Lightweight Directory Access Protocol

LDAP definiert eine Schnittstelle für den Zugriff auf hierarchisch organisierte und verteilt gespeicherte Verzeichnisse. Häufig werden dort Benutzerdaten abgelegt, zum Beispiel in Microsofts Active Directory.

Beispiel

Anmelden und wieder abmelden

#include <ldap.h>

int
main (int argc, char * argv[])
{
	char        * user = "cn=admin";
	char        * pass = "secret";
	LDAP        * conn = NULL;
	struct berval cred = { .bv_val = (char *) pass,
	                       .bv_len = strlen  (pass) };
	ldap_initialize  (&conn, "ldap://localhost");
	ldap_sasl_bind_s (conn, user, LDAP_SASL_SIMPLE, &cred, NULL, NULL, NULL);
	/* … */
	ldap_unbind_ext_s (conn, NULL, NULL);
	return 0;
}

Bibliothek installieren

apt install libldap2-dev

Übersetzen und binden mit:

gcc -g -Wall -lldap -o ldap ldap.c

API-Referenz

struct ldap_url_desc
char *	ldap_strdup	(const char * p)
void *	ldap_memalloc	(ber_len_t s)
void *	ldap_memcalloc	(ber_len_t n, ber_len_t s)
void *	ldap_memrealloc	(void * p, ber_len_t s)
void	ldap_memfree	(void * p)
void	ldap_memvfree	(void ** v)
char *	lud_scheme	ldap	Schema
char *	lud_host	durmstrang	Hostname
int	lud_port	384	Portnummer
char *	lud_dn	dc=illusioni,dc=de	Suchbasis
char **	lud_attrs	NULL	Attribute
int	lud_scope	NULL	LDAP_SCOPE_…
char *	lud_filter	NULL	Suchfilter
char **	lud_exts	NULL	Erweiterungen
int	lud_crit_exts	false	Kritische Erweiterung
int	ldap_is_ldap_url	(const char * url)
int	ldap_url_parse	(const char * url,
		LDAPURLDesc ** lud)
void	ldap_free_urldesc	(LDAPURLDesc * lud)
struct ldapmsg
char *	ldap_get_dn	(LDAP * ld, LDAPMessage * entry)
int	ldap_str2dn	(const char * str,
		LDAPDN * dn, unsigned flags)
void	ldap_dnfree	(LDAPDN dn)
int	ldap_dn2str	(LDAPDN dn,
		char ** str, unsigned flags)
char **	ldap_explode_dn	(const char * dn, int notypes)
char **	ldap_explode_rdn	(const char * rdn, int notypes)
char *	ldap_dn2ufn	(const char * dn)
char *	ldap_dn2dcedn	(const char * dn)
char *	ldap_dcedn2dn	(const char * dn)
char *	ldap_dn2ad_canonical	(const char * dn)
char *	ldap_err2string	(int err)
struct ldapcontrol
char *	ldctl_oid
struct berval	ldctl_value
char	ldctl_iscritical
int	ldap_result	(LDAP * ld, int msgid, int all,
		struct timeval * timeout,
		LDAPMessage ** result)
int	ldap_abandon_ext	(LDAP * ld, int msgid,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls)

Mit Server verbinden

int	ldap_initialize	(LDAP ** ld, char * uri)
int	ldap_simple_bind_s	(LDAP * ld, const char * who, const char * passwd)
int	ldap_sasl_bind	(LDAP * ld, const char * dn, const char * mechanism,
		struct berval * cred,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[], int * msgid)
int	ldap_sasl_bind_s	(LDAP * ld, const char * dn, const char * mechanism,
		struct berval * cred,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[],
		struct berval ** servercred)
int	ldap_sasl_interactive_bind_s	(LDAP * ld, const char * dn, const char * mechs,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[],
		unsigned flags,
		LDAP_SASL_INTERACT_PROC * interact,
		void * defaults)
int	ldap_sasl_interactive_bind	(LDAP * ld, const char * dn, const char * mechs,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[],
		unsigned flags,
		LDAP_SASL_INTERACT_PROC * interact,
		void * defaults,
		LDAPMessage * result,
		const char ** rmech, int * msgid)
int	ldap_parse_sasl_bind_result	(LDAP * ld, LDAPMessage * res,
		struct berval ** servercred, int freeit)
int	(LDAP_SASL_INTERACT_PROC)	(LDAP * ld, unsigned flags, void * defaults, void * sasl_interact)
int	ldap_unbind	(LDAP * ld)
int	ldap_unbind_s	(LDAP * ld)
int	ldap_unbind_ext	(LDAP * ld,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[])
int	ldap_unbind_ext_s	(LDAP * ld,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[])

