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Fix uncontrolled recursion in os_xml _ReadElem (issue #1953) a #2175

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Merged
atomicturtle merged 1 commit into from
Jan 24, 2026
+88 −23
Merged

Fix uncontrolled recursion in os_xml _ReadElem (issue #1953) a #2175

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65 changes: 42 additions & 23 deletions src/os_xml/os_xml.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ static int _writecontent(const char *str, size_t size, unsigned int parent, OS_X
static int _writememory(const char *str, XML_TYPE type, size_t size,
unsigned int parent, OS_XML *_lxml) __attribute__((nonnull));
static int _xml_fgetc(FILE *fp) __attribute__((nonnull));
static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml) __attribute__((nonnull));
static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml, unsigned int recursion_level) __attribute__((nonnull));
static int _getattributes(FILE *fp, unsigned int parent, OS_XML *_lxml) __attribute__((nonnull));
static void xml_error(OS_XML *_lxml, const char *msg, ...) __attribute__((format(printf, 2, 3), nonnull));

Expand Down Expand Up @@ -118,7 +118,7 @@ int OS_ReadXML(const char *file, OS_XML *_lxml)
/* Zero the line */
_line = 1;

if ((r = _ReadElem(fp, 0, _lxml)) < 0) { /* First position */
if ((r = _ReadElem(fp, 0, _lxml, 0)) < 0) { /* First position */
if (r != LEOF) {
fclose(fp);
return (-1);
Expand Down Expand Up @@ -166,21 +166,32 @@ static int _oscomment(FILE *fp)
return (0);
}

static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml, unsigned int recursion_level)
{
int c;
unsigned int count = 0;
unsigned int _currentlycont = 0;
short int location = -1;
int retval = -1;

int prevv = 0;
char elem[XML_MAXSIZE + 1];
char cont[XML_MAXSIZE + 1];
char closedelim[XML_MAXSIZE + 1];
char *elem = NULL;
char *cont = NULL;
char *closedelim = NULL;

memset(elem, '\0', XML_MAXSIZE + 1);
memset(cont, '\0', XML_MAXSIZE + 1);
memset(closedelim, '\0', XML_MAXSIZE + 1);
if (++recursion_level > 1024) {
xml_error(_lxml, "XMLERR: Max recursion level reached.");
return (-1);
}

elem = (char *)calloc(XML_MAXSIZE + 1, sizeof(char));
cont = (char *)calloc(XML_MAXSIZE + 1, sizeof(char));
closedelim = (char *)calloc(XML_MAXSIZE + 1, sizeof(char));

if (!elem || !cont || !closedelim) {
xml_error(_lxml, "XMLERR: Memory error.");
goto end;
}

while ((c = _xml_fgetc(fp)) != EOF) {
if (c == '\\') {
Expand All @@ -194,15 +205,15 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
/* Max size */
if (count >= XML_MAXSIZE) {
xml_error(_lxml, "XMLERR: String overflow.");
return (-1);
goto end;
}

/* Check for comments */
if (c == _R_CONFS) {
int r = 0;
if ((r = _oscomment(fp)) < 0) {
xml_error(_lxml, "XMLERR: Comment not closed.");
return (-1);
goto end;
} else if (r == 1) {
continue;
}
Expand All @@ -213,7 +224,7 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
if (c == _R_CONFS) {
if ((c = fgetc(fp)) == '/') {
xml_error(_lxml, "XMLERR: Element not opened.");
return (-1);
goto end;
} else {
ungetc(c, fp);
}
Expand All @@ -235,19 +246,19 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
}

if (_writememory(elem, XML_ELEM, count + 1, parent, _lxml) < 0) {
return (-1);
goto end;
}
_currentlycont = _lxml->cur - 1;
if (isspace(c)) {
if ((_ga = _getattributes(fp, parent, _lxml)) < 0) {
return (-1);
goto end;
}
}

/* If the element is closed already (finished in />) */
if ((_ge == '/') || (_ga == '/')) {
if (_writecontent("\0", 2, _currentlycont, _lxml) < 0) {
return (-1);
goto end;
}
_lxml->ck[_currentlycont] = 1;
_currentlycont = 0;
Expand All @@ -259,7 +270,8 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
memset(cont, '\0', XML_MAXSIZE);

if (parent > 0) {
return (0);
retval = 0;
goto end;
}
} else {
count = 0;
Expand All @@ -271,10 +283,10 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
closedelim[count] = '\0';
if (strcmp(closedelim, elem) != 0) {
xml_error(_lxml, "XMLERR: Element '%s' not closed.", elem);
return (-1);
goto end;
}
if (_writecontent(cont, strlen(cont) + 1, _currentlycont, _lxml) < 0) {
return (-1);
goto end;
}
_lxml->ck[_currentlycont] = 1;
memset(elem, '\0', XML_MAXSIZE);
Expand All @@ -284,7 +296,8 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
count = 0;
location = -1;
if (parent > 0) {
return (0);
retval = 0;
goto end;
}
} else if ((location == 1) && (c == _R_CONFS) && (prevv == 0)) {
if ((c = fgetc(fp)) == '/') {
Expand All @@ -295,8 +308,8 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
ungetc(c, fp);
ungetc(_R_CONFS, fp);

if (_ReadElem(fp, parent + 1, _lxml) < 0) {
return (-1);
if (_ReadElem(fp, parent + 1, _lxml, recursion_level) < 0) {
goto end;
}
count = 0;
}
Expand All @@ -315,11 +328,17 @@ static int _ReadElem(FILE *fp, unsigned int parent, OS_XML *_lxml)
}
}
if (location == -1) {
return (LEOF);
retval = LEOF;
goto end;
}

xml_error(_lxml, "XMLERR: End of file and some elements were not closed.");
return (-1);

end:
free(elem);
free(cont);
free(closedelim);
return (retval);
}

static int _writememory(const char *str, XML_TYPE type, size_t size,
Expand Down
46 changes: 46 additions & 0 deletions src/tests/regressions/issue_1953_xml_recursion.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "os_xml.h"

int main(void) {
const char *xml_file = "issue_1953_recursion.xml";
FILE *fp;
int i;
OS_XML xml;

/* Create a file with deep recursion */
fp = fopen(xml_file, "w");
if (!fp) {
perror("fopen");
return 1;
}

/* Write 2000 levels of recursion, which exceeds the 1024 limit */
for (i = 0; i < 2000; i++) {
fprintf(fp, "<e>");
}
for (i = 0; i < 2000; i++) {
fprintf(fp, "</e>");
}
fclose(fp);

/* Try to parse it */
if (OS_ReadXML(xml_file, &xml) < 0) {
/* Check if error matches expected "Max recursion level reached" */
if (strstr(xml.err, "Max recursion level reached")) {
printf("PASS: Correctly detected recursion limit.\n");
unlink(xml_file);
return 0;
} else {
printf("FAIL: Failed with unexpected error: %s\n", xml.err);
unlink(xml_file);
return 1;
}
}

printf("FAIL: Should have failed parsing but succeeded.\n");
unlink(xml_file);
return 1;
}