/* 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. **/ #include "orconfig.h" #ifndef _LARGEFILE64_SOURCE /** * Temporarily required for O_LARGEFILE flag. Needs to be removed * with the libevent fix. */ #define _LARGEFILE64_SOURCE #endif /** Malloc mprotect limit in bytes. */ #define MALLOC_MP_LIM 1048576 #include #include #include #include "sandbox.h" #include "container.h" #include "torlog.h" #include "torint.h" #include "util.h" #include "tor_queue.h" #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 #if defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && \ defined(HAVE_BACKTRACE_SYMBOLS_FD) && defined(HAVE_SIGACTION) #define USE_BACKTRACE #define EXPOSE_CLEAN_BACKTRACE #include "backtrace.h" #endif #ifdef USE_BACKTRACE #include #endif /**Determines if at least one sandbox is active.*/ static int sandbox_active = 0; /** Holds the parameter list configuration for the sandbox.*/ static sandbox_cfg_t *filter_dynamic = NULL; /** Holds a list of pre-recorded results from getaddrinfo().*/ static sb_addr_info_t *sb_addr_info = NULL; #undef SCMP_CMP #define SCMP_CMP(a,b,c) ((struct scmp_arg_cmp){(a),(b),(c),0}) #define SCMP_CMP4(a,b,c,d) ((struct scmp_arg_cmp){(a),(b),(c),(d)}) /* We use a wrapper here because these masked comparisons seem to be pretty * verbose. Also, it's important to cast to scmp_datum_t before negating the * mask, since otherwise the negation might get applied to a 32 bit value, and * the high bits of the value might get masked out improperly. */ #define SCMP_CMP_MASKED(a,b,c) \ SCMP_CMP4((a), SCMP_CMP_MASKED_EQ, ~(scmp_datum_t)(b), (c)) /** 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(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(writev), SCMP_SYS(exit_group), SCMP_SYS(exit), SCMP_SYS(madvise), #ifdef __NR_stat64 // getaddrinfo uses this.. SCMP_SYS(stat64), #endif /* * These socket syscalls are not required on x86_64 and not supported with * some libseccomp versions (eg: 1.0.1) */ #if defined(__i386) SCMP_SYS(recv), SCMP_SYS(send), #endif // socket syscalls SCMP_SYS(bind), SCMP_SYS(connect), SCMP_SYS(getsockname), SCMP_SYS(recvmsg), SCMP_SYS(recvfrom), SCMP_SYS(sendto), SCMP_SYS(unlink) }; /* These macros help avoid the error where the number of filters we add on a * single rule don't match the arg_cnt param. */ #define seccomp_rule_add_0(ctx,act,call) \ seccomp_rule_add((ctx),(act),(call),0) #define seccomp_rule_add_1(ctx,act,call,f1) \ seccomp_rule_add((ctx),(act),(call),1,(f1)) #define seccomp_rule_add_2(ctx,act,call,f1,f2) \ seccomp_rule_add((ctx),(act),(call),2,(f1),(f2)) #define seccomp_rule_add_3(ctx,act,call,f1,f2,f3) \ seccomp_rule_add((ctx),(act),(call),3,(f1),(f2),(f3)) #define seccomp_rule_add_4(ctx,act,call,f1,f2,f3,f4) \ seccomp_rule_add((ctx),(act),(call),4,(f1),(f2),(f3),(f4)) /** * Function responsible for setting up the rt_sigaction syscall for * the seccomp filter sandbox. */ static int sb_rt_sigaction(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { unsigned i; int rc; int param[] = { SIGINT, SIGTERM, SIGPIPE, SIGUSR1, SIGUSR2, SIGHUP, SIGCHLD, #ifdef SIGXFSZ SIGXFSZ #endif }; (void) filter; for (i = 0; i < ARRAY_LENGTH(param); i++) { rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigaction), SCMP_CMP(0, SCMP_CMP_EQ, param[i])); if (rc) break; } return rc; } /** * Function responsible for setting up the execve syscall for * the seccomp filter sandbox. */ 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) { smp_param_t *param = elem->param; if (param != NULL && param->prot == 1 && param->syscall == SCMP_SYS(execve)) { rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(execve), SCMP_CMP(0, SCMP_CMP_EQ, param->value)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add execve syscall, received " "libseccomp error %d", rc); return rc; } } } return 0; } /** * Function responsible for setting up the time syscall for * the seccomp filter sandbox. */ static int sb_time(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { (void) filter; return seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(time), SCMP_CMP(0, SCMP_CMP_EQ, 0)); } /** * Function responsible for setting up the accept4 syscall for * the seccomp filter sandbox. */ static int sb_accept4(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void)filter; #ifdef __i386__ rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketcall), SCMP_CMP(0, SCMP_CMP_EQ, 18)); if (rc) { return rc; } #endif rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(accept4), SCMP_CMP_MASKED(3, SOCK_CLOEXEC|SOCK_NONBLOCK, 0)); if (rc) { return rc; } return 0; } #ifdef __NR_mmap2 /** * Function responsible for setting up the mmap2 syscall for * the seccomp filter sandbox. */ static int sb_mmap2(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void)filter; rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ), SCMP_CMP(3, SCMP_CMP_EQ, MAP_PRIVATE)); if (rc) { return rc; } rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap2), 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 /** * Function responsible for setting up the open syscall for * the seccomp filter sandbox. */ 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) { smp_param_t *param = elem->param; if (param != NULL && param->prot == 1 && param->syscall == SCMP_SYS(open)) { rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), SCMP_CMP(0, SCMP_CMP_EQ, param->value)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add open syscall, received " "libseccomp error %d", rc); return rc; } } } rc = seccomp_rule_add_1(ctx, SCMP_ACT_ERRNO(-1), SCMP_SYS(open), SCMP_CMP_MASKED(1, O_CLOEXEC, O_RDONLY)); 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__sysctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc; (void) filter; (void) ctx; rc = seccomp_rule_add_0(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(_sysctl)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add _sysctl syscall, " "received libseccomp error %d", rc); return rc; } return 0; } /** * Function responsible for setting up the rename syscall for * the seccomp filter sandbox. */ static int sb_rename(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) { smp_param_t *param = elem->param; if (param != NULL && param->prot == 1 && param->syscall == SCMP_SYS(rename)) { rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rename), SCMP_CMP(0, SCMP_CMP_EQ, param->value), SCMP_CMP(1, SCMP_CMP_EQ, param->value2)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add rename syscall, received " "libseccomp error %d", rc); return rc; } } } return 0; } /** * Function responsible for setting up the openat syscall for * the seccomp filter sandbox. */ 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) { smp_param_t *param = elem->param; if (param != NULL && param->prot == 1 && param->syscall == SCMP_SYS(openat)) { rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), SCMP_CMP(0, SCMP_CMP_EQ, AT_FDCWD), SCMP_CMP(1, SCMP_CMP_EQ, param->value), 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; } /** * Function responsible for setting up the socket syscall for * the seccomp filter sandbox. */ static int sb_socket(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; int i; (void) filter; #ifdef __i386__ rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket)); if (rc) return rc; #endif rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), SCMP_CMP(0, SCMP_CMP_EQ, PF_FILE), SCMP_CMP_MASKED(1, SOCK_CLOEXEC|SOCK_NONBLOCK, SOCK_STREAM)); if (rc) return rc; for (i = 0; i < 2; ++i) { const int pf = i ? PF_INET : PF_INET6; rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), SCMP_CMP(0, SCMP_CMP_EQ, pf), SCMP_CMP_MASKED(1, SOCK_CLOEXEC|SOCK_NONBLOCK, SOCK_STREAM), SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_TCP)); if (rc) return rc; rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), SCMP_CMP(0, SCMP_CMP_EQ, pf), SCMP_CMP_MASKED(1, SOCK_CLOEXEC|SOCK_NONBLOCK, SOCK_DGRAM), SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_IP)); if (rc) return rc; } rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 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; } /** * Function responsible for setting up the socketpair syscall for * the seccomp filter sandbox. */ static int sb_socketpair(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; #ifdef __i386__ rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketpair)); if (rc) return rc; #endif rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socketpair), SCMP_CMP(0, SCMP_CMP_EQ, PF_FILE), SCMP_CMP(1, SCMP_CMP_EQ, SOCK_STREAM|SOCK_CLOEXEC)); if (rc) return rc; return 0; } /** * Function responsible for setting up the setsockopt syscall for * the seccomp filter sandbox. */ static int sb_setsockopt(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; #ifdef __i386__ rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt)); if (rc) return rc; #endif rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), SCMP_CMP(1, SCMP_CMP_EQ, SOL_SOCKET), SCMP_CMP(2, SCMP_CMP_EQ, SO_REUSEADDR)); if (rc) return rc; #ifdef IP_TRANSPARENT rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), SCMP_CMP(1, SCMP_CMP_EQ, SOL_IP), SCMP_CMP(2, SCMP_CMP_EQ, IP_TRANSPARENT)); if (rc) return rc; #endif return 0; } /** * Function responsible for setting up the getsockopt syscall for * the seccomp filter sandbox. */ static int sb_getsockopt(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; #ifdef __i386__ rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt)); if (rc) return rc; #endif rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt), 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 /** * Function responsible for setting up the fcntl64 syscall for * the seccomp filter sandbox. */ static int sb_fcntl64(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), SCMP_CMP(1, SCMP_CMP_EQ, F_GETFL)); if (rc) return rc; rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), 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_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), SCMP_CMP(1, SCMP_CMP_EQ, F_GETFD)); if (rc) return rc; rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl64), SCMP_CMP(1, SCMP_CMP_EQ, F_SETFD), SCMP_CMP(2, SCMP_CMP_EQ, FD_CLOEXEC)); if (rc) return rc; return 0; } #endif /** * Function responsible for setting up the epoll_ctl syscall for * the seccomp filter sandbox. * * Note: basically allows everything but will keep for now.. */ static int sb_epoll_ctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_ADD)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_MOD)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), SCMP_CMP(1, SCMP_CMP_EQ, EPOLL_CTL_DEL)); if (rc) return rc; return 0; } /** * Function responsible for setting up the fcntl64 syscall for * the seccomp filter sandbox. * * NOTE: if multiple filters need to be added, the PR_SECCOMP parameter needs * to be whitelisted in this function. */ static int sb_prctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(prctl), SCMP_CMP(0, SCMP_CMP_EQ, PR_SET_DUMPABLE)); if (rc) return rc; return 0; } /** * Function responsible for setting up the fcntl64 syscall for * the seccomp filter sandbox. * * NOTE: does not NEED to be here.. currently only occurs before filter; will * keep just in case for the future. */ static int sb_mprotect(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), SCMP_CMP(2, SCMP_CMP_EQ, PROT_NONE)); if (rc) return rc; return 0; } /** * Function responsible for setting up the rt_sigprocmask syscall for * the seccomp filter sandbox. */ static int sb_rt_sigprocmask(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), SCMP_CMP(0, SCMP_CMP_EQ, SIG_UNBLOCK)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), SCMP_CMP(0, SCMP_CMP_EQ, SIG_SETMASK)); if (rc) return rc; return 0; } /** * Function responsible for setting up the flock syscall for * the seccomp filter sandbox. * * NOTE: does not need to be here, occurs before filter is applied. */ static int