diff options
Diffstat (limited to 'src/common/compat.c')
| -rw-r--r-- | src/common/compat.c | 116 |
1 files changed, 111 insertions, 5 deletions
diff --git a/src/common/compat.c b/src/common/compat.c index 55fb55a045..7e8eec189a 100644 --- a/src/common/compat.c +++ b/src/common/compat.c @@ -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> @@ -1078,7 +1081,7 @@ 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 +1090,7 @@ 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 +1166,7 @@ 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 @@ -1487,7 +1490,7 @@ tor_socketpair(int family, int type, int protocol, tor_socket_t fd[2]) #ifdef NEED_ERSATZ_SOCKETPAIR -static INLINE socklen_t +static inline socklen_t SIZEOF_SOCKADDR(int domain) { switch (domain) { @@ -1966,17 +1969,99 @@ 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); @@ -2000,6 +2085,20 @@ 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\".", @@ -2053,6 +2152,12 @@ 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 @@ -2100,6 +2205,7 @@ switch_id(const char *user) #else (void)user; + (void)flags; log_warn(LD_CONFIG, "User specified but switching users is unsupported on your OS."); |