From 9f740868fc36761de27df3935513bdebf8852d19 Mon Sep 17 00:00:00 2001
From: Stefan Berger <stefanb@linux.ibm.com>
Date: Wed, 16 Feb 2022 11:17:47 -0500
Subject: [PATCH] swtpm: Check header size indicator against expected size (CID
 375869)

This fix addresses Coverity issue CID 375869.

Check the header size indicated in the header of the state against the
expected size and return an error code in case the header size indicator
is different. There was only one header size so far since blobheader was
introduced, so we don't need to deal with different sizes.

Without this fix a specially craft header could have cause out-of-bounds
accesses on the byte array containing the swtpm's state.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 src/swtpm/swtpm_nvstore.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/swtpm/swtpm_nvstore.c b/src/swtpm/swtpm_nvstore.c
index 437088370e11..144d8975ec54 100644
--- a/src/swtpm/swtpm_nvstore.c
+++ b/src/swtpm/swtpm_nvstore.c
@@ -1075,6 +1075,7 @@ SWTPM_NVRAM_CheckHeader(unsigned char *data, uint32_t length,
                         uint8_t *hdrversion, bool quiet)
 {
     blobheader *bh = (blobheader *)data;
+    uint16_t hdrsize;
 
     if (length < sizeof(bh)) {
         if (!quiet)
@@ -1100,8 +1101,16 @@ SWTPM_NVRAM_CheckHeader(unsigned char *data, uint32_t length,
         return TPM_BAD_VERSION;
     }
 
+    hdrsize = ntohs(bh->hdrsize);
+    if (hdrsize != sizeof(blobheader)) {
+        logprintf(STDERR_FILENO,
+                  "bad header size: %u != %zu\n",
+                  hdrsize, sizeof(blobheader));
+        return TPM_BAD_DATASIZE;
+    }
+
     *hdrversion = bh->version;
-    *dataoffset = ntohs(bh->hdrsize);
+    *dataoffset = hdrsize;
     *hdrflags = ntohs(bh->flags);
 
     return TPM_SUCCESS;
-- 
2.34.1.428.gdcc0cd074f0c