postgresql/contrib/sepgsql/label.c
2012-06-10 15:20:04 -04:00

936 lines
23 KiB
C

/* -------------------------------------------------------------------------
*
* contrib/sepgsql/label.c
*
* Routines to support SELinux labels (security context)
*
* Copyright (c) 2010-2012, PostgreSQL Global Development Group
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/genam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/pg_attribute.h"
#include "catalog/pg_class.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_proc.h"
#include "commands/dbcommands.h"
#include "commands/seclabel.h"
#include "libpq/auth.h"
#include "libpq/libpq-be.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/tqual.h"
#include "sepgsql.h"
#include <selinux/label.h>
/*
* Saved hook entries (if stacked)
*/
static ClientAuthentication_hook_type next_client_auth_hook = NULL;
static needs_fmgr_hook_type next_needs_fmgr_hook = NULL;
static fmgr_hook_type next_fmgr_hook = NULL;
/*
* client_label_*
*
* security label of the database client. Initially the client security label
* is equal to client_label_peer, and can be changed by one or more calls to
* sepgsql_setcon(), and also be temporarily overridden during execution of a
* trusted-procedure.
*
* sepgsql_setcon() is a transaction-aware operation; a (sub-)transaction
* rollback should also rollback the current client security label. Therefore
* we use the list client_label_pending of pending_label to keep track of which
* labels were set during the (sub-)transactions.
*/
static char *client_label_peer = NULL; /* set by getpeercon(3) */
static List *client_label_pending = NIL; /* pending list being set by
* sepgsql_setcon() */
static char *client_label_committed = NULL; /* set by sepgsql_setcon(),
* and already committed */
static char *client_label_func = NULL; /* set by trusted procedure */
typedef struct
{
SubTransactionId subid;
char *label;
} pending_label;
/*
* sepgsql_get_client_label
*
* Returns the current security label of the client. All code should use this
* routine to get the current label, instead of referring to the client_label_*
* variables above.
*/
char *
sepgsql_get_client_label(void)
{
/* trusted procedure client label override */
if (client_label_func)
return client_label_func;
/* uncommitted sepgsql_setcon() value */
if (client_label_pending)
{
pending_label *plabel = llast(client_label_pending);
if (plabel->label)
return plabel->label;
}
else if (client_label_committed)
return client_label_committed; /* set by sepgsql_setcon() committed */
/* default label */
Assert(client_label_peer != NULL);
return client_label_peer;
}
/*
* sepgsql_set_client_label
*
* This routine tries to switch the current security label of the client, and
* checks related permissions. The supplied new label shall be added to the
* client_label_pending list, then saved at transaction-commit time to ensure
* transaction-awareness.
*/
static void
sepgsql_set_client_label(const char *new_label)
{
const char *tcontext;
MemoryContext oldcxt;
pending_label *plabel;
/* Reset to the initial client label, if NULL */
if (!new_label)
tcontext = client_label_peer;
else
{
if (security_check_context_raw((security_context_t) new_label) < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_NAME),
errmsg("SELinux: invalid security label: \"%s\"",
new_label)));
tcontext = new_label;
}
/* Check process:{setcurrent} permission. */
sepgsql_avc_check_perms_label(sepgsql_get_client_label(),
SEPG_CLASS_PROCESS,
SEPG_PROCESS__SETCURRENT,
NULL,
true);
/* Check process:{dyntransition} permission. */
sepgsql_avc_check_perms_label(tcontext,
SEPG_CLASS_PROCESS,
SEPG_PROCESS__DYNTRANSITION,
NULL,
true);
/*
* Append the supplied new_label on the pending list until the current
* transaction is committed.
*/
oldcxt = MemoryContextSwitchTo(CurTransactionContext);
plabel = palloc0(sizeof(pending_label));
plabel->subid = GetCurrentSubTransactionId();
if (new_label)
plabel->label = pstrdup(new_label);
client_label_pending = lappend(client_label_pending, plabel);
MemoryContextSwitchTo(oldcxt);
}
/*
* sepgsql_xact_callback
*
* A callback routine of transaction commit/abort/prepare. Commmit or abort
* changes in the client_label_pending list.
