upstream: improve the error message for u2f enrollment errors by

making ssh-keygen be solely responsible for printing the error message and
convertint some more common error responses from the middleware to a useful
ssherr.h status code. more detail remains visible via -v of course.

also remove indepedent copy of sk-api.h declarations in sk-usbhid.c
and just include it.

feedback & ok markus@

OpenBSD-Commit-ID: a4a8ffa870d9a3e0cfd76544bcdeef5c9fb1f1bb

8 files changed, 43 insertions, 81 deletions

diff --git a/PROTOCOL.u2f b/PROTOCOL.u2f
index fd0cd0de0..58f75ba28 100644
--- a/PROTOCOL.u2f
+++ b/PROTOCOL.u2f
@@ -249,6 +249,7 @@ The middleware library need only expose a handful of functions:
         #define SSH_SK_ERR_GENERAL              -1
         #define SSH_SK_ERR_UNSUPPORTED          -2
         #define SSH_SK_ERR_PIN_REQUIRED         -3
+        #define SSH_SK_ERR_DEVICE_NOT_FOUND     -4
 
         struct sk_enroll_response {
                 uint8_t *public_key;
diff --git a/sk-api.h b/sk-api.h
index 93d6a1229..170fd4470 100644
--- a/sk-api.h
+++ b/sk-api.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sk-api.h,v 1.7 2020/01/06 02:00:46 djm Exp $ */
+/* $OpenBSD: sk-api.h,v 1.8 2020/01/25 23:13:09 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -36,6 +36,7 @@
 #define SSH_SK_ERR_GENERAL              -1
 #define SSH_SK_ERR_UNSUPPORTED          -2
 #define SSH_SK_ERR_PIN_REQUIRED         -3
+#define SSH_SK_ERR_DEVICE_NOT_FOUND     -4
 
 struct sk_enroll_response {
         uint8_t *public_key;
diff --git a/sk-usbhid.c b/sk-usbhid.c
index cf783e205..2148e1d79 100644
--- a/sk-usbhid.c
+++ b/sk-usbhid.c
@@ -37,9 +37,19 @@
 #include <fido/credman.h>
 
 #ifndef SK_STANDALONE
-#include "log.h"
-#include "xmalloc.h"
-#endif
+# include "log.h"
+# include "xmalloc.h"
+/*
+ * If building as part of OpenSSH, then rename exported functions.
+ * This must be done before including sk-api.h.
+ */
+# define sk_api_version         ssh_sk_api_version
+# define sk_enroll              ssh_sk_enroll
+# define sk_sign                ssh_sk_sign
+# define sk_load_resident_keys  ssh_sk_load_resident_keys
+#endif /* !SK_STANDALONE */
+
+#include "sk-api.h"
 
 /* #define SK_DEBUG 1 */
 
@@ -54,63 +64,6 @@
         } while (0)
 #endif
 
-#define SK_VERSION_MAJOR        0x00040000 /* current API version */
-
-/* Flags */
-#define SK_USER_PRESENCE_REQD           0x01
-#define SK_USER_VERIFICATION_REQD       0x04
-#define SK_RESIDENT_KEY                 0x20
-
-/* Algs */
-#define SK_ECDSA                0x00
-#define SK_ED25519              0x01
-
-/* Error codes */
-#define SSH_SK_ERR_GENERAL              -1
-#define SSH_SK_ERR_UNSUPPORTED          -2
-#define SSH_SK_ERR_PIN_REQUIRED         -3
-
-struct sk_enroll_response {
-        uint8_t *public_key;
-        size_t public_key_len;
-        uint8_t *key_handle;
-        size_t key_handle_len;
-        uint8_t *signature;
-        size_t signature_len;
-        uint8_t *attestation_cert;
-        size_t attestation_cert_len;
-};
-
-struct sk_sign_response {
-        uint8_t flags;
-        uint32_t counter;
-        uint8_t *sig_r;
-        size_t sig_r_len;
-        uint8_t *sig_s;
-        size_t sig_s_len;
-};
-
-struct sk_resident_key {
-        uint32_t alg;
-        size_t slot;
-        char *application;
-        struct sk_enroll_response key;
-};
-
-struct sk_option {
-        char *name;
-        char *value;
-        uint8_t required;
-};
-
-/* If building as part of OpenSSH, then rename exported functions */
-#if !defined(SK_STANDALONE)
-#define sk_api_version          ssh_sk_api_version
-#define sk_enroll               ssh_sk_enroll
-#define sk_sign                 ssh_sk_sign
-#define sk_load_resident_keys   ssh_sk_load_resident_keys
-#endif
-
 /* Return the version of the middleware API */
 uint32_t sk_api_version(void);
 
