* New upstream release (closes: #536182). Yes, I know 5.3p1 has been out

  for a while, but there's no GSSAPI patch available for it yet.
  - Change the default cipher order to prefer the AES CTR modes and the
    revised "arcfour256" mode to CBC mode ciphers that are susceptible to
    CPNI-957037 "Plaintext Recovery Attack Against SSH".
  - Add countermeasures to mitigate CPNI-957037-style attacks against the
    SSH protocol's use of CBC-mode ciphers. Upon detection of an invalid
    packet length or Message Authentication Code, ssh/sshd will continue
    reading up to the maximum supported packet length rather than
    immediately terminating the connection. This eliminates most of the
    known differences in behaviour that leaked information about the
    plaintext of injected data which formed the basis of this attack
    (closes: #506115, LP: #379329).
  - ForceCommand directive now accepts commandline arguments for the
    internal-sftp server (closes: #524423, LP: #362511).
  - Add AllowAgentForwarding to available Match keywords list (closes:
    #540623).
  - Make ssh(1) send the correct channel number for
    SSH2_MSG_CHANNEL_SUCCESS and SSH2_MSG_CHANNEL_FAILURE messages to
    avoid triggering 'Non-public channel' error messages on sshd(8) in
    openssh-5.1.
  - Avoid printing 'Non-public channel' warnings in sshd(8), since the
    ssh(1) has sent incorrect channel numbers since ~2004 (this reverts a
    behaviour introduced in openssh-5.1; closes: #496017).
* Update to GSSAPI patch from
  http://www.sxw.org.uk/computing/patches/openssh-5.2p1-gsskex-all-20090726.patch,
  including cascading credentials support (LP: #416958).

1 files changed, 151 insertions, 10 deletions

diff --git a/gss-serv.c b/gss-serv.c
index 9227b797c..365e48d88 100644
--- a/gss-serv.c
+++ b/gss-serv.c
@@ -1,7 +1,7 @@
 /* $OpenBSD: gss-serv.c,v 1.22 2008/05/08 12:02:23 djm Exp $ */
 
 /*
- * Copyright (c) 2001-2008 Simon Wilkinson. All rights reserved.
+ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -46,6 +46,7 @@
 #include "session.h"
 #include "misc.h"
 #include "servconf.h"
+#include "uidswap.h"
 
 #include "ssh-gss.h"
 #include "monitor_wrap.h"
@@ -54,10 +55,10 @@ extern ServerOptions options;
 
 static ssh_gssapi_client gssapi_client =
     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
-    GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
+    GSS_C_NO_CREDENTIAL, GSS_C_NO_NAME,  NULL, {NULL, NULL, NULL}, 0, 0};
 
 ssh_gssapi_mech gssapi_null_mech =
-    { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
+    { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL, NULL};
 
 #ifdef KRB5
 extern ssh_gssapi_mech gssapi_kerberos_mech;
@@ -131,12 +132,13 @@ ssh_gssapi_server_mechanisms() {
 
         ssh_gssapi_supported_oids(&supported);
         return (ssh_gssapi_kex_mechs(supported, &ssh_gssapi_server_check_mech,
-            NULL));
+            NULL, NULL));
 }
 
 /* Unprivileged */
 int
-ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data) {
+ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data,
+    const char *dummy) {
         Gssctxt *ctx = NULL;
         int res;
  
@@ -156,7 +158,9 @@ ssh_gssapi_supported_oids(gss_OID_set *oidset)
         gss_OID_set supported;
 
         gss_create_empty_oid_set(&min_status, oidset);
-        gss_indicate_mechs(&min_status, &supported);
+
+        if (GSS_ERROR(gss_indicate_mechs(&min_status, &supported)))
+                return;
 
         while (supported_mechs[i]->name != NULL) {
                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
@@ -280,8 +284,48 @@ OM_uint32
 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 {
         int i = 0;
+        int equal = 0;
+        gss_name_t new_name = GSS_C_NO_NAME;
+        gss_buffer_desc ename = GSS_C_EMPTY_BUFFER;
+
+        if (options.gss_store_rekey && client->used && ctx->client_creds) {
+                if (client->mech->oid.length != ctx->oid->length ||
+                    (memcmp(client->mech->oid.elements,
+                     ctx->oid->elements, ctx->oid->length) !=0)) {
+                        debug("Rekeyed credentials have different mechanism");
+                        return GSS_S_COMPLETE;
+                }
+
+                if ((ctx->major = gss_inquire_cred_by_mech(&ctx->minor, 
+                    ctx->client_creds, ctx->oid, &new_name, 
+                    NULL, NULL, NULL))) {
+                        ssh_gssapi_error(ctx);
+                        return (ctx->major);
+                }
+
+                ctx->major = gss_compare_name(&ctx->minor, client->name, 
+                    new_name, &equal);
+
+                if (GSS_ERROR(ctx->major)) {
+                        ssh_gssapi_error(ctx);
+                        return (ctx->major);
+                }
+ 
+                if (!equal) {
+                        debug("Rekeyed credentials have different name");
+                        return GSS_S_COMPLETE;
+                }
 
