[libxml2] Harden the buffer code and make it more compatible

[Daniel Veillard <veillard src gnome org>]

commit 9ee02f80a4d674bac96f88b5a241825aad453a7a
Author: Daniel Veillard <veillard redhat com>
Date:   Mon Jul 16 19:57:42 2012 +0800

    Harden the buffer code and make it more compatible
    
    Mimic the old xmlBuffer strcture in xmlBuf to avaoid catastrophic
    failures in case of old code directly reading ctxt->input->buf->buffer
    
    Check on all buffer entry points if an error previously occured on
    the buffer, and fail the operation if this is the case, the buffer
    becomes immutable and unreadable.

 buf.c |   77 +++++++++++++++++++++++++++++++++++++++-------------------------
 1 files changed, 47 insertions(+), 30 deletions(-)
---
diff --git a/buf.c b/buf.c
index 6ab7106..c2123aa 100644
--- a/buf.c
+++ b/buf.c
@@ -32,15 +32,19 @@
 /**
  * xmlBuf:
  *
- * A buffer structure
+ * A buffer structure. The base of the structure is somehow compatible
+ * with struct _xmlBuffer to limit risks on application which accessed
+ * directly the input->buf->buffer structures.
  */
 
 struct _xmlBuf {
     xmlChar *content;		/* The buffer content UTF8 */
-    size_t use;		        /* The buffer size used */
-    size_t size;		/* The buffer size */
+    unsigned int compat_use;    /* for binary compatibility */
+    unsigned int compat_size;   /* for binary compatibility */
     xmlBufferAllocationScheme alloc; /* The realloc method */
     xmlChar *contentIO;		/* in IO mode we may have a different base */
+    size_t use;		        /* The buffer size used */
+    size_t size;		/* The buffer size */
     xmlBufferPtr buffer;        /* wrapper for an old buffer */
     int error;                  /* an error code if a failure occured */
 };
@@ -91,6 +95,8 @@ xmlBufCreate(void) {
 	xmlBufMemoryError(NULL, "creating buffer");
         return(NULL);
     }
+    ret->compat_use = 0;
+    ret->compat_size = 0;
     ret->use = 0;
     ret->error = 0;
     ret->buffer = NULL;
@@ -123,6 +129,8 @@ xmlBufCreateSize(size_t size) {
 	xmlBufMemoryError(NULL, "creating buffer");
         return(NULL);
     }
+    ret->compat_use = 0;
+    ret->compat_size = 0;
     ret->use = 0;
     ret->error = 0;
     ret->buffer = NULL;
@@ -197,6 +205,13 @@ xmlBufCreateStatic(void *mem, size_t size) {
 	xmlBufMemoryError(NULL, "creating buffer");
         return(NULL);
     }
+    if (size < INT_MAX) {
+        ret->compat_use = size;
+        ret->compat_size = size;
+    } else {
+        ret->compat_use = 0;
+        ret->compat_size = 0;
+    }
     ret->use = size;
     ret->size = size;
     ret->alloc = XML_BUFFER_ALLOC_IMMUTABLE;
@@ -234,10 +249,10 @@ xmlBufGetAllocationScheme(xmlBufPtr buf) {
 int
 xmlBufSetAllocationScheme(xmlBufPtr buf,
                           xmlBufferAllocationScheme scheme) {
-    if (buf == NULL) {
+    if ((buf == NULL) || (buf->error != 0)) {
 #ifdef DEBUG_BUFFER
         xmlGenericError(xmlGenericErrorContext,
-		"xmlBufSetAllocationScheme: buf == NULL\n");
+		"xmlBufSetAllocationScheme: buf == NULL or in error\n");
 #endif
         return(-1);
     }
@@ -299,7 +314,7 @@ xmlBufFree(xmlBufPtr buf) {
  */
 void
 xmlBufEmpty(xmlBufPtr buf) {
-    if (buf == NULL) return;
+    if ((buf == NULL) || (buf->error != 0)) return;
     if (buf->content == NULL) return;
     buf->use = 0;
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) {
@@ -330,7 +345,7 @@ xmlBufEmpty(xmlBufPtr buf) {
  */
 size_t
 xmlBufShrink(xmlBufPtr buf, size_t len) {
-    if (buf == NULL) return(0);
+    if ((buf == NULL) || (buf->error != 0)) return(0);
     if (len == 0) return(0);
     if (len > buf->use) return(0);
 
