ldap_get_dn, ldap_explode_dn, ldap_explode_rdn, ldap_dn2ufn − LDAP DN handling routines


OpenLDAP LDAP (libldap, −lldap)


#include <ldap.h>

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 )


These routines allow LDAP entry names (Distinguished Names, or DNs) to be obtained, parsed, converted to a user-friendly form, and tested. A DN has the form described in RFC 4414 "Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names".

The ldap_get_dn() routine takes an entry as returned by ldap_first_entry(3) or ldap_next_entry(3) and returns a copy of the entry’s DN. Space for the DN will be obtained dynamically and should be freed by the caller using ldap_memfree(3).

ldap_str2dn() parses a string representation of a distinguished name contained in str into its components, which are stored in dn as ldap_ava structures, arranged in LDAPAVA, LDAPRDN, and LDAPDN terms. Space for dn will be obtained dynamically and should be freed by the caller using ldap_dnfree(3). The LDAPDN is defined as:

typedef struct ldap_ava {
char *la_attr;
struct berval *la_value;
unsigned la_flags;


The attribute types and the attribute values are not normalized. The la_flags can be either LDAP_AVA_STRING or LDAP_AVA_BINARY, the latter meaning that the value is BER/DER encoded and thus must be represented as, quoting from RFC 4514, " ... an octothorpe character (’#’ ASCII 35) followed by the hexadecimal representation of each of the bytes of the BER encoding of the X.500 AttributeValue." The flags parameter to ldap_str2dn() can be




which defines what DN syntax is expected (according to RFC 4514, RFC 1779 and DCE, respectively). The format can be ORed to the flags





The latter is a shortcut for all the previous limitations.

LDAP_DN_P_NO_SPACES does not allow extra spaces in the dn; the default is to silently eliminate spaces around AVA separators (’=’), RDN component separators (’+’ for LDAPv3/LDAPv2 or ’,’ for DCE) and RDN separators (’,’ LDAPv3/LDAPv2 or ’/’ for DCE).

LDAP_DN_P_NO_SPACE_AFTER_RDN does not allow a single space after RDN separators.

ldap_dn2str() performs the inverse operation, yielding in str a string representation of dn. It allows the same values for flags as ldap_str2dn(), plus



for user-friendly naming (RFC 1781) and AD canonical.

The following routines are viewed as deprecated in favor of ldap_str2dn() and ldap_dn2str(). They are provided to support legacy applications.

The ldap_explode_dn() routine takes a DN as returned by ldap_get_dn() and breaks it up into its component parts. Each part is known as a Relative Distinguished Name, or RDN. ldap_explode_dn() returns a NULL-terminated array, each component of which contains an RDN from the DN. The notypes parameter is used to request that only the RDN values be returned, not their types. For example, the DN "cn=Bob, c=US" would return as either { "cn=Bob", "c=US", NULL } or { "Bob", "US", NULL }, depending on whether notypes was 0 or 1, respectively. Assertion values in RDN strings may included escaped characters. The result can be freed by calling ldap_value_free(3).

Similarly, the ldap_explode_rdn() routine takes an RDN as returned by ldap_explode_dn(dn,0) and breaks it up into its "type=value" component parts (or just "value", if the notypes parameter is set). Note the value is not unescaped. The result can be freed by calling ldap_value_free(3).

ldap_dn2ufn() is used to turn a DN as returned by ldap_get_dn(3) into a more user-friendly form, stripping off all type names. See "Using the Directory to Achieve User Friendly Naming" (RFC 1781) for more details on the UFN format. Due to the ambiguous nature of the format, it is generally only used for display purposes. The space for the UFN returned is obtained dynamically and the user is responsible for freeing it via a call to ldap_memfree(3).

ldap_dn2dcedn() is used to turn a DN as returned by ldap_get_dn(3) into a DCE-style DN, e.g. a string with most-significant to least significant rdns separated by slashes (’/’); rdn components are separated by commas (’,’). Only printable chars (e.g. LDAPv2 printable string) are allowed, at least in this implementation. ldap_dcedn2dn() performs the opposite operation. ldap_dn2ad_canonical() turns a DN into a AD canonical name, which is basically a DCE dn with attribute types omitted. The trailing domain, if present, is turned in a DNS-like domain. The space for the returned value is obtained dynamically and the user is responsible for freeing it via a call to ldap_memfree(3).


If an error occurs in ldap_get_dn(), NULL is returned and the ld_errno field in the ld parameter is set to indicate the error. See ldap_error(3) for a description of possible error codes. ldap_explode_dn(), ldap_explode_rdn(), ldap_dn2ufn(), ldap_dn2dcedn(), ldap_dcedn2dn(), and ldap_dn2ad_canonical() will return NULL with errno(3) set appropriately in case of trouble.


These routines dynamically allocate memory that the caller must free.


ldap(3), ldap_error(3), ldap_first_entry(3), ldap_memfree(3), ldap_value_free(3)


OpenLDAP Software is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>. OpenLDAP Software is derived from University of Michigan LDAP 3.3 Release.

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