*/
static void
sepgsql_xact_callback(XactEvent event, void *arg)
{
if (event == XACT_EVENT_COMMIT)
{
if (client_label_pending != NIL)
{
pending_label *plabel = llast(client_label_pending);
char *new_label;
if (plabel->label)
new_label = MemoryContextStrdup(TopMemoryContext,
plabel->label);
else
new_label = NULL;
if (client_label_committed)
pfree(client_label_committed);
client_label_committed = new_label;
/*
* XXX - Note that items of client_label_pending are allocated on
* CurTransactionContext, thus, all acquired memory region shall
* be released implicitly.
*/
client_label_pending = NIL;
}
}
else if (event == XACT_EVENT_ABORT)
client_label_pending = NIL;
}
/*
* sepgsql_subxact_callback
*
* A callback routine of sub-transaction start/abort/commit. Releases all
* security labels that are set within the sub-transaction that is aborted.
*/
static void
sepgsql_subxact_callback(SubXactEvent event, SubTransactionId mySubid,
SubTransactionId parentSubid, void *arg)
{
ListCell *cell;
ListCell *prev;
ListCell *next;
if (event == SUBXACT_EVENT_ABORT_SUB)
{
prev = NULL;
for (cell = list_head(client_label_pending); cell; cell = next)
{
pending_label *plabel = lfirst(cell);
next = lnext(cell);
if (plabel->subid == mySubid)
client_label_pending
= list_delete_cell(client_label_pending, cell, prev);
else
prev = cell;
}
}
}
/*
* sepgsql_client_auth
*
* Entrypoint of the client authentication hook.
* It switches the client label according to getpeercon(), and the current
* performing mode according to the GUC setting.
*/
static void
sepgsql_client_auth(Port *port, int status)
{
if (next_client_auth_hook)
(*next_client_auth_hook) (port, status);
/*
* In the case when authentication failed, the supplied socket shall be
* closed soon, so we don't need to do anything here.
*/
if (status != STATUS_OK)
return;
/*
* Getting security label of the peer process using API of libselinux.
*/
if (getpeercon_raw(port->sock, &client_label_peer) < 0)
ereport(FATAL,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: unable to get peer label: %m")));
/*
* Switch the current performing mode from INTERNAL to either DEFAULT or
* PERMISSIVE.
*/
if (sepgsql_get_permissive())
sepgsql_set_mode(SEPGSQL_MODE_PERMISSIVE);
else
sepgsql_set_mode(SEPGSQL_MODE_DEFAULT);
}
/*
* sepgsql_needs_fmgr_hook
*
* It informs the core whether the supplied function is trusted procedure,
* or not. If true, sepgsql_fmgr_hook shall be invoked at start, end, and
* abort time of function invocation.
*/
static bool
sepgsql_needs_fmgr_hook(Oid functionId)
{
ObjectAddress object;
if (next_needs_fmgr_hook &&
(*next_needs_fmgr_hook) (functionId))
return true;
/*
* SELinux needs the function to be called via security_definer wrapper,
* if this invocation will take a domain-transition. We call these
* functions as trusted-procedure, if the security policy has a rule that
* switches security label of the client on execution.
*/
if (sepgsql_avc_trusted_proc(functionId) != NULL)
return true;
/*
* Even if not a trusted-procedure, this function should not be inlined
* unless the client has db_procedure:{execute} permission. Please note
* that it shall be actually failed later because of same reason with
* ACL_EXECUTE.
*/
object.classId = ProcedureRelationId;
object.objectId = functionId;
object.objectSubId = 0;
if (!sepgsql_avc_check_perms(&object,
SEPG_CLASS_DB_PROCEDURE,
SEPG_DB_PROCEDURE__EXECUTE,
SEPGSQL_AVC_NOAUDIT, false))
return true;
return false;
}
/*
* sepgsql_fmgr_hook
*
* It switches security label of the client on execution of trusted
* procedures.
