From 56f7b1bc95a2a3eeb420e069e7655fb181ade5cf Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Fri, 14 Jul 2017 13:02:46 -0400
Subject: [PATCH] Preserve GSS context on init/accept failure

After gss_init_sec_context() or gss_accept_sec_context() has created a
context, don't delete the mechglue context on failures from subsequent
calls, even if the mechanism deletes the mech-specific context (which
is allowed by RFC 2744 but not preferred).  Check for union contexts
with no mechanism context in each GSS function which accepts a
gss_ctx_id_t.

CVE-2017-11462:

RFC 2744 permits a GSS-API implementation to delete an existing
security context on a second or subsequent call to
gss_init_sec_context() or gss_accept_sec_context() if the call results
in an error.  This API behavior has been found to be dangerous,
leading to the possibility of memory errors in some callers.  For
safety, GSS-API implementations should instead preserve existing
security contexts on error until the caller deletes them.

All versions of MIT krb5 prior to this change may delete acceptor
contexts on error.  Versions 1.13.4 through 1.13.7, 1.14.1 through
1.14.5, and 1.15 through 1.15.1 may also delete initiator contexts on
error.

ticket: 8598 (new)
target_version: 1.15-next
target_version: 1.14-next
tags: pullup

Upstream-Status: Backport
CVE: CVE-2017-11462

Signed-off-by: Catalin Enache <catalin.enache@windriver.com>
---
 src/lib/gssapi/mechglue/g_accept_sec_context.c  | 22 +++++++++++++++-------
 src/lib/gssapi/mechglue/g_complete_auth_token.c |  2 ++
 src/lib/gssapi/mechglue/g_context_time.c        |  2 ++
 src/lib/gssapi/mechglue/g_delete_sec_context.c  | 14 ++++++++------
 src/lib/gssapi/mechglue/g_exp_sec_context.c     |  2 ++
 src/lib/gssapi/mechglue/g_init_sec_context.c    | 19 +++++++++++--------
 src/lib/gssapi/mechglue/g_inq_context.c         |  2 ++
 src/lib/gssapi/mechglue/g_prf.c                 |  2 ++
 src/lib/gssapi/mechglue/g_process_context.c     |  2 ++
 src/lib/gssapi/mechglue/g_seal.c                |  4 ++++
 src/lib/gssapi/mechglue/g_sign.c                |  2 ++
 src/lib/gssapi/mechglue/g_unseal.c              |  2 ++
 src/lib/gssapi/mechglue/g_unwrap_aead.c         |  2 ++
 src/lib/gssapi/mechglue/g_unwrap_iov.c          |  4 ++++
 src/lib/gssapi/mechglue/g_verify.c              |  2 ++
 src/lib/gssapi/mechglue/g_wrap_aead.c           |  2 ++
 src/lib/gssapi/mechglue/g_wrap_iov.c            |  8 ++++++++
 17 files changed, 72 insertions(+), 21 deletions(-)

diff --git a/src/lib/gssapi/mechglue/g_accept_sec_context.c b/src/lib/gssapi/mechglue/g_accept_sec_context.c
index ddaf874..f28e2b1 100644
--- a/src/lib/gssapi/mechglue/g_accept_sec_context.c
+++ b/src/lib/gssapi/mechglue/g_accept_sec_context.c
@@ -216,6 +216,8 @@ gss_cred_id_t *		d_cred;
     } else {
 	union_ctx_id = (gss_union_ctx_id_t)*context_handle;
 	selected_mech = union_ctx_id->mech_type;
+	if (union_ctx_id->internal_ctx_id == GSS_C_NO_CONTEXT)
+	    return (GSS_S_NO_CONTEXT);
     }
 
     /* Now create a new context if we didn't get one. */
@@ -234,9 +236,6 @@ gss_cred_id_t *		d_cred;
 	    free(union_ctx_id);
 	    return (status);
 	}
-
-	/* set the new context handle to caller's data */
-	*context_handle = (gss_ctx_id_t)union_ctx_id;
     }
 
     /*
@@ -277,8 +276,10 @@ gss_cred_id_t *		d_cred;
 					d_cred ? &tmp_d_cred : NULL);
 
