From 1fbb577ee26becacf53b92c53df356aaf227ea73 Mon Sep 17 00:00:00 2001 From: Tim Peters Date: Wed, 19 Dec 2001 04:41:35 +0000 Subject: SF bug #494738: binascii_b2a_base64 overwrites memory. binascii_b2a_base64(): We didn't allocate enough buffer space for very short inputs (e.g., a 1-byte input can produce a 5-byte output, but we only allocated 2 bytes). I expect that malloc overheads absorbed the overrun in practice, but computing a correct upper bound is a very simple change. --- Misc/ACKS | 1 + Modules/binascii.c | 8 +++++--- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/Misc/ACKS b/Misc/ACKS index 1ebf774..3616e57 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -92,6 +92,7 @@ Benjamin Collar Jeffery Collins Matt Conway David M. Cooke +David Costanzo Scott Cotton Greg Couch Steve Cousins diff --git a/Modules/binascii.c b/Modules/binascii.c index 643450c..9ef3054 100644 --- a/Modules/binascii.c +++ b/Modules/binascii.c @@ -137,7 +137,7 @@ static char table_a2b_base64[] = { #define BASE64_PAD '=' /* Max binary chunk size; limited only by available memory */ -#define BASE64_MAXBIN (INT_MAX/2 - sizeof(PyStringObject)) +#define BASE64_MAXBIN (INT_MAX/2 - sizeof(PyStringObject) - 3) static unsigned char table_b2a_base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; @@ -436,8 +436,10 @@ binascii_b2a_base64(PyObject *self, PyObject *args) return NULL; } - /* We're lazy and allocate to much (fixed up later) */ - if ( (rv=PyString_FromStringAndSize(NULL, bin_len*2)) == NULL ) + /* We're lazy and allocate too much (fixed up later). + "+3" leaves room for up to two pad characters and a trailing + newline. Note that 'b' gets encoded as 'Yg==\n' (1 in, 5 out). */ + if ( (rv=PyString_FromStringAndSize(NULL, bin_len*2 + 3)) == NULL ) return NULL; ascii_data = (unsigned char *)PyString_AsString(rv); -- cgit v0.12