From ecc43dce8e2cd19f635841e788421d0f4bd72cce Mon Sep 17 00:00:00 2001

From: Nick Wellnhofer <wellnhofer@aevum.de>

Date: Tue, 8 Mar 2022 20:10:02 +0100

Subject: [PATCH] [CVE-2022-29824] Fix integer overflows in xmlBuf and

 xmlBuffer

In several places, the code handling string buffers didn't check for

integer overflow or used wrong types for buffer sizes. This could

result in out-of-bounds writes or other memory errors when working on

large, multi-gigabyte buffers.

Thanks to Felix Wilhelm for the report.

---

 buf.c  | 86 +++++++++++++++++++++++-----------------------------------

 tree.c | 72 ++++++++++++++++++------------------------------

 2 files changed, 61 insertions(+), 97 deletions(-)

diff --git a/buf.c b/buf.c

index 24368d37..40a5ee06 100644

--- a/buf.c

+++ b/buf.c

@@ -30,6 +30,10 @@

 #include <libxml/parserInternals.h> /* for XML_MAX_TEXT_LENGTH */

 #include "buf.h"

+#ifndef SIZE_MAX

+#define SIZE_MAX ((size_t) -1)

+#endif

+

 #define WITH_BUFFER_COMPAT

 /**

@@ -156,6 +160,8 @@ xmlBufPtr

 xmlBufCreateSize(size_t size) {

     xmlBufPtr ret;

+    if (size == SIZE_MAX)

+        return(NULL);

     ret = (xmlBufPtr) xmlMalloc(sizeof(xmlBuf));

     if (ret == NULL) {

 	xmlBufMemoryError(NULL, "creating buffer");

@@ -166,8 +172,8 @@ xmlBufCreateSize(size_t size) {

     ret->error = 0;

     ret->buffer = NULL;

     ret->alloc = xmlBufferAllocScheme;

-    ret->size = (size ? size+2 : 0);         /* +1 for ending null */

-    ret->compat_size = (int) ret->size;

+    ret->size = (size ? size + 1 : 0);         /* +1 for ending null */

+    ret->compat_size = (ret->size > INT_MAX ? INT_MAX : ret->size);

     if (ret->size){

         ret->content = (xmlChar *) xmlMallocAtomic(ret->size * sizeof(xmlChar));

         if (ret->content == NULL) {

@@ -442,23 +448,17 @@ xmlBufGrowInternal(xmlBufPtr buf, size_t len) {

     CHECK_COMPAT(buf)

     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return(0);

-    if (buf->use + len < buf->size)

+    if (len < buf->size - buf->use)

         return(buf->size - buf->use);

+    if (len > SIZE_MAX - buf->use)

+        return(0);

-    /*

-     * Windows has a BIG problem on realloc timing, so we try to double

-     * the buffer size (if that's enough) (bug 146697)

-     * Apparently BSD too, and it's probably best for linux too

-     * On an embedded system this may be something to change

-     */

-#if 1

-    if (buf->size > (size_t) len)

-        size = buf->size * 2;

-    else

-        size = buf->use + len + 100;

-#else

-    size = buf->use + len + 100;

-#endif

+    if (buf->size > (size_t) len) {

+        size = buf->size > SIZE_MAX / 2 ? SIZE_MAX : buf->size * 2;

+    } else {

+        size = buf->use + len;

+        size = size > SIZE_MAX - 100 ? SIZE_MAX : size + 100;

+    }

     if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {

         /*

@@ -744,7 +744,7 @@ xmlBufIsEmpty(const xmlBufPtr buf)

 int

 xmlBufResize(xmlBufPtr buf, size_t size)

 {

-    unsigned int newSize;

+    size_t newSize;

     xmlChar* rebuf = NULL;

     size_t start_buf;

@@ -772,9 +772,13 @@ xmlBufResize(xmlBufPtr buf, size_t size)

 	case XML_BUFFER_ALLOC_IO:

 	case XML_BUFFER_ALLOC_DOUBLEIT:

 	    /*take care of empty case*/

-	    newSize = (buf->size ? buf->size*2 : size + 10);

+            if (buf->size == 0) {

+                newSize = (size > SIZE_MAX - 10 ? SIZE_MAX : size + 10);

+            } else {

+                newSize = buf->size;

+            }

 	    while (size > newSize) {

-	        if (newSize > UINT_MAX / 2) {

+	        if (newSize > SIZE_MAX / 2) {

 	            xmlBufMemoryError(buf, "growing buffer");

 	            return 0;

