upstream: Remove support for loading HostBasedAuthentication keys

directly in ssh(1) and always use ssh-keysign.  This removes one of the few
remaining reasons why ssh(1) might be setuid.  ok markus@

OpenBSD-Commit-ID: 97f01e1448707129a20d75f86bad5d27c3cf0b7d

3 files changed, 9 insertions, 39 deletions

diff --git a/ssh.c b/ssh.c
index 3367e9137..33d7ea2ba 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.484 2018/07/16 07:06:50 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.485 2018/07/16 11:05:41 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1411,16 +1411,12 @@ main(int ac, char **av)
                 debug3("timeout: %d ms remain after connect", timeout_ms);
 
         /*
-         * If we successfully made the connection, load the host private key
-         * in case we will need it later for hostbased
-         * authentication. This must be done before releasing extra
-         * privileges, because the file is only readable by root.
-         * If we cannot access the private keys, load the public keys
-         * instead and try to execute the ssh-keysign helper instead.
+         * If we successfully made the connection and we have hostbased auth
+         * enabled, load the public keys so we can later use the ssh-keysign
+         * helper to sign challenges.
          */
         sensitive_data.nkeys = 0;
         sensitive_data.keys = NULL;
-        sensitive_data.external_keysign = 0;
         if (options.hostbased_authentication) {
                 sensitive_data.nkeys = 11;
                 sensitive_data.keys = xcalloc(sensitive_data.nkeys,
@@ -1439,27 +1435,7 @@ main(int ac, char **av)
 #define L_CERT(p,o) \
         check_load(sshkey_load_cert(p, &(sensitive_data.keys[o])), p, "cert")
 
-                PRIV_START;
-                L_KEYCERT(KEY_ECDSA, _PATH_HOST_ECDSA_KEY_FILE, 1);
-                L_KEYCERT(KEY_ED25519, _PATH_HOST_ED25519_KEY_FILE, 2);
-                L_KEYCERT(KEY_RSA, _PATH_HOST_RSA_KEY_FILE, 3);
-                L_KEYCERT(KEY_DSA, _PATH_HOST_DSA_KEY_FILE, 4);
-                L_KEY(KEY_ECDSA, _PATH_HOST_ECDSA_KEY_FILE, 5);
-                L_KEY(KEY_ED25519, _PATH_HOST_ED25519_KEY_FILE, 6);
-                L_KEY(KEY_RSA, _PATH_HOST_RSA_KEY_FILE, 7);
-                L_KEY(KEY_DSA, _PATH_HOST_DSA_KEY_FILE, 8);
-                L_KEYCERT(KEY_XMSS, _PATH_HOST_XMSS_KEY_FILE, 9);
-                L_KEY(KEY_XMSS, _PATH_HOST_XMSS_KEY_FILE, 10);
-                PRIV_END;
-
-                if (options.hostbased_authentication == 1 &&
-                    sensitive_data.keys[0] == NULL &&
-                    sensitive_data.keys[5] == NULL &&
-                    sensitive_data.keys[6] == NULL &&
-                    sensitive_data.keys[7] == NULL &&
-                    sensitive_data.keys[8] == NULL &&
-                    sensitive_data.keys[9] == NULL &&
-                    sensitive_data.keys[10] == NULL) {
+                if (options.hostbased_authentication == 1) {
                         L_CERT(_PATH_HOST_ECDSA_KEY_FILE, 1);
                         L_CERT(_PATH_HOST_ED25519_KEY_FILE, 2);
                         L_CERT(_PATH_HOST_RSA_KEY_FILE, 3);
@@ -1470,7 +1446,6 @@ main(int ac, char **av)
                         L_PUBKEY(_PATH_HOST_DSA_KEY_FILE, 8);
                         L_CERT(_PATH_HOST_XMSS_KEY_FILE, 9);
                         L_PUBKEY(_PATH_HOST_XMSS_KEY_FILE, 10);
-                        sensitive_data.external_keysign = 1;
                 }
         }
         /*
diff --git a/sshconnect.h b/sshconnect.h
index dd648b096..6bba62ad0 100644
--- a/sshconnect.h
+++ b/sshconnect.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.h,v 1.32 2018/02/10 09:25:35 djm Exp $ */
+/* $OpenBSD: sshconnect.h,v 1.33 2018/07/16 11:05:41 dtucker Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -28,7 +28,6 @@ typedef struct Sensitive Sensitive;
 struct Sensitive {
         struct sshkey   **keys;
         int             nkeys;
-        int             external_keysign;
 };
 
 struct addrinfo;
diff --git a/sshconnect2.c b/sshconnect2.c
index fb90e8afc..7b0e18f28 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.280 2018/07/11 18:55:11 markus Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.281 2018/07/16 11:05:41 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -1990,12 +1990,8 @@ userauth_hostbased(Authctxt *authctxt)
 #ifdef DEBUG_PK
         sshbuf_dump(b, stderr);
 #endif
-        if (authctxt->sensitive->external_keysign)
-                r = ssh_keysign(private, &sig, &siglen,
-                    sshbuf_ptr(b), sshbuf_len(b));
-        else if ((r = sshkey_sign(private, &sig, &siglen,
-            sshbuf_ptr(b), sshbuf_len(b), NULL, datafellows)) != 0)
-                debug("%s: sshkey_sign: %s", __func__, ssh_err(r));
+        r = ssh_keysign(private, &sig, &siglen,
+            sshbuf_ptr(b), sshbuf_len(b));
         if (r != 0) {
                 error("sign using hostkey %s %s failed",
                     sshkey_ssh_name(private), fp);