From: Ken Sharp <ken.sharp@artifex.com>
Date: Thu, 23 Aug 2018 14:42:02 +0000 (+0100)
Subject: Bug 699665 "memory corruption in aesdecode"
X-Git-Url: http://git.ghostscript.com/?p=ghostpdl.git;a=commitdiff_plain;h=8e9ce501

Bug 699665 "memory corruption in aesdecode"

The specimen file calls aesdecode without specifying the key to be
used, though it does manage to do enough work with the PDF interpreter
routines to get access to aesdecode (which isn't normally available).

This causes us to read uninitialised memory, which can (and often does)
lead to a segmentation fault.

In this commit we set the key to NULL explicitly during intialisation
and then check it before we read it. If its NULL we just return.

It seems bizarre that we don't return error codes, we should probably
look into that at some point, but this prevents the code trying to
read uninitialised memory.
---

diff --git a/base/aes.c b/base/aes.c
index a6bce93..e86f000 100644
--- a/base/aes.c
+++ b/base/aes.c
@@ -662,6 +662,9 @@ void aes_crypt_ecb( aes_context *ctx,
     }
 #endif
 
+    if (ctx == NULL || ctx->rk == NULL)
+        return;
+
     RK = ctx->rk;
 
     GET_ULONG_LE( X0, input,  0 ); X0 ^= *RK++;
diff --git a/base/saes.c b/base/saes.c
index 6db0e8b..307ed74 100644
--- a/base/saes.c
+++ b/base/saes.c
@@ -120,6 +120,7 @@ s_aes_process(stream_state * ss, stream_cursor_read * pr,
         gs_throw(gs_error_VMerror, "could not allocate aes context");
         return ERRC;
       }
+      memset(state->ctx, 0x00, sizeof(aes_context));
       if (state->keylength < 1 || state->keylength > SAES_MAX_KEYLENGTH) {
         gs_throw1(gs_error_rangecheck, "invalid aes key length (%d bytes)",
                 state->keylength);