From e9aed242ccf6c569491b34e5455e9ea9b78cd29a Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sun, 20 Jun 2021 23:33:13 +0000
Subject: [PATCH 1/1] libsec: emulate openssl asn1 when generating x509 csr

when trying to request certificates from letsencrypt,
their test api would reject our csr because of
"tuncated sequence" unless we force subectAltName
by passing multiple domains (as comma separated list).

apparently, we need to provide the context specific tag
"cont [ 0 ]" for the extensions even when we do have
any extensions for the csr (triggered when we need to
have subjectAltNames).

for this, we change mkcont() to take a Elist* instead,
which then can be nil when not used. also put the tag
number argument first, which makes it easier to read.
---
 sys/src/libsec/port/x509.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/sys/src/libsec/port/x509.c b/sys/src/libsec/port/x509.c
index 5b4d24952..404d64ff3 100644
--- a/sys/src/libsec/port/x509.c
+++ b/sys/src/libsec/port/x509.c
@@ -2576,9 +2576,9 @@ asn1encodedigest(DigestState* (*fun)(uchar*, ulong, uchar*, DigestState*), uchar
 }
 
 static Elem
-mkcont(Elem e, int num)
+mkcont(int num, Elist *l)
 {
-	e = mkseq(mkel(e, nil));
+	Elem e = mkseq(l);
 	e.tag.class = Context;
 	e.tag.num = num;
 	return e;
@@ -2592,7 +2592,7 @@ mkaltname(char *s)
 
 	for(i=0; i<nelem(DN_oid); i++){
 		if(strstr(s, DN_oid[i].prefix) != nil)
-			return mkcont(mkDN(s), 4); /* DN */
+			return mkcont(4, mkel(mkDN(s), nil)); /* DN */
 	}
 	e = mkstring(s, IA5String);
 	e.tag.class = Context;
@@ -2652,12 +2652,13 @@ mkextensions(char *alts, int req)
 	if((sl = mkaltnames(alts)) != nil)
 		xl = mkextel(mkseq(sl), (Ints*)&oid_subjectAltName, xl);
 	if(xl != nil){
-		if(req) return mkel(mkcont(mkseq(
-			mkel(mkoid((Ints*)&oid_extensionRequest),
-			mkel(mkset(mkel(mkseq(xl), nil)), nil))), 0), nil);
-		return mkel(mkcont(mkseq(xl), 3), nil);
+		xl = mkel(mkseq(xl), nil);
+		if(req)
+			xl = mkel(mkseq(
+				mkel(mkoid((Ints*)&oid_extensionRequest),
+				mkel(mkset(xl), nil))), nil);
 	}
-	return nil;
+	return xl;
 }
 
 static char*
@@ -2763,7 +2764,7 @@ X509rsagen(RSApriv *priv, char *subj, ulong valid[2], int *certlen)
 	alts = splitalts(subj);
 
 	e = mkseq(
-		mkel(mkcont(mkint(2), 0),
+		mkel(mkcont(0, mkel(mkint(2), nil)),
 		mkel(mkint(serial),
 		mkel(mkalg(sigalg),
 		mkel(mkDN(subj),
@@ -2776,7 +2777,7 @@ X509rsagen(RSApriv *priv, char *subj, ulong valid[2], int *certlen)
 			mkel(mkalg(ALG_rsaEncryption),
 			mkel(mkbits(pkbytes->data, pkbytes->len),
 			nil))),
-		mkextensions(alts, 0)))))))));
+		mkel(mkcont(3, mkextensions(alts, 0)), nil)))))))));
 	freebytes(pkbytes);
 	if(encode(e, &certinfobytes) != ASN_OK)
 		goto errret;
@@ -2842,7 +2843,7 @@ X509rsareq(RSApriv *priv, char *subj, int *certlen)
 			mkel(mkalg(ALG_rsaEncryption),
 			mkel(mkbits(pkbytes->data, pkbytes->len),
 			nil))),
-		mkextensions(alts, 1)))));
+		mkel(mkcont(0, mkextensions(alts, 1)), nil)))));
 	freebytes(pkbytes);
 	if(encode(e, &certinfobytes) != ASN_OK)
 		goto errret;
-- 
2.44.0