From c069e4f179d5e6653a84fb236816c375dca82515 Mon Sep 17 00:00:00 2001

From: William Roberts <william.c.roberts@intel.com>

Date: Fri, 21 May 2021 12:22:31 -0500

Subject: [PATCH] tpm2_import: fix fixed AES key CVE-2021-3565

tpm2_import used a fixed AES key for the inner wrapper, which means that

a MITM attack would be able to unwrap the imported key. Even the

use of an encrypted session will not prevent this. The TPM only

encrypts the first parameter which is the fixed symmetric key.

To fix this, ensure the key size is 16 bytes or bigger and use

OpenSSL to generate a secure random AES key.

Fixes: #2738

Signed-off-by: William Roberts <william.c.roberts@intel.com>

---

 tools/tpm2_import.c | 12 +++++++++++-

 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/tpm2_import.c b/tools/tpm2_import.c

index cfb6f207ba9c..f44326c87e7e 100644

--- a/tools/tpm2_import.c

+++ b/tools/tpm2_import.c

@@ -118,7 +118,17 @@ static tool_rc key_import(ESYS_CONTEXT *ectx, TPM2B_PUBLIC *parent_pub,

     TPM2B_DATA enc_sensitive_key = {

         .size = parent_pub->publicArea.parameters.rsaDetail.symmetric.keyBits.sym / 8

     };

-    memset(enc_sensitive_key.buffer, 0xFF, enc_sensitive_key.size);

+

+    if(enc_sensitive_key.size < 16) {

+        LOG_ERR("Calculated wrapping keysize is less than 16 bytes, got: %u", enc_sensitive_key.size);

+        return tool_rc_general_error;

+    }

+

+    int ossl_rc = RAND_bytes(enc_sensitive_key.buffer, enc_sensitive_key.size);

+    if (ossl_rc != 1) {

+        LOG_ERR("RAND_bytes failed: %s", ERR_error_string(ERR_get_error(), NULL));

+        return tool_rc_general_error;

+    }

     /*

      * Calculate the object name.

-- 

2.31.0