From 8d415b8911be26b12b85497f7cc57143b5321787 Mon Sep 17 00:00:00 2001 From: Maks Verver Date: Tue, 8 Apr 2025 13:13:55 +0200 Subject: [PATCH] [CVE-2025-32414] python: Read at most len/4 characters. Fixes #889 by reserving space in the buffer for UTF-8 encoding of text. --- python/libxml.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/python/libxml.c b/python/libxml.c index 5dea50260..0a1e408bd 100644 --- a/python/libxml.c +++ b/python/libxml.c @@ -237,7 +237,9 @@ xmlPythonFileReadRaw (void * context, char * buffer, int len) { file = (PyObject *) context; 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) { printf("xmlPythonFileReadRaw: result is NULL\n"); return(-1); @@ -272,10 +274,12 @@ xmlPythonFileReadRaw (void * context, char * buffer, int len) { Py_DECREF(ret); return(-1); } - if (lenread > len) - memcpy(buffer, data, len); - else - memcpy(buffer, data, lenread); + if (lenread < 0 || lenread > len) { + printf("xmlPythonFileReadRaw: invalid lenread\n"); + Py_DECREF(ret); + return(-1); + } + memcpy(buffer, data, lenread); Py_DECREF(ret); return(lenread); } @@ -299,7 +303,9 @@ xmlPythonFileRead (void * context, char * buffer, int len) { file = (PyObject *) context; 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) { printf("xmlPythonFileRead: result is NULL\n"); return(-1); @@ -334,10 +340,12 @@ xmlPythonFileRead (void * context, char * buffer, int len) { Py_DECREF(ret); return(-1); } - if (lenread > len) - memcpy(buffer, data, len); - else - memcpy(buffer, data, lenread); + if (lenread < 0 || lenread > len) { + printf("xmlPythonFileRead: invalid lenread\n"); + Py_DECREF(ret); + return(-1); + } + memcpy(buffer, data, lenread); Py_DECREF(ret); return(lenread); }