/* ------------------------------------------------------------------------- * * contrib/sepgsql/selinux.c * * Interactions between userspace and selinux in kernelspace, * using libselinux api. * * Copyright (c) 2010-2012, PostgreSQL Global Development Group * * ------------------------------------------------------------------------- */ #include "postgres.h" #include "knl/knl_variable.h" #include "lib/stringinfo.h" #include "sepgsql.h" /* * selinux_catalog * * This mapping table enables to translate the name of object classes and * access vectors to/from their own codes. * When we ask SELinux whether the required privileges are allowed or not, * we use security_compute_av(3). It needs us to represent object classes * and access vectors using 'external' codes defined in the security policy. * It is determinded in the runtime, not build time. So, it needs an internal * service to translate object class/access vectors which we want to check * into the code which kernel want to be given. */ static struct { const char* class_name; uint16 class_code; struct { const char* av_name; uint32 av_code; } av[32]; } selinux_catalog[] = { {"process", SEPG_CLASS_PROCESS, {{"transition", SEPG_PROCESS__TRANSITION}, {"dyntransition", SEPG_PROCESS__DYNTRANSITION}, {"setcurrent", SEPG_PROCESS__SETCURRENT}, {NULL, 0UL}}}, {"file", SEPG_CLASS_FILE, {{"read", SEPG_FILE__READ}, {"write", SEPG_FILE__WRITE}, {"create", SEPG_FILE__CREATE}, {"getattr", SEPG_FILE__GETATTR}, {"unlink", SEPG_FILE__UNLINK}, {"rename", SEPG_FILE__RENAME}, {"append", SEPG_FILE__APPEND}, {NULL, 0UL}}}, {"dir", SEPG_CLASS_DIR, {{"read", SEPG_DIR__READ}, {"write", SEPG_DIR__WRITE}, {"create", SEPG_DIR__CREATE}, {"getattr", SEPG_DIR__GETATTR}, {"unlink", SEPG_DIR__UNLINK}, {"rename", SEPG_DIR__RENAME}, {"search", SEPG_DIR__SEARCH}, {"add_name", SEPG_DIR__ADD_NAME}, {"remove_name", SEPG_DIR__REMOVE_NAME}, {"rmdir", SEPG_DIR__RMDIR}, {"reparent", SEPG_DIR__REPARENT}, {NULL, 0UL}}}, {"lnk_file", SEPG_CLASS_LNK_FILE, {{"read", SEPG_LNK_FILE__READ}, {"write", SEPG_LNK_FILE__WRITE}, {"create", SEPG_LNK_FILE__CREATE}, {"getattr", SEPG_LNK_FILE__GETATTR}, {"unlink", SEPG_LNK_FILE__UNLINK}, {"rename", SEPG_LNK_FILE__RENAME}, {NULL, 0UL}}}, {"chr_file", SEPG_CLASS_CHR_FILE, {{"read", SEPG_CHR_FILE__READ}, {"write", SEPG_CHR_FILE__WRITE}, {"create", SEPG_CHR_FILE__CREATE}, {"getattr", SEPG_CHR_FILE__GETATTR}, {"unlink", SEPG_CHR_FILE__UNLINK}, {"rename", SEPG_CHR_FILE__RENAME}, {NULL, 0UL}}}, {"blk_file", SEPG_CLASS_BLK_FILE, {{"read", SEPG_BLK_FILE__READ}, {"write", SEPG_BLK_FILE__WRITE}, {"create", SEPG_BLK_FILE__CREATE}, {"getattr", SEPG_BLK_FILE__GETATTR}, {"unlink", SEPG_BLK_FILE__UNLINK}, {"rename", SEPG_BLK_FILE__RENAME}, {NULL, 0UL}}}, {"sock_file", SEPG_CLASS_SOCK_FILE, {{"read", SEPG_SOCK_FILE__READ}, {"write", SEPG_SOCK_FILE__WRITE}, {"create", SEPG_SOCK_FILE__CREATE}, {"getattr", SEPG_SOCK_FILE__GETATTR}, {"unlink", SEPG_SOCK_FILE__UNLINK}, {"rename", SEPG_SOCK_FILE__RENAME}, {NULL, 0UL}}}, {"fifo_file", SEPG_CLASS_FIFO_FILE, {{"read", SEPG_FIFO_FILE__READ}, {"write", SEPG_FIFO_FILE__WRITE}, {"create", SEPG_FIFO_FILE__CREATE}, {"getattr", SEPG_FIFO_FILE__GETATTR}, {"unlink", SEPG_FIFO_FILE__UNLINK}, {"rename", SEPG_FIFO_FILE__RENAME}, {NULL, 