diff options
Diffstat (limited to 'src/common/compat.c')
| -rw-r--r-- | src/common/compat.c | 239 |
1 files changed, 198 insertions, 41 deletions
diff --git a/src/common/compat.c b/src/common/compat.c index 7d72b4b7fd..af61f024ef 100644 --- a/src/common/compat.c +++ b/src/common/compat.c @@ -1,12 +1,12 @@ /* Copyright (c) 2003-2004, Roger Dingledine * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2015, The Tor Project, Inc. */ + * Copyright (c) 2007-2016, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file compat.c * \brief Wrappers to make calls more portable. This code defines - * functions such as tor_malloc, tor_snprintf, get/set various data types, + * functions such as tor_snprintf, get/set various data types, * renaming, setting socket options, switching user IDs. It is basically * where the non-portable items are conditionally included depending on * the platform. @@ -71,6 +71,9 @@ #ifdef HAVE_SYS_STATVFS_H #include <sys/statvfs.h> #endif +#ifdef HAVE_SYS_CAPABILITY_H +#include <sys/capability.h> +#endif #ifdef _WIN32 #include <conio.h> @@ -573,14 +576,17 @@ tor_vasprintf(char **strp, const char *fmt, va_list args) int len, r; va_list tmp_args; va_copy(tmp_args, args); - len = vsnprintf(buf, sizeof(buf), fmt, tmp_args); + /* vsnprintf() was properly checked but tor_vsnprintf() available so + * why not use it? */ + len = tor_vsnprintf(buf, sizeof(buf), fmt, tmp_args); va_end(tmp_args); if (len < (int)sizeof(buf)) { *strp = tor_strdup(buf); return len; } strp_tmp = tor_malloc(len+1); - r = vsnprintf(strp_tmp, len+1, fmt, args); + /* use of tor_vsnprintf() will ensure string is null terminated */ + r = tor_vsnprintf(strp_tmp, len+1, fmt, args); if (r != len) { tor_free(strp_tmp); *strp = NULL; @@ -714,7 +720,8 @@ strtok_helper(char *cp, const char *sep) } /** Implementation of strtok_r for platforms whose coders haven't figured out - * how to write one. Hey guys! You can use this code here for free! */ + * how to write one. Hey, retrograde libc developers! You can use this code + * here for free! */ char * tor_strtok_r_impl(char *str, const char *sep, char **lasts) { @@ -1078,7 +1085,7 @@ static int n_sockets_open = 0; static tor_mutex_t *socket_accounting_mutex = NULL; /** Helper: acquire the socket accounting lock. */ -static INLINE void +static inline void socket_accounting_lock(void) { if (PREDICT_UNLIKELY(!socket_accounting_mutex)) @@ -1087,7 +1094,7 @@ socket_accounting_lock(void) } /** Helper: release the socket accounting lock. */ -static INLINE void +static inline void socket_accounting_unlock(void) { tor_mutex_release(socket_accounting_mutex); @@ -1163,7 +1170,7 @@ tor_close_socket(tor_socket_t s) #ifdef DEBUG_SOCKET_COUNTING /** Helper: if DEBUG_SOCKET_COUNTING is enabled, remember that <b>s</b> is * now an open socket. */ -static INLINE void +static inline void mark_socket_open(tor_socket_t s) { /* XXXX This bitarray business will NOT work on windows: sockets aren't @@ -1486,6 +1493,20 @@ tor_socketpair(int family, int type, int protocol, tor_socket_t fd[2]) } #ifdef NEED_ERSATZ_SOCKETPAIR + +static inline socklen_t +SIZEOF_SOCKADDR(int domain) +{ + switch (domain) { + case AF_INET: + return sizeof(struct sockaddr_in); + case AF_INET6: + return sizeof(struct sockaddr_in6); + default: + return 0; + } +} + /** * Helper used to implement socketpair on systems that lack it, by * making a direct connection to localhost. @@ -1501,13 +1522,21 @@ tor_ersatz_socketpair(int family, int type, int protocol, tor_socket_t fd[2]) tor_socket_t listener = TOR_INVALID_SOCKET; tor_socket_t connector = TOR_INVALID_SOCKET; tor_socket_t acceptor = TOR_INVALID_SOCKET; - struct sockaddr_in listen_addr; - struct sockaddr_in connect_addr; + tor_addr_t listen_tor_addr; + struct sockaddr_storage connect_addr_ss, listen_addr_ss; + struct sockaddr *listen_addr = (struct sockaddr *) &listen_addr_ss; + uint16_t listen_port = 0; + tor_addr_t connect_tor_addr; + uint16_t connect_port = 0; + struct sockaddr *connect_addr = (struct sockaddr *) &connect_addr_ss; socklen_t size; int saved_errno = -1; + int ersatz_domain = AF_INET; - memset(&connect_addr, 0, sizeof(connect_addr)); - memset(&listen_addr, 0, sizeof(listen_addr)); + memset(&connect_tor_addr, 