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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_OBJ — X509_NAME lookup and enumeration functions

#include <openssl/x509.h>

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

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

int
X509_NAME_entry_count(const X509_NAME *name);

X509_NAME_ENTRY *
X509_NAME_get_entry(const X509_NAME *name, int loc);

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

int
X509_NAME_get_text_by_OBJ(X509_NAME *name, const 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.

() retrieves the X509_NAME_ENTRY from name corresponding to index loc. Acceptable values for loc run from 0 to (name) - 1.

() and () retrieve the "text" from the first entry in name which matches nid or obj. At most len bytes will be written and the text written to buf will be NUL terminated. If buf is NULL, nothing is written, but the return value is calculated as usual.

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

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() returns the index of the next matching entry, -1 if not found, or -2 if the nid does not correspond to a valid OID.

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

X509_NAME_entry_count() returns the total number of entries in name.

X509_NAME_get_entry() returns an internal pointer which must not be freed by the caller or NULL if the index is invalid.

X509_NAME_get_text_by_NID() and X509_NAME_get_text_by_OBJ() return the length of the output string written, not counting the terminating NUL, or -1 if no match is found.

In some cases of failure of X509_NAME_get_index_by_NID() and X509_NAME_get_text_by_NID(), the reason can be determined with ERR_get_error(3).

Process all entries:

int i;
X509_NAME_ENTRY *e;

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;
X509_NAME_ENTRY *e;

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

d2i_X509_NAME(3), X509_NAME_ENTRY_get_object(3), X509_NAME_new(3)

These functions first appeared in SSLeay 0.8.0 and have been available since OpenBSD 2.4.

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.

July 2, 2022 OpenBSD-7.3