From 5cec67e3f8d56e6e5fda2f90e102950cbb09e3d1 Mon Sep 17 00:00:00 2001
From: Daniel Veillard <veillard@redhat.com>
Date: Tue, 14 Apr 2015 17:41:48 +0800
Subject: [PATCH] CVE-2015-1819 Enforce the reader to run in constant memory
To: libvir-list@redhat.com

One of the operation on the reader could resolve entities
leading to the classic expansion issue. Make sure the
buffer used for xmlreader operation is bounded.
Introduce a new allocation type for the buffers for this effect.

Signed-off-by: Daniel Veillard <veillard@redhat.com>
---
 buf.c                 | 43 ++++++++++++++++++++++++++++++++++++++++++-
 include/libxml/tree.h |  3 ++-
 xmlreader.c           | 20 +++++++++++++++++++-
 3 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/buf.c b/buf.c
index d1756c4..b52e41d 100644
--- a/buf.c
+++ b/buf.c
@@ -27,6 +27,7 @@
 #include <libxml/tree.h>
 #include <libxml/globals.h>
 #include <libxml/tree.h>
+#include <libxml/parserInternals.h> /* for XML_MAX_TEXT_LENGTH */
 #include "buf.h"
 
 #define WITH_BUFFER_COMPAT
@@ -299,7 +300,8 @@ xmlBufSetAllocationScheme(xmlBufPtr buf,
     if ((scheme == XML_BUFFER_ALLOC_DOUBLEIT) ||
         (scheme == XML_BUFFER_ALLOC_EXACT) ||
         (scheme == XML_BUFFER_ALLOC_HYBRID) ||
-        (scheme == XML_BUFFER_ALLOC_IMMUTABLE)) {
+        (scheme == XML_BUFFER_ALLOC_IMMUTABLE) ||
+	(scheme == XML_BUFFER_ALLOC_BOUNDED)) {
 	buf->alloc = scheme;
         if (buf->buffer)
             buf->buffer->alloc = scheme;
@@ -458,6 +460,18 @@ xmlBufGrowInternal(xmlBufPtr buf, size_t len) {
     size = buf->use + len + 100;
 #endif
 
+    if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {
+        /*
+	 * Used to provide parsing limits
+	 */
+        if ((buf->use + len >= XML_MAX_TEXT_LENGTH) ||
+	    (buf->size >= XML_MAX_TEXT_LENGTH)) {
+	    xmlBufMemoryError(buf, "buffer error: text too long\n");
+	    return(0);
+	}
+	if (size >= XML_MAX_TEXT_LENGTH)
+	    size = XML_MAX_TEXT_LENGTH;
+    }
     if ((buf->alloc == XML_BUFFER_ALLOC_IO) && (buf->contentIO != NULL)) {
         size_t start_buf = buf->content - buf->contentIO;
 
@@ -739,6 +753,15 @@ xmlBufResize(xmlBufPtr buf, size_t size)
     CHECK_COMPAT(buf)
 
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return(0);
+    if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {
+        /*
+	 * Used to provide parsing limits
+	 */
+        if (size >= XML_MAX_TEXT_LENGTH) {
+	    xmlBufMemoryError(buf, "buffer error: text too long\n");
+	    return(0);
+	}
+    }
 
     /* Don't resize if we don't have to */
     if (size < buf->size)
@@ -867,6 +890,15 @@ xmlBufAdd(xmlBufPtr buf, const xmlChar *str, int len) {
 