@@ -161,7 +114,7 @@ skdebug(const char *func, const char *fmt, ...)
 uint32_t
 sk_api_version(void)
 {
-        return SK_VERSION_MAJOR;
+        return SSH_SK_VERSION_MAJOR;
 }
 
 /* Select the first identified FIDO device attached to the system */
@@ -426,10 +379,10 @@ pack_public_key(uint32_t alg, const fido_cred_t *cred,
 {
         switch(alg) {
 #ifdef WITH_OPENSSL
-        case SK_ECDSA:
+        case SSH_SK_ECDSA:
                 return pack_public_key_ecdsa(cred, response);
 #endif /* WITH_OPENSSL */
-        case SK_ED25519:
+        case SSH_SK_ED25519:
                 return pack_public_key_ed25519(cred, response);
         default:
                 return -1;
@@ -441,6 +394,7 @@ fidoerr_to_skerr(int fidoerr)
 {
         switch (fidoerr) {
         case FIDO_ERR_UNSUPPORTED_OPTION:
+        case FIDO_ERR_UNSUPPORTED_ALGORITHM:
                 return SSH_SK_ERR_UNSUPPORTED;
         case FIDO_ERR_PIN_REQUIRED:
         case FIDO_ERR_PIN_INVALID:
@@ -516,11 +470,11 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
         *enroll_response = NULL;
         switch(alg) {
 #ifdef WITH_OPENSSL
-        case SK_ECDSA:
+        case SSH_SK_ECDSA:
                 cose_alg = COSE_ES256;
                 break;
 #endif /* WITH_OPENSSL */
-        case SK_ED25519:
+        case SSH_SK_ED25519:
                 cose_alg = COSE_EDDSA;
                 break;
         default:
@@ -528,6 +482,7 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
                 goto out;
         }
         if (device == NULL && (device = pick_first_device()) == NULL) {
+                ret = SSH_SK_ERR_DEVICE_NOT_FOUND;
                 skdebug(__func__, "pick_first_device failed");
                 goto out;
         }
@@ -546,7 +501,7 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
                     fido_strerr(r));
                 goto out;
         }
-        if ((r = fido_cred_set_rk(cred, (flags & SK_RESIDENT_KEY) != 0 ?
+        if ((r = fido_cred_set_rk(cred, (flags & SSH_SK_RESIDENT_KEY) != 0 ?
             FIDO_OPT_TRUE : FIDO_OPT_OMIT)) != FIDO_OK) {
                 skdebug(__func__, "fido_cred_set_rk: %s", fido_strerr(r));
                 goto out;
@@ -717,10 +672,10 @@ pack_sig(uint32_t  alg, fido_assert_t *assert,
 {
         switch(alg) {
 #ifdef WITH_OPENSSL
-        case SK_ECDSA:
+        case SSH_SK_ECDSA:
                 return pack_sig_ecdsa(assert, response);
 #endif /* WITH_OPENSSL */
-        case SK_ED25519:
+        case SSH_SK_ED25519:
                 return pack_sig_ed25519(assert, response);
         default:
                 return -1;
@@ -804,7 +759,7 @@ sk_sign(uint32_t alg, const uint8_t *message, size_t message_len,
                 goto out;
         }
         if ((r = fido_assert_set_up(assert,
-            (flags & SK_USER_PRESENCE_REQD) ?
+            (flags & SSH_SK_USER_PRESENCE_REQD) ?
             FIDO_OPT_TRUE : FIDO_OPT_FALSE)) != FIDO_OK) {
                 skdebug(__func__, "fido_assert_set_up: %s", fido_strerr(r));
                 goto out;
@@ -951,15 +906,15 @@ read_rks(const char *devpath, const char *pin,
 
                         switch (fido_cred_type(cred)) {
                         case COSE_ES256:
-                                srk->alg = SK_ECDSA;
+                                srk->alg = SSH_SK_ECDSA;
                                 break;
                         case COSE_EDDSA:
-                                srk->alg = SK_ED25519;
+                                srk->alg = SSH_SK_ED25519;
                                 break;
                         default:
                                 skdebug(__func__, "unsupported key type %d",
                                     fido_cred_type(cred));
-                                goto out;
+                                goto out; /* XXX free rk and continue */
                         }
 