*/
static void
sepgsql_fmgr_hook(FmgrHookEventType event,
FmgrInfo *flinfo, Datum *private)
{
struct
{
char *old_label;
char *new_label;
Datum next_private;
} *stack;
switch (event)
{
case FHET_START:
stack = (void *) DatumGetPointer(*private);
if (!stack)
{
MemoryContext oldcxt;
oldcxt = MemoryContextSwitchTo(flinfo->fn_mcxt);
stack = palloc(sizeof(*stack));
stack->old_label = NULL;
stack->new_label = sepgsql_avc_trusted_proc(flinfo->fn_oid);
stack->next_private = 0;
MemoryContextSwitchTo(oldcxt);
/*
* process:transition permission between old and new label,
* when user tries to switch security label of the client on
* execution of trusted procedure.
*/
if (stack->new_label)
sepgsql_avc_check_perms_label(stack->new_label,
SEPG_CLASS_PROCESS,
SEPG_PROCESS__TRANSITION,
NULL, true);
*private = PointerGetDatum(stack);
}
Assert(!stack->old_label);
if (stack->new_label)
{
stack->old_label = client_label_func;
client_label_func = stack->new_label;
}
if (next_fmgr_hook)
(*next_fmgr_hook) (event, flinfo, &stack->next_private);
break;
case FHET_END:
case FHET_ABORT:
stack = (void *) DatumGetPointer(*private);
if (next_fmgr_hook)
(*next_fmgr_hook) (event, flinfo, &stack->next_private);
if (stack->new_label)
{
client_label_func = stack->old_label;
stack->old_label = NULL;
}
break;
default:
elog(ERROR, "unexpected event type: %d", (int) event);
break;
}
}
/*
* sepgsql_init_client_label
*
* Initializes the client security label and sets up related hooks for client
* label management.
*/
void
sepgsql_init_client_label(void)
{
/*
* Set up dummy client label.
*
* XXX - note that PostgreSQL launches background worker process like
* autovacuum without authentication steps. So, we initialize sepgsql_mode
* with SEPGSQL_MODE_INTERNAL, and client_label with the security context
* of server process. Later, it also launches background of user session.
* In this case, the process is always hooked on post-authentication, and
* we can initialize the sepgsql_mode and client_label correctly.
*/
if (getcon_raw(&client_label_peer) < 0)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: failed to get server security label: %m")));
/* Client authentication hook */
next_client_auth_hook = ClientAuthentication_hook;
ClientAuthentication_hook = sepgsql_client_auth;
/* Trusted procedure hooks */
next_needs_fmgr_hook = needs_fmgr_hook;
needs_fmgr_hook = sepgsql_needs_fmgr_hook;
next_fmgr_hook = fmgr_hook;
fmgr_hook = sepgsql_fmgr_hook;
/* Transaction/Sub-transaction callbacks */
RegisterXactCallback(sepgsql_xact_callback, NULL);
RegisterSubXactCallback(sepgsql_subxact_callback, NULL);
}
/*
* sepgsql_get_label
*
* It returns a security context of the specified database object.
* If unlabeled or incorrectly labeled, the system "unlabeled" label
* shall be returned.
*/
char *
sepgsql_get_label(Oid classId, Oid objectId, int32 subId)
{
ObjectAddress object;
char *label;
object.classId = classId;
object.objectId = objectId;
object.objectSubId = subId;
label = GetSecurityLabel(&object, SEPGSQL_LABEL_TAG);
if (!label || security_check_context_raw((security_context_t) label))
{
security_context_t unlabeled;
if (security_get_initial_context_raw("unlabeled", &unlabeled) < 0)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: failed to get initial security label: %m")));
PG_TRY();
{
label = pstrdup(unlabeled);
}
PG_CATCH();
{
freecon(unlabeled);
PG_RE_THROW();
}
PG_END_TRY();
freecon(unlabeled);
}
return label;
}
/*
* sepgsql_object_relabel
*
* An entrypoint of SECURITY LABEL statement
*/
void
sepgsql_object_relabel(const ObjectAddress *object, const char *seclabel)
{
/*
* validate format of the supplied security label, if it is security
* context of selinux.
