EAP-pwd peer: Fix last fragment length validation

All but the last fragment had their length checked against the remaining
room in the reassembly buffer. This allowed a suitably constructed last
fragment frame to try to add extra data that would go beyond the buffer.
The length validation code in wpabuf_put_data() prevents an actual
buffer write overflow from occurring, but this results in process
termination. (CVE-2015-5315)

Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/src/eap_peer/eap_pwd.c b/src/eap_peer/eap_pwd.c
index 1f785443ee5acea64896aa3e770721d7cb6f5325..75ceef1b0157c651ebd5926a642c199eff2a0727 100644 (file)
--- a/src/eap_peer/eap_pwd.c
+++ b/src/eap_peer/eap_pwd.c
@@ -903,7 +903,7 @@ eap_pwd_process(struct eap_sm *sm, void *priv, struct eap_method_ret *ret,
        /*
         * buffer and ACK the fragment
         */
-       if (EAP_PWD_GET_MORE_BIT(lm_exch)) {
+       if (EAP_PWD_GET_MORE_BIT(lm_exch) || data->in_frag_pos) {
                data->in_frag_pos += len;
                if (data->in_frag_pos > wpabuf_size(data->inbuf)) {
                        wpa_printf(MSG_INFO, "EAP-pwd: Buffer overflow attack "
@@ -916,7 +916,8 @@ eap_pwd_process(struct eap_sm *sm, void *priv, struct eap_method_ret *ret,
                        return NULL;
                }
                wpabuf_put_data(data->inbuf, pos, len);
-
+       }
+       if (EAP_PWD_GET_MORE_BIT(lm_exch)) {
                resp = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
                                     EAP_PWD_HDR_SIZE,
                                     EAP_CODE_RESPONSE, eap_get_id(reqData));
@@ -930,10 +931,8 @@ eap_pwd_process(struct eap_sm *sm, void *priv, struct eap_method_ret *ret,
         * we're buffering and this is the last fragment
         */
        if (data->in_frag_pos) {
-               wpabuf_put_data(data->inbuf, pos, len);
                wpa_printf(MSG_DEBUG, "EAP-pwd: Last fragment, %d bytes",
                           (int) len);
-               data->in_frag_pos += len;
                pos = wpabuf_head_u8(data->inbuf);
                len = data->in_frag_pos;
        }