0UL}}}, {"db_database", SEPG_CLASS_DB_DATABASE, { {"create", SEPG_DB_DATABASE__CREATE}, {"drop", SEPG_DB_DATABASE__DROP}, {"getattr", SEPG_DB_DATABASE__GETATTR}, {"setattr", SEPG_DB_DATABASE__SETATTR}, {"relabelfrom", SEPG_DB_DATABASE__RELABELFROM}, {"relabelto", SEPG_DB_DATABASE__RELABELTO}, {"access", SEPG_DB_DATABASE__ACCESS}, {"load_module", SEPG_DB_DATABASE__LOAD_MODULE}, {NULL, 0UL}, }}, {"db_schema", SEPG_CLASS_DB_SCHEMA, { {"create", SEPG_DB_SCHEMA__CREATE}, {"drop", SEPG_DB_SCHEMA__DROP}, {"getattr", SEPG_DB_SCHEMA__GETATTR}, {"setattr", SEPG_DB_SCHEMA__SETATTR}, {"relabelfrom", SEPG_DB_SCHEMA__RELABELFROM}, {"relabelto", SEPG_DB_SCHEMA__RELABELTO}, {"search", SEPG_DB_SCHEMA__SEARCH}, {"add_name", SEPG_DB_SCHEMA__ADD_NAME}, {"remove_name", SEPG_DB_SCHEMA__REMOVE_NAME}, {NULL, 0UL}, }}, {"db_table", SEPG_CLASS_DB_TABLE, { {"create", SEPG_DB_TABLE__CREATE}, {"drop", SEPG_DB_TABLE__DROP}, {"getattr", SEPG_DB_TABLE__GETATTR}, {"setattr", SEPG_DB_TABLE__SETATTR}, {"relabelfrom", SEPG_DB_TABLE__RELABELFROM}, {"relabelto", SEPG_DB_TABLE__RELABELTO}, {"select", SEPG_DB_TABLE__SELECT}, {"update", SEPG_DB_TABLE__UPDATE}, {"insert", SEPG_DB_TABLE__INSERT}, {"delete", SEPG_DB_TABLE__DELETE}, {"lock", SEPG_DB_TABLE__LOCK}, {NULL, 0UL}, }}, {"db_sequence", SEPG_CLASS_DB_SEQUENCE, { {"create", SEPG_DB_SEQUENCE__CREATE}, {"drop", SEPG_DB_SEQUENCE__DROP}, {"getattr", SEPG_DB_SEQUENCE__GETATTR}, {"setattr", SEPG_DB_SEQUENCE__SETATTR}, {"relabelfrom", SEPG_DB_SEQUENCE__RELABELFROM}, {"relabelto", SEPG_DB_SEQUENCE__RELABELTO}, {"get_value", SEPG_DB_SEQUENCE__GET_VALUE}, {"next_value", SEPG_DB_SEQUENCE__NEXT_VALUE}, {"set_value", SEPG_DB_SEQUENCE__SET_VALUE}, {NULL, 0UL}, }}, {"db_procedure", SEPG_CLASS_DB_PROCEDURE, { {"create", SEPG_DB_PROCEDURE__CREATE}, {"drop", SEPG_DB_PROCEDURE__DROP}, {"getattr", SEPG_DB_PROCEDURE__GETATTR}, {"setattr", SEPG_DB_PROCEDURE__SETATTR}, {"relabelfrom", SEPG_DB_PROCEDURE__RELABELFROM}, {"relabelto", SEPG_DB_PROCEDURE__RELABELTO}, {"execute", SEPG_DB_PROCEDURE__EXECUTE}, {"entrypoint", SEPG_DB_PROCEDURE__ENTRYPOINT}, {"install", SEPG_DB_PROCEDURE__INSTALL}, {NULL, 0UL}, }}, {"db_column", SEPG_CLASS_DB_COLUMN, { {"create", SEPG_DB_COLUMN__CREATE}, {"drop", SEPG_DB_COLUMN__DROP}, {"getattr", SEPG_DB_COLUMN__GETATTR}, {"setattr", SEPG_DB_COLUMN__SETATTR}, {"relabelfrom", SEPG_DB_COLUMN__RELABELFROM}, {"relabelto", SEPG_DB_COLUMN__RELABELTO}, {"select", SEPG_DB_COLUMN__SELECT}, {"update", SEPG_DB_COLUMN__UPDATE}, {"insert", SEPG_DB_COLUMN__INSERT}, {NULL, 0UL}, }}, {"db_tuple", SEPG_CLASS_DB_TUPLE, { {"relabelfrom", SEPG_DB_TUPLE__RELABELFROM}, {"relabelto", SEPG_DB_TUPLE__RELABELTO}, {"select", SEPG_DB_TUPLE__SELECT}, {"update", SEPG_DB_TUPLE__UPDATE}, {"insert", SEPG_DB_TUPLE__INSERT}, {"delete", SEPG_DB_TUPLE__DELETE}, {NULL, 0UL}, }}, {"db_blob", SEPG_CLASS_DB_BLOB, { {"create", SEPG_DB_BLOB__CREATE}, {"drop", SEPG_DB_BLOB__DROP}, {"getattr", SEPG_DB_BLOB__GETATTR}, {"setattr", SEPG_DB_BLOB__SETATTR}, {"relabelfrom", SEPG_DB_BLOB__RELABELFROM}, {"relabelto", SEPG_DB_BLOB__RELABELTO}, {"read", SEPG_DB_BLOB__READ}, {"write", SEPG_DB_BLOB__WRITE}, {"import", SEPG_DB_BLOB__IMPORT}, {"export", SEPG_DB_BLOB__EXPORT}, {NULL, 