diff options
Diffstat (limited to 'src/lib/sandbox/sandbox.c')
| -rw-r--r-- | src/lib/sandbox/sandbox.c | 246 |
1 files changed, 216 insertions, 30 deletions
diff --git a/src/lib/sandbox/sandbox.c b/src/lib/sandbox/sandbox.c index df676fad2f..e6e556eb59 100644 --- a/src/lib/sandbox/sandbox.c +++ b/src/lib/sandbox/sandbox.c @@ -1,7 +1,7 @@ /* Copyright (c) 2001 Matej Pfajfar. * Copyright (c) 2001-2004, Roger Dingledine. * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2019, The Tor Project, Inc. */ + * Copyright (c) 2007-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -38,13 +38,12 @@ #include "lib/err/torerr.h" #include "lib/log/log.h" #include "lib/cc/torint.h" -#include "lib/net/resolve.h" #include "lib/malloc/malloc.h" #include "lib/string/scanf.h" -#include "tor_queue.h" -#include "ht.h" -#include "siphash.h" +#include "ext/tor_queue.h" +#include "ext/ht.h" +#include "ext/siphash.h" #define DEBUGGING_CLOSE @@ -83,7 +82,7 @@ #if defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && \ defined(HAVE_BACKTRACE_SYMBOLS_FD) && defined(HAVE_SIGACTION) #define USE_BACKTRACE -#define EXPOSE_CLEAN_BACKTRACE +#define BACKTRACE_PRIVATE #include "lib/err/backtrace.h" #endif /* defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && ... */ @@ -118,6 +117,10 @@ #endif /* defined(__i386__) || ... */ +#ifdef M_SYSCALL +#define SYSCALL_NAME_DEBUGGING +#endif + /**Determines if at least one sandbox is active.*/ static int sandbox_active = 0; /** Holds the parameter list configuration for the sandbox.*/ @@ -134,6 +137,10 @@ static sandbox_cfg_t *filter_dynamic = NULL; * 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)) +/* For negative constants, the rule to add depends on the glibc version. */ +#define SCMP_CMP_NEG(a,op,b) (libc_negative_constant_needs_cast() ? \ + (SCMP_CMP((a), (op), (unsigned int)(b))) : \ + (SCMP_CMP_STR((a), (op), (b)))) /** Variable used for storing all syscall numbers that will be allowed with the * stage 1 general Tor sandbox. @@ -144,6 +151,7 @@ static int filter_nopar_gen[] = { SCMP_SYS(clock_gettime), SCMP_SYS(close), SCMP_SYS(clone), + SCMP_SYS(dup), #ifdef __NR_clone3 SCMP_SYS(clone3), #endif @@ -169,6 +177,7 @@ static int filter_nopar_gen[] = { #ifdef __NR_fstat64 SCMP_SYS(fstat64), #endif + SCMP_SYS(fsync), SCMP_SYS(futex), SCMP_SYS(getdents), SCMP_SYS(getdents64), @@ -198,6 +207,8 @@ static int filter_nopar_gen[] = { #ifdef __NR__llseek SCMP_SYS(_llseek), #endif + // glob uses this.. + SCMP_SYS(lstat), SCMP_SYS(mkdir), SCMP_SYS(mlockall), #ifdef __NR_mmap @@ -268,13 +279,27 @@ static int filter_nopar_gen[] = { SCMP_SYS(listen), SCMP_SYS(connect), SCMP_SYS(getsockname), +#ifdef ENABLE_NSS +#ifdef __NR_getpeername + SCMP_SYS(getpeername), +#endif +#endif SCMP_SYS(recvmsg), SCMP_SYS(recvfrom), SCMP_SYS(sendto), SCMP_SYS(unlink), +#ifdef __NR_unlinkat + SCMP_SYS(unlinkat), +#endif SCMP_SYS(poll) }; +/* opendir is not a syscall but it will use either open or openat. We do not + * want the decision to allow open/openat to be the callers reponsability, so + * we create a phony syscall number for opendir and sb_opendir will choose the + * correct syscall. */ +#define PHONY_OPENDIR_SYSCALL -2 + /* 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) \ @@ -288,6 +313,8 @@ static int filter_nopar_gen[] = { #define seccomp_rule_add_4(ctx,act,call,f1,f2,f3,f4) \ seccomp_rule_add((ctx),(act),(call),4,(f1),(f2),(f3),(f4)) +static const char *sandbox_get_interned_string(const char *str); + /** * Function responsible for setting up the rt_sigaction syscall for * the seccomp filter sandbox. @@ -298,6 +325,7 @@ sb_rt_sigaction(scmp_filter_ctx ctx, sandbox_cfg_t *filter) unsigned i; int rc; int param[] = { SIGINT, SIGTERM, SIGPIPE, SIGUSR1, SIGUSR2, SIGHUP, SIGCHLD, + SIGSEGV, SIGILL, SIGFPE, SIGBUS, SIGSYS, SIGIO, #ifdef SIGXFSZ SIGXFSZ #endif @@ -427,31 +455,59 @@ sb_mmap2(scmp_filter_ctx ctx, sandbox_cfg_t *filter) #endif #endif -/* Return true if we think we're running with a libc that always uses - * openat on linux. */ +/* Return true the libc version is greater or equal than + * <b>major</b>.<b>minor</b>. Returns false otherwise. */ static int -libc_uses_openat_for_everything(void) +is_libc_at_least(int major, int minor) { #ifdef CHECK_LIBC_VERSION const char *version = gnu_get_libc_version(); if (version == NULL) return 0; - int major = -1; - int minor = -1; + int libc_major = -1; + int libc_minor = -1; - tor_sscanf(version, "%d.%d", &major, &minor); - if (major >= 3) + tor_sscanf(version, "%d.%d", &libc_major, &libc_minor); + if (libc_major > major) return 1; - else if (major == 2 && minor >= 26) + else if (libc_major == major && libc_minor >= minor) return 1; else return 0; -#else /* !(defined(CHECK_LIBC_VERSION)) */ +#else /* !defined(CHECK_LIBC_VERSION) */ + (void)major; + (void)minor; return 0; #endif /* defined(CHECK_LIBC_VERSION) */ } +/* Return true if we think we're running with a libc that uses openat for the + * open function on linux. */ +static int +libc_uses_openat_for_open(void) +{ + return is_libc_at_least(2, 26); +} + +/* Return true if we think we're running with a libc that uses openat for the + * opendir function on linux. */ +static int +libc_uses_openat_for_opendir(void) +{ + // libc 2.27 and above or between 2.15 (inclusive) and 2.22 (exclusive) + return is_libc_at_least(2, 27) || + (is_libc_at_least(2, 15) && !is_libc_at_least(2, 22)); +} + +/* Return true if we think we're running with a libc that needs to cast + * negative arguments like AT_FDCWD for seccomp rules. */ +static int +libc_negative_constant_needs_cast(void) +{ + return is_libc_at_least(2, 27); +} + /** Allow a single file to be opened. If <b>use_openat</b> is true, * we're using a libc that remaps all the opens into openats. */ static int @@ -459,7 +515,7 @@ allow_file_open(scmp_filter_ctx ctx, int use_openat, const char *file) { if (use_openat) { return seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), - SCMP_CMP(0, SCMP_CMP_EQ, (unsigned int)AT_FDCWD), + SCMP_CMP_NEG(0, SCMP_CMP_EQ, AT_FDCWD), SCMP_CMP_STR(1, SCMP_CMP_EQ, file)); } else { return seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), @@ -477,7 +533,7 @@ sb_open(scmp_filter_ctx ctx, sandbox_cfg_t *filter) int rc; sandbox_cfg_t *elem = NULL; - int use_openat = libc_uses_openat_for_everything(); + int use_openat = libc_uses_openat_for_open(); // for each dynamic parameter filters for (elem = filter; elem != NULL; elem = elem->next) { @@ -595,7 +651,7 @@ sb_openat(scmp_filter_ctx ctx, sandbox_cfg_t *filter) 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_NEG(0, SCMP_CMP_EQ, AT_FDCWD), SCMP_CMP_STR(1, SCMP_CMP_EQ, param->value), SCMP_CMP(2, SCMP_CMP_EQ, O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY| O_CLOEXEC)); @@ -610,6 +666,30 @@ sb_openat(scmp_filter_ctx ctx, sandbox_cfg_t *filter) return 0; } +static int +sb_opendir(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 + == PHONY_OPENDIR_SYSCALL) { + rc = allow_file_open(ctx, libc_uses_openat_for_opendir(), param->value); + 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. @@ -650,6 +730,15 @@ sb_socket(scmp_filter_ctx ctx, sandbox_cfg_t *filter) } } +#ifdef ENABLE_NSS + rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), + SCMP_CMP(0, SCMP_CMP_EQ, PF_INET), + SCMP_CMP(1, SCMP_CMP_EQ, SOCK_STREAM), + SCMP_CMP(2, SCMP_CMP_EQ, IPPROTO_IP)); + if (rc) + return rc; +#endif + rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), SCMP_CMP(0, SCMP_CMP_EQ, PF_UNIX), SCMP_CMP_MASKED(1, SOCK_CLOEXEC|SOCK_NONBLOCK, SOCK_STREAM), @@ -801,6 +890,12 @@ sb_getsockopt(scmp_filter_ctx ctx, sandbox_cfg_t *filter) if (rc) return rc; + 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_ACCEPTCONN)); + if (rc) + return rc; + #ifdef HAVE_SYSTEMD rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockopt), SCMP_CMP(1, SCMP_CMP_EQ, SOL_SOCKET), @@ -909,7 +1004,7 @@ sb_epoll_ctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) * the seccomp filter sandbox. * * NOTE: if multiple filters need to be added, the PR_SECCOMP parameter needs - * to be whitelisted in this function. + * to be allowlisted in this function. */ static int sb_prctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter) @@ -1109,6 +1204,7 @@ static sandbox_filter_func_t filter_func[] = { sb_chmod, sb_open, sb_openat, + sb_opendir, sb_rename, #ifdef __NR_fcntl64 sb_fcntl64, @@ -1133,9 +1229,42 @@ static sandbox_filter_func_t filter_func[] = { sb_kill }; +/** + * Return the interned (and hopefully sandbox-permitted) string equal + * to @a str. + * + * Return NULL if `str` is NULL, or `str` is not an interned string. + **/ const char * sandbox_intern_string(const char *str) { + const char *interned = sandbox_get_interned_string(str); + + if (sandbox_active && str != NULL && interned == NULL) { + log_warn(LD_BUG, "No interned sandbox parameter found for %s", str); + } + + return interned ? interned : str; +} + +/** + * Return true if the sandbox is running and we are missing an interned string + * equal to @a str. + */ +bool +sandbox_interned_string_is_missing(const char *str) +{ + return sandbox_active && sandbox_get_interned_string(str) == NULL; +} + +/** + * Try to find and return the interned string equal to @a str. + * + * If there is no such string, return NULL. + **/ +static const char * +sandbox_get_interned_string(const char *str) +{ sandbox_cfg_t *elem; if (str == NULL) @@ -1154,9 +1283,7 @@ sandbox_intern_string(const char *str) } } - if (sandbox_active) - log_warn(LD_BUG, "No interned sandbox parameter found for %s", str); - return str; + return NULL; } /* DOCDOC */ @@ -1428,6 +1555,19 @@ sandbox_cfg_allow_openat_filename(sandbox_cfg_t **cfg, char *file) return 0; } +int +sandbox_cfg_allow_opendir_dirname(sandbox_cfg_t **cfg, char *dir) +{ + sandbox_cfg_t *elem = NULL; + + elem = new_element(PHONY_OPENDIR_SYSCALL, dir); + + elem->next = *cfg; + *cfg = elem; + + return 0; +} + /** * Function responsible for going through the parameter syscall filters and * call each function pointer in the list. @@ -1471,6 +1611,28 @@ add_noparam_filter(scmp_filter_ctx ctx) } } + if (is_libc_at_least(2, 33)) { +#ifdef __NR_newfstatat + // Libc 2.33 uses this syscall to implement both fstat() and stat(). + // + // The trouble is that to implement fstat(fd, &st), it calls: + // newfstatat(fs, "", &st, AT_EMPTY_PATH) + // We can't detect this usage in particular, because "" is a pointer + // we don't control. And we can't just look for AT_EMPTY_PATH, since + // AT_EMPTY_PATH only has effect when the path string is empty. + // + // So our only solution seems to be allowing all fstatat calls, which + // means that an attacker can stat() anything on the filesystem. That's + // not a great solution, but I can't find a better one. + rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat)); + if (rc != 0) { + log_err(LD_BUG,"(Sandbox) failed to add newfstatat() syscall; " + "received libseccomp error %d", rc); + return rc; + } +#endif + } + return 0; } @@ -1520,15 +1682,16 @@ install_syscall_filter(sandbox_cfg_t* cfg) // marking the sandbox as active sandbox_active = 1; - tor_make_getaddrinfo_cache_active(); end: seccomp_release(ctx); return (rc < 0 ? -rc : rc); } +#ifdef SYSCALL_NAME_DEBUGGING #include "lib/sandbox/linux_syscalls.inc" +/** Return a string containing the name of a given syscall (if we know it) */ static const char * get_syscall_name(int syscall_num) { @@ -1546,6 +1709,28 @@ get_syscall_name(int syscall_num) } } +/** Return the syscall number from a ucontext_t that we got in a signal + * handler (if we know how to do that). */ +static int +get_syscall_from_ucontext(const ucontext_t *ctx) +{ + return (int) ctx->uc_mcontext.M_SYSCALL; +} +#else +static const char * +get_syscall_name(int syscall_num) +{ + (void) syscall_num; + return "unknown"; +} +static int +get_syscall_from_ucontext(const ucontext_t *ctx) +{ + (void) ctx; + return -1; +} +#endif + #ifdef USE_BACKTRACE #define MAX_DEPTH 256 static void *syscall_cb_buf[MAX_DEPTH]; @@ -1561,7 +1746,6 @@ sigsys_debugging(int nr, siginfo_t *info, void *void_context) { ucontext_t *ctx = (ucontext_t *) (void_context); const char *syscall_name; - int syscall; #ifdef USE_BACKTRACE size_t depth; int n_fds, i; @@ -1576,7 +1760,7 @@ sigsys_debugging(int nr, siginfo_t *info, void *void_context) if (!ctx) return; - syscall = (int) ctx->uc_mcontext.M_SYSCALL; + int syscall = get_syscall_from_ucontext(ctx); #ifdef USE_BACKTRACE depth = backtrace(syscall_cb_buf, MAX_DEPTH); @@ -1734,6 +1918,13 @@ sandbox_cfg_allow_openat_filename(sandbox_cfg_t **cfg, char *file) } int +sandbox_cfg_allow_opendir_dirname(sandbox_cfg_t **cfg, char *dir) +{ + (void)cfg; (void)dir; + return 0; +} + +int sandbox_cfg_allow_stat_filename(sandbox_cfg_t **cfg, char *file) { (void)cfg; (void)file; @@ -1767,9 +1958,4 @@ sandbox_is_active(void) return 0; } -void -sandbox_disable_getaddrinfo_cache(void) -{ -} - #endif /* !defined(USE_LIBSECCOMP) */ |