@@ -380,7 +395,7 @@ xmlBufGrowInternal(xmlBufPtr buf, size_t len) {
     size_t size;
     xmlChar *newbuf;
 
-    if (buf == NULL) return(0);
+    if ((buf == NULL) || (buf->error != 0)) return(0);
 
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return(0);
     if (buf->use + len < buf->size)
@@ -476,10 +491,10 @@ size_t
 xmlBufDump(FILE *file, xmlBufPtr buf) {
     size_t ret;
 
-    if (buf == NULL) {
+    if ((buf == NULL) || (buf->error != 0)) {
 #ifdef DEBUG_BUFFER
         xmlGenericError(xmlGenericErrorContext,
-		"xmlBufDump: buf == NULL\n");
+		"xmlBufDump: buf == NULL or in error\n");
 #endif
 	return(0);
     }
@@ -508,7 +523,7 @@ xmlBufDump(FILE *file, xmlBufPtr buf) {
 xmlChar *
 xmlBufContent(const xmlBufPtr buf)
 {
-    if(!buf)
+    if ((!buf) || (buf->error))
         return NULL;
 
     return(buf->content);
@@ -526,7 +541,7 @@ xmlBufContent(const xmlBufPtr buf)
 xmlChar *
 xmlBufEnd(const xmlBufPtr buf)
 {
-    if(!buf)
+    if ((!buf) || (buf->error))
         return NULL;
 
     return(&buf->content[buf->use]);
@@ -545,7 +560,7 @@ xmlBufEnd(const xmlBufPtr buf)
  */
 int
 xmlBufAddLen(xmlBufPtr buf, size_t len) {
-    if ((buf == NULL) || (len > (buf->size - buf->use)))
+    if ((buf == NULL) || (buf->error) || (len > (buf->size - buf->use)))
         return(-1);
     buf->use += len;
     if (buf->size > buf->use)
@@ -566,7 +581,7 @@ xmlBufAddLen(xmlBufPtr buf, size_t len) {
  */
 int
 xmlBufErase(xmlBufPtr buf, size_t len) {
-    if ((buf == NULL) || (len > buf->use))
+    if ((buf == NULL) || (buf->error) || (len > buf->use))
         return(-1);
     buf->use -= len;
     buf->content[buf->use] = 0;
@@ -585,7 +600,7 @@ xmlBufErase(xmlBufPtr buf, size_t len) {
 size_t
 xmlBufLength(const xmlBufPtr buf)
 {
-    if (!buf)
+    if ((!buf) || (buf->error))
         return 0;
 
     return(buf->use);
@@ -603,7 +618,7 @@ xmlBufLength(const xmlBufPtr buf)
 size_t
 xmlBufUse(const xmlBufPtr buf)
 {
-    if (!buf)
+    if ((!buf) || (buf->error))
         return 0;
 
     return(buf->use);
@@ -623,7 +638,7 @@ xmlBufUse(const xmlBufPtr buf)
 size_t
 xmlBufAvail(const xmlBufPtr buf)
 {
-    if (!buf)
+    if ((!buf) || (buf->error))
         return 0;
 
     return(buf->size - buf->use);
@@ -640,7 +655,7 @@ xmlBufAvail(const xmlBufPtr buf)
 int
 xmlBufIsEmpty(const xmlBufPtr buf)
 {
-    if(!buf)
+    if ((!buf) || (buf->error))
         return(-1);
 
     return(buf->use == 0);
@@ -662,7 +677,7 @@ xmlBufResize(xmlBufPtr buf, size_t size)
     xmlChar* rebuf = NULL;
     size_t start_buf;
 