 	    /* If there's more work to do, keep going... */
-	    if (status == GSS_S_CONTINUE_NEEDED)
+	    if (status == GSS_S_CONTINUE_NEEDED) {
+		*context_handle = (gss_ctx_id_t)union_ctx_id;
 		return GSS_S_CONTINUE_NEEDED;
+	    }
 
 	    /* if the call failed, return with failure */
 	    if (status != GSS_S_COMPLETE) {
@@ -364,14 +365,22 @@ gss_cred_id_t *		d_cred;
 		*mech_type = gssint_get_public_oid(actual_mech);
 	    if (ret_flags != NULL)
 		*ret_flags = temp_ret_flags;
-	    return	(status);
+	    *context_handle = (gss_ctx_id_t)union_ctx_id;
+	    return GSS_S_COMPLETE;
     } else {
 
 	status = GSS_S_BAD_MECH;
     }
 
 error_out:
-    if (union_ctx_id) {
+	/*
+	 * RFC 2744 5.1 requires that we not create a context on a failed first
+	 * call to accept, and recommends that on a failed subsequent call we
+	 * make the caller responsible for calling gss_delete_sec_context.
+	 * Even if the mech deleted its context, keep the union context around
+	 * for the caller to delete.
+	 */
+    if (union_ctx_id && *context_handle == GSS_C_NO_CONTEXT) {
 	if (union_ctx_id->mech_type) {
 	    if (union_ctx_id->mech_type->elements)
 		free(union_ctx_id->mech_type->elements);
@@ -384,7 +393,6 @@ error_out:
 					 GSS_C_NO_BUFFER);
 	}
 	free(union_ctx_id);
-	*context_handle = GSS_C_NO_CONTEXT;
     }
 
     if (src_name)
diff --git a/src/lib/gssapi/mechglue/g_complete_auth_token.c b/src/lib/gssapi/mechglue/g_complete_auth_token.c
index 9181551..4bcb47e 100644
--- a/src/lib/gssapi/mechglue/g_complete_auth_token.c
+++ b/src/lib/gssapi/mechglue/g_complete_auth_token.c
@@ -52,6 +52,8 @@ gss_complete_auth_token (OM_uint32 *minor_status,
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return GSS_S_NO_CONTEXT;
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech != NULL) {
diff --git a/src/lib/gssapi/mechglue/g_context_time.c b/src/lib/gssapi/mechglue/g_context_time.c
index 2ff8d09..c947e76 100644
--- a/src/lib/gssapi/mechglue/g_context_time.c
+++ b/src/lib/gssapi/mechglue/g_context_time.c
@@ -58,6 +58,8 @@ OM_uint32 *		time_rec;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
diff --git a/src/lib/gssapi/mechglue/g_delete_sec_context.c b/src/lib/gssapi/mechglue/g_delete_sec_context.c
index 4bf0dec..574ff02 100644
--- a/src/lib/gssapi/mechglue/g_delete_sec_context.c
+++ b/src/lib/gssapi/mechglue/g_delete_sec_context.c
@@ -87,12 +87,14 @@ gss_buffer_t		output_token;
     if (GSSINT_CHK_LOOP(ctx))
 	return (GSS_S_CALL_INACCESSIBLE_READ | GSS_S_NO_CONTEXT);
 
-    status = gssint_delete_internal_sec_context(minor_status,
-						ctx->mech_type,
-						&ctx->internal_ctx_id,
-						output_token);
-    if (status)
-	return status;
+    if (ctx->internal_ctx_id != GSS_C_NO_CONTEXT) {
+	status = gssint_delete_internal_sec_context(minor_status,
+						    ctx->mech_type,
+						    &ctx->internal_ctx_id,
+						    output_token);
+	if (status)
+	    return status;
+    }
 
     /* now free up the space for the union context structure */
     free(ctx->mech_type->elements);
diff --git a/src/lib/gssapi/mechglue/g_exp_sec_context.c b/src/lib/gssapi/mechglue/g_exp_sec_context.c
index b637452..1d7990b 100644
--- a/src/lib/gssapi/mechglue/g_exp_sec_context.c
+++ b/src/lib/gssapi/mechglue/g_exp_sec_context.c
@@ -95,6 +95,8 @@ gss_buffer_t		interprocess_token;
      */
 
     ctx = (gss_union_ctx_id_t) *context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
     if (!mech)
 	return GSS_S_BAD_MECH;
diff --git a/src/lib/gssapi/mechglue/g_init_sec_context.c b/src/lib/gssapi/mechglue/g_init_sec_context.c
index 9f154b8..e2df1ce 100644
--- a/src/lib/gssapi/mechglue/g_init_sec_context.c
+++ b/src/lib/gssapi/mechglue/g_init_sec_context.c
@@ -192,8 +192,13 @@ OM_uint32 *		time_rec;
 