0UL}, }}, {"db_language", SEPG_CLASS_DB_LANGUAGE, { {"create", SEPG_DB_LANGUAGE__CREATE}, {"drop", SEPG_DB_LANGUAGE__DROP}, {"getattr", SEPG_DB_LANGUAGE__GETATTR}, {"setattr", SEPG_DB_LANGUAGE__SETATTR}, {"relabelfrom", SEPG_DB_LANGUAGE__RELABELFROM}, {"relabelto", SEPG_DB_LANGUAGE__RELABELTO}, {"implement", SEPG_DB_LANGUAGE__IMPLEMENT}, {"execute", SEPG_DB_LANGUAGE__EXECUTE}, {NULL, 0UL}, }}, {"db_view", SEPG_CLASS_DB_VIEW, { {"create", SEPG_DB_VIEW__CREATE}, {"drop", SEPG_DB_VIEW__DROP}, {"getattr", SEPG_DB_VIEW__GETATTR}, {"setattr", SEPG_DB_VIEW__SETATTR}, {"relabelfrom", SEPG_DB_VIEW__RELABELFROM}, {"relabelto", SEPG_DB_VIEW__RELABELTO}, {"expand", SEPG_DB_VIEW__EXPAND}, {NULL, 0UL}, }}, }; /* * sepgsql_mode * * SEPGSQL_MODE_DISABLED: Disabled on runtime * SEPGSQL_MODE_DEFAULT: Same as system settings * SEPGSQL_MODE_PERMISSIVE: Always permissive mode * SEPGSQL_MODE_INTERNAL: Same as permissive, except for no audit logs */ static int sepgsql_mode = SEPGSQL_MODE_INTERNAL; /* * sepgsql_is_enabled */ bool sepgsql_is_enabled(void) { return (sepgsql_mode != SEPGSQL_MODE_DISABLED ? true : false); } /* * sepgsql_get_mode */ int sepgsql_get_mode(void) { return sepgsql_mode; } /* * sepgsql_set_mode */ int sepgsql_set_mode(int new_mode) { int old_mode = sepgsql_mode; sepgsql_mode = new_mode; return old_mode; } /* * sepgsql_getenforce * * It returns whether the current working mode tries to enforce access * control decision, or not. It shall be enforced when sepgsql_mode is * SEPGSQL_MODE_DEFAULT and system is running in enforcing mode. */ bool sepgsql_getenforce(void) { if (sepgsql_mode == SEPGSQL_MODE_DEFAULT && selinux_status_getenforce() > 0) return true; return false; } /* * sepgsql_audit_log * * It generates a security audit record. In the default, it writes out * audit records into standard PG's logfile. It also allows to set up * external audit log receiver, such as auditd in Linux, using the * sepgsql_audit_hook. * * SELinux can control what should be audited and should not using * "auditdeny" and "auditallow" rules in the security policy. In the * default, all the access violations are audited, and all the access * allowed are not audited. But we can set up the security policy, so * we can have exceptions. So, it is necessary to follow the suggestion * come from the security policy. (av_decision.auditallow and auditdeny) * * Security audit is an important feature, because it enables us to check * what was happen if we have a security incident. In fact, ISO/IEC15408 * defines several security functionalities for audit features. */ void sepgsql_audit_log( bool denied, const char* scontext, const char* tcontext, uint16 tclass, uint32 audited, const char* audit_name) { StringInfoData buf; const char* class_name = NULL; const char* av_name = NULL; int i; /* lookup name of the object class */ Assert(tclass < SEPG_CLASS_MAX); class_name = selinux_catalog[tclass].class_name; /* lookup name of the permissions */ initStringInfo(&buf); appendStringInfo(&buf, "%s {", (denied ? "denied" : "allowed")); for (i = 0; selinux_catalog[tclass].av[i].av_name; i++) { if (audited & (1UL << i)) { av_name = selinux_catalog[tclass].av[i].av_name; appendStringInfo(&buf, " %s", av_name); } } appendStringInfo(&buf, " }"); /* * Call external audit module, if