*/
if (seclabel &&
security_check_context_raw((security_context_t) seclabel) < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_NAME),
errmsg("SELinux: invalid security label: \"%s\"", seclabel)));
/*
* Do actual permission checks for each object classes
*/
switch (object->classId)
{
case DatabaseRelationId:
sepgsql_database_relabel(object->objectId, seclabel);
break;
case NamespaceRelationId:
sepgsql_schema_relabel(object->objectId, seclabel);
break;
case RelationRelationId:
if (object->objectSubId == 0)
sepgsql_relation_relabel(object->objectId,
seclabel);
else
sepgsql_attribute_relabel(object->objectId,
object->objectSubId,
seclabel);
break;
case ProcedureRelationId:
sepgsql_proc_relabel(object->objectId, seclabel);
break;
default:
elog(ERROR, "unsupported object type: %u", object->classId);
break;
}
}
/*
* TEXT sepgsql_getcon(VOID)
*
* It returns the security label of the client.
*/
PG_FUNCTION_INFO_V1(sepgsql_getcon);
Datum
sepgsql_getcon(PG_FUNCTION_ARGS)
{
char *client_label;
if (!sepgsql_is_enabled())
PG_RETURN_NULL();
client_label = sepgsql_get_client_label();
PG_RETURN_TEXT_P(cstring_to_text(client_label));
}
/*
* BOOL sepgsql_setcon(TEXT)
*
* It switches the security label of the client.
*/
PG_FUNCTION_INFO_V1(sepgsql_setcon);
Datum
sepgsql_setcon(PG_FUNCTION_ARGS)
{
const char *new_label;
if (PG_ARGISNULL(0))
new_label = NULL;
else
new_label = TextDatumGetCString(PG_GETARG_DATUM(0));
sepgsql_set_client_label(new_label);
PG_RETURN_BOOL(true);
}
/*
* TEXT sepgsql_mcstrans_in(TEXT)
*
* It translate the given qualified MLS/MCS range into raw format
* when mcstrans daemon is working.
*/
PG_FUNCTION_INFO_V1(sepgsql_mcstrans_in);
Datum
sepgsql_mcstrans_in(PG_FUNCTION_ARGS)
{
text *label = PG_GETARG_TEXT_P(0);
char *raw_label;
char *result;
if (!sepgsql_is_enabled())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("sepgsql is not enabled")));
if (selinux_trans_to_raw_context(text_to_cstring(label),
&raw_label) < 0)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: could not translate security label: %m")));
PG_TRY();
{
result = pstrdup(raw_label);
}
PG_CATCH();
{
freecon(raw_label);
PG_RE_THROW();
}
PG_END_TRY();
freecon(raw_label);
PG_RETURN_TEXT_P(cstring_to_text(result));
}
/*
* TEXT sepgsql_mcstrans_out(TEXT)
*
* It translate the given raw MLS/MCS range into qualified format
* when mcstrans daemon is working.
