From d7657811964eac1cb9743bb98649278ad948f0d2 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. CVE: CVE-2025-32414 Upstream-Status: Backport [https://gitlab.gnome.org/GNOME/libxml2/-/commit/d7657811964eac1cb9743bb98649278ad948f0d2] Signed-off-by: Peter Marko --- python/libxml.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/python/libxml.c b/python/libxml.c index 1fe8d685..2bf14078 100644 --- a/python/libxml.c +++ b/python/libxml.c @@ -248,7 +248,9 @@ 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); @@ -283,10 +285,12 @@ 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); } @@ -310,7 +314,9 @@ 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); @@ -345,10 +351,12 @@ 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); }