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package/tpm2-tools: backport CVE-2021-3565 security fix

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Fixes CVE-2021-3565: A flaw was found in tpm2-tools in versions before 5.1.1
and before 4.3.2.  tpm2_import used a fixed AES key for the inner wrapper,
potentially allowing a MITM attacker to unwrap the inner portion and reveal
the key being imported.  The highest threat from this vulnerability is to
data confidentiality.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Peter Korsgaard 2021-07-12 23:03:07 +02:00
parent 941160a0a2
commit 18c59c32a0
1 changed files with 47 additions and 0 deletions
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47
package/tpm2-tools/0001-tpm2_import-fix-fixed-AES-key-CVE-2021-3565.patch Normal file
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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>
Signed-off-by: Peter Korsgaard <peter@korsgaard.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 cfb6f207..f44326c8 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.
--
2.20.1