-        gss_buffer_desc ename;
+                debug("Marking rekeyed credentials for export");
+
+                gss_release_name(&ctx->minor, &client->name);
+                gss_release_cred(&ctx->minor, &client->creds);
+                client->name = new_name;
+                client->creds = ctx->client_creds;
+                ctx->client_creds = GSS_C_NO_CREDENTIAL;
+                client->updated = 1;
+                return GSS_S_COMPLETE;
+        }
 
         client->mech = NULL;
 
@@ -296,6 +340,13 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
         if (client->mech == NULL)
                 return GSS_S_FAILURE;
 
+        if (ctx->client_creds &&
+            (ctx->major = gss_inquire_cred_by_mech(&ctx->minor,
+             ctx->client_creds, ctx->oid, &client->name, NULL, NULL, NULL))) {
+                ssh_gssapi_error(ctx);
+                return (ctx->major);
+        }
+
         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
             &client->displayname, NULL))) {
                 ssh_gssapi_error(ctx);
@@ -313,6 +364,8 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
                 return (ctx->major);
         }
 
+        gss_release_buffer(&ctx->minor, &ename);
+
         /* We can't copy this structure, so we just move the pointer to it */
         client->creds = ctx->client_creds;
         ctx->client_creds = GSS_C_NO_CREDENTIAL;
@@ -360,7 +413,7 @@ ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 
 /* Privileged */
 int
-ssh_gssapi_userok(char *user)
+ssh_gssapi_userok(char *user, struct passwd *pw)
 {
         OM_uint32 lmin;
 
@@ -370,9 +423,11 @@ ssh_gssapi_userok(char *user)
                 return 0;
         }
         if (gssapi_client.mech && gssapi_client.mech->userok)
-                if ((*gssapi_client.mech->userok)(&gssapi_client, user))
+                if ((*gssapi_client.mech->userok)(&gssapi_client, user)) {
+                        gssapi_client.used = 1;
+                        gssapi_client.store.owner = pw;
                         return 1;
-                else {
+                } else {
                         /* Destroy delegated credentials if userok fails */
                         gss_release_buffer(&lmin, &gssapi_client.displayname);
                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
@@ -385,4 +440,90 @@ ssh_gssapi_userok(char *user)
         return (0);
 }
 
+/* These bits are only used for rekeying. The unpriviledged child is running 
+ * as the user, the monitor is root.
+ *
+ * In the child, we want to :
+ *    *) Ask the monitor to store our credentials into the store we specify
+ *    *) If it succeeds, maybe do a PAM update
+ */
+
+/* Stuff for PAM */
+
+#ifdef USE_PAM
+static int ssh_gssapi_simple_conv(int n, const struct pam_message **msg, 
+    struct pam_response **resp, void *data)
+{
+        return (PAM_CONV_ERR);
+}
+#endif
+
+void
+ssh_gssapi_rekey_creds() {
+        int ok;
+        int ret;
+#ifdef USE_PAM
+        pam_handle_t *pamh = NULL;
+        struct pam_conv pamconv = {ssh_gssapi_simple_conv, NULL};
+        char *envstr;
+#endif
+
+        if (gssapi_client.store.filename == NULL && 
+            gssapi_client.store.envval == NULL &&
+            gssapi_client.store.envvar == NULL)
+                return;
+ 
+        ok = PRIVSEP(ssh_gssapi_update_creds(&gssapi_client.store));
+
+        if (!ok)
+                return;
+
+        debug("Rekeyed credentials stored successfully");
+
+        /* Actually managing to play with the ssh pam stack from here will
+         * be next to impossible. In any case, we may want different options
+         * for rekeying. So, use our own :)
+         */
+#ifdef USE_PAM  
+        if (!use_privsep) {
+                debug("Not even going to try and do PAM with privsep disabled");
+                return;
+        }
+
+        ret = pam_start("sshd-rekey", gssapi_client.store.owner->pw_name,
+            &pamconv, &pamh);
+        if (ret)
+                return;
+
+        xasprintf(&envstr, "%s=%s", gssapi_client.store.envvar, 
+            gssapi_client.store.envval);
+
+        ret = pam_putenv(pamh, envstr);
+        if (!ret)
+                pam_setcred(pamh, PAM_REINITIALIZE_CRED);
+        pam_end(pamh, PAM_SUCCESS);
+#endif
+}
+
+int 
+ssh_gssapi_update_creds(ssh_gssapi_ccache *store) {
+        int ok = 0;
+
+        /* Check we've got credentials to store */
+        if (!gssapi_client.updated)
+                return 0;
+
+        gssapi_client.updated = 0;
+
+        temporarily_use_uid(gssapi_client.store.owner);
+        if (gssapi_client.mech && gssapi_client.mech->updatecreds)
+                ok = (*gssapi_client.mech->updatecreds)(store, &gssapi_client);
+        else
+                debug("No update function for this mechanism");
+
+        restore_uid();
+
+        return ok;
+}
+
 #endif