0, sizeof(connect_tor_addr)); + memset(&connect_addr_ss, 0, sizeof(connect_addr_ss)); + memset(&listen_tor_addr, 0, sizeof(listen_tor_addr)); + memset(&listen_addr_ss, 0, sizeof(listen_addr_ss)); if (protocol #ifdef AF_UNIX @@ -1524,47 +1553,71 @@ tor_ersatz_socketpair(int family, int type, int protocol, tor_socket_t fd[2]) return -EINVAL; } - listener = tor_open_socket(AF_INET, type, 0); - if (!SOCKET_OK(listener)) - return -tor_socket_errno(-1); - memset(&listen_addr, 0, sizeof(listen_addr)); - listen_addr.sin_family = AF_INET; - listen_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); - listen_addr.sin_port = 0; /* kernel chooses port. */ - if (bind(listener, (struct sockaddr *) &listen_addr, sizeof (listen_addr)) - == -1) + listener = tor_open_socket(ersatz_domain, type, 0); + if (!SOCKET_OK(listener)) { + int first_errno = tor_socket_errno(-1); + if (first_errno == SOCK_ERRNO(EPROTONOSUPPORT) + && ersatz_domain == AF_INET) { + /* Assume we're on an IPv6-only system */ + ersatz_domain = AF_INET6; + listener = tor_open_socket(ersatz_domain, type, 0); + if (!SOCKET_OK(listener)) { + /* Keep the previous behaviour, which was to return the IPv4 error. + * (This may be less informative on IPv6-only systems.) + * XX/teor - is there a better way to decide which errno to return? + * (I doubt we care much either way, once there is an error.) + */ + return -first_errno; + } + } + } + /* If there is no 127.0.0.1 or ::1, this will and must fail. Otherwise, we + * risk exposing a socketpair on a routable IP address. (Some BSD jails + * use a routable address for localhost. Fortunately, they have the real + * AF_UNIX socketpair.) */ + if (ersatz_domain == AF_INET) { + tor_addr_from_ipv4h(&listen_tor_addr, INADDR_LOOPBACK); + } else { + tor_addr_parse(&listen_tor_addr, "[::1]"); + } + tor_assert(tor_addr_is_loopback(&listen_tor_addr)); + size = tor_addr_to_sockaddr(&listen_tor_addr, + 0 /* kernel chooses port. */, + listen_addr, + sizeof(listen_addr_ss)); + if (bind(listener, listen_addr, size) == -1) goto tidy_up_and_fail; if (listen(listener, 1) == -1) goto tidy_up_and_fail; - connector = tor_open_socket(AF_INET, type, 0); + connector = tor_open_socket(ersatz_domain, type, 0); if (!SOCKET_OK(connector)) goto tidy_up_and_fail; /* We want to find out the port number to connect to. */ - size = sizeof(connect_addr); - if (getsockname(listener, (struct sockaddr *) &connect_addr, &size) == -1) + size = sizeof(connect_addr_ss); + if (getsockname(listener, connect_addr, &size) == -1) goto tidy_up_and_fail; - if (size != sizeof (connect_addr)) + if (size != SIZEOF_SOCKADDR (connect_addr->sa_family)) goto abort_tidy_up_and_fail; - if (connect(connector, (struct sockaddr *) &connect_addr, - sizeof(connect_addr)) == -1) + if (connect(connector, connect_addr, size) == -1) goto tidy_up_and_fail; - size = sizeof(listen_addr); - acceptor = tor_accept_socket(listener, - (struct sockaddr *) &listen_addr, &size); + size = sizeof(listen_addr_ss); + acceptor = tor_accept_socket(listener, listen_addr, &size); if (!SOCKET_OK(acceptor)) goto tidy_up_and_fail; - if (size != sizeof(listen_addr)) + if (size != SIZEOF_SOCKADDR(listen_addr->sa_family)) goto abort_tidy_up_and_fail; /* Now check we are talking to ourself by matching port and host on the two sockets. */ - if (getsockname(connector, (struct sockaddr *) &connect_addr, &size) == -1) + if (getsockname(connector, connect_addr, &size) == -1) goto tidy_up_and_fail; - if (size != sizeof (connect_addr) - || listen_addr.sin_family != connect_addr.sin_family - || listen_addr.sin_addr.s_addr != connect_addr.sin_addr.s_addr - || listen_addr.sin_port != connect_addr.sin_port) { + /* Set *_tor_addr and *_port to the address and port that was used */ + tor_addr_from_sockaddr(&listen_tor_addr, listen_addr, &listen_port); + tor_addr_from_sockaddr(&connect_tor_addr, connect_addr, &connect_port); + if (size != SIZEOF_SOCKADDR (connect_addr->sa_family) + || tor_addr_compare(&listen_tor_addr, &connect_tor_addr, CMP_SEMANTIC) + || listen_port != connect_port) { goto abort_tidy_up_and_fail; } tor_close_socket(listener); @@ -1590,6 +1643,9 @@ tor_ersatz_socketpair(int family, int type, int protocol, tor_socket_t fd[2]) tor_close_socket(acceptor); return -saved_errno; } + +#undef SIZEOF_SOCKADDR + #endif /* Return the maximum number of allowed sockets. */ @@ -1917,17 +1973,99 @@ tor_getpwuid(uid_t uid) } #endif +/** Return true iff we were compiled with capability support, and capabilities + * seem to work. **/ +int +have_capability_support(void) +{ +#ifdef HAVE_LINUX_CAPABILITIES + cap_t caps = cap_get_proc(); + if (caps == NULL) + return 0; + cap_free(caps); + return 1; +#else + return 0; +#endif +} + +#ifdef HAVE_LINUX_CAPABILITIES +/** Helper. Drop all capabilities but a small set, and set PR_KEEPCAPS as + * appropriate. + * + * If pre_setuid, retain only CAP_NET_BIND_SERVICE, CAP_SETUID, and + * CAP_SETGID, and use PR_KEEPCAPS to ensure that capabilities persist across + * setuid(). + * + * If not pre_setuid, retain only CAP_NET_BIND_SERVICE, and disable + * PR_KEEPCAPS. + * + * Return 0 on success, and -1 on failure. + */ +static int +drop_capabilities(int pre_setuid) +{ + /* We keep these three capabilities, and these only, as we setuid. + * After we setuid, we drop all but the first. */ + const cap_value_t caplist[] = { + CAP_NET_BIND_SERVICE, CAP_SETUID, CAP_SETGID + }; + const char *where = pre_setuid ? "pre-setuid" : "post-setuid"; + const int n_effective = pre_setuid ? 3 : 1; + const int n_permitted = pre_setuid ? 3 : 1; + const int n_inheritable = 1; + const int keepcaps = pre_setuid ? 1 : 0; + + /* Sets whether we keep capabilities across a setuid. */ + if (prctl(PR_SET_KEEPCAPS, keepcaps) < 0) { + log_warn(LD_CONFIG, "Unable to call prctl() %s: %s", + where, strerror(errno)); + return -1; + } + + cap_t caps = cap_get_proc(); + if (!caps) { + log_warn(LD_CONFIG, "Unable to call cap_get_proc() %s: %s", + where, strerror(errno)); + return -1; + } + cap_clear(caps); + + cap_set_flag(caps, CAP_EFFECTIVE, n_effective, caplist, CAP_SET); + cap_set_flag(caps, CAP_PERMITTED, n_permitted, caplist, CAP_SET); + cap_set_flag(caps, CAP_INHERITABLE, n_inheritable, caplist, CAP_SET); + + int r = cap_set_proc(caps); + cap_free(caps); + if (r < 0) { + log_warn(LD_CONFIG, "No permission to set capabilities %s: %s", + where, strerror(errno)); + return -1; + } + + return 0; +} +#endif + /** Call setuid and setgid to run as <b>user</b> and switch to their * primary group. Return 0 on success. On failure, log and return -1. + * + * If SWITCH_ID_KEEP_BINDLOW is set in 'flags', try to use the capability + * system to retain the abilitity to bind low ports. + * + * If SWITCH_ID_WARN_IF_NO_CAPS is set in flags, also warn if we have + * don't have capability support. */ int -switch_id(const char *user) +switch_id(const char *user, const unsigned flags) { #ifndef _WIN32 const struct passwd *pw = NULL; uid_t old_uid; gid_t old_gid; static int have_already_switched_id = 0; + const int keep_bindlow = !!(flags & SWITCH_ID_KEEP_BINDLOW); + const int warn_if_no_caps = !!(flags & SWITCH_ID_WARN_IF_NO_CAPS); tor_assert(user); @@ -1951,6 +2089,20 @@ switch_id(const char *user) return -1; } +#ifdef HAVE_LINUX_CAPABILITIES + (void) warn_if_no_caps; + if (keep_bindlow) { + if (drop_capabilities(1)) + return -1; + } +#else + (void) keep_bindlow; + if (warn_if_no_caps) { + log_warn(LD_CONFIG, "KeepBindCapabilities set, but no capability support " + "on this system."); + } +#endif + /* Properly switch egid,gid,euid,uid here or bail out */ if (setgroups(1, &pw->pw_gid)) { log_warn(LD_GENERAL, "Error setting groups to gid %d: \"%s\".", @@ -2004,6 +2156,12 @@ switch_id(const char *user) /* We've properly switched egid, gid, euid, uid, and supplementary groups if * we're here. */ +#ifdef HAVE_LINUX_CAPABILITIES + if (keep_bindlow) { + if (drop_capabilities(0)) + return -1; + } +#endif #if !defined(CYGWIN) && !defined(__CYGWIN__) /* If we tried to drop privilege to a group/user other than root, attempt to @@ -2051,9 +2209,9 @@ switch_id(const char *user) #else (void)user; + (void)flags; - log_warn(LD_CONFIG, - "User specified but switching users is unsupported on your OS."); + log_warn(LD_CONFIG, "Switching users is unsupported on your OS."); return -1; #endif } @@ -2537,8 +2695,7 @@ static int uname_result_is_set = 0; /** Return a pointer to a description of our platform. */ -const char * -get_uname(void) +MOCK_IMPL(const char *, get_uname, (void)) { #ifdef HAVE_UNAME struct utsname u; |