 	/* copy the supplied context handle */
 	union_ctx_id->internal_ctx_id = GSS_C_NO_CONTEXT;
-    } else
+    } else {
 	union_ctx_id = (gss_union_ctx_id_t)*context_handle;
+	if (union_ctx_id->internal_ctx_id == GSS_C_NO_CONTEXT) {
+	    status = GSS_S_NO_CONTEXT;
+	    goto end;
+	}
+    }
 
     /*
      * get the appropriate cred handle from the union cred struct.
@@ -224,15 +229,13 @@ OM_uint32 *		time_rec;
 
     if (status != GSS_S_COMPLETE && status != GSS_S_CONTINUE_NEEDED) {
 	/*
-	 * The spec says the preferred method is to delete all context info on
-	 * the first call to init, and on all subsequent calls make the caller
-	 * responsible for calling gss_delete_sec_context.  However, if the
-	 * mechanism decided to delete the internal context, we should also
-	 * delete the union context.
+	 * RFC 2744 5.19 requires that we not create a context on a failed
+	 * first call to init, and recommends that on a failed subsequent call
+	 * we make the caller responsible for calling gss_delete_sec_context.
+	 * Even if the mech deleted its context, keep the union context around
+	 * for the caller to delete.
 	 */
 	map_error(minor_status, mech);
-	if (union_ctx_id->internal_ctx_id == GSS_C_NO_CONTEXT)
-	    *context_handle = GSS_C_NO_CONTEXT;
 	if (*context_handle == GSS_C_NO_CONTEXT) {
 	    free(union_ctx_id->mech_type->elements);
 	    free(union_ctx_id->mech_type);
diff --git a/src/lib/gssapi/mechglue/g_inq_context.c b/src/lib/gssapi/mechglue/g_inq_context.c
index 6f1c71e..6c0d98d 100644
--- a/src/lib/gssapi/mechglue/g_inq_context.c
+++ b/src/lib/gssapi/mechglue/g_inq_context.c
@@ -104,6 +104,8 @@ gss_inquire_context(
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (!mech || !mech->gss_inquire_context || !mech->gss_display_name ||
diff --git a/src/lib/gssapi/mechglue/g_prf.c b/src/lib/gssapi/mechglue/g_prf.c
index fcca3e4..9e168ad 100644
--- a/src/lib/gssapi/mechglue/g_prf.c
+++ b/src/lib/gssapi/mechglue/g_prf.c
@@ -59,6 +59,8 @@ gss_pseudo_random (OM_uint32 *minor_status,
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return GSS_S_NO_CONTEXT;
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech != NULL) {
diff --git a/src/lib/gssapi/mechglue/g_process_context.c b/src/lib/gssapi/mechglue/g_process_context.c
index bc260ae..3968b5d 100644
--- a/src/lib/gssapi/mechglue/g_process_context.c
+++ b/src/lib/gssapi/mechglue/g_process_context.c
@@ -61,6 +61,8 @@ gss_buffer_t		token_buffer;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
diff --git a/src/lib/gssapi/mechglue/g_seal.c b/src/lib/gssapi/mechglue/g_seal.c
index f17241c..3db1ee0 100644
--- a/src/lib/gssapi/mechglue/g_seal.c
+++ b/src/lib/gssapi/mechglue/g_seal.c
@@ -92,6 +92,8 @@ gss_wrap( OM_uint32 *minor_status,
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+        return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
@@ -226,6 +228,8 @@ gss_wrap_size_limit(OM_uint32  *minor_status,
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+        return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (!mech)
diff --git a/src/lib/gssapi/mechglue/g_sign.c b/src/lib/gssapi/mechglue/g_sign.c
index 86d641a..03fbd8c 100644
--- a/src/lib/gssapi/mechglue/g_sign.c
+++ b/src/lib/gssapi/mechglue/g_sign.c
@@ -94,6 +94,8 @@ gss_buffer_t		msg_token;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
diff --git a/src/lib/gssapi/mechglue/g_unseal.c b/src/lib/gssapi/mechglue/g_unseal.c
index 3e8053c..c208635 100644
--- a/src/lib/gssapi/mechglue/g_unseal.c
+++ b/src/lib/gssapi/mechglue/g_unseal.c
@@ -76,6 +76,8 @@ gss_qop_t *		qop_state;
      * call it.
      */
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
diff --git a/src/lib/gssapi/mechglue/g_unwrap_aead.c b/src/lib/gssapi/mechglue/g_unwrap_aead.c
index e78bff2..0682bd8 100644
--- a/src/lib/gssapi/mechglue/g_unwrap_aead.c
+++ b/src/lib/gssapi/mechglue/g_unwrap_aead.c
@@ -186,6 +186,8 @@ gss_qop_t		*qop_state;
      * call it.
      */
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (!mech)
diff --git a/src/lib/gssapi/mechglue/g_unwrap_iov.c b/src/lib/gssapi/mechglue/g_unwrap_iov.c
index c0dd314..599be2c 100644
--- a/src/lib/gssapi/mechglue/g_unwrap_iov.c
+++ b/src/lib/gssapi/mechglue/g_unwrap_iov.c
@@ -89,6 +89,8 @@ int			iov_count;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
@@ -128,6 +130,8 @@ gss_verify_mic_iov(OM_uint32 *minor_status, gss_ctx_id_t context_handle,
 
