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X509_NAME_GET_INDEX_BY_NID(3) Library Functions Manual X509_NAME_GET_INDEX_BY_NID(3)

X509_NAME_get_index_by_NID, X509_NAME_get_index_by_OBJ, X509_NAME_entry_count, X509_NAME_get_entry, X509_NAME_get_text_by_NID, X509_NAME_get_text_by_OBJX509_NAME lookup and enumeration functions

#include <openssl/x509.h>

X509_NAME_get_index_by_NID(X509_NAME *name, int nid, int lastpos);

X509_NAME_get_index_by_OBJ(X509_NAME *name, ASN1_OBJECT *obj, int lastpos);

X509_NAME_entry_count(X509_NAME *name);

X509_NAME_get_entry(X509_NAME *name, int loc);

X509_NAME_get_text_by_NID(X509_NAME *name, int nid, char *buf, int len);

X509_NAME_get_text_by_OBJ(X509_NAME *name, ASN1_OBJECT *obj, char *buf, int len);

These functions allow an X509_NAME structure to be examined. The X509_NAME structure is the same as the ASN.1 Name type defined in RFC 2459 (and elsewhere) and used, for example, in certificate subject and issuer names.

() and () retrieve the next index matching nid or obj after lastpos. lastpos should initially be set to -1. If there are no more entries, -1 is returned. If nid is invalid (doesn't correspond to a valid OID), -2 is returned.

() returns the total number of entries in name.

() retrieves the X509_NAME_ENTRY from name corresponding to index loc. Acceptable values for loc run from 0 to X509_NAME_entry_count(name) - 1. The value returned is an internal pointer which must not be freed.

() and () retrieve the "text" from the first entry in name which matches nid or obj. If no such entry exists, -1 is returned. At most len bytes will be written and the text written to buf will be NUL terminated. The length of the output string written is returned excluding the terminating NUL. If buf is NULL then the amount of space needed in buf (excluding the final NUL) is returned.

All relevant NID_* and OBJ_* codes can be found in the header files <openssl/obj_mac.h> and <openssl/objects.h>.

Applications which could pass invalid NIDs to () should check for the return value of -2. Alternatively the NID validity can be determined first by checking that (nid) is not NULL.

X509_NAME_get_index_by_NID() and X509_NAME_get_index_by_OBJ() return the index of the next matching entry or -1 if not found.

X509_NAME_entry_count() returns the total number of entries.

X509_NAME_get_entry() returns an X509_NAME pointer to the requested entry or NULL if the index is invalid.

Process all entries:

int i;

for (i = 0; i < X509_NAME_entry_count(nm); i++) {
	e = X509_NAME_get_entry(nm, i);
	/* Do something with e */

Process all commonName entries:

int lastpos = -1;

for (;;) {
	lastpos = X509_NAME_get_index_by_NID(nm, NID_commonName, lastpos);
	if (lastpos == -1)
	e = X509_NAME_get_entry(nm, lastpos);
	/* Do something with e */

d2i_X509_NAME(3), ERR_get_error(3), X509_NAME_new(3)

X509_NAME_get_text_by_NID() and X509_NAME_get_text_by_OBJ() are legacy functions which have various limitations which make them of minimal use in practice. They can only find the first matching entry and will copy the contents of the field verbatim: this can be highly confusing if the target is a multicharacter string type like a BMPString or a UTF8String.

For a more general solution, X509_NAME_get_index_by_NID() or X509_NAME_get_index_by_OBJ() should be used, followed by X509_NAME_get_entry() on any matching indices and then the various X509_NAME_ENTRY utility functions on the result.

December 25, 2016 OpenBSD-6.1