svn rev #25473: trunk/src/ include/krb5/ kdc/ plugins/preauth/cksum_body/

ghudson@MIT.EDU ghudson at MIT.EDU
Mon Nov 14 16:45:33 EST 2011


http://src.mit.edu/fisheye/changelog/krb5/?cs=25473
Commit By: ghudson
Log Message:
ticket: 7017
subject: Simplify and fix kdcpreauth request_body callback
target_version: 1.10
tags: pullup

Alter the contract for the kdcpreauth request_body callback so that it
returns an alias to the encoded body instead of a fresh copy.  At the
beginning of AS request processing, save a copy of the encoded request
body, or the encoded inner request body for FAST requests.  Previously
the request_body callback would re-encode the request structure, which
in some cases has been modified by the AS request code.

No kdcpreauth modules currently use the request_body callback, but
PKINIT will need to start using it in order to handle FAST requests
correctly.


Changed Files:
U   trunk/src/include/krb5/preauth_plugin.h
U   trunk/src/kdc/do_as_req.c
U   trunk/src/kdc/do_tgs_req.c
U   trunk/src/kdc/fast_util.c
U   trunk/src/kdc/kdc_preauth.c
U   trunk/src/kdc/kdc_util.h
U   trunk/src/plugins/preauth/cksum_body/cksum_body_main.c
Modified: trunk/src/include/krb5/preauth_plugin.h
===================================================================
--- trunk/src/include/krb5/preauth_plugin.h	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/include/krb5/preauth_plugin.h	2011-11-14 21:45:33 UTC (rev 25473)
@@ -351,15 +351,12 @@
                       krb5_keyblock *keys);
 
     /*
-     * Get the request structure, re-encoded using DER.  Unless the client
-     * implementation is the same as the server implementation, there's a good
-     * chance that the result will not match what the client sent, so don't
-     * create any fatal errors if it doesn't match up.  Free the resulting data
-     * object with krb5_free_data.
+     * Get the encoded request body, which is sometimes needed for checksums.
+     * For a FAST request this is the encoded inner request body.  The returned
+     * pointer is an alias and should not be freed.
      */
-    krb5_error_code (*request_body)(krb5_context context,
-                                    krb5_kdcpreauth_rock rock,
-                                    krb5_data **body_out);
+    krb5_data *(*request_body)(krb5_context context,
+                               krb5_kdcpreauth_rock rock);
 
     /* Get a pointer to the FAST armor key, or NULL if the request did not use
      * FAST.  The returned pointer is an alias and should not be freed. */

Modified: trunk/src/kdc/do_as_req.c
===================================================================
--- trunk/src/kdc/do_as_req.c	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/kdc/do_as_req.c	2011-11-14 21:45:33 UTC (rev 25473)
@@ -120,6 +120,7 @@
     krb5_keyblock session_key;
     unsigned int c_flags;
     krb5_data *req_pkt;
+    krb5_data *inner_body;
     struct kdc_request_state *rstate;
     char *sname, *cname;
     void *pa_context;
@@ -396,6 +397,7 @@
     }
 
     krb5_free_pa_data(kdc_context, state->e_data);
+    krb5_free_data(kdc_context, state->inner_body);
     kdc_free_rstate(state->rstate);
     krb5_free_kdc_req(kdc_context, state->request);
     assert(did_log != 0);
@@ -492,13 +494,23 @@
         state->status = "Finding req_body";
         goto errout;
     }
-    errcode = kdc_find_fast(&state->request, &encoded_req_body,
-                            NULL /*TGS key*/, NULL, state->rstate);
+    errcode = kdc_find_fast(&state->request, &encoded_req_body, NULL, NULL,
+                            state->rstate, &state->inner_body);
     if (errcode) {
         state->status = "error decoding FAST";
         goto errout;
     }
+    if (state->inner_body == NULL) {
+        /* Not a FAST request; copy the encoded request body. */
+        errcode = krb5_copy_data(kdc_context, &encoded_req_body,
+                                 &state->inner_body);
+        if (errcode) {
+            state->status = "storing req body";
+            goto errout;
+        }
+    }
     state->rock.request = state->request;
+    state->rock.inner_body = state->inner_body;
     state->rock.rstate = state->rstate;
     if (!state->request->client) {
         state->status = "NULL_CLIENT";

Modified: trunk/src/kdc/do_tgs_req.c
===================================================================
--- trunk/src/kdc/do_tgs_req.c	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/kdc/do_tgs_req.c	2011-11-14 21:45:33 UTC (rev 25473)
@@ -176,7 +176,7 @@
     scratch.length = pa_tgs_req->length;
     scratch.data = (char *) pa_tgs_req->contents;
     errcode = kdc_find_fast(&request, &scratch, subkey,
-                            header_ticket->enc_part2->session, state);
+                            header_ticket->enc_part2->session, state, NULL);
     if (errcode !=0) {
         status = "kdc_find_fast";
         goto cleanup;

Modified: trunk/src/kdc/fast_util.c
===================================================================
--- trunk/src/kdc/fast_util.c	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/kdc/fast_util.c	2011-11-14 21:45:33 UTC (rev 25473)
@@ -126,11 +126,12 @@
               krb5_data *checksummed_data,
               krb5_keyblock *tgs_subkey,
               krb5_keyblock *tgs_session,
-              struct kdc_request_state *state)
+              struct kdc_request_state *state,
+              krb5_data **inner_body_out)
 {
     krb5_error_code retval = 0;
     krb5_pa_data *fast_padata, *cookie_padata = NULL;
-    krb5_data scratch;
+    krb5_data scratch, *inner_body = NULL;
     krb5_fast_req * fast_req = NULL;
     krb5_kdc_req *request = *requestptr;
     krb5_fast_armored_req *fast_armored_req = NULL;
@@ -138,6 +139,8 @@
     krb5_boolean cksum_valid;
     krb5_keyblock empty_keyblock;
 