Einträge suchen

Das Hilfsprogramm ldapsearch sucht und filtert Einträge. Die C-Schnittstelle verpackt Einträge in denopalen Datentyp LDAPMessage und bietet Iteratoren über die Attribute und die Werte innerhalb eines Attributs.

int	ldap_search_ext	(LDAP * ld, char * base, int scope,
		char * filter,
		char * attrs[],
		int attrsonly,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		struct timeval * timeout,
		int sizelimit,
		int * msgid)
int	ldap_search_ext_s	(LDAP * ld, char * base, int scope,
		char * filter,
		char * attrs[],
		int attrsonly,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		struct timeval * timeout,
		int sizelimit,
		LDAPMessage ** res)
int	ldap_count_entries	(LDAP * ld, LDAPMessage * result)
LDAPMessage *	ldap_first_entry	(LDAP * ld, LDAPMessage * result)
LDAPMessage *	ldap_next_entry	(LDAP * ld, LDAPMessage * entry)
char *	ldap_first_attribute	(LDAP * ld, LDAPMessage * entry, BerElement ** ber)
char *	ldap_next_attribute	(LDAP * ld, LDAPMessage * entry, BerElement * ber)
int	ldap_count_values	(char ** vals)
int	ldap_count_values_len	(struct berval ** vals)
void	ldap_value_free	(char ** vals)
void	ldap_value_free_len	(struct berval ** vals)
char **	ldap_get_values	(LDAP * ld, LDAPMessage * entry, char * attr)
struct berval **	ldap_get_values_len	(LDAP * ld, LDAPMessage * entry, char * attr)
int	ldap_msgfree	(LDAPMessage * msg)
int	ldap_msgtype	(LDAPMessage * msg)
int	ldap_msgid	(LDAPMessage * msg)

Einträge modifizieren

Das Hilfsprogramm ldapmodify verarbeitet Dateien im LDIF-Format, um Einträge zu modifizieren.

dn: Dn
changetype: modify
delete: Type
-
add: Type
Type: Value
-
replace: Type
Type: Value

Die C-Schnittstelle verwendet dazu eine verkettete Liste von Modifikator-Objekten.

struct ldapmod
int	mod_op
char *	mod_type
struct ldapmod *	mod_next
union mod_vals
char **	modv_strvals
struct berval **	modv_bvals
int	ldap_add_ext	(LDAP * ld, const char * dn,
		LDAPMod ** attrs,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		int * msgid)
int	ldap_add_ext_s	(LDAP * ld, const char * dn,
		LDAPMod ** attrs,
		LDAPControl * sctrls,
		LDAPControl * cctrls)
int	ldap_modify_ext	(LDAP * ld, char * dn,
		LDAPMod * mods[],
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		int * msgid)
int	ldap_modify_ext_s	(LDAP * ld, char * dn,
		LDAPMod * mods[],
		LDAPControl ** sctrls,
		LDAPControl ** cctrls)
void	ldap_mods_free	(LDAPMod ** mods,
		int freemods)
int	ldap_delete	(LDAP * ld, char * dn)
int	ldap_delete_s	(LDAP * ld, char * dn)
int	ldap_delete_ext	(LDAP * ld, char * dn,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		int * msgid)
int	ldap_delete_ext_s	(LDAP * ld, char * dn,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls)
int	ldap_rename	(LDAP * ld, const char * dn,
		const char * newrdn,
		const char * newparent,
		int deleteoldrdn,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[],
		int * msgid)
int	ldap_rename_s	(LDAP * ld, const char * dn,
		const char * newrdn,
		const char * newparent,
		int deleteoldrdn,
		LDAPControl * sctrls[],
		LDAPControl * cctrls[])
int	ldap_compare_ext	(LDAP * ld, char * dn, char * attr,
		const struct berval * bvalue,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		int * msgid)
int	ldap_compare_ext_s	(LDAP * ld, char * dn, char * attr,
		const struct berval * bvalue,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls)
int	ldap_extended_operation	(LDAP * ld, const char * requestoid,
		const struct berval * requestdata,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		int * msgid)
int	ldap_extended_operation_s	(LDAP * ld, const char * requestoid,
		const struct berval * requestdata,
		LDAPControl ** sctrls,
		LDAPControl ** cctrls,
		char ** retoid,
		struct berval ** retdata)