sb_flock(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(flock), SCMP_CMP(1, SCMP_CMP_EQ, LOCK_EX|LOCK_NB)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(flock), SCMP_CMP(1, SCMP_CMP_EQ, LOCK_UN)); if (rc) return rc; return 0; } /** * Function responsible for setting up the futex syscall for * the seccomp filter sandbox. */ static int sb_futex(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; // can remove rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAKE_PRIVATE)); if (rc) return rc; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), SCMP_CMP(1, SCMP_CMP_EQ, FUTEX_WAIT_PRIVATE)); if (rc) return rc; return 0; } /** * Function responsible for setting up the mremap syscall for * the seccomp filter sandbox. * * NOTE: so far only occurs before filter is applied. */ static int sb_mremap(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mremap), SCMP_CMP(3, SCMP_CMP_EQ, MREMAP_MAYMOVE)); if (rc) return rc; return 0; } /** * Function responsible for setting up the poll syscall for * the seccomp filter sandbox. */ static int sb_poll(scmp_filter_ctx ctx, sandbox_cfg_t *filter) { int rc = 0; (void) filter; rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(poll), SCMP_CMP(1, SCMP_CMP_EQ, 1), SCMP_CMP(2, SCMP_CMP_EQ, 10)); if (rc) return rc; return 0; } #ifdef __NR_stat64 /** * Function responsible for setting up the stat64 syscall for * the seccomp filter sandbox. */ 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) { smp_param_t *param = elem->param; if (param != NULL && param->prot == 1 && (param->syscall == SCMP_SYS(open) || param->syscall == SCMP_SYS(stat64))) { rc = seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(stat64), SCMP_CMP(0, SCMP_CMP_EQ, param->value)); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add open syscall, received " "libseccomp error %d", rc); return rc; } } } return 0; } #endif /** * Array of function pointers responsible for filtering different syscalls at * a parameter level. */ static sandbox_filter_func_t filter_func[] = { sb_rt_sigaction, sb_rt_sigprocmask, sb_execve, sb_time, sb_accept4, #ifdef __NR_mmap2 sb_mmap2, #endif sb_open, sb_openat, sb__sysctl, sb_rename, #ifdef __NR_fcntl64 sb_fcntl64, #endif sb_epoll_ctl, sb_prctl, sb_mprotect, sb_flock, sb_futex, sb_mremap, sb_poll, #ifdef __NR_stat64 sb_stat64, #endif sb_socket, sb_setsockopt, sb_getsockopt, sb_socketpair }; const char * sandbox_intern_string(const char *str) { sandbox_cfg_t *elem; if (str == NULL) return NULL; for (elem = filter_dynamic; elem != NULL; elem = elem->next) { smp_param_t *param = elem->param; if (param->prot) { if (!strcmp(str, (char*)(param->value))) { return (char*)param->value; } if (param->value2 && !strcmp(str, (char*)param->value2)) { return (char*)param->value2; } } } if (sandbox_active) log_warn(LD_BUG, "No interned sandbox parameter found for %s", str); return str; } /** DOCDOC */ static int prot_strings_helper(strmap_t *locations, char **pr_mem_next_p, size_t *pr_mem_left_p, intptr_t *value_p) { char *param_val; size_t param_size; void *location; if (*value_p == 0) return 0; param_val = (char*) *value_p; param_size = strlen(param_val) + 1; location = strmap_get(locations, param_val); if (location) { // We already interned this string. tor_free(param_val); *value_p = (intptr_t) location; return 0; } else if (*pr_mem_left_p >= param_size) { // copy to protected location = *pr_mem_next_p; memcpy(location, param_val, param_size); // re-point el parameter to protected tor_free(param_val); *value_p = (intptr_t) location; strmap_set(locations, location, location); /* good real estate advice */ // move next available protected memory *pr_mem_next_p += param_size; *pr_mem_left_p -= param_size; return 0; } else { log_err(LD_BUG,"(Sandbox) insufficient protected memory!"); return -1; } } /** * Protects all the strings in the sandbox's parameter list configuration. It * works by calculating the total amount of memory required by the parameter * list, allocating the memory using