386__ rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 0); if (rc) return rc; #endif rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 3, SCMP_CMP(0, SCMP_CMP_EQ, PF_FILE), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK), SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_IP)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 3, SCMP_CMP(0, SCMP_CMP_EQ, PF_INET), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_STREAM|SOCK_CLOEXEC), SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_TCP)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 3, SCMP_CMP(0, SCMP_CMP_EQ, PF_INET), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK), SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_IP)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 3, SCMP_CMP(0, SCMP_CMP_EQ, PF_NETLINK), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_RAW), SCMP_CMP(2, SCMP_CMP_EQ, 0)); if (rc) return rc; return 0; } static int sb_socketpair(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; #ifdef __i386__ rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketpair), 0); if (rc) return rc; #endif rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketpair), 2, SCMP_CMP(0, SCMP_CMP_EQ, PF_FILE), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_STREAM|SOCK_CLOEXEC)); if (rc) return rc; return 0; } static int sb_setsockopt(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; #ifdef __i386__ rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 0); if (rc) return rc; #endif rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 2, SCMP_CMP(1, SCMP_CMP_EQ, SOL_SOCKET), SCMP_CMP(2, SCMP_CMP_EQ, SO_REUSEADDR)); if (rc) return rc; return 0; } static int sb_getsockopt(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; #ifdef __i386__ rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt), 0); if (rc) return rc; #endif rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt), 2, SCMP_CMP(1, SCMP_CMP_EQ, SOL_SOCKET), SCMP_CMP(2, SCMP_CMP_EQ, SO_ERROR)); if (rc) return rc; return 0; } #ifdef __NR_fcntl64 static int sb_fcntl64(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), 1, SCMP_CMP(1, SCMP_CMP_EQ, F_GETFL)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), 2, SCMP_CMP(1, SCMP_CMP_EQ, F_SETFL), SCMP_CMP(2, SCMP_CMP_EQ, O_RDWR|O_NONBLOCK)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), 1, SCMP_CMP(1, SCMP_CMP_EQ, F_GETFD)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), 2, SCMP_CMP(1, SCMP_CMP_EQ, F_SETFD), SCMP_CMP(2, SCMP_CMP_EQ, FD_CLOEXEC)); if (rc) return rc; return 0; } #endif // allows everything but will keep for now.. static int sb_epoll_ctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), 1, SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_ADD)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), 1, SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_MOD)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), 1, SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_DEL)); if (rc) return rc; return 0; } /** * If multiple filters need to be added, seccomp needs to be whitelisted in * this list. */ static int sb_prctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(prctl), 1, SCMP_CMP(0, SCMP_CMP_EQ, PR_SET_DUMPABLE)); if (rc) return rc; return 0; } /** * does not NEED tobe here.. only occurs before filter */ static int sb_mprotect(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 1, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 1, SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 1, SCMP_CMP(2, SCMP_CMP_EQ, PROT_NONE)); if (rc) return rc; return 0; } static int sb_rt_sigprocmask(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 1, SCMP_CMP(0, SCMP_CMP_EQ, SIG_UNBLOCK)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 