sepgsql_contexts (5) - Linux Manuals

sepgsql_contexts: userspace SELinux labeling interface and configuration file format for the RDBMS objects context backend

NAME

selabel_db - userspace SELinux labeling interface and configuration file format for the RDBMS objects context backend

SYNOPSIS

#include <selinux/label.h>

int selabel_lookup(struct selabel_handle *hnd, char **context,
const char *object_name, int object_type);

int selabel_lookup_raw(struct selabel_handle *hnd, char **context,
const char *object_name, int object_type);

DESCRIPTION

The DB contexts backend maps from a pair of object name and class into security contexts. It is used to find the appropriate context for database objects when relabeling a certain database. The returned context must be freed using freecon(3).
selabel_lookup(3) describes the function with its return and error codes.

The object_name should be a fully qualified name using the hierarchy of database objects. For example, the pg_class table in the postgres database and pg_catalog schema should be qualified as:

Bpostgres.pg_catalog.pg_class

The NOTES section has further information on database support for namespace hierarchies.

The object_type argument should be set to one of the following values:

SELABEL_DB_DATABASE

The object_name argument specifies the name of a database itself, such as "postgres".

SELABEL_DB_SCHEMA

The object_name argument specifies the name of a schema object, such as "postgres.public".

SELABEL_DB_TABLE

The object_name argument specifies the name of a table object, such as "postgres.public.my_table"

SELABEL_DB_COLUMN

The object_name argument specifies the name of a column object, such as "postgres.public.my_table.user_id"

SELABEL_DB_TUPLE

The object_name argument specifies the name of a table object which contains the tuples to be relabeled, such as "postgresql.public.my_table". Note that we have no way to identify individual tuple objects, except for WHERE clause on DML statements, because it has no name.

SELABEL_DB_PROCEDURE

The object_name argument specifies the name of a procedure object, such as "postgres.public.my_func". Note that we don't support lookup of individual security contexts for procedures which have the same name but different arguments.

SELABEL_DB_SEQUENCE

The object_name argument specifies the name of a sequence object, such as "postgres.public.my_seq".

SELABEL_DB_BLOB

The object_name argument specifies the name of a large object, such as "postgres.16308". Note that a large object does not have a name, so it is identified by its identifier value.

SELABEL_DB_VIEW

The object_name argument specifies the name of a view object, such as "postgres.public.my_view".

SELABEL_DB_LANGUAGE

The object_name argument specifies the name of a language object, such as "postgres.public.tcl".

SELABEL_DB_EXCEPTION

The object_name argument specifies the name of a exception object.

SELABEL_DB_DATATYPE

The object_name argument specifies the name of a type or domain object, such as postgres.public.my_type.

Any messages generated by selabel_lookup(3) are sent to stderr by default, although this can be changed by selinux_set_callback(3).

selabel_lookup_raw(3) behaves identically to selabel_lookup(3) but does not perform context translation.

The FILES section details the configuration files used to determine the database object context.

OPTIONS

In addition to the global options described in selabel_open(3), this backend recognizes the following options:

SELABEL_OPT_PATH

A non-null value for this option specifies a path to a file that will be opened in lieu of the standard DB contexts file. It tries to open the specfile designed for SE-PostgreSQL as default, so if another RDBMS uses this interface, it needs to give an explicit specfile designed for that RDBMS (see the FILES section for details).

FILES

The database context file used to retrieve a context depends on the SELABEL_OPT_PATH parameter passed to selabel_open(3). If NULL, then the SELABEL_OPT_PATH value will default to the active policy database contexts location (as returned by selinux_sepgsql_context_path(3)), otherwise the actual SELABEL_OPT_PATH value specified is used (this option must be used to support databases other than SE-PostgreSQL).

The default database object contexts file is:

/etc/selinux/{SELINUXTYPE}/contexts/sepgsql_context

Where {SELINUXTYPE} is the entry from the selinux configuration file config (see selinux_config(5)).

The entries within the database contexts file are shown in the Object Name String Values and FILE FORMAT sections.

Object Name String Values

The string name assigned to each object_type argument that can be present in the database contexts file are:

object_type	Text Name
SELABEL_DB_DATABASE	db_database
SELABEL_DB_SCHEMA	db_schema
SELABEL_DB_VIEW	db_view
SELABEL_DB_LANGUAGE	db_language
SELABEL_DB_TABLE	db_table
SELABEL_DB_COLUMN	db_column
SELABEL_DB_TUPLE	db_tuple
SELABEL_DB_PROCEDURE	db_procedure
SELABEL_DB_SEQUENCE	db_sequence
SELABEL_DB_BLOB	db_blob
SELABEL_DB_EXCEPTION	db_exception
SELABEL_DB_DATATYPE	db_datatype

FILE FORMAT

Each line within the database contexts file is as follows:

object_type object_name context

Where:

object_type

This is the string representation of the object type shown in the Object Name String Values section.

object_name

The key used to obtain the context based on the object_type.

The entry can contain '*' for wildcard matching or '?' for substitution.

Note that if the '*' is used, then be aware that the order of entries in the file is important. The '*' on its own is used to ensure a default fallback context is assigned and should be the last entry in the object_type block.

context

The security context that will be applied to the object.

The following example is for SE-PostgreSQL:

# ./contexts/sepgsql_contexts file
# object_type object_name context
db_database my_database system_u:object_r:sepgsql_db_t:s0
db_database * system_u:object_r:sepgsql_db_t:s0
db_schema *.* system_u:object_r:sepgsql_schema_t:s0
db_tuple row_low system_u:object_r:sepgsql_table_t:s0
db_tuple row_high system_u:object_r:sepgsql_table_t:s0:c1023
db_tuple *.*.* system_u:object_r:sepgsql_table_t:s0

NOTES

1.

A suitable database contexts file needs to be written for the target RDBMS and the SELABEL_OPT_PATH option must be used in selabel_open(3) to load it.

2.

The hierarchy of the namespace for database objects depends on the RDBMS, however the selabel* interfaces do not have any specific support for a namespace hierarchy.

SE-PostgreSQL has a namespace hierarchy where a database is the top level object with the schema being the next level. Under the schema object there can be other types of objects such as tables and procedures. This hierarchy is supported as follows:

If a security context is required for "my_table" table in the "public" schema within the "postgres" database, then the selabel_lookup(3) parameters for object_type would be SELABEL_DB_TABLE and the object_name would be "postgres.public.my_table", the security context (if available), would be returned in context.

3.

If contexts are to be validated, then the global option SELABEL_OPT_VALIDATE must be set before calling selabel_open(3). If this is not set, then it is possible for an invalid context to be returned.