+    if (inner_body_out != NULL)
+        *inner_body_out = NULL;
     scratch.data = NULL;
     krb5_clear_error_message(kdc_context);
     memset(&empty_keyblock, 0, sizeof(krb5_keyblock));
@@ -192,6 +195,14 @@
                                     &plaintext);
             if (retval == 0)
                 retval = decode_krb5_fast_req(&plaintext, &fast_req);
+            if (retval == 0 && inner_body_out != NULL) {
+                retval = fetch_asn1_field((unsigned char *)plaintext.data,
+                                          1, 2, &scratch);
+                if (retval == 0) {
+                    retval = krb5_copy_data(kdc_context, &scratch,
+                                            &inner_body);
+                }
+            }
             if (plaintext.data)
                 free(plaintext.data);
         }
@@ -247,6 +258,11 @@
             }
         }
     }
+    if (retval == 0 && inner_body_out != NULL) {
+        *inner_body_out = inner_body;
+        inner_body = NULL;
+    }
+    krb5_free_data(kdc_context, inner_body);
     if (fast_req)
         krb5_free_fast_req( kdc_context, fast_req);
     if (fast_armored_req)

Modified: trunk/src/kdc/kdc_preauth.c
===================================================================
--- trunk/src/kdc/kdc_preauth.c	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/kdc/kdc_preauth.c	2011-11-14 21:45:33 UTC (rev 25473)
@@ -543,11 +543,10 @@
     free(keys);
 }
 
-static krb5_error_code
-request_body(krb5_context context, krb5_kdcpreauth_rock rock,
-             krb5_data **body_out)
+static krb5_data *
+request_body(krb5_context context, krb5_kdcpreauth_rock rock)
 {
-    return encode_krb5_kdc_req_body(rock->request, body_out);
+    return rock->inner_body;
 }
 
 static krb5_keyblock *

Modified: trunk/src/kdc/kdc_util.h
===================================================================
--- trunk/src/kdc/kdc_util.h	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/kdc/kdc_util.h	2011-11-14 21:45:33 UTC (rev 25473)
@@ -348,10 +348,19 @@
     KRB5_FAST_REPLY_KEY_REPLACED = 0x02
 };
 
+/*
+ * If *requestptr contains FX_FAST padata, compute the armor key, verify the
+ * checksum over checksummed_data, decode the FAST request, and substitute
+ * *requestptr with the inner request.  Set the armor_key, cookie, and
+ * fast_options fields in state.  state->cookie will be set for a non-FAST
+ * request if it contains FX_COOKIE padata.  If inner_body_out is non-NULL, set
+ * *inner_body_out to a copy of the encoded inner body, or to NULL if the
+ * request is not a FAST request.
+ */
 krb5_error_code
 kdc_find_fast (krb5_kdc_req **requestptr,  krb5_data *checksummed_data,
                krb5_keyblock *tgs_subkey, krb5_keyblock *tgs_session,
-               struct kdc_request_state *state);
+               struct kdc_request_state *state, krb5_data **inner_body_out);
 
 krb5_error_code
 kdc_fast_response_handle_padata (struct kdc_request_state *state,
@@ -383,6 +392,7 @@
 /* Information handle for kdcpreauth callbacks.  All pointers are aliases. */
 struct krb5_kdcpreauth_rock_st {
     krb5_kdc_req *request;
+    krb5_data *inner_body;
     krb5_db_entry *client;
     krb5_key_data *client_key;
     struct kdc_request_state *rstate;

Modified: trunk/src/plugins/preauth/cksum_body/cksum_body_main.c
===================================================================
--- trunk/src/plugins/preauth/cksum_body/cksum_body_main.c	2011-11-14 18:02:52 UTC (rev 25472)
+++ trunk/src/plugins/preauth/cksum_body/cksum_body_main.c	2011-11-14 21:45:33 UTC (rev 25473)
@@ -403,17 +403,7 @@
     }
     cb->free_keys(kcontext, rock, keys);
 
-    /* Rebuild a copy of the client's request-body.  If we were serious
-     * about doing this with any chance of working interoperability, we'd
-     * extract the structure directly from the req_pkt structure.  This
-     * will probably work if it's us on both ends, though. */
-    req_body = NULL;
-    if (cb->request_body(kcontext, rock, &req_body) != 0) {
-        krb5_free_keyblock(kcontext, key);
-        stats->failures++;
-        (*respond)(arg, KRB5KDC_ERR_PREAUTH_FAILED, NULL, NULL, NULL);
-        return;
-    }
+    req_body = cb->request_body(kcontext, rock);
 
 #ifdef DEBUG
     fprintf(stderr, "AS key type %d, checksum type %d, %d bytes.\n",
@@ -428,7 +418,6 @@
                                     req_body, &checksum, &valid);
 
     /* Clean up. */
-    krb5_free_data(kcontext, req_body);
     krb5_free_keyblock(kcontext, key);
 
     /* Evaluate our results. */




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