Fix IAKERB context export/import [CVE-2015-2698]

The patches for CVE-2015-2696 contained a regression in the newly
added IAKERB iakerb_gss_export_sec_context() function, which could
cause it to corrupt memory.  Fix the regression by properly
dereferencing the context_handle pointer before casting it.

Also, the patches did not implement an IAKERB gss_import_sec_context()
function, under the erroneous belief that an exported IAKERB context
would be tagged as a krb5 context.  Implement it now to allow IAKERB
contexts to be successfully exported and imported after establishment.

CVE-2015-2698:

In any MIT krb5 release with the patches for CVE-2015-2696 applied, an
application which calls gss_export_sec_context() may experience memory
corruption if the context was established using the IAKERB mechanism.
Historically, some vulnerabilities of this nature can be translated
into remote code execution, though the necessary exploits must be
tailored to the individual application and are usually quite
complicated.

    CVSSv2 Vector: AV:N/AC:H/Au:S/C:C/I:C/A:C/E:POC/RL:OF/RC:C

ticket: 8273 (new)
target_version: 1.14
tags: pullup

diff --git a/src/lib/gssapi/krb5/gssapiP_krb5.h b/src/lib/gssapi/krb5/gssapiP_krb5.h
index 97e090d099f3672e9fe67c969c1615dc0710922c..16635006db1513811c4fce4003b2d0b78bc1c026 100644 (file)
--- a/src/lib/gssapi/krb5/gssapiP_krb5.h
+++ b/src/lib/gssapi/krb5/gssapiP_krb5.h
@@ -1397,6 +1397,11 @@ OM_uint32 KRB5_CALLCONV
 iakerb_gss_export_sec_context(OM_uint32 *minor_status,
                               gss_ctx_id_t *context_handle,
                               gss_buffer_t interprocess_token);
+
+OM_uint32 KRB5_CALLCONV
+iakerb_gss_import_sec_context(OM_uint32 *minor_status,
+                              const gss_buffer_t interprocess_token,
+                              gss_ctx_id_t *context_handle);
 #endif /* LEAN_CLIENT */
 
 OM_uint32 KRB5_CALLCONV

diff --git a/src/lib/gssapi/krb5/gssapi_krb5.c b/src/lib/gssapi/krb5/gssapi_krb5.c
index c4dfdd6fbd1338c6ad8bb2a395fff7cafa8de82b..aea60dc09fd76ae8ca54f75df5ba8e3b85d43f8c 100644 (file)
--- a/src/lib/gssapi/krb5/gssapi_krb5.c
+++ b/src/lib/gssapi/krb5/gssapi_krb5.c
@@ -970,7 +970,7 @@ static struct gss_config iakerb_mechanism = {
     NULL,
 #else
     iakerb_gss_export_sec_context,
-    NULL,
+    iakerb_gss_import_sec_context,
 #endif
     krb5_gss_inquire_cred_by_mech,
     krb5_gss_inquire_names_for_mech,

diff --git a/src/lib/gssapi/krb5/iakerb.c b/src/lib/gssapi/krb5/iakerb.c
index e25862df47d9c8323b01216f52904836a0888bef..32a341ec58dc05f16a35329dd9564c418cfac9b8 100644 (file)
--- a/src/lib/gssapi/krb5/iakerb.c
+++ b/src/lib/gssapi/krb5/iakerb.c
@@ -1057,7 +1057,7 @@ iakerb_gss_export_sec_context(OM_uint32 *minor_status,
                               gss_buffer_t interprocess_token)
 {
     OM_uint32 maj;
-    iakerb_ctx_id_t ctx = (iakerb_ctx_id_t)context_handle;
+    iakerb_ctx_id_t ctx = (iakerb_ctx_id_t)*context_handle;
 
     /* We don't currently support exporting partially established contexts. */
     if (!ctx->established)
@@ -1072,13 +1072,41 @@ iakerb_gss_export_sec_context(OM_uint32 *minor_status,
     return maj;
 }
 
-/*
- * Until we implement partial context exports, there are no IAKERB exported
- * context tokens, only tokens for the underlying krb5 context.  So we do not
- * need to implement an iakerb_gss_import_sec_context() yet; it would be
- * unreachable except via a manually constructed token.
- */
+OM_uint32 KRB5_CALLCONV
+iakerb_gss_import_sec_context(OM_uint32 *minor_status,
+                              gss_buffer_t interprocess_token,
+                              gss_ctx_id_t *context_handle)
+{
+    OM_uint32 maj, tmpmin;
+    krb5_error_code code;
+    gss_ctx_id_t gssc;
+    krb5_gss_ctx_id_t kctx;
+    iakerb_ctx_id_t ctx;
+
+    maj = krb5_gss_import_sec_context(minor_status, interprocess_token, &gssc);
+    if (maj != GSS_S_COMPLETE)
+        return maj;
+    kctx = (krb5_gss_ctx_id_t)gssc;
+
+    if (!kctx->established) {
+        /* We don't currently support importing partially established
+         * contexts. */
+        krb5_gss_delete_sec_context(&tmpmin, &gssc, GSS_C_NO_BUFFER);
+        return GSS_S_FAILURE;
+    }
 
+    code = iakerb_alloc_context(&ctx, kctx->initiate);
+    if (code != 0) {
+        krb5_gss_delete_sec_context(&tmpmin, &gssc, GSS_C_NO_BUFFER);
+        *minor_status = code;
+        return GSS_S_FAILURE;
+    }
+
+    ctx->gssc = gssc;
+    ctx->established = 1;
+    *context_handle = (gss_ctx_id_t)ctx;
+    return GSS_S_COMPLETE;
+}
 #endif /* LEAN_CLIENT */
 
 OM_uint32 KRB5_CALLCONV