 	        }

@@ -782,15 +786,15 @@ xmlBufResize(xmlBufPtr buf, size_t size)

 	    }

 	    break;

 	case XML_BUFFER_ALLOC_EXACT:

-	    newSize = size+10;

+            newSize = (size > SIZE_MAX - 10 ? SIZE_MAX : size + 10);

 	    break;

         case XML_BUFFER_ALLOC_HYBRID:

             if (buf->use < BASE_BUFFER_SIZE)

                 newSize = size;

             else {

-                newSize = buf->size * 2;

+                newSize = buf->size;

                 while (size > newSize) {

-                    if (newSize > UINT_MAX / 2) {

+                    if (newSize > SIZE_MAX / 2) {

                         xmlBufMemoryError(buf, "growing buffer");

                         return 0;

                     }

@@ -800,7 +804,7 @@ xmlBufResize(xmlBufPtr buf, size_t size)

             break;

 	default:

-	    newSize = size+10;

+            newSize = (size > SIZE_MAX - 10 ? SIZE_MAX : size + 10);

 	    break;

     }

@@ -866,7 +870,7 @@ xmlBufResize(xmlBufPtr buf, size_t size)

  */

 int

 xmlBufAdd(xmlBufPtr buf, const xmlChar *str, int len) {

-    unsigned int needSize;

+    size_t needSize;

     if ((str == NULL) || (buf == NULL) || (buf->error))

 	return -1;

@@ -888,8 +892,10 @@ xmlBufAdd(xmlBufPtr buf, const xmlChar *str, int len) {

     if (len < 0) return -1;

     if (len == 0) return 0;

-    needSize = buf->use + len + 2;

-    if (needSize > buf->size){

+    if ((size_t) len >= buf->size - buf->use) {

+        if ((size_t) len >= SIZE_MAX - buf->use)

+            return(-1);

+        needSize = buf->use + len + 1;

 	if (buf->alloc == XML_BUFFER_ALLOC_BOUNDED) {

 	    /*

 	     * Used to provide parsing limits

@@ -1025,31 +1031,7 @@ xmlBufCat(xmlBufPtr buf, const xmlChar *str) {

  */

 int

 xmlBufCCat(xmlBufPtr buf, const char *str) {

-    const char *cur;

-

-    if ((buf == NULL) || (buf->error))

-        return(-1);

-    CHECK_COMPAT(buf)

-    if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;

-    if (str == NULL) {

-#ifdef DEBUG_BUFFER

-        xmlGenericError(xmlGenericErrorContext,

-		"xmlBufCCat: str == NULL\n");

-#endif

-	return -1;

-    }

-    for (cur = str;*cur != 0;cur++) {

-        if (buf->use  + 10 >= buf->size) {

-            if (!xmlBufResize(buf, buf->use+10)){

-		xmlBufMemoryError(buf, "growing buffer");

-                return XML_ERR_NO_MEMORY;

-            }

-        }

-        buf->content[buf->use++] = *cur;

-    }

-    buf->content[buf->use] = 0;

-    UPDATE_COMPAT(buf)

-    return 0;

+    return xmlBufCat(buf, (const xmlChar *) str);

 }

 /**

diff --git a/tree.c b/tree.c

index 9d94aa42..86afb7d6 100644

--- a/tree.c

+++ b/tree.c

@@ -7104,6 +7104,8 @@ xmlBufferPtr

 xmlBufferCreateSize(size_t size) {

     xmlBufferPtr ret;

+    if (size >= UINT_MAX)

+        return(NULL);

     ret = (xmlBufferPtr) xmlMalloc(sizeof(xmlBuffer));

     if (ret == NULL) {

 	xmlTreeErrMemory("creating buffer");

@@ -7111,7 +7113,7 @@ xmlBufferCreateSize(size_t size) {

     }

     ret->use = 0;

     ret->alloc = xmlBufferAllocScheme;

-    ret->size = (size ? size+2 : 0);         /* +1 for ending null */

+    ret->size = (size ? size + 1 : 0);         /* +1 for ending null */

     if (ret->size){

         ret->content = (xmlChar *) xmlMallocAtomic(ret->size * sizeof(xmlChar));

         if (ret->content == NULL) {

@@ -7171,6 +7173,8 @@ xmlBufferCreateStatic(void *mem, size_t size) {

     if ((mem == NULL) || (size == 0))

         return(NULL);

+    if (size > UINT_MAX)

