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From c069e4f179d5e6653a84fb236816c375dca82515 Mon Sep 17 00:00:00 2001
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From: William Roberts <william.c.roberts@intel.com>
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Date: Fri, 21 May 2021 12:22:31 -0500
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Subject: [PATCH] tpm2_import: fix fixed AES key CVE-2021-3565
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tpm2_import used a fixed AES key for the inner wrapper, which means that
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a MITM attack would be able to unwrap the imported key. Even the
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use of an encrypted session will not prevent this. The TPM only
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encrypts the first parameter which is the fixed symmetric key.
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To fix this, ensure the key size is 16 bytes or bigger and use
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OpenSSL to generate a secure random AES key.
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Fixes: #2738
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Signed-off-by: William Roberts <william.c.roberts@intel.com>
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---
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tools/tpm2_import.c | 12 +++++++++++-
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1 file changed, 11 insertions(+), 1 deletion(-)
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diff --git a/tools/tpm2_import.c b/tools/tpm2_import.c
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index cfb6f207ba9c..f44326c87e7e 100644
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--- a/tools/tpm2_import.c
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+++ b/tools/tpm2_import.c
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@@ -118,7 +118,17 @@ static tool_rc key_import(ESYS_CONTEXT *ectx, TPM2B_PUBLIC *parent_pub,
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TPM2B_DATA enc_sensitive_key = {
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.size = parent_pub->publicArea.parameters.rsaDetail.symmetric.keyBits.sym / 8
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};
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- memset(enc_sensitive_key.buffer, 0xFF, enc_sensitive_key.size);
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+
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+ if(enc_sensitive_key.size < 16) {
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+ LOG_ERR("Calculated wrapping keysize is less than 16 bytes, got: %u", enc_sensitive_key.size);
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+ return tool_rc_general_error;
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+ }
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+
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+ int ossl_rc = RAND_bytes(enc_sensitive_key.buffer, enc_sensitive_key.size);
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+ if (ossl_rc != 1) {
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+ LOG_ERR("RAND_bytes failed: %s", ERR_error_string(ERR_get_error(), NULL));
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+ return tool_rc_general_error;
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+ }
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/*
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* Calculate the object name.
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--
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2.31.0
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