1, SCMP_CMP(0, SCMP_CMP_EQ, SIG_SETMASK)); if (rc) return rc; return 0; } /** * does not NEED tobe here.. only occurs before filter */ static int sb_flock(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(flock), 1, SCMP_CMP(1, SCMP_CMP_EQ, LOCK_EX|LOCK_NB)); if (rc) return rc; return 0; } static int sb_futex(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; // can remove rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 1, SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 1, SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAKE_PRIVATE)); if (rc) return rc; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 1, SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAIT_PRIVATE)); if (rc) return rc; return 0; } /** * does not NEED tobe here.. only occurs before filter */ static int sb_mremap(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mremap), 1, SCMP_CMP(3, SCMP_CMP_EQ, MREMAP_MAYMOVE)); if (rc) return rc; return 0; } static int sb_poll(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(poll), 2, SCMP_CMP(1, SCMP_CMP_EQ, 1), SCMP_CMP(2, SCMP_CMP_EQ, 10)); if (rc) return rc; return 0; } #ifdef __NR_stat64 static int sb_stat64(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; sandbox_cfg_t *elem = NULL; // for each dynamic parameter filters for (elem = filter; elem != NULL; elem = elem->next) { if (elem->prot == 1 && (elem->syscall == SCMP_SYS(open) || elem->syscall == SCMP_SYS(stat64))) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(stat64), 1, SCMP_CMP(0, SCMP_CMP_EQ, elem->param)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add open syscall, received libseccomp " "error %d", rc); return rc; } } } return 0; } #endif static sandbox_filter_func_t filter_func[] = { sb_rt_sigaction, sb_rt_sigprocmask, sb_execve, sb_time, sb_accept4, sb_mmap2, sb_open, sb_openat, sb_fcntl64, sb_epoll_ctl, sb_prctl, sb_mprotect, sb_flock, sb_futex, sb_mremap, sb_poll, sb_stat64, sb_socket, sb_setsockopt, sb_getsockopt, sb_socketpair }; const char* sandbox_intern_string(const char *param) { sandbox_cfg_t *elem; if (param == NULL) return NULL; for (elem = filter_dynamic; elem != NULL; elem = elem->next) { if (elem->prot && !strncmp(param, (char*)(elem->param), MAX_PARAM_LEN)) { return (char*)(elem->param); } } log_warn(LD_BUG, "(Sandbox) Parameter %s not found", param); return param; } static char* prot_strdup(char* str) { int param_size = 0; char *res = NULL; if (str == NULL) goto out; // allocating protected memory region for parameter param_size = 1 + strnlen(str, MAX_PARAM_LEN); if (param_size == MAX_PARAM_LEN) { log_warn(LD_BUG, "(Sandbox) Parameter length too large!"); } res = (char*) mmap(NULL, param_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); if (!res) { log_err(LD_BUG,"(Sandbox) failed allocate protected memory!"); goto out; } // copying from non protected to protected + pointer reassign memcpy(res, str, param_size); // protecting from writes if (mprotect(res, param_size, PROT_READ)) { log_err(LD_BUG,"(Sandbox) failed to protect memory!"); return NULL; } out: return res; } #ifdef __NR_stat64 int sandbox_cfg_allow_stat64_filename(sandbox_cfg_t **cfg, char *file, char fr) { sandbox_cfg_t *elem = NULL; elem = (sandbox_cfg_t*) malloc(sizeof(sandbox_cfg_t)); elem->syscall = SCMP_SYS(stat64); elem->pindex = 0; elem->param = (intptr_t) prot_strdup((char*) file); elem->prot = 1; elem->next = *cfg; *cfg = elem; if (fr) tor_free_(file); return 0; } int sandbox_cfg_allow_stat64_filename_array(sandbox_cfg_t **cfg, int num, ...) { int rc = 0, i; va_list ap; va_start(ap, num); for (i = 0; i < num; i++) { char *fn = va_arg(ap, char*); char fr = (char) va_arg(ap, int); rc = sandbox_cfg_allow_stat64_filename(cfg, fn, fr); if(rc) { log_err(LD_BUG,"(Sandbox) failed on par %d", i); goto end; } } end: va_end(ap); return 0; } #endif int sandbox_cfg_allow_open_filename(sandbox_cfg_t **cfg, char *file, char fr) { sandbox_cfg_t *elem = NULL; elem = (sandbox_cfg_t*) malloc(sizeof(sandbox_cfg_t)); elem->syscall = SCMP_SYS(open); elem->pindex = 0; elem->param = (intptr_t) prot_strdup((char*) file); elem->prot = 1; elem->next = *cfg; *cfg = elem; if (fr) tor_free_(file); return 0; } int sandbox_cfg_allow_open_filename_array(sandbox_cfg_t **cfg, int num, ...) { int rc = 0, i; va_list ap; va_start(ap, num); for (i = 0; i < num; i++) { char *fn = va_arg(ap, char*); char fr = (char) va_arg(ap, int); rc = sandbox_cfg_allow_open_filename(cfg, fn, fr); if(rc) { log_err(LD_BUG,"(Sandbox) failed on par %d", i); goto end; } } end: va_end(ap); return 0; } int sandbox_cfg_allow_openat_filename(sandbox_cfg_t **cfg, char *file, char fr) { sandbox_cfg_t *elem = NULL; elem = (sandbox_cfg_t*) malloc(sizeof(sandbox_cfg_t)); elem->syscall = SCMP_SYS(openat); elem->pindex = 1; elem->param = (intptr_t) prot_strdup((char*) file);; elem->prot = 1; elem->next = *cfg; *cfg = elem; if (fr) tor_free_(file); return 0; } int sandbox_cfg_allow_openat_filename_array(sandbox_cfg_t **cfg, int num, ...) { int rc = 0, i; va_list ap; va_start(ap, num); for (i = 0; i < num; i++) { char *fn = va_arg(ap, char*); char fr = (char) va_arg(ap, int); rc = sandbox_cfg_allow_openat_filename(cfg, fn, fr); if(rc) { log_err(LD_BUG,"(Sandbox) failed on par %d", i); goto end; } } end: va_end(ap); return 0; } int sandbox_cfg_allow_execve(sandbox_cfg_t **cfg, char *com) { sandbox_cfg_t *elem = NULL; elem = (sandbox_cfg_t*) malloc(sizeof(sandbox_cfg_t)); elem->syscall = SCMP_SYS(openat); elem->pindex = 1; elem->param = (intptr_t) prot_strdup((char*) com);; elem->prot = 1; elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_execve_array(sandbox_cfg_t **cfg, int num, ...) { int rc = 0, i; va_list ap; va_start(ap, num); for (i = 0; i < num; i++) { char *fn = va_arg(ap, char*); rc = sandbox_cfg_allow_execve(cfg, fn); if(rc) { log_err(LD_BUG,"(Sandbox) failed on par %d", i); goto end; } } end: va_end(ap); return 0; } static int add_param_filter(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) { int i, rc = 0; // function pointer for (i = 0; i < ARRAY_LENGTH(filter_func); i++) { if ((filter_func[i])(ctx, cfg)) { log_err(LD_BUG,"(Sandbox) failed to add syscall %d, received libseccomp " "error %d", i, rc); return rc; } } return 0; } static int add_noparam_filter(scmp_filter_ctx ctx) { int i, rc = 0; // add general filters for (i = 0; i < ARRAY_LENGTH(filter_nopar_gen); i++) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, filter_nopar_gen[i], 0); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add syscall index %d, " "received libseccomp error %d", i, rc); return rc; } } return 0; } /** * Function responsible for setting up and enabling a global syscall filter. * The function is a prototype developed for stage 1 of sandboxing Tor. * Returns 0 on success. */ static int install_syscall_filter(sandbox_cfg_t* cfg) { int rc = 0; scmp_filter_ctx ctx; ctx = seccomp_init(SCMP_ACT_TRAP); if (ctx == NULL) { log_err(LD_BUG,"(Sandbox) failed to initialise libseccomp context"); rc = -1; goto end; } // add parameter filters if ((rc = add_param_filter(ctx, cfg))) { log_err(LD_BUG, "(Sandbox) failed to add param filters!"); goto end; } // adding filters with no parameters if ((rc = add_noparam_filter(ctx))) { log_err(LD_BUG, "(Sandbox) failed to add param filters!"); goto end; } rc = seccomp_load(ctx); end: seccomp_release(ctx); return (rc < 0 ? -rc : rc); } /** Additional file descriptor to use when logging seccomp2 failures */ static int sigsys_debugging_fd = -1; /** Use the file descriptor fd to log seccomp2 failures. */ static void