     /* Select the approprate underlying mechanism routine and call it. */
     ctx = (gss_union_ctx_id_t)context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return GSS_S_NO_CONTEXT;
     mech = gssint_get_mechanism(ctx->mech_type);
     if (mech == NULL)
 	return GSS_S_BAD_MECH;
diff --git a/src/lib/gssapi/mechglue/g_verify.c b/src/lib/gssapi/mechglue/g_verify.c
index 1578ae1..8996fce 100644
--- a/src/lib/gssapi/mechglue/g_verify.c
+++ b/src/lib/gssapi/mechglue/g_verify.c
@@ -65,6 +65,8 @@ gss_qop_t *		qop_state;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
diff --git a/src/lib/gssapi/mechglue/g_wrap_aead.c b/src/lib/gssapi/mechglue/g_wrap_aead.c
index 96cdf3c..7fe3b7b 100644
--- a/src/lib/gssapi/mechglue/g_wrap_aead.c
+++ b/src/lib/gssapi/mechglue/g_wrap_aead.c
@@ -256,6 +256,8 @@ gss_buffer_t		output_message_buffer;
      * call it.
      */
     ctx = (gss_union_ctx_id_t)context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
     if (!mech)
 	return (GSS_S_BAD_MECH);
diff --git a/src/lib/gssapi/mechglue/g_wrap_iov.c b/src/lib/gssapi/mechglue/g_wrap_iov.c
index 40cd98f..14447c4 100644
--- a/src/lib/gssapi/mechglue/g_wrap_iov.c
+++ b/src/lib/gssapi/mechglue/g_wrap_iov.c
@@ -93,6 +93,8 @@ int			iov_count;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
@@ -151,6 +153,8 @@ int			iov_count;
      */
 
     ctx = (gss_union_ctx_id_t) context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return (GSS_S_NO_CONTEXT);
     mech = gssint_get_mechanism (ctx->mech_type);
 
     if (mech) {
@@ -190,6 +194,8 @@ gss_get_mic_iov(OM_uint32 *minor_status, gss_ctx_id_t context_handle,
 
     /* Select the approprate underlying mechanism routine and call it. */
     ctx = (gss_union_ctx_id_t)context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return GSS_S_NO_CONTEXT;
     mech = gssint_get_mechanism(ctx->mech_type);
     if (mech == NULL)
 	return GSS_S_BAD_MECH;
@@ -218,6 +224,8 @@ gss_get_mic_iov_length(OM_uint32 *minor_status, gss_ctx_id_t context_handle,
 
     /* Select the approprate underlying mechanism routine and call it. */
     ctx = (gss_union_ctx_id_t)context_handle;
+    if (ctx->internal_ctx_id == GSS_C_NO_CONTEXT)
+	return GSS_S_NO_CONTEXT;
     mech = gssint_get_mechanism(ctx->mech_type);
     if (mech == NULL)
 	return GSS_S_BAD_MECH;
-- 
2.10.2