     needSize = buf->use + len + 2;
     if (needSize > buf->size){
+	if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {
+	    /*
+	     * Used to provide parsing limits
+	     */
+	    if (needSize >= XML_MAX_TEXT_LENGTH) {
+		xmlBufMemoryError(buf, "buffer error: text too long\n");
+		return(-1);
+	    }
+	}
         if (!xmlBufResize(buf, needSize)){
 	    xmlBufMemoryError(buf, "growing buffer");
             return XML_ERR_NO_MEMORY;
@@ -938,6 +970,15 @@ xmlBufAddHead(xmlBufPtr buf, const xmlChar *str, int len) {
     }
     needSize = buf->use + len + 2;
     if (needSize > buf->size){
+	if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {
+	    /*
+	     * Used to provide parsing limits
+	     */
+	    if (needSize >= XML_MAX_TEXT_LENGTH) {
+		xmlBufMemoryError(buf, "buffer error: text too long\n");
+		return(-1);
+	    }
+	}
         if (!xmlBufResize(buf, needSize)){
 	    xmlBufMemoryError(buf, "growing buffer");
             return XML_ERR_NO_MEMORY;
diff --git a/include/libxml/tree.h b/include/libxml/tree.h
index 7e06686..d904a44 100644
--- a/include/libxml/tree.h
+++ b/include/libxml/tree.h
@@ -76,7 +76,8 @@ typedef enum {
     XML_BUFFER_ALLOC_EXACT,	/* grow only to the minimal size */
     XML_BUFFER_ALLOC_IMMUTABLE, /* immutable buffer */
     XML_BUFFER_ALLOC_IO,	/* special allocation scheme used for I/O */
-    XML_BUFFER_ALLOC_HYBRID	/* exact up to a threshold, and doubleit thereafter */
+    XML_BUFFER_ALLOC_HYBRID,	/* exact up to a threshold, and doubleit thereafter */
+    XML_BUFFER_ALLOC_BOUNDED	/* limit the upper size of the buffer */
 } xmlBufferAllocationScheme;
 
 /**
diff --git a/xmlreader.c b/xmlreader.c
index 00083d0..4fabaa9 100644
--- a/xmlreader.c
+++ b/xmlreader.c
@@ -2077,6 +2077,9 @@ xmlNewTextReader(xmlParserInputBufferPtr input, const char *URI) {
 		"xmlNewTextReader : malloc failed\n");
 	return(NULL);
     }
+    /* no operation on a reader should require a huge buffer */
+    xmlBufSetAllocationScheme(ret->buffer,
+			      XML_BUFFER_ALLOC_BOUNDED);
     ret->sax = (xmlSAXHandler *) xmlMalloc(sizeof(xmlSAXHandler));
     if (ret->sax == NULL) {
 	xmlBufFree(ret->buffer);
@@ -3602,6 +3605,7 @@ xmlTextReaderConstValue(xmlTextReaderPtr reader) {
 	    return(((xmlNsPtr) node)->href);
         case XML_ATTRIBUTE_NODE:{
 	    xmlAttrPtr attr = (xmlAttrPtr) node;
+	    const xmlChar *ret;
 
 	    if ((attr->children != NULL) &&
 	        (attr->children->type == XML_TEXT_NODE) &&
@@ -3615,10 +3619,21 @@ xmlTextReaderConstValue(xmlTextReaderPtr reader) {
                                         "xmlTextReaderSetup : malloc failed\n");
                         return (NULL);
                     }
+		    xmlBufSetAllocationScheme(reader->buffer,
+		                              XML_BUFFER_ALLOC_BOUNDED);
                 } else
                     xmlBufEmpty(reader->buffer);
 	        xmlBufGetNodeContent(reader->buffer, node);
-		return(xmlBufContent(reader->buffer));
+		ret = xmlBufContent(reader->buffer);
+		if (ret == NULL) {
+		    /* error on the buffer best to reallocate */
+		    xmlBufFree(reader->buffer);
+		    reader->buffer = xmlBufCreateSize(100);
+		    xmlBufSetAllocationScheme(reader->buffer,
+		                              XML_BUFFER_ALLOC_BOUNDED);
+		    ret = BAD_CAST "";
+		}
+		return(ret);
 	    }
 	    break;
 	}
@@ -5117,6 +5132,9 @@ xmlTextReaderSetup(xmlTextReaderPtr reader,
                         "xmlTextReaderSetup : malloc failed\n");
         return (-1);
     }
+    /* no operation on a reader should require a huge buffer */
+    xmlBufSetAllocationScheme(reader->buffer,
+			      XML_BUFFER_ALLOC_BOUNDED);
     if (reader->sax == NULL)
 	reader->sax = (xmlSAXHandler *) xmlMalloc(sizeof(xmlSAXHandler));
     if (reader->sax == NULL) {
-- 
2.5.0