+        return(NULL);

     ret = (xmlBufferPtr) xmlMalloc(sizeof(xmlBuffer));

     if (ret == NULL) {

@@ -7318,28 +7322,23 @@ xmlBufferShrink(xmlBufferPtr buf, unsigned int len) {

  */

 int

 xmlBufferGrow(xmlBufferPtr buf, unsigned int len) {

-    int size;

+    unsigned int size;

     xmlChar *newbuf;

     if (buf == NULL) return(-1);

     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return(0);

-    if (len + buf->use < buf->size) return(0);

+    if (len < buf->size - buf->use)

+        return(0);

+    if (len > UINT_MAX - buf->use)

+        return(-1);

-    /*

-     * Windows has a BIG problem on realloc timing, so we try to double

-     * the buffer size (if that's enough) (bug 146697)

-     * Apparently BSD too, and it's probably best for linux too

-     * On an embedded system this may be something to change

-     */

-#if 1

-    if (buf->size > len)

-        size = buf->size * 2;

-    else

-        size = buf->use + len + 100;

-#else

-    size = buf->use + len + 100;

-#endif

+    if (buf->size > (size_t) len) {

+        size = buf->size > UINT_MAX / 2 ? UINT_MAX : buf->size * 2;

+    } else {

+        size = buf->use + len;

+        size = size > UINT_MAX - 100 ? UINT_MAX : size + 100;

+    }

     if ((buf->alloc == XML_BUFFER_ALLOC_IO) && (buf->contentIO != NULL)) {

         size_t start_buf = buf->content - buf->contentIO;

@@ -7466,7 +7465,10 @@ xmlBufferResize(xmlBufferPtr buf, unsigned int size)

 	case XML_BUFFER_ALLOC_IO:

 	case XML_BUFFER_ALLOC_DOUBLEIT:

 	    /*take care of empty case*/

-	    newSize = (buf->size ? buf->size : size + 10);

+            if (buf->size == 0)

+                newSize = (size > UINT_MAX - 10 ? UINT_MAX : size + 10);

+            else

+                newSize = buf->size;

 	    while (size > newSize) {

 	        if (newSize > UINT_MAX / 2) {

 	            xmlTreeErrMemory("growing buffer");

@@ -7476,7 +7478,7 @@ xmlBufferResize(xmlBufferPtr buf, unsigned int size)

 	    }

 	    break;

 	case XML_BUFFER_ALLOC_EXACT:

-	    newSize = size+10;

+	    newSize = (size > UINT_MAX - 10 ? UINT_MAX : size + 10);;

 	    break;

         case XML_BUFFER_ALLOC_HYBRID:

             if (buf->use < BASE_BUFFER_SIZE)

@@ -7494,7 +7496,7 @@ xmlBufferResize(xmlBufferPtr buf, unsigned int size)

             break;

 	default:

-	    newSize = size+10;

+	    newSize = (size > UINT_MAX - 10 ? UINT_MAX : size + 10);;

 	    break;

     }

@@ -7580,8 +7582,10 @@ xmlBufferAdd(xmlBufferPtr buf, const xmlChar *str, int len) {

     if (len < 0) return -1;

     if (len == 0) return 0;

-    needSize = buf->use + len + 2;

-    if (needSize > buf->size){

+    if ((unsigned) len >= buf->size - buf->use) {

+        if ((unsigned) len >= UINT_MAX - buf->use)

+            return XML_ERR_NO_MEMORY;

+        needSize = buf->use + len + 1;

         if (!xmlBufferResize(buf, needSize)){

 	    xmlTreeErrMemory("growing buffer");

             return XML_ERR_NO_MEMORY;

@@ -7694,29 +7698,7 @@ xmlBufferCat(xmlBufferPtr buf, const xmlChar *str) {

  */

 int

 xmlBufferCCat(xmlBufferPtr buf, const char *str) {

-    const char *cur;

-

-    if (buf == NULL)

-        return(-1);

-    if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;

-    if (str == NULL) {

-#ifdef DEBUG_BUFFER

-        xmlGenericError(xmlGenericErrorContext,

-		"xmlBufferCCat: str == NULL\n");

-#endif

-	return -1;

-    }

-    for (cur = str;*cur != 0;cur++) {

-        if (buf->use  + 10 >= buf->size) {

-            if (!xmlBufferResize(buf, buf->use+10)){

-		xmlTreeErrMemory("growing buffer");

-                return XML_ERR_NO_MEMORY;

-            }

-        }

-        buf->content[buf->use++] = *cur;

-    }

-    buf->content[buf->use] = 0;

-    return 0;

+    return xmlBufferCat(buf, (const xmlChar *) str);

 }

 /**

-- 

2.36.0