sigsys_set_debugging_fd(int fd) { sigsys_debugging_fd = fd; } /** * Function called when a SIGSYS is caught by the application. It notifies the * user that an error has occurred and either terminates or allows the * application to continue execution, based on the DEBUGGING_CLOSE symbol. */ static void sigsys_debugging(int nr, siginfo_t *info, void *void_context) { ucontext_t *ctx = (ucontext_t *) (void_context); char message[64]; int rv = 0, syscall, length, err; (void) nr; if (info->si_code != SYS_SECCOMP) return; if (!ctx) return; syscall = ctx->uc_mcontext.gregs[REG_SYSCALL]; /* XXXX Avoid use of snprintf; it isn't on the list of Stuff You're Allowed * To Do In A Signal Handler. */ length = snprintf(message, sizeof(message), "\n\n(Sandbox) bad syscall (%d) was caught.\n", syscall); err = 0; if (sigsys_debugging_fd >= 0) { rv = write(sigsys_debugging_fd, message, length); err += rv != length; } rv = write(STDOUT_FILENO, message, length); err += rv != length; if (err) _exit(2); #if defined(DEBUGGING_CLOSE) _exit(1); #endif // DEBUGGING_CLOSE } /** * Function that adds a handler for SIGSYS, which is the signal thrown * when the application is issuing a syscall which is not allowed. The * main purpose of this function is to help with debugging by identifying * filtered syscalls. */ static int install_sigsys_debugging(void) { struct sigaction act; sigset_t mask; memset(&act, 0, sizeof(act)); sigemptyset(&mask); sigaddset(&mask, SIGSYS); act.sa_sigaction = &sigsys_debugging; act.sa_flags = SA_SIGINFO; if (sigaction(SIGSYS, &act, NULL) < 0) { log_err(LD_BUG,"(Sandbox) Failed to register SIGSYS signal handler"); return -1; } if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) { log_err(LD_BUG,"(Sandbox) Failed call to sigprocmask()"); return -2; } return 0; } static int register_cfg(sandbox_cfg_t* cfg) { sandbox_cfg_t *elem = NULL; if (filter_dynamic == NULL) { filter_dynamic = cfg; return 0; } for (elem = filter_dynamic; elem->next != NULL; elem = elem->next); elem->next = cfg; return 0; } #endif // USE_LIBSECCOMP #ifdef USE_LIBSECCOMP /** * Initialises the syscall sandbox filter for any linux architecture, taking * into account various available features for different linux flavours. */ static int initialise_libseccomp_sandbox(sandbox_cfg_t* cfg) { if (install_sigsys_debugging()) return -1; if (install_syscall_filter(cfg)) return -2; if (register_cfg(cfg)) return -3; return 0; } #endif // USE_LIBSECCOMP sandbox_cfg_t* sandbox_cfg_new() { return NULL; } int sandbox_init(sandbox_cfg_t* cfg) { #if defined(USE_LIBSECCOMP) return initialise_libseccomp_sandbox(cfg); #elif defined(_WIN32) log_warn(LD_BUG,"Windows sandboxing is not implemented. The feature is " "currently disabled."); return 0; #elif defined(TARGET_OS_MAC) log_warn(LD_BUG,"Mac OSX sandboxing is not implemented. The feature is " "currently disabled"); return 0; #else log_warn(LD_BUG,"Sandboxing is not implemented for your platform. The " "feature is currently disabled"); return 0; #endif } /** * Enables the stage 1 general sandbox. It applies a syscall filter which does * not restrict any Tor features. The filter is representative for the whole * application. */ int tor_global_sandbox(void) { #if defined(USE_LIBSECCOMP) return initialise_libseccomp_sandbox(NULL); #elif defined(_WIN32) log_warn(LD_BUG,"Windows sandboxing is not implemented. The feature is " "currently disabled."); return 0; #elif defined(TARGET_OS_MAC) log_warn(LD_BUG,"Mac OSX sandboxing is not implemented. The feature is " "currently disabled"); return 0; #else log_warn(LD_BUG,"Sandboxing is not implemented for your platform. The " "feature is currently disabled"); return 0; #endif } void sandbox_set_debugging_fd(int fd) { #ifdef USE_LIBSECCOMP sigsys_set_debugging_fd(fd); #else (void)fd; #endif }