Not sure how much coffee I was lacking when I did this, but clearly
using ASN1_tag2str() is quite wrong.

Index: mft.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/mft.c,v
diff -u -p -r1.116 mft.c
--- mft.c	24 May 2024 12:57:20 -0000	1.116
+++ mft.c	11 Jun 2024 07:38:38 -0000
@@ -367,7 +367,7 @@ mft_parse_econtent(const char *fn, struc
 	if (OBJ_obj2nid(mft_asn1->fileHashAlg) != NID_sha256) {
 		warnx("%s: RFC 6486 section 4.2.1: fileHashAlg: "
 		    "want SHA256 object, have %s (NID %d)", fn,
-		    ASN1_tag2str(OBJ_obj2nid(mft_asn1->fileHashAlg)),
+		    nid2str(OBJ_obj2nid(mft_asn1->fileHashAlg)),
 		    OBJ_obj2nid(mft_asn1->fileHashAlg));
 		goto out;
 	}
Index: rsc.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/rsc.c,v
diff -u -p -r1.34 rsc.c
--- rsc.c	21 Feb 2024 09:17:06 -0000	1.34
+++ rsc.c	11 Jun 2024 07:38:26 -0000
@@ -254,7 +254,7 @@ rsc_check_digesttype(const char *fn, str
 
 	if ((nid = OBJ_obj2nid(obj)) != NID_sha256) {
 		warnx("%s: RSC DigestAlgorithmIdentifier: want SHA256, have %s"
-		    " (NID %d)", fn, ASN1_tag2str(nid), nid);
+		    " (NID %d)", fn, nid2str(nid), nid);
 		return 0;
 	}