mmap, and protecting it from writes with * mprotect(). */ static int prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) { int ret = 0; size_t pr_mem_size = 0, pr_mem_left = 0; char *pr_mem_next = NULL, *pr_mem_base; sandbox_cfg_t *el = NULL; strmap_t *locations = NULL; // get total number of bytes required to mmap. (Overestimate.) for (el = cfg; el != NULL; el = el->next) { pr_mem_size += strlen((char*) el->param->value) + 1; if (el->param->value2) pr_mem_size += strlen((char*) el->param->value2) + 1; } // allocate protected memory with MALLOC_MP_LIM canary pr_mem_base = (char*) mmap(NULL, MALLOC_MP_LIM + pr_mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); if (pr_mem_base == MAP_FAILED) { log_err(LD_BUG,"(Sandbox) failed allocate protected memory! mmap: %s", strerror(errno)); ret = -1; goto out; } pr_mem_next = pr_mem_base + MALLOC_MP_LIM; pr_mem_left = pr_mem_size; locations = strmap_new(); // change el value pointer to protected for (el = cfg; el != NULL; el = el->next) { if (prot_strings_helper(locations, &pr_mem_next, &pr_mem_left, &el->param->value) < 0) { ret = -2; goto out; } if (prot_strings_helper(locations, &pr_mem_next, &pr_mem_left, &el->param->value2) < 0) { ret = -2; goto out; } el->param->prot = 1; } // protecting from writes if (mprotect(pr_mem_base, MALLOC_MP_LIM + pr_mem_size, PROT_READ)) { log_err(LD_BUG,"(Sandbox) failed to protect memory! mprotect: %s", strerror(errno)); ret = -3; goto out; } /* * Setting sandbox restrictions so the string memory cannot be tampered with */ // no mremap of the protected base address ret = seccomp_rule_add_1(ctx, SCMP_ACT_KILL, SCMP_SYS(mremap), SCMP_CMP(0, SCMP_CMP_EQ, (intptr_t) pr_mem_base)); if (ret) { log_err(LD_BUG,"(Sandbox) mremap protected memory filter fail!"); return ret; } // no munmap of the protected base address ret = seccomp_rule_add_1(ctx, SCMP_ACT_KILL, SCMP_SYS(munmap), SCMP_CMP(0, SCMP_CMP_EQ, (intptr_t) pr_mem_base)); if (ret) { log_err(LD_BUG,"(Sandbox) munmap protected memory filter fail!"); return ret; } /* * Allow mprotect with PROT_READ|PROT_WRITE because openssl uses it, but * never over the memory region used by the protected strings. * * PROT_READ|PROT_WRITE was originally fully allowed in sb_mprotect(), but * had to be removed due to limitation of libseccomp regarding intervals. * * There is a restriction on how much you can mprotect with R|W up to the * size of the canary. */ ret = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), SCMP_CMP(0, SCMP_CMP_LT, (intptr_t) pr_mem_base), SCMP_CMP(1, SCMP_CMP_LE, MALLOC_MP_LIM), SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); if (ret) { log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (LT)!"); return ret; } ret = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), SCMP_CMP(0, SCMP_CMP_GT, (intptr_t) pr_mem_base + pr_mem_size + MALLOC_MP_LIM), SCMP_CMP(1, SCMP_CMP_LE, MALLOC_MP_LIM), SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); if (ret) { log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (GT)!"); return ret; } out: strmap_free(locations, NULL); return ret; } /** * Auxiliary function used in order to allocate a sandbox_cfg_t element and set * it's values according the the parameter list. All elements are initialised * with the 'prot' field set to false, as the pointer is not protected at this * point. */ static sandbox_cfg_t* new_element2(int syscall, intptr_t value, intptr_t value2) { smp_param_t *param = NULL; sandbox_cfg_t *elem = tor_malloc_zero(sizeof(sandbox_cfg_t)); param = elem->param = tor_malloc_zero(sizeof(smp_param_t)); param->syscall = syscall; param->value = value; param->value2 = value2; param->prot = 0; return elem; } static sandbox_cfg_t* new_element(int syscall, intptr_t value) { return new_element2(syscall, value, 0); } #ifdef __NR_stat64 #define SCMP_stat SCMP_SYS(stat64) #else #define SCMP_stat SCMP_SYS(stat) #endif int sandbox_cfg_allow_stat_filename(sandbox_cfg_t **cfg, char *file) { sandbox_cfg_t *elem = NULL; elem = new_element(SCMP_stat, (intptr_t)(void*) file); if (!elem) { log_err(LD_BUG,"(Sandbox) failed to register parameter!"); return -1; } elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_stat_filename_array(sandbox_cfg_t **cfg, ...) { int rc = 0; char *fn = NULL; va_list ap; va_start(ap, cfg); while ((fn = va_arg(ap, char*)) != NULL) { rc = sandbox_cfg_allow_stat_filename(cfg, fn); if (rc) { log_err(LD_BUG,"(Sandbox) sandbox_cfg_allow_stat_filename_array fail"); goto end; } } end: va_end(ap); return 0; } int sandbox_cfg_allow_open_filename(sandbox_cfg_t **cfg, char *file) { sandbox_cfg_t *elem = NULL; elem = new_element(SCMP_SYS(open), (intptr_t)(void *) file); if (!elem) { log_err(LD_BUG,"(Sandbox) failed to register parameter!"); return -1; } elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_rename(sandbox_cfg_t **cfg, char *file1, char *file2) { sandbox_cfg_t *elem = NULL; elem = new_element2(SCMP_SYS(rename), (intptr_t)(void *) file1, (intptr_t)(void *) file2); if (!elem) { log_err(LD_BUG,"(Sandbox) failed to register parameter!"); return -1; } elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_open_filename_array(sandbox_cfg_t **cfg, ...) { int rc = 0; char *fn = NULL; va_list ap; va_start(ap, cfg); while ((fn = va_arg(ap, char*)) != NULL) { rc = sandbox_cfg_allow_open_filename(cfg, fn); if (rc) { log_err(LD_BUG,"(Sandbox) sandbox_cfg_allow_open_filename_array fail"); goto end; } } end: va_end(ap); return 0; } int sandbox_cfg_allow_openat_filename(sandbox_cfg_t **cfg, char *file) { sandbox_cfg_t *elem = NULL; elem = new_element(SCMP_SYS(openat), (intptr_t)(void *) file); if (!elem) { log_err(LD_BUG,"(Sandbox) failed to register parameter!"); return -1; } elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_openat_filename_array(sandbox_cfg_t **cfg, ...) { int rc = 0; char *fn = NULL; va_list ap; va_start(ap, cfg); while ((fn = va_arg(ap, char*)) != NULL) { rc = sandbox_cfg_allow_openat_filename(cfg, fn); if (rc) { log_err(LD_BUG,"(Sandbox) sandbox_cfg_allow_openat_filename_array fail"); goto end; } } end: va_end(ap); return 0; } int sandbox_cfg_allow_execve(sandbox_cfg_t **cfg, const char *com) { sandbox_cfg_t *elem = NULL; elem = new_element(SCMP_SYS(execve), (intptr_t)(void *) com); if (!elem) { log_err(LD_BUG,"(Sandbox) failed to register parameter!"); return -1; } elem->next = *cfg; *cfg = elem; return 0; } int sandbox_cfg_allow_execve_array(sandbox_cfg_t **cfg, ...) { int rc = 0; char *fn = NULL; va_list ap; va_start(ap, cfg); while ((fn = va_arg(ap, char*)) != NULL) { rc = sandbox_cfg_allow_execve(cfg, fn); if (rc) { log_err(LD_BUG,"(Sandbox) sandbox_cfg_allow_execve_array failed"); goto end; } } end: va_end(ap); return 0; } int sandbox_getaddrinfo(const char *name, const char *servname, const struct addrinfo *hints, struct addrinfo **res) { sb_addr_info_t *el; if (servname != NULL) return -1; *res = NULL; for (el = sb_addr_info; el; el = el->next) { if (!strcmp(el->name, name)) { *res = tor_malloc(sizeof(struct addrinfo)); memcpy(*res, el->info, sizeof(struct addrinfo)); /* XXXX What if there are multiple items in the list? */ return 0; } } if (!sandbox_active) { if (getaddrinfo(name, NULL, hints, res)) { log_err(LD_BUG,"(Sandbox) getaddrinfo failed!"); return -1; } return 0; } // getting here means something went wrong log_err(LD_BUG,"(Sandbox) failed to get address %s!", name); if (*res) { tor_free(*res); res = NULL; } return -1; } int sandbox_add_addrinfo(const char* name) { int ret; struct addrinfo hints; sb_addr_info_t *el = NULL; el = tor_malloc(sizeof(sb_addr_info_t)); memset(&hints, 0, sizeof(hints)); hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; ret = getaddrinfo(name, NULL, &hints, &(el->info)); if (ret) { log_err(LD_BUG,"(Sandbox) failed to getaddrinfo"); ret = -2; tor_free(el); goto out; } el->name = tor_strdup(name); el->next = sb_addr_info; sb_addr_info = el; out: return ret; } /** * Function responsible for going through the parameter syscall filters