diff options
Diffstat (limited to 'REORG.TODO/nscd/selinux.c')
| -rw-r--r-- | REORG.TODO/nscd/selinux.c | 453 |
1 files changed, 453 insertions, 0 deletions
diff --git a/REORG.TODO/nscd/selinux.c b/REORG.TODO/nscd/selinux.c new file mode 100644 index 0000000000..f7bcd8e4c8 --- /dev/null +++ b/REORG.TODO/nscd/selinux.c @@ -0,0 +1,453 @@ +/* SELinux access controls for nscd. + Copyright (C) 2004-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Matthew Rickard <mjricka@epoch.ncsc.mil>, 2004. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include "config.h" +#include <error.h> +#include <errno.h> +#include <libintl.h> +#include <pthread.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <syslog.h> +#include <unistd.h> +#include <sys/prctl.h> +#include <selinux/avc.h> +#include <selinux/selinux.h> +#ifdef HAVE_LIBAUDIT +# include <libaudit.h> +#endif + +#include "dbg_log.h" +#include "selinux.h" + + +#ifdef HAVE_SELINUX +/* Global variable to tell if the kernel has SELinux support. */ +int selinux_enabled; + +/* Define mappings of request type to AVC permission name. */ +static const char *perms[LASTREQ] = +{ + [GETPWBYNAME] = "getpwd", + [GETPWBYUID] = "getpwd", + [GETGRBYNAME] = "getgrp", + [GETGRBYGID] = "getgrp", + [GETHOSTBYNAME] = "gethost", + [GETHOSTBYNAMEv6] = "gethost", + [GETHOSTBYADDR] = "gethost", + [GETHOSTBYADDRv6] = "gethost", + [SHUTDOWN] = "admin", + [GETSTAT] = "getstat", + [INVALIDATE] = "admin", + [GETFDPW] = "shmempwd", + [GETFDGR] = "shmemgrp", + [GETFDHST] = "shmemhost", + [GETAI] = "gethost", + [INITGROUPS] = "getgrp", + [GETSERVBYNAME] = "getserv", + [GETSERVBYPORT] = "getserv", + [GETFDSERV] = "shmemserv", + [GETNETGRENT] = "getnetgrp", + [INNETGR] = "getnetgrp", + [GETFDNETGR] = "shmemnetgrp", +}; + +/* Store an entry ref to speed AVC decisions. */ +static struct avc_entry_ref aeref; + +/* Thread to listen for SELinux status changes via netlink. */ +static pthread_t avc_notify_thread; + +#ifdef HAVE_LIBAUDIT +/* Prototype for supporting the audit daemon */ +static void log_callback (const char *fmt, ...); +#endif + +/* Prototypes for AVC callback functions. */ +static void *avc_create_thread (void (*run) (void)); +static void avc_stop_thread (void *thread); +static void *avc_alloc_lock (void); +static void avc_get_lock (void *lock); +static void avc_release_lock (void *lock); +static void avc_free_lock (void *lock); + +/* AVC callback structures for use in avc_init. */ +static const struct avc_log_callback log_cb = +{ +#ifdef HAVE_LIBAUDIT + .func_log = log_callback, +#else + .func_log = dbg_log, +#endif + .func_audit = NULL +}; +static const struct avc_thread_callback thread_cb = +{ + .func_create_thread = avc_create_thread, + .func_stop_thread = avc_stop_thread +}; +static const struct avc_lock_callback lock_cb = +{ + .func_alloc_lock = avc_alloc_lock, + .func_get_lock = avc_get_lock, + .func_release_lock = avc_release_lock, + .func_free_lock = avc_free_lock +}; + +#ifdef HAVE_LIBAUDIT +/* The audit system's netlink socket descriptor */ +static int audit_fd = -1; + +/* When an avc denial occurs, log it to audit system */ +static void +log_callback (const char *fmt, ...) +{ + if (audit_fd >= 0) + { + va_list ap; + va_start (ap, fmt); + + char *buf; + int e = vasprintf (&buf, fmt, ap); + if (e < 0) + { + buf = alloca (BUFSIZ); + vsnprintf (buf, BUFSIZ, fmt, ap); + } + + /* FIXME: need to attribute this to real user, using getuid for now */ + audit_log_user_avc_message (audit_fd, AUDIT_USER_AVC, buf, NULL, NULL, + NULL, getuid ()); + + if (e >= 0) + free (buf); + + va_end (ap); + } +} + +/* Initialize the connection to the audit system */ +static void +audit_init (void) +{ + audit_fd = audit_open (); + if (audit_fd < 0 + /* If kernel doesn't support audit, bail out */ + && errno != EINVAL && errno != EPROTONOSUPPORT && errno != EAFNOSUPPORT) + dbg_log (_("Failed opening connection to the audit subsystem: %m")); +} + + +# ifdef HAVE_LIBCAP +static const cap_value_t new_cap_list[] = + { CAP_AUDIT_WRITE }; +# define nnew_cap_list (sizeof (new_cap_list) / sizeof (new_cap_list[0])) +static const cap_value_t tmp_cap_list[] = + { CAP_AUDIT_WRITE, CAP_SETUID, CAP_SETGID }; +# define ntmp_cap_list (sizeof (tmp_cap_list) / sizeof (tmp_cap_list[0])) + +cap_t +preserve_capabilities (void) +{ + if (getuid () != 0) + /* Not root, then we cannot preserve anything. */ + return NULL; + + if (prctl (PR_SET_KEEPCAPS, 1) == -1) + { + dbg_log (_("Failed to set keep-capabilities")); + do_exit (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed")); + /* NOTREACHED */ + } + + cap_t tmp_caps = cap_init (); + cap_t new_caps = NULL; + if (tmp_caps != NULL) + new_caps = cap_init (); + + if (tmp_caps == NULL || new_caps == NULL) + { + if (tmp_caps != NULL) + cap_free (tmp_caps); + + dbg_log (_("Failed to initialize drop of capabilities")); + do_exit (EXIT_FAILURE, 0, _("cap_init failed")); + } + + /* There is no reason why these should not work. */ + cap_set_flag (new_caps, CAP_PERMITTED, nnew_cap_list, + (cap_value_t *) new_cap_list, CAP_SET); + cap_set_flag (new_caps, CAP_EFFECTIVE, nnew_cap_list, + (cap_value_t *) new_cap_list, CAP_SET); + + cap_set_flag (tmp_caps, CAP_PERMITTED, ntmp_cap_list, + (cap_value_t *) tmp_cap_list, CAP_SET); + cap_set_flag (tmp_caps, CAP_EFFECTIVE, ntmp_cap_list, + (cap_value_t *) tmp_cap_list, CAP_SET); + + int res = cap_set_proc (tmp_caps); + + cap_free (tmp_caps); + + if (__glibc_unlikely (res != 0)) + { + cap_free (new_caps); + dbg_log (_("Failed to drop capabilities")); + do_exit (EXIT_FAILURE, 0, _("cap_set_proc failed")); + } + + return new_caps; +} + +void +install_real_capabilities (cap_t new_caps) +{ + /* If we have no capabilities there is nothing to do here. */ + if (new_caps == NULL) + return; + + if (cap_set_proc (new_caps)) + { + cap_free (new_caps); + dbg_log (_("Failed to drop capabilities")); + do_exit (EXIT_FAILURE, 0, _("cap_set_proc failed")); + /* NOTREACHED */ + } + + cap_free (new_caps); + + if (prctl (PR_SET_KEEPCAPS, 0) == -1) + { + dbg_log (_("Failed to unset keep-capabilities")); + do_exit (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed")); + /* NOTREACHED */ + } +} +# endif /* HAVE_LIBCAP */ +#endif /* HAVE_LIBAUDIT */ + +/* Determine if we are running on an SELinux kernel. Set selinux_enabled + to the result. */ +void +nscd_selinux_enabled (int *selinux_enabled) +{ + *selinux_enabled = is_selinux_enabled (); + if (*selinux_enabled < 0) + { + dbg_log (_("Failed to determine if kernel supports SELinux")); + do_exit (EXIT_FAILURE, 0, NULL); + } +} + + +/* Create thread for AVC netlink notification. */ +static void * +avc_create_thread (void (*run) (void)) +{ + int rc; + + rc = + pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL); + if (rc != 0) + do_exit (EXIT_FAILURE, rc, _("Failed to start AVC thread")); + + return &avc_notify_thread; +} + + +/* Stop AVC netlink thread. */ +static void +avc_stop_thread (void *thread) +{ + pthread_cancel (*(pthread_t *) thread); +} + + +/* Allocate a new AVC lock. */ +static void * +avc_alloc_lock (void) +{ + pthread_mutex_t *avc_mutex; + + avc_mutex = malloc (sizeof (pthread_mutex_t)); + if (avc_mutex == NULL) + do_exit (EXIT_FAILURE, errno, _("Failed to create AVC lock")); + pthread_mutex_init (avc_mutex, NULL); + + return avc_mutex; +} + + +/* Acquire an AVC lock. */ +static void +avc_get_lock (void *lock) +{ + pthread_mutex_lock (lock); +} + + +/* Release an AVC lock. */ +static void +avc_release_lock (void *lock) +{ + pthread_mutex_unlock (lock); +} + + +/* Free an AVC lock. */ +static void +avc_free_lock (void *lock) +{ + pthread_mutex_destroy (lock); + free (lock); +} + + +/* Initialize the user space access vector cache (AVC) for NSCD along with + log/thread/lock callbacks. */ +void +nscd_avc_init (void) +{ + avc_entry_ref_init (&aeref); + + if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0) + do_exit (EXIT_FAILURE, errno, _("Failed to start AVC")); + else + dbg_log (_("Access Vector Cache (AVC) started")); +#ifdef HAVE_LIBAUDIT + audit_init (); +#endif +} + + +/* Check the permission from the caller (via getpeercon) to nscd. + Returns 0 if access is allowed, 1 if denied, and -1 on error. + + The SELinux policy, enablement, and permission bits are all dynamic and the + caching done by glibc is not entirely correct. This nscd support should be + rewritten to use selinux_check_permission. A rewrite is risky though and + requires some refactoring. Currently we use symbolic mappings instead of + compile time constants (which SELinux upstream says are going away), and we + use security_deny_unknown to determine what to do if selinux-policy* doesn't + have a definition for the the permission or object class we are looking + up. */ +int +nscd_request_avc_has_perm (int fd, request_type req) +{ + /* Initialize to NULL so we know what to free in case of failure. */ + security_context_t scon = NULL; + security_context_t tcon = NULL; + security_id_t ssid = NULL; + security_id_t tsid = NULL; + int rc = -1; + security_class_t sc_nscd; + access_vector_t perm; + int avc_deny_unknown; + + /* Check if SELinux denys or allows unknown object classes + and permissions. It is 0 if they are allowed, 1 if they + are not allowed and -1 on error. */ + if ((avc_deny_unknown = security_deny_unknown ()) == -1) + dbg_log (_("Error querying policy for undefined object classes " + "or permissions.")); + + /* Get the security class for nscd. If this fails we will likely be + unable to do anything unless avc_deny_unknown is 0. */ + sc_nscd = string_to_security_class ("nscd"); + if (sc_nscd == 0 && avc_deny_unknown == 1) + dbg_log (_("Error getting security class for nscd.")); + + /* Convert permission to AVC bits. */ + perm = string_to_av_perm (sc_nscd, perms[req]); + if (perm == 0 && avc_deny_unknown == 1) + dbg_log (_("Error translating permission name " + "\"%s\" to access vector bit."), perms[req]); + + /* If the nscd security class was not found or perms were not + found and AVC does not deny unknown values then allow it. */ + if ((sc_nscd == 0 || perm == 0) && avc_deny_unknown == 0) + return 0; + + if (getpeercon (fd, &scon) < 0) + { + dbg_log (_("Error getting context of socket peer")); + goto out; + } + if (getcon (&tcon) < 0) + { + dbg_log (_("Error getting context of nscd")); + goto out; + } + if (avc_context_to_sid (scon, &ssid) < 0 + || avc_context_to_sid (tcon, &tsid) < 0) + { + dbg_log (_("Error getting sid from context")); + goto out; + } + + /* The SELinux API for avc_has_perm conflates access denied and error into + the return code -1, while nscd_request_avs_has_perm has distinct error + (-1) and denied (1) return codes. We map the avc_has_perm access denied or + error into an access denied at the nscd interface level (we do accurately + report error for the getpeercon, getcon, and avc_context_to_sid interfaces + used above). */ + rc = avc_has_perm (ssid, tsid, sc_nscd, perm, &aeref, NULL) < 0; + +out: + if (scon) + freecon (scon); + if (tcon) + freecon (tcon); + if (ssid) + sidput (ssid); + if (tsid) + sidput (tsid); + + return rc; +} + + +/* Wrapper to get AVC statistics. */ +void +nscd_avc_cache_stats (struct avc_cache_stats *cstats) +{ + avc_cache_stats (cstats); +} + + +/* Print the AVC statistics to stdout. */ +void +nscd_avc_print_stats (struct avc_cache_stats *cstats) +{ + printf (_("\nSELinux AVC Statistics:\n\n" + "%15u entry lookups\n" + "%15u entry hits\n" + "%15u entry misses\n" + "%15u entry discards\n" + "%15u CAV lookups\n" + "%15u CAV hits\n" + "%15u CAV probes\n" + "%15u CAV misses\n"), + cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses, + cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits, + cstats->cav_probes, cstats->cav_misses); +} + +#endif /* HAVE_SELINUX */ |