*/
PG_FUNCTION_INFO_V1(sepgsql_mcstrans_out);
Datum
sepgsql_mcstrans_out(PG_FUNCTION_ARGS)
{
text *label = PG_GETARG_TEXT_P(0);
char *qual_label;
char *result;
if (!sepgsql_is_enabled())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("sepgsql is not currently enabled")));
if (selinux_raw_to_trans_context(text_to_cstring(label),
&qual_label) < 0)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: could not translate security label: %m")));
PG_TRY();
{
result = pstrdup(qual_label);
}
PG_CATCH();
{
freecon(qual_label);
PG_RE_THROW();
}
PG_END_TRY();
freecon(qual_label);
PG_RETURN_TEXT_P(cstring_to_text(result));
}
/*
* quote_object_names
*
* It tries to quote the supplied identifiers
*/
static char *
quote_object_name(const char *src1, const char *src2,
const char *src3, const char *src4)
{
StringInfoData result;
const char *temp;
initStringInfo(&result);
if (src1)
{
temp = quote_identifier(src1);
appendStringInfo(&result, "%s", temp);
if (src1 != temp)
pfree((void *) temp);
}
if (src2)
{
temp = quote_identifier(src2);
appendStringInfo(&result, ".%s", temp);
if (src2 != temp)
pfree((void *) temp);
}
if (src3)
{
temp = quote_identifier(src3);
appendStringInfo(&result, ".%s", temp);
if (src3 != temp)
pfree((void *) temp);
}
if (src4)
{
temp = quote_identifier(src4);
appendStringInfo(&result, ".%s", temp);
if (src4 != temp)
pfree((void *) temp);
}
return result.data;
}
/*
* exec_object_restorecon
*
* This routine is a helper called by sepgsql_restorecon; it set up
* initial security labels of database objects within the supplied
* catalog OID.
*/
static void
exec_object_restorecon(struct selabel_handle * sehnd, Oid catalogId)
{
Relation rel;
SysScanDesc sscan;
HeapTuple tuple;
char *database_name = get_database_name(MyDatabaseId);
char *namespace_name;
Oid namespace_id;
char *relation_name;
/*
* Open the target catalog. We don't want to allow writable accesses by
* other session during initial labeling.
*/
rel = heap_open(catalogId, AccessShareLock);
sscan = systable_beginscan(rel, InvalidOid, false,
SnapshotNow, 0, NULL);
while (HeapTupleIsValid(tuple = systable_getnext(sscan)))
{
Form_pg_database datForm;
Form_pg_namespace nspForm;
Form_pg_class relForm;
Form_pg_attribute attForm;
Form_pg_proc proForm;
char *objname;
int objtype = 1234;
ObjectAddress object;
security_context_t context;
/*
* The way to determine object name depends on object classes. So, any
* branches set up `objtype', `objname' and `object' here.
*/
switch (catalogId)
{
case DatabaseRelationId:
datForm = (Form_pg_database) GETSTRUCT(tuple);
objtype = SELABEL_DB_DATABASE;
objname = quote_object_name(NameStr(datForm->datname),
NULL, NULL, NULL);
object.classId = DatabaseRelationId;
object.objectId = HeapTupleGetOid(tuple);
object.objectSubId = 0;
break;
case NamespaceRelationId:
nspForm = (Form_pg_namespace) GETSTRUCT(tuple);
objtype = SELABEL_DB_SCHEMA;
objname = quote_object_name(database_name,
NameStr(nspForm->nspname),
NULL, NULL);
object.classId = NamespaceRelationId;
object.objectId = HeapTupleGetOid(tuple);
object.objectSubId = 0;
break;
case RelationRelationId:
relForm = (Form_pg_class) GETSTRUCT(tuple);
if (relForm->relkind == RELKIND_RELATION)
objtype = SELABEL_DB_TABLE;
else if (relForm->relkind == RELKIND_SEQUENCE)
objtype = SELABEL_DB_SEQUENCE;
else if (relForm->relkind == RELKIND_VIEW)
objtype = SELABEL_DB_VIEW;
else
continue; /* no need to assign security label */
namespace_name = get_namespace_name(relForm->relnamespace);
objname = quote_object_name(database_name,
namespace_name,
NameStr(relForm->relname),
NULL);
pfree(namespace_name);
object.classId = RelationRelationId;
object.objectId = HeapTupleGetOid(tuple);
object.objectSubId = 0;