                         if ((r = pack_public_key(srk->alg, cred,
diff --git a/ssh-keygen.c b/ssh-keygen.c
index 29013a20f..8df55f2c2 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.393 2020/01/25 23:02:13 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.394 2020/01/25 23:13:09 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -3579,7 +3579,7 @@ main(int argc, char **argv)
                         if (r == 0)
                                 break;
                         if (r != SSH_ERR_KEY_WRONG_PASSPHRASE)
-                                exit(1); /* error message already printed */
+                                fatal("Key enrollment failed: %s", ssh_err(r));
                         if (passphrase != NULL)
                                 freezero(passphrase, strlen(passphrase));
                         passphrase = read_passphrase("Enter PIN for security "
diff --git a/ssh-sk-helper.c b/ssh-sk-helper.c
index a4be9d369..2f93ad716 100644
--- a/ssh-sk-helper.c
+++ b/ssh-sk-helper.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk-helper.c,v 1.8 2020/01/10 23:43:26 djm Exp $ */
+/* $OpenBSD: ssh-sk-helper.c,v 1.9 2020/01/25 23:13:09 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -63,7 +63,7 @@ reply_error(int r, char *fmt, ...)
         va_start(ap, fmt);
         xvasprintf(&msg, fmt, ap);
         va_end(ap);
-        error("%s: %s", __progname, msg);
+        debug("%s: %s", __progname, msg);
         free(msg);
 
         if (r >= 0)
diff --git a/ssh-sk.c b/ssh-sk.c
index 3f5eed62d..a8d4de832 100644
--- a/ssh-sk.c
+++ b/ssh-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk.c,v 1.24 2020/01/06 02:00:47 djm Exp $ */
+/* $OpenBSD: ssh-sk.c,v 1.25 2020/01/25 23:13:09 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -338,6 +338,8 @@ skerr_to_ssherr(int skerr)
                 return SSH_ERR_FEATURE_UNSUPPORTED;
         case SSH_SK_ERR_PIN_REQUIRED:
                 return SSH_ERR_KEY_WRONG_PASSPHRASE;
+        case SSH_SK_ERR_DEVICE_NOT_FOUND:
+                return SSH_ERR_DEVICE_NOT_FOUND;
         case SSH_SK_ERR_GENERAL:
         default:
                 return SSH_ERR_INVALID_FORMAT;
@@ -490,7 +492,7 @@ sshsk_enroll(int type, const char *provider_path, const char *device,
         /* enroll key */
         if ((r = skp->sk_enroll(alg, challenge, challenge_len, application,
             flags, pin, opts, &resp)) != 0) {
-                error("Security key provider \"%s\" returned failure %d",
+                debug("%s: provider \"%s\" returned failure %d", __func__,
                     provider_path, r);
                 r = skerr_to_ssherr(r);
                 goto out;
diff --git a/ssherr.c b/ssherr.c
index 38974f51b..bd954aadd 100644
--- a/ssherr.c
+++ b/ssherr.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ssherr.c,v 1.9 2019/12/30 09:24:45 djm Exp $  */
+/*      $OpenBSD: ssherr.c,v 1.10 2020/01/25 23:13:09 djm Exp $ */
 /*
  * Copyright (c) 2011 Damien Miller
  *
@@ -143,6 +143,8 @@ ssh_err(int n)
                 return "signature algorithm not supported";
         case SSH_ERR_FEATURE_UNSUPPORTED:
                 return "requested feature not supported";
+        case SSH_ERR_DEVICE_NOT_FOUND:
+                return "device not found";
         default:
                 return "unknown error";
         }
diff --git a/ssherr.h b/ssherr.h
index 520bd4964..085e75274 100644
--- a/ssherr.h
+++ b/ssherr.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ssherr.h,v 1.7 2019/12/30 09:24:45 djm Exp $  */
+/*      $OpenBSD: ssherr.h,v 1.8 2020/01/25 23:13:09 djm Exp $  */
 /*
  * Copyright (c) 2011 Damien Miller
  *
@@ -81,6 +81,7 @@
 #define SSH_ERR_NUMBER_TOO_LARGE                -57
 #define SSH_ERR_SIGN_ALG_UNSUPPORTED            -58
 #define SSH_ERR_FEATURE_UNSUPPORTED             -59
+#define SSH_ERR_DEVICE_NOT_FOUND                -60
 
 /* Translate a numeric error code to a human-readable error string */
 const char *ssh_err(int n);