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diff sk-ecdsa.c @ 1855:35d504d59c05

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Implement server-side support for sk-ecdsa U2F-backed keys (#142) * Implement server-side support for sk-ecdsa U2F-backed keys * Fix out-of-bounds read on normal ecdsa-sha2-[identifier] keys * Fix one more potential out-of-bounds read * Check if nistp256 curve is used in sk-ecdsa-sha2- key It's the only allowed curve per PROTOCOL.u2f specification * Implement server-side support for sk-ed25519 FIDO2-backed keys * Keys with type sk-* make no sense as host keys, so they should be disabled * fix typo * Make sk-ecdsa call buf_ecdsa_verify This reduces code duplication, the SK code just handles the different message format. * Reduce sk specific code The application id can be stored in signkey, then we don't need to call sk-specific functions from svr-authpubkey * Remove debugging output, which causes compilation errors with DEBUG_TRACE disabled * Proper cleanup of sk_app Co-authored-by: Matt Johnston <[email protected]>
author egor-duda <egor-duda@users.noreply.github.com>
date Sat, 22 Jan 2022 16:53:04 +0300
parents
children 333688ec53d0
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sk-ecdsa.c	Sat Jan 22 16:53:04 2022 +0300
@@ -0,0 +1,47 @@
+#include "includes.h"
+
+#if DROPBEAR_SK_ECDSA
+
+#include "dbutil.h"
+#include "ecc.h"
+#include "ecdsa.h"
+#include "sk-ecdsa.h"
+
+int buf_sk_ecdsa_verify(buffer *buf, const ecc_key *key, const buffer *data_buf, const char* app, unsigned int applen) {
+	hash_state hs;
+	unsigned char subhash[SHA256_HASH_SIZE];
+	buffer *sk_buffer = NULL, *sig_buffer = NULL;
+	unsigned char flags;
+	unsigned int counter;
+	int ret;
+
+	TRACE(("buf_sk_ecdsa_verify"))
+
+	/* from https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.u2f */
+	/* ecdsa signature to verify (r, s) */
+	sig_buffer = buf_getbuf(buf);
+
+	flags = buf_getbyte (buf);
+	counter = buf_getint (buf);
+	/* create the message to be signed */
+	sk_buffer = buf_new (2*SHA256_HASH_SIZE+5);
+	sha256_init (&hs);
+	sha256_process (&hs, app, applen);
+	sha256_done (&hs, subhash);
+	buf_putbytes (sk_buffer, subhash, sizeof (subhash));
+	buf_putbyte (sk_buffer, flags);
+	buf_putint (sk_buffer, counter);
+	sha256_init (&hs);
+	sha256_process (&hs, data_buf->data, data_buf->len);
+	sha256_done (&hs, subhash);
+	buf_putbytes (sk_buffer, subhash, sizeof (subhash));
+
+	ret = buf_ecdsa_verify(sig_buffer, key, sk_buffer);
+	buf_free(sk_buffer);
+	buf_free(sig_buffer);
+
+	TRACE(("leave buf_sk_ecdsa_verify, ret=%d", ret))
+	return ret;
+}
+
+#endif /* DROPBEAR_SK_ECDSA */