Binärdaten kodieren

struct berval
ber_len_t	bv_len
char *	bv_val
void	ber_bvfree	(struct berval * bv)
void	ber_bvecfree	(struct berval ** bvec)
void	ber_bvecadd	(struct berval *** bvec, struct berval * bv)
void	ber_bvarray_free	(struct berval * bvarray)
void	ber_bvarray_add	(BerVarray * bvarray, BerValue * bv)
struct berval *	ber_bvdup	(const struct berval * bv)
struct berval *	ber_dupbv	(const struct berval * dst, struct berval * src)
struct berval *	ber_bvstr	(const char * str)
struct berval *	ber_bvstrdup	(const char * str)
struct berval *	ber_str2bv	(const char * str, ber_len_t len, int dup, struct berval * bv)
BerElement *	ber_alloc_t	(int options)
BerElement *	ber_init	(struct berval * bv)
void	ber_init2	(BerElement * ber, struct berval * bv, int options)
void	ber_free	(BerElement * ber, int freebuf)
Kodierung
int	ber_flush	(Sockbuf * sb, BerElement * ber, int freeit)
int	ber_flush2	(Sockbuf * sb, BerElement * ber, int freeit)
int	ber_printf	(BerElement * ber, const char * fmt, ...)
int	ber_put_int	(BerElement * ber, ber_int_t num, ber_tag_t tag)
int	ber_put_enum	(BerElement * ber, ber_int_t num, ber_tag_t tag)
int	ber_put_ostring	(BerElement * ber, const char * str, ber_len_t len, ber_tag_t tag)
int	ber_put_string	(BerElement * ber, const char * str, ber_tag_t tag)
int	ber_put_null	(BerElement * ber, ber_tag_t tag)
int	ber_put_boolean	(BerElement * ber, ber_int_t bool, ber_tag_t tag)
int	ber_put_bitstring	(BerElement * ber, const char * str, ber_len_t blen, ber_tag_t tag)
int	ber_start_seq	(BerElement * ber, ber_tag_t tag)
int	ber_start_set	(BerElement * ber, ber_tag_t tag)
int	ber_put_seq	(BerElement * ber)
Dekodierung
ber_tag_t	ber_get_next	(Sockbuf * sb, ber_len_t * len, BerElement * ber)
ber_tag_t	ber_skip_tag	(BerElement * ber, ber_len_t * len)
ber_tag_t	ber_peek_tag	(BerElement * ber, ber_len_t * len)
ber_tag_t	ber_scanf	(BerElement * ber, const char * fmt, ...)
ber_tag_t	ber_get_int	(BerElement * ber, ber_int_t * num)
ber_tag_t	ber_get_enum	(BerElement * ber, ber_int_t * num)
ber_tag_t	ber_get_stringb	(BerElement * ber, char * buf, ber_len_t * len)
ber_tag_t	ber_get_stringa	(BerElement * ber, char ** buf)
ber_tag_t	ber_get_stringal	(BerElement * ber, struct berval ** bv)
ber_tag_t	ber_get_stringbv	(BerElement * ber, struct berval * bv, int alloc)
ber_tag_t	ber_get_null	(BerElement * ber)
ber_tag_t	ber_get_boolean	(BerElement * ber, ber_int_t * bool)
ber_tag_t	ber_get_bitstringa	(BerElement * ber, char ** buf, ber_len_t * blen)
ber_tag_t	ber_first_element	(BerElement * ber, ber_len_t * len, char ** cookie)
ber_tag_t	ber_next_element	(BerElement * ber, ber_len_t * len, const char * cookie)

Unterbau anbinden

Backend be
Connection conn
Operation op
Ava { char * ava_type; berval ava_value; }
Filter

Literatur

OpenLDAP
RFC 4510–4519: LDAP Technical Specification Road Map, 2006

LDAP_MOD_ADD	Hinzufügen
LDAP_MOD_REPLACE	Ändern
LDAP_MOD_DELETE	Löschen