3 files changed, 29 insertions, 14 deletions

diff --git a/PROTOCOL.u2f b/PROTOCOL.u2f
index a587480be..bd60f9fac 100644
--- a/PROTOCOL.u2f
+++ b/PROTOCOL.u2f
@@ -138,7 +138,7 @@ The signature returned from U2F hardware takes the following format:
 For use in the SSH protocol, we wish to avoid server-side parsing of ASN.1
 format data in the pre-authentication attack surface. Therefore, the
 signature format used on the wire in SSH2_USERAUTH_REQUEST packets will
-be reformatted slightly:
+be reformatted slightly and the ecdsa_signature_blob value has the encoding:
 
         mpint           r
         mpint           s
@@ -184,6 +184,10 @@ The middleware library need only expose a handful of functions:
         /* Flags */
         #define SSH_SK_USER_PRESENCE_REQD       0x01
 
+        /* Algs */
+        #define SSH_SK_ECDSA                   0x00
+        #define SSH_SK_ED25519                 0x01
+
         struct sk_enroll_response {
                 uint8_t *public_key;
                 size_t public_key_len;
@@ -208,12 +212,12 @@ The middleware library need only expose a handful of functions:
         uint32_t sk_api_version(void);
 
         /* Enroll a U2F key (private key generation) */
-        int sk_enroll(const uint8_t *challenge, size_t challenge_len,
+        int sk_enroll(int alg, const uint8_t *challenge, size_t challenge_len,
             const char *application, uint8_t flags,
             struct sk_enroll_response **enroll_response);
 
         /* Sign a challenge */
-        int sk_sign(const uint8_t *message, size_t message_len,
+        int sk_sign(int alg, const uint8_t *message, size_t message_len,
             const char *application,
             const uint8_t *key_handle, size_t key_handle_len,
             uint8_t flags, struct sk_sign_response **sign_response);
diff --git a/sk-api.h b/sk-api.h
index 2af0ef6f0..5ada30a3d 100644
--- a/sk-api.h
+++ b/sk-api.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sk-api.h,v 1.1 2019/10/31 21:16:20 djm Exp $ */
+/* $OpenBSD: sk-api.h,v 1.2 2019/11/12 19:32:30 markus Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -26,6 +26,10 @@
 /* Flags */
 #define SSH_SK_USER_PRESENCE_REQD       0x01
 
+/* Algs */
+#define SSH_SK_ECDSA                    0x00
+#define SSH_SK_ED25519                  0x01
+
 struct sk_enroll_response {
         uint8_t *public_key;
         size_t public_key_len;
@@ -46,19 +50,19 @@ struct sk_sign_response {
         size_t sig_s_len;
 };
 
-#define SSH_SK_VERSION_MAJOR            0x00010000 /* current API version */
+#define SSH_SK_VERSION_MAJOR            0x00020000 /* current API version */
 #define SSH_SK_VERSION_MAJOR_MASK       0xffff0000
 
 /* Return the version of the middleware API */
 uint32_t sk_api_version(void);
 
 /* Enroll a U2F key (private key generation) */
-int sk_enroll(const uint8_t *challenge, size_t challenge_len,
+int sk_enroll(int alg, const uint8_t *challenge, size_t challenge_len,
     const char *application, uint8_t flags,
     struct sk_enroll_response **enroll_response);
 
 /* Sign a challenge */
-int sk_sign(const uint8_t *message, size_t message_len,
+int sk_sign(int alg, const uint8_t *message, size_t message_len,
     const char *application, const uint8_t *key_handle, size_t key_handle_len,
     uint8_t flags, struct sk_sign_response **sign_response);
 
diff --git a/ssh-sk.c b/ssh-sk.c
index 43f808efc..a9da765eb 100644
--- a/ssh-sk.c
+++ b/ssh-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk.c,v 1.6 2019/11/12 19:31:45 markus Exp $ */
+/* $OpenBSD: ssh-sk.c,v 1.7 2019/11/12 19:32:30 markus Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -49,12 +49,12 @@ struct sshsk_provider {
         uint32_t (*sk_api_version)(void);
 
         /* Enroll a U2F key (private key generation) */
-        int (*sk_enroll)(const uint8_t *challenge, size_t challenge_len,
-            const char *application, uint8_t flags,
+        int (*sk_enroll)(int alg, const uint8_t *challenge,
+            size_t challenge_len, const char *application, uint8_t flags,
             struct sk_enroll_response **enroll_response);
 
         /* Sign a challenge */
-        int (*sk_sign)(const uint8_t *message, size_t message_len,
+        int (*sk_sign)(int alg, const uint8_t *message, size_t message_len,
             const char *application,
             const uint8_t *key_handle, size_t key_handle_len,
             uint8_t flags, struct sk_sign_response **sign_response);
@@ -243,13 +243,17 @@ sshsk_enroll(int type, const char *provider_path, const char *application,
         size_t challenge_len;
         struct sk_enroll_response *resp = NULL;
         int r = SSH_ERR_INTERNAL_ERROR;
+        int alg;
 
         *keyp = NULL;
         if (attest)
                 sshbuf_reset(attest);
         switch (type) {
         case KEY_ECDSA_SK:
+                alg = SSH_SK_ECDSA;
+                break;
         case KEY_ED25519_SK:
+                alg = SSH_SK_ED25519;
                 break;
         default:
                 error("%s: unsupported key type", __func__);
@@ -287,7 +291,7 @@ sshsk_enroll(int type, const char *provider_path, const char *application,
         }
         /* XXX validate flags? */
         /* enroll key */
-        if ((r = skp->sk_enroll(challenge, challenge_len, application,
+        if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
             flags, &resp)) != 0) {
                 error("Security key provider %s returned failure %d",
                     provider_path, r);
@@ -427,7 +431,7 @@ sshsk_sign(const char *provider_path, const struct sshkey *key,
 {
         struct sshsk_provider *skp = NULL;
         int r = SSH_ERR_INTERNAL_ERROR;
-        int type;
+        int type, alg;
         struct sk_sign_response *resp = NULL;
         struct sshbuf *inner_sig = NULL, *sig = NULL;
         uint8_t message[32];
@@ -439,7 +443,10 @@ sshsk_sign(const char *provider_path, const struct sshkey *key,
         type = sshkey_type_plain(key->type);
         switch (type) {
         case KEY_ECDSA_SK:
+                alg = SSH_SK_ECDSA;
+                break;
         case KEY_ED25519_SK:
+                alg = SSH_SK_ED25519;
                 break;
         default:
                 return SSH_ERR_INVALID_ARGUMENT;
@@ -462,7 +469,7 @@ sshsk_sign(const char *provider_path, const struct sshkey *key,
                 r = SSH_ERR_INTERNAL_ERROR;
                 goto out;
         }
-        if ((r = skp->sk_sign(message, sizeof(message),
+        if ((r = skp->sk_sign(alg, message, sizeof(message),
             key->sk_application,
             sshbuf_ptr(key->sk_key_handle), sshbuf_len(key->sk_key_handle),
             key->sk_flags, &resp)) != 0) {