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

(back ported from commit 3db8dfec1ef50ddd78d6ba9503185995876a39fd)

ticket: 8316 (new)
version_fixed: 1.12.5
status: resolved

diff --git a/src/lib/gssapi/krb5/gssapiP_krb5.h b/src/lib/gssapi/krb5/gssapiP_krb5.h
index b14788dde8909c273dfe928a39386add8e51fce2..1ae40c9fb2ea8705a88489b499f2a005e03189ef 100644 (file)
--- a/src/lib/gssapi/krb5/gssapiP_krb5.h
+++ b/src/lib/gssapi/krb5/gssapiP_krb5.h
@@ -1393,6 +1393,11 @@ 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 61a6922a4142cde8c910008e34dd2de771afe69c..4931f863ff085f6b9368254ee7d175c323d3346b 100644 (file)
--- a/src/lib/gssapi/krb5/gssapi_krb5.c
+++ b/src/lib/gssapi/krb5/gssapi_krb5.c
@@ -945,7 +945,7 @@ 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 4662bd9fe382fdde657abaa6db06fa47ad69d8b7..48beaee7756d4202dfc713bf4dfe2039da917ced 100644 (file)
--- a/src/lib/gssapi/krb5/iakerb.c
+++ b/src/lib/gssapi/krb5/iakerb.c
@@ -1061,7 +1061,7 @@ 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)
@@ -1076,13 +1076,41 @@ iakerb_gss_export_sec_context(OM_uint32 *minor_status,
     return maj;
 }
 
-/*
- * Until we implement partial context exports, there are no SPNEGO 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