break;
case AttributeRelationId:
attForm = (Form_pg_attribute) GETSTRUCT(tuple);
if (get_rel_relkind(attForm->attrelid) != RELKIND_RELATION)
continue; /* no need to assign security label */
objtype = SELABEL_DB_COLUMN;
namespace_id = get_rel_namespace(attForm->attrelid);
namespace_name = get_namespace_name(namespace_id);
relation_name = get_rel_name(attForm->attrelid);
objname = quote_object_name(database_name,
namespace_name,
relation_name,
NameStr(attForm->attname));
pfree(namespace_name);
pfree(relation_name);
object.classId = RelationRelationId;
object.objectId = attForm->attrelid;
object.objectSubId = attForm->attnum;
break;
case ProcedureRelationId:
proForm = (Form_pg_proc) GETSTRUCT(tuple);
objtype = SELABEL_DB_PROCEDURE;
namespace_name = get_namespace_name(proForm->pronamespace);
objname = quote_object_name(database_name,
namespace_name,
NameStr(proForm->proname),
NULL);
pfree(namespace_name);
object.classId = ProcedureRelationId;
object.objectId = HeapTupleGetOid(tuple);
object.objectSubId = 0;
break;
default:
elog(ERROR, "unexpected catalog id: %u", catalogId);
objname = NULL; /* for compiler quiet */
break;
}
if (selabel_lookup_raw(sehnd, &context, objname, objtype) == 0)
{
PG_TRY();
{
/*
* Check SELinux permission to relabel the fetched object,
* then do the actual relabeling.
*/
sepgsql_object_relabel(&object, context);
SetSecurityLabel(&object, SEPGSQL_LABEL_TAG, context);
}
PG_CATCH();
{
freecon(context);
PG_RE_THROW();
}
PG_END_TRY();
freecon(context);
}
else if (errno == ENOENT)
ereport(WARNING,
(errmsg("SELinux: no initial label assigned for %s (type=%d), skipping",
objname, objtype)));
else
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: could not determine initial security label for %s (type=%d): %m", objname, objtype)));
pfree(objname);
}
systable_endscan(sscan);
heap_close(rel, NoLock);
}
/*
* BOOL sepgsql_restorecon(TEXT specfile)
*
* This function tries to assign initial security labels on all the object
* within the current database, according to the system setting.
* It is typically invoked by sepgsql-install script just after initdb, to
* assign initial security labels.
*
* If @specfile is not NULL, it uses explicitly specified specfile, instead
* of the system default.
*/
PG_FUNCTION_INFO_V1(sepgsql_restorecon);
Datum
sepgsql_restorecon(PG_FUNCTION_ARGS)
{
struct selabel_handle *sehnd;
struct selinux_opt seopts;
/*
* SELinux has to be enabled on the running platform.
*/
if (!sepgsql_is_enabled())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("sepgsql is not currently enabled")));
/*
* Check DAC permission. Only superuser can set up initial security
* labels, like root-user in filesystems
*/
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("SELinux: must be superuser to restore initial contexts")));
/*
* Open selabel_lookup(3) stuff. It provides a set of mapping between an
* initial security label and object class/name due to the system setting.
*/
if (PG_ARGISNULL(0))
{
seopts.type = SELABEL_OPT_UNUSED;
seopts.value = NULL;
}
else
{
seopts.type = SELABEL_OPT_PATH;
seopts.value = TextDatumGetCString(PG_GETARG_DATUM(0));
}
sehnd = selabel_open(SELABEL_CTX_DB, &seopts, 1);
if (!sehnd)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("SELinux: failed to initialize labeling handle: %m")));
PG_TRY();
{
exec_object_restorecon(sehnd, DatabaseRelationId);
exec_object_restorecon(sehnd, NamespaceRelationId);
exec_object_restorecon(sehnd, RelationRelationId);
exec_object_restorecon(sehnd, AttributeRelationId);
exec_object_restorecon(sehnd, ProcedureRelationId);
}
PG_CATCH();
{
selabel_close(sehnd);
PG_RE_THROW();
}
PG_END_TRY();
selabel_close(sehnd);
PG_RETURN_BOOL(true);
}