loaded */ appendStringInfo(&buf, " scontext=%s tcontext=%s tclass=%s", scontext, tcontext, class_name); if (audit_name) appendStringInfo(&buf, " name=\"%s\"", audit_name); ereport(LOG, (errmsg("SELinux: %s", buf.data))); } /* * sepgsql_compute_avd * * It actually asks SELinux what permissions are allowed on a pair of * the security contexts and object class. It also returns what permissions * should be audited on access violation or allowed. * In most cases, subject's security context (scontext) is a client, and * target security context (tcontext) is a database object. * * The access control decision shall be set on the given av_decision. * The av_decision.allowed has a bitmask of SEPG___ * to suggest a set of allowed actions in this object class. */ void sepgsql_compute_avd(const char* scontext, const char* tcontext, uint16 tclass, struct av_decision* avd) { const char* tclass_name = NULL; security_class_t tclass_ex; struct av_decision avd_ex; int i, deny_unknown = security_deny_unknown(); /* Get external code of the object class */ Assert(tclass < SEPG_CLASS_MAX); Assert(tclass == selinux_catalog[tclass].class_code); tclass_name = selinux_catalog[tclass].class_name; tclass_ex = string_to_security_class(tclass_name); if (tclass_ex == 0) { /* * If the current security policy does not support permissions * corresponding to database objects, we fill up them with dummy data. * If security_deny_unknown() returns positive value, undefined * permissions should be denied. Otherwise, allowed */ avd->allowed = (security_deny_unknown() > 0 ? 0 : ~0); avd->auditallow = 0U; avd->auditdeny = ~0U; avd->flags = 0; return; } /* * Ask SELinux what is allowed set of permissions on a pair of the * security contexts and the given object class. */ if (security_compute_av_flags_raw( (security_context_t)scontext, (security_context_t)tcontext, tclass_ex, 0, &avd_ex) < 0) ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR), errmsg("SELinux could not compute av_decision: " "scontext=%s tcontext=%s tclass=%s: %m", scontext, tcontext, tclass_name))); /* * SELinux returns its access control decision as a set of permissions * represented in external code which depends on run-time environment. So, * we need to translate it to the internal representation before returning * results for the caller. */ memset(avd, 0, sizeof(struct av_decision)); for (i = 0; selinux_catalog[tclass].av[i].av_name; i++) { access_vector_t av_code_ex; const char* av_name = selinux_catalog[tclass].av[i].av_name; uint32 av_code = selinux_catalog[tclass].av[i].av_code; av_code_ex = string_to_av_perm(tclass_ex, av_name); if (av_code_ex == 0) { /* fill up undefined permissions */ if (!deny_unknown) avd->allowed |= av_code; avd->auditdeny |= av_code; continue; } if (avd_ex.allowed & av_code_ex) avd->allowed |= av_code; if (avd_ex.auditallow & av_code_ex) avd->auditallow |= av_code; if (avd_ex.auditdeny & av_code_ex) avd->auditdeny |= av_code; } return; } /* * sepgsql_compute_create * * It returns a default security context to be assigned on a new database * object. SELinux compute it based on a combination of client, upper object * which owns the new object and object class. * * For example, when a client (staff_u:staff_r:staff_t:s0) tries to