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[CVE-2025-32414] python: Read at most len/4 characters.

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Fixes #889 by reserving space in the buffer for UTF-8 encoding of text.
This commit is contained in:
Maks Verver
2025-04-08 13:13:55 +02:00
committed by Nick Wellnhofer
parent 38cc2b53ed
commit 8d415b8911
1 changed files with 18 additions and 10 deletions
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28
python/libxml.c
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@ -237,7 +237,9 @@ xmlPythonFileReadRaw (void * context, char * buffer, int len) {
file = (PyObject *) context; file = (PyObject *) context;
if (file == NULL) return(-1); if (file == NULL) return(-1);
ret = PyObject_CallMethod(file, (char *) "read", (char *) "(i)", len); /* When read() returns a string, the length is in characters not bytes, so
request at most len / 4 characters to leave space for UTF-8 encoding. */
ret = PyObject_CallMethod(file, (char *) "read", (char *) "(i)", len / 4);
if (ret == NULL) { if (ret == NULL) {
printf("xmlPythonFileReadRaw: result is NULL\n"); printf("xmlPythonFileReadRaw: result is NULL\n");
return(-1); return(-1);
@ -272,10 +274,12 @@ xmlPythonFileReadRaw (void * context, char * buffer, int len) {
Py_DECREF(ret); Py_DECREF(ret);
return(-1); return(-1);
} }
if (lenread > len) if (lenread < 0 || lenread > len) {
memcpy(buffer, data, len); printf("xmlPythonFileReadRaw: invalid lenread\n");
else Py_DECREF(ret);
memcpy(buffer, data, lenread); return(-1);
}
memcpy(buffer, data, lenread);
Py_DECREF(ret); Py_DECREF(ret);
return(lenread); return(lenread);
} }
@ -299,7 +303,9 @@ xmlPythonFileRead (void * context, char * buffer, int len) {
file = (PyObject *) context; file = (PyObject *) context;
if (file == NULL) return(-1); if (file == NULL) return(-1);
ret = PyObject_CallMethod(file, (char *) "io_read", (char *) "(i)", len); /* When io_read() returns a string, the length is in characters not bytes, so
request at most len / 4 characters to leave space for UTF-8 encoding. */
ret = PyObject_CallMethod(file, (char *) "io_read", (char *) "(i)", len / 4);
if (ret == NULL) { if (ret == NULL) {
printf("xmlPythonFileRead: result is NULL\n"); printf("xmlPythonFileRead: result is NULL\n");
return(-1); return(-1);
@ -334,10 +340,12 @@ xmlPythonFileRead (void * context, char * buffer, int len) {
Py_DECREF(ret); Py_DECREF(ret);
return(-1); return(-1);
} }
if (lenread > len) if (lenread < 0 || lenread > len) {
memcpy(buffer, data, len); printf("xmlPythonFileRead: invalid lenread\n");
else Py_DECREF(ret);
memcpy(buffer, data, lenread); return(-1);
}
memcpy(buffer, data, lenread);
Py_DECREF(ret); Py_DECREF(ret);
return(lenread); return(lenread);
} }