From 034e5dbf92ea3a7ea7c9322e47a3a50ff23f7b55 Mon Sep 17 00:00:00 2001 From: Ben Wagner Date: Tue, 22 Feb 2022 20:37:43 -0500 Subject: [PATCH] [psaux] Full bounds check for OtherSubr 19. It is possible for OtherSubr 19 to be invoked when `decoder->buildchar` is NULL (so that `decoder->len_buildchar` is 0), the `blend` is non-NULL with `blend->num_designs` set to 2, and the user supplied `idx` to be large (for example 0xFFFFFFFE). Since these are all `FT_UInt32` the existing bounds check overflows in a well defined manner, allowing for an invalid call to `memcpy`. In addition, it is possible to call OtherSubr 19 with `decoder->len_buildchar`, `blend->num_designs`, and `idx` all zero (implying that `blend->weight_vector` and `decoder->buildchar` are NULL). This passes the bounds check (it is logically always fine to copy nothing starting at index zero) but may invoke undefined behavior in `ft_memcpy` if it is backed by `memcpy`. Calling `memcpy` with either the `src` or `dst` NULL is undefined behavior (even if `count` is zero). * src/psaux/psintrp.c (cf2_interpT2CharString): Correctly check that `blend->num_designs` can be copied to `decoder->buildchar[idx]`. Also avoid passing NULL to `ft_memcpy`. Bug: https://crbug.com/1299259 --- src/psaux/psintrp.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/src/psaux/psintrp.c b/src/psaux/psintrp.c index c550533a0..6c640eebd 100644 --- a/src/psaux/psintrp.c +++ b/src/psaux/psintrp.c @@ -1900,7 +1900,8 @@ /* WeightVector */ { FT_UInt idx; - PS_Blend blend = decoder->blend; + PS_Blend blend = decoder->blend; + FT_UInt len_buildchar = decoder->len_buildchar; if ( arg_cnt != 1 || !blend ) @@ -1908,14 +1909,15 @@ idx = (FT_UInt)cf2_stack_popInt( opStack ); - if ( idx + blend->num_designs > - decoder->len_buildchar ) + if ( len_buildchar < blend->num_designs || + len_buildchar - blend->num_designs < idx ) goto Unexpected_OtherSubr; - ft_memcpy( &decoder->buildchar[idx], - blend->weight_vector, - blend->num_designs * - sizeof ( blend->weight_vector[0] ) ); + if ( decoder->buildchar && blend->weight_vector ) + ft_memcpy( &decoder->buildchar[idx], + blend->weight_vector, + blend->num_designs * + sizeof ( blend->weight_vector[0] ) ); } break;