create * a new table within a schema (system_u:object_r:sepgsql_schema_t:s0), * SELinux looks-up its security policy. If it has a special rule on the * combination of these security contexts and object class (db_table), * it returns the security context suggested by the special rule. * Otherwise, it returns the security context of schema, as is. * * We expect the caller already applies sanity/validation checks on the * given security context. * * scontext: security context of the subject (mostly, peer process). * tcontext: security context of the upper database object. * tclass: class code (SEPG_CLASS_*) of the new object in creation */ char* sepgsql_compute_create(const char* scontext, const char* tcontext, uint16 tclass) { security_context_t ncontext; security_class_t tclass_ex; const char* tclass_name = NULL; char* result = NULL; /* Get external code of the object class */ Assert(tclass < SEPG_CLASS_MAX); tclass_name = selinux_catalog[tclass].class_name; tclass_ex = string_to_security_class(tclass_name); /* * Ask SELinux what is the default context for the given object class on a * pair of security contexts */ if (security_compute_create_raw((security_context_t)scontext, (security_context_t)tcontext, tclass_ex, &ncontext) < 0) ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR), errmsg("SELinux could not compute a new context: " "scontext=%s tcontext=%s tclass=%s: %m", scontext, tcontext, tclass_name))); /* * libselinux returns malloc()'ed string, so we need to copy it on the * palloc()'ed region. */ PG_TRY(); { result = pstrdup(ncontext); } PG_CATCH(); { freecon(ncontext); PG_RE_THROW(); } PG_END_TRY(); freecon(ncontext); return result; } /* * sepgsql_check_perms * * It makes access control decision without userspace caching mechanism. * If SELinux denied the required accesses on the pair of security labels, * it raises an error or returns false. * * scontext: security label of the subject (mostly, peer process) * tcontext: security label of the object being referenced * tclass: class code (SEPG_CLASS_*) of the object being referenced * required: a mask of required permissions (SEPG___) * audit_name: a human readable object name for audit logs, or NULL. * abort: true, if caller wants to raise an error on access violation */ bool sepgsql_check_perms( const char* scontext, const char* tcontext, uint16 tclass, uint32 required, const char* audit_name, bool abort) { struct av_decision avd; uint32 denied; uint32 audited; bool result = true; sepgsql_compute_avd(scontext, tcontext, tclass, &avd); denied = required & ~avd.allowed; if (sepgsql_get_debug_audit()) audited = (denied ? denied : required); else audited = (denied ? (denied & avd.auditdeny) : (required & avd.auditallow)); if (denied && sepgsql_getenforce() > 0 && (avd.flags & SELINUX_AVD_FLAGS_PERMISSIVE) == 0) result = false; /* * It records a security audit for the request, if needed. But, when * SE-PgSQL performs 'internal' mode, it needs to keep silent. */ if (audited && sepgsql_mode != SEPGSQL_MODE_INTERNAL) { sepgsql_audit_log(denied, scontext, tcontext, tclass, audited, audit_name); } if (!result && abort) ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), errmsg("SELinux: security policy violation"))); return result; }