Add minimal manpage documenting the misnamed X509V3_EXT_get_nid()

This avoids a dangling reference in i2s_ASN1_ENUMERATED_TABLE.
To complete this manual, someone will need to document X509V3_EXT_METHOD,
but that's for a much more rainy day than today.

2 files changed, 92 insertions, 2 deletions

diff --git a/lib/libcrypto/man/X509V3_EXT_get_nid.3 b/lib/libcrypto/man/X509V3_EXT_get_nid.3
new file mode 100644
index 00000000000..657db0e61e0
--- /dev/null
+++ b/lib/libcrypto/man/X509V3_EXT_get_nid.3
@@ -0,0 +1,89 @@
+.\" $OpenBSD: X509V3_EXT_get_nid.3,v 1.1 2024/05/12 11:49:47 tb Exp $
+.\"
+.\" Copyright (c) 2024 Theo Buehler <tb@openbsd.org>
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.Dd $Mdocdate: May 12 2024 $
+.Dt X509V3_EXT_GET_NID 3
+.Os
+.Sh NAME
+.Nm X509V3_EXT_get_nid ,
+.Nm X509V3_EXT_get
+.Nd retrieve X.509v3 certificate extension methods
+.Sh SYNOPSIS
+.In openssl/x509v3.h
+.Ft const X509V3_EXT_METHOD *
+.Fo X509V3_EXT_get_nid
+.Fa "int nid"
+.Fc
+.Ft const X509V3_EXT_METHOD *
+.Fo X509V3_EXT_get
+.Fa "X509_EXTENSION *ext"
+.Fc
+.Sh DESCRIPTION
+An X.509v3 certificate extension contains an Object Identifier (OID),
+a boolean criticality indicator, and an opaque extension value
+.Vt ASN1_OCTET_STRING
+whose meaning is determined by the OID.
+The library's
+.Vt X509V3_EXT_METHOD
+type,
+which is not yet documented in detail,
+contains a numeric identifier to represent the OID and various
+handlers for encoding, decoding, printing, and configuring the
+extension's value.
+Criticality is handled separately, for example as an argument to
+.Xr X509V3_add1_i2d 3 .
+.Sh RETURN VALUES
+.Fn X509V3_EXT_get_nid
+returns the
+.Vt X509V3_EXT_METHOD
+corresponding to the numeric identifier
+.Fa nid ,
+or
+.Dv NULL
+if there is none.
+.Pp
+.Fn X509V3_EXT_get
+returns the built-in
+.Vt X509V3_EXT_METHOD
+associated with the extension type of
+.Fa ext ,
+or
+.Dv NULL
+if there is none.
+.Sh SEE ALSO
+.Xr i2s_ASN1_ENUMERATED_TABLE 3 ,
+.Xr OBJ_create 3 ,
+.Xr X509_EXTENSION_get_object 3 ,
+.Xr X509V3_get_d2i 3
+.Sh STANDARDS
+RFC 5280: Internet X.509 Public Key Infrastructure Certificate and
+Certificate Revocation List (CRL) Profile
+.Bl -dash -compact
+.It
+section 4.2: Certificate Extensions
+.El
+.Sh HISTORY
+These functions first appeared in OpenSSL 0.9.2b and
+have been available since
+.Ox 2.6 .
+.Sh CAVEATS
+LibreSSL only supports built-in extension methods.
+Other implementations have incomplete support for custom extension methods,
+whose API is not threadsafe, does not affect the behavior of
+.Xr X509_verify_cert 3 ,
+and has various other surprising quirks.
+If custom extensions were added, both functions will prefer them
+over built-in methods.
diff --git a/lib/libcrypto/man/X509_EXTENSION_set_object.3 b/lib/libcrypto/man/X509_EXTENSION_set_object.3
index dcfe075ebdd..3f6c7709a5c 100644
--- a/lib/libcrypto/man/X509_EXTENSION_set_object.3
+++ b/lib/libcrypto/man/X509_EXTENSION_set_object.3
@@ -1,4 +1,4 @@
-.\" $OpenBSD: X509_EXTENSION_set_object.3,v 1.17 2023/04/30 19:40:23 tb Exp $
+.\" $OpenBSD: X509_EXTENSION_set_object.3,v 1.18 2024/05/12 11:49:47 tb Exp $
 .\" full merge up to: OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
 .\"
 .\" This file is a derived work.
@@ -65,7 +65,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 .\" OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: April 30 2023 $
+.Dd $Mdocdate: May 12 2024 $
 .Dt X509_EXTENSION_SET_OBJECT 3
 .Os
 .Sh NAME
@@ -297,6 +297,7 @@ pointer.
 .Xr X509_check_issued 3 ,
 .Xr X509_get_extension_flags 3 ,
 .Xr X509_REQ_add_extensions 3 ,
+.Xr X509V3_EXT_get_nid 3 ,
 .Xr X509V3_EXT_print 3 ,
 .Xr X509V3_extensions_print 3 ,
 .Xr X509V3_get_d2i 3 ,