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(0);
 
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return(0);
@@ -771,7 +786,7 @@ int
 xmlBufAdd(xmlBufPtr buf, const xmlChar *str, int len) {
     unsigned int needSize;
 
-    if ((str == NULL) || (buf == NULL)) {
+    if ((str == NULL) || (buf == NULL) || (buf->error)) {
 	return -1;
     }
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;
@@ -820,7 +835,7 @@ int
 xmlBufAddHead(xmlBufPtr buf, const xmlChar *str, int len) {
     unsigned int needSize;
 
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;
     if (str == NULL) {
@@ -885,7 +900,7 @@ xmlBufAddHead(xmlBufPtr buf, const xmlChar *str, int len) {
  */
 int
 xmlBufCat(xmlBufPtr buf, const xmlChar *str) {
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;
     if (str == NULL) return -1;
@@ -906,7 +921,7 @@ int
 xmlBufCCat(xmlBufPtr buf, const char *str) {
     const char *cur;
 
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE) return -1;
     if (str == NULL) {
@@ -942,7 +957,7 @@ xmlBufCCat(xmlBufPtr buf, const char *str) {
  */
 int
 xmlBufWriteCHAR(xmlBufPtr buf, const xmlChar *string) {
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE)
         return(-1);
@@ -962,7 +977,7 @@ xmlBufWriteCHAR(xmlBufPtr buf, const xmlChar *string) {
  */
 int
 xmlBufWriteChar(xmlBufPtr buf, const char *string) {
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE)
         return(-1);
@@ -985,7 +1000,7 @@ xmlBufWriteChar(xmlBufPtr buf, const char *string) {
 int
 xmlBufWriteQuotedString(xmlBufPtr buf, const xmlChar *string) {
     const xmlChar *cur, *base;
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(-1);
     if (buf->alloc == XML_BUFFER_ALLOC_IMMUTABLE)
         return(-1);
@@ -1076,7 +1091,7 @@ xmlBufferPtr
 xmlBufBackToBuffer(xmlBufPtr buf) {
     xmlBufferPtr ret;
 
-    if (buf == NULL)
+    if ((buf == NULL) || (buf->error))
         return(NULL);
     if (buf->buffer == NULL) {
         xmlBufFree(buf);
@@ -1128,7 +1143,7 @@ int
 xmlBufMergeBuffer(xmlBufPtr buf, xmlBufferPtr buffer) {
     int ret;
 
-    if (buffer == NULL)
+    if ((buf == NULL) || (buf->error))
         return(0);
     if ((buf != NULL) && (buffer->content != NULL) && (buffer->use > 0)) {
         ret = xmlBufAdd(buf, buffer->content, buffer->use);
@@ -1148,7 +1163,7 @@ xmlBufMergeBuffer(xmlBufPtr buf, xmlBufferPtr buffer) {
  */
 int
 xmlBufResetInput(xmlBufPtr buf, xmlParserInputPtr input) {
-    if ((input == NULL) || (buf == NULL))
+    if ((input == NULL) || (buf == NULL) || (buf->error))
         return(-1);
     input->base = input->cur = buf->content;
     input->end = &buf->content[buf->use];
@@ -1168,6 +1183,8 @@ size_t
 xmlBufGetInputBase(xmlBufPtr buf, xmlParserInputPtr input) {
     size_t base;
 
+    if ((input == NULL) || (buf == NULL) || (buf->error))
+        return(-1);
     base = input->base - buf->content;
     /*
      * We could do some pointer arythmetic checks but that's probably
@@ -1193,7 +1210,7 @@ xmlBufGetInputBase(xmlBufPtr buf, xmlParserInputPtr input) {
 int
 xmlBufSetInputBaseCur(xmlBufPtr buf, xmlParserInputPtr input,
                       size_t base, size_t cur) {
-    if ((input == NULL) || (buf == NULL))
+    if ((input == NULL) || (buf == NULL) || (buf->error))
         return(-1);
     input->base = &buf->content[base];
     input->cur = input->base + cur;