From 07c32fb3da0731570508e519e4cfaaaaf646ccfb Mon Sep 17 00:00:00 2001
From: Ori Bernstein <ori@eigenstate.org>
Date: Sun, 18 Jul 2021 15:30:35 +0000
Subject: [PATCH] auth/rsa2jwk: add code to produce jwk rsa keys

This is useful for acmed, and possibly other web
technologies.
---
 sys/src/cmd/auth/mkfile    |  5 ++-
 sys/src/cmd/auth/rsa2jwk.c | 87 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+), 2 deletions(-)
 create mode 100644 sys/src/cmd/auth/rsa2jwk.c

diff --git a/sys/src/cmd/auth/mkfile b/sys/src/cmd/auth/mkfile
index bf5dbff2d..a3a9bcd68 100644
--- a/sys/src/cmd/auth/mkfile
+++ b/sys/src/cmd/auth/mkfile
@@ -26,6 +26,7 @@ TARG=\
 	readnvram\
 	rsa2asn1\
 	rsa2csr\
+	rsa2jwk\
 	rsa2pub\
 	rsa2ssh\
 	rsa2x509\
@@ -106,10 +107,10 @@ nuke:V:
 	rm -f *.[$OS] *.[$OS].a [$OS].* y.tab.? y.debug y.output $TARG *.acid
 
 $O.%:	$LIB
-$O.rsa2asn1 $O.rsa2ssh $O.rsafill $O.rsa2x509 $O.rsa2pub $O.rsa2csr: rsa2any.$O
+$O.rsa2asn1 $O.rsa2ssh $O.rsafill $O.rsa2x509 $O.rsa2pub $O.rsa2csr $O.rsa2jwk: rsa2any.$O
 $O.authsrv $O.guard.srv: secureidcheck.$O
 
-rsa2asn1.$O rsa2ssh.$O rsafill.$O rsa2x509.$O rsa2pub.$O rsa2csr.$O: rsa2any.h
+rsa2asn1.$O rsa2ssh.$O rsafill.$O rsa2x509.$O rsa2pub.$O rsa2csr.$O rsa2jwk.$O: rsa2any.h
 
 $BIN/netkey:V:	$O.netkey
 	cp $O.netkey /$objtype/bin/netkey
diff --git a/sys/src/cmd/auth/rsa2jwk.c b/sys/src/cmd/auth/rsa2jwk.c
new file mode 100644
index 000000000..606c1473b
--- /dev/null
+++ b/sys/src/cmd/auth/rsa2jwk.c
@@ -0,0 +1,87 @@
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+#include <mp.h>
+#include <libsec.h>
+#include "rsa2any.h"
+
+#define between(x,min,max)	(((min-1-x) & (x-max-1))>>8)
+
+int
+encurl64chr(int o)
+{
+	int c;
+
+	c  = between(o,  0, 25) & ('A'+o);
+	c |= between(o, 26, 51) & ('a'+(o-26));
+	c |= between(o, 52, 61) & ('0'+(o-52));
+	c |= between(o, 62, 62) & ('-');
+	c |= between(o, 63, 63) & ('_');
+	return c;
+}
+
+char*
+encurl64(void *in, int n)
+{
+	int lim;
+	char *out, *p;
+
+	lim = 4*n/3 + 5;
+	if((out = malloc(lim)) == nil)
+		sysfatal("malloc: %r");
+	enc64x(out, lim, in, n, encurl64chr);
+	if((p = strchr(out, '=')) != nil)
+		*p = 0;
+	return out;
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: auth/rsa2pub [file]\n");
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	uchar nbuf[8192], ebuf[512];
+	char *nstr, *estr;
+	RSApriv *k;
+	int nlen, elen;
+
+	fmtinstall('[', encodefmt);
+	quotefmtinstall();
+
+	ARGBEGIN{
+	default:
+		usage();
+	}ARGEND
+
+	if(argc > 1)
+		usage();
+
+	if((k = getrsakey(argc, argv, 0, nil)) == nil)
+		sysfatal("%r");
+
+	nlen = (mpsignif(k->pub.n)+7)/8;
+	if(nlen >= sizeof(nbuf))
+		sysfatal("key too big");
+	mptobe(k->pub.n, nbuf, nlen, nil);
+	nstr = encurl64(nbuf, nlen);
+
+	elen = (mpsignif(k->pub.ek)+7)/8;
+	if(elen >= sizeof(ebuf))
+		sysfatal("key too big");
+	mptobe(k->pub.ek, ebuf, elen, nil);
+	estr = encurl64(ebuf, elen);
+
+	print(
+		"{"
+		"\"kty\": \"RSA\","
+		"\"n\": \"%s\","
+		"\"e\": \"%s\""
+		"}\n",
+		nstr, estr);
+	exits(nil);
+}