auth/rsa2asn1: implement private key export with -a flag (thanks kvik)

kvik writes:

I needed to convert the RSA private key that was laying around in
secstore into a format understood by UNIX® tools like SSH.

With asn12rsa(8) we can go from the ASN.1/DER to Plan 9 format, but not
back - so I wrote the libsec function asn1encodeRSApriv(2) and used it in
rsa2asn1(8) by adding the -a flag which causes the full private key to be
encoded and output.

1 files changed, 14 insertions, 4 deletions

diff --git a/sys/src/cmd/auth/rsa2asn1.c b/sys/src/cmd/auth/rsa2asn1.c
index 51f82282e..cf7bfc77d 100644
--- a/sys/src/cmd/auth/rsa2asn1.c
+++ b/sys/src/cmd/auth/rsa2asn1.c
@@ -5,10 +5,12 @@
 #include <libsec.h>
 #include "rsa2any.h"
 
+int privatekey = 0;
+
 void
 usage(void)
 {
-	fprint(2, "usage: auth/rsa2asn1 [file]\n");
+	fprint(2, "usage: auth/rsa2asn1 [-a] [file]\n");
 	exits("usage");
 }
 
@@ -20,6 +22,9 @@ main(int argc, char **argv)
 	int n;
 
 	ARGBEGIN{
+	case 'a':
+		privatekey = 1;
+		break;
 	default:
 		usage();
 	}ARGEND
@@ -27,10 +32,15 @@ main(int argc, char **argv)
 	if(argc > 1)
 		usage();
 
-	if((k = getrsakey(argc, argv, 0, nil)) == nil)
+	if((k = getrsakey(argc, argv, privatekey, nil)) == nil)
 		sysfatal("%r");
-	if((n = asn1encodeRSApub(&k->pub, buf, sizeof(buf))) < 0)
-		sysfatal("asn1encodeRSApub: %r");
+	if(privatekey){
+		if((n = asn1encodeRSApriv(k, buf, sizeof(buf))) < 0)
+			sysfatal("asn1encodeRSApriv: %r");
+	}else{
+		if((n = asn1encodeRSApub(&k->pub, buf, sizeof(buf))) < 0)
+			sysfatal("asn1encodeRSApub: %r");
+	}
 	if(write(1, buf, n) != n)
 		sysfatal("write: %r");
 	exits(nil);