and * call each function pointer in the list. */ static int add_param_filter(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) { unsigned i; int 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; } /** * Function responsible of loading the libseccomp syscall filters which do not * have parameter filtering. */ static int add_noparam_filter(scmp_filter_ctx ctx) { unsigned i; int rc = 0; // add general filters for (i = 0; i < ARRAY_LENGTH(filter_nopar_gen); i++) { rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, filter_nopar_gen[i]); if (rc != 0) { log_err(LD_BUG,"(Sandbox) failed to add syscall index %d (NR=%d), " "received libseccomp error %d", i, filter_nopar_gen[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; } // protectign sandbox parameter strings if ((rc = prot_strings(ctx, cfg))) { 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; } // loading the seccomp2 filter if ((rc = seccomp_load(ctx))) { log_err(LD_BUG, "(Sandbox) failed to load!"); goto end; } // marking the sandbox as active sandbox_active = 1; end: seccomp_release(ctx); return (rc < 0 ? -rc : rc); } #ifdef USE_BACKTRACE #define MAX_DEPTH 256 static void *syscall_cb_buf[MAX_DEPTH]; #endif /** * 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 number[32]; int syscall; #ifdef USE_BACKTRACE int depth; int n_fds, i; const int *fds = NULL; #endif (void) nr; if (info->si_code != SYS_SECCOMP) return; if (!ctx) return; syscall = (int) ctx->uc_mcontext.gregs[REG_SYSCALL]; #ifdef USE_BACKTRACE depth = backtrace(syscall_cb_buf, MAX_DEPTH); /* Clean up the top stack frame so we get the real function * name for the most recently failing function. */ clean_backtrace(syscall_cb_buf, depth, ctx); #endif format_dec_number_sigsafe(syscall, number, sizeof(number)); tor_log_err_sigsafe("(Sandbox) Caught a bad syscall attempt (syscall ", number, ")\n", NULL); #ifdef USE_BACKTRACE n_fds = tor_log_get_sigsafe_err_fds(&fds); for (i=0; i < n_fds; ++i) backtrace_symbols_fd(syscall_cb_buf, depth, fds[i]); #endif #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; } /** * Function responsible of registering the sandbox_cfg_t list of parameter * syscall filters to the existing parameter list. This is used for incipient * multiple-sandbox support. */ 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; } int sandbox_is_active(void) { return sandbox_active != 0; } #endif // USE_LIBSECCOMP sandbox_cfg_t* sandbox_cfg_new(void) { return NULL; } int sandbox_init(sandbox_cfg_t *cfg) { #if defined(USE_LIBSECCOMP) return initialise_libseccomp_sandbox(cfg); #elif defined(_WIN32) (void)cfg; log_warn(LD_BUG,"Windows sandboxing is not implemented. The feature is " "currently disabled."); return 0; #elif defined(TARGET_OS_MAC) (void)cfg; log_warn(LD_BUG,"Mac OSX sandboxing is not implemented. The feature is " "currently disabled"); return 0; #else (void)cfg; log_warn(LD_BUG,"Sandboxing is not implemented for your platform. The " "feature is currently disabled"); return 0; #endif } #ifndef USE_LIBSECCOMP int sandbox_cfg_allow_open_filename(sandbox_cfg_t **cfg, char *file) { (void)cfg; (void)file; return 0; } int sandbox_cfg_allow_open_filename_array(sandbox_cfg_t **cfg, ...) { (void)cfg; return 0; } int sandbox_cfg_allow_openat_filename(sandbox_cfg_t **cfg, char *file) { (void)cfg; (void)file; return 0; } int sandbox_cfg_allow_openat_filename_array(sandbox_cfg_t **cfg, ...) { (void)cfg; return 0; } int sandbox_cfg_allow_execve(sandbox_cfg_t **cfg, const char *com) { (void)cfg; (void)com; return 0; } int sandbox_cfg_allow_execve_array(sandbox_cfg_t **cfg, ...) { (void)cfg; return 0; } int sandbox_cfg_allow_stat_filename(sandbox_cfg_t **cfg, char *file) { (void)cfg; (void)file; return 0; } int sandbox_cfg_allow_stat_filename_array(sandbox_cfg_t **cfg, ...) { (void)cfg; return 0; } int sandbox_cfg_allow_rename(sandbox_cfg_t **cfg, char *file1, char *file2) { (void)cfg; (void)file1; (void)file2; return 0; } int sandbox_is_active(void) { return 0; } #endif