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examples/element_declarations.c: Resolve recursion

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Sebastian Pipping 2022-10-30 17:44:32 +01:00
parent 7483d04a18
commit 48bc51fcf1
1 changed files with 68 additions and 10 deletions
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78
expat/examples/element_declarations.c
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@ -37,7 +37,9 @@
USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <expat.h>
#ifdef XML_LARGE_SIZE
@ -52,6 +54,33 @@
# define XML_FMT_STR "s"
#endif
// While traversing the XML_Content tree, we avoid recursion
// to not be vulnerable to a denial of service attack.
typedef struct StackStruct {
const XML_Content *model;
unsigned level;
struct StackStruct *prev;
} Stack;
static Stack *
stackPushMalloc(Stack *stackTop, const XML_Content *model, unsigned level) {
Stack *const newStackTop = malloc(sizeof(Stack));
if (! newStackTop) {
return NULL;
}
newStackTop->model = model;
newStackTop->level = level;
newStackTop->prev = stackTop;
return newStackTop;
}
static Stack *
stackPopFree(Stack *stackTop) {
Stack *const newStackTop = stackTop->prev;
free(stackTop);
return newStackTop;
}
static char *
contentTypeName(enum XML_Content_Type contentType) {
switch (contentType) {
@ -89,8 +118,8 @@ contentQuantName(enum XML_Content_Quant contentQuant) {
}
static void
dumpContentModel(const XML_Content *model, unsigned level,
const XML_Content *root) {
dumpContentModelElement(const XML_Content *model, unsigned level,
const XML_Content *root) {
// Indent
unsigned u = 0;
for (; u < level; u++) {
@ -108,21 +137,47 @@ dumpContentModel(const XML_Content *model, unsigned level,
}
printf(", numchildren=%d", model->numchildren);
printf("\n");
}
// Children
for (u = 0; u < model->numchildren; u++) {
dumpContentModel(model->children + u, level + 1, root);
static bool
dumpContentModel(const XML_Char *name, const XML_Content *root) {
printf("Element \"%" XML_FMT_STR "\":\n", name);
Stack *stackTop = NULL;
stackTop = stackPushMalloc(stackTop, root, 1);
if (! stackTop) {
return false;
}
while (stackTop) {
const XML_Content *const model = stackTop->model;
const unsigned level = stackTop->level;
dumpContentModelElement(model, level, root);
stackTop = stackPopFree(stackTop);
for (size_t u = model->numchildren; u >= 1; u--) {
stackTop
= stackPushMalloc(stackTop, model->children + (u - 1), level + 1);
if (! stackTop) {
return false;
}
}
}
printf("\n");
return true;
}
static void XMLCALL
handleElementDeclaration(void *userData, const XML_Char *name,
XML_Content *model) {
XML_Parser parser = (XML_Parser)userData;
printf("Element \"%" XML_FMT_STR "\":\n", name);
dumpContentModel(model, 1, model);
printf("\n");
const bool success = dumpContentModel(name, model);
XML_FreeContentModel(parser, model);
if (! success) {
XML_StopParser(parser, /* resumable= */ XML_FALSE);
}
}
int
@ -157,10 +212,13 @@ main(void) {
done = feof(stdin);
if (XML_ParseBuffer(parser, (int)len, done) == XML_STATUS_ERROR) {
enum XML_Error errorCode = XML_GetErrorCode(parser);
if (errorCode == XML_ERROR_ABORTED) {
errorCode = XML_ERROR_NO_MEMORY;
}
fprintf(stderr,
"Parse error at line %" XML_FMT_INT_MOD "u:\n%" XML_FMT_STR "\n",
XML_GetCurrentLineNumber(parser),
XML_ErrorString(XML_GetErrorCode(parser)));
XML_GetCurrentLineNumber(parser), XML_ErrorString(errorCode));
XML_ParserFree(parser);
return 1;
}