From 28d8e756676c5efc6979a0606d82d0223558fbff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Wed, 17 Mar 2021 16:29:00 +0400
Subject: [PATCH] tpm2: CryptSym: fix AES output IV
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The TPM is supposed to provide the output IV in the ivInOut parameter in
CryptSymmetricEncrypt. In the case of using the openssl routines, the
output IV is missed, and the resulting output from the TPM is in the
input IV.

OpenSSL unfortunately does not export EVP_CIPHER_CTX_iv() until
tags/OpenSSL_1_1_0, so we have to fall back to the reference code for
previous OpenSSL versions.

Signed-off-by: William Roberts <william.c.roberts@intel.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 configure.ac                       |  1 +
 src/tpm2/crypto/openssl/CryptSym.c | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/configure.ac b/configure.ac
index 2895bc9..f113f17 100644
--- a/configure.ac
+++ b/configure.ac
@@ -165,6 +165,7 @@ AS_IF([test "x$enable_use_openssl_functions" != "xno"], [
 	AC_CHECK_LIB([crypto], [EVP_aes_128_cbc],, not_found=1)
 	AC_CHECK_LIB([crypto], [EVP_des_ede3_cbc],, not_found=1)
 	AC_CHECK_LIB([crypto], [DES_random_key],, not_found=1)
+	AC_CHECK_LIB([crypto], [EVP_CIPHER_CTX_iv],, not_found=1)
 	if test "x$not_found" = "x0"; then
 		use_openssl_functions_symmetric=1
 		use_openssl_functions_for="symmetric (AES, TDES) "
diff --git a/src/tpm2/crypto/openssl/CryptSym.c b/src/tpm2/crypto/openssl/CryptSym.c
index 7aa90da..856def6 100644
--- a/src/tpm2/crypto/openssl/CryptSym.c
+++ b/src/tpm2/crypto/openssl/CryptSym.c
@@ -531,6 +531,7 @@ CryptSymmetricEncrypt(
     BYTE                 keyToUse[MAX_SYM_KEY_BYTES];
     UINT16               keyToUseLen = (UINT16)sizeof(keyToUse);
     TPM_RC               retVal = TPM_RC_SUCCESS;
+    int                  ivLen;
 
     pAssert(dOut != NULL && key != NULL && dIn != NULL);
     if(dSize == 0)
@@ -595,6 +596,14 @@ CryptSymmetricEncrypt(
     if (EVP_EncryptFinal_ex(ctx, pOut + outlen1, &outlen2) != 1)
         ERROR_RETURN(TPM_RC_FAILURE);
 
+    if (ivInOut) {
+        ivLen = EVP_CIPHER_CTX_iv_length(ctx);
+        if (ivLen < 0 || (size_t)ivLen > sizeof(ivInOut->t.buffer))
+            ERROR_RETURN(TPM_RC_FAILURE);
+
+        ivInOut->t.size = ivLen;
+        memcpy(ivInOut->t.buffer, EVP_CIPHER_CTX_iv(ctx), ivInOut->t.size);
+    }
  Exit:
     if (retVal == TPM_RC_SUCCESS && pOut != dOut)
         memcpy(dOut, pOut, outlen1 + outlen2);
@@ -636,6 +645,7 @@ CryptSymmetricDecrypt(
     BYTE                 keyToUse[MAX_SYM_KEY_BYTES];
     UINT16               keyToUseLen = (UINT16)sizeof(keyToUse);
     TPM_RC               retVal = TPM_RC_SUCCESS;
+    int                  ivLen;
 
     // These are used but the compiler can't tell because they are initialized
     // in case statements and it can't tell if they are always initialized
@@ -707,6 +717,15 @@ CryptSymmetricDecrypt(
 
     pAssert((int)buffersize >= outlen1 + outlen2);
 
+    if (ivInOut) {
+        ivLen = EVP_CIPHER_CTX_iv_length(ctx);
+        if (ivLen < 0 || (size_t)ivLen > sizeof(ivInOut->t.buffer))
+            ERROR_RETURN(TPM_RC_FAILURE);
+
+        ivInOut->t.size = ivLen;
+        memcpy(ivInOut->t.buffer, EVP_CIPHER_CTX_iv(ctx), ivInOut->t.size);
+    }
+
  Exit:
     if (retVal == TPM_RC_SUCCESS) {
         pAssert(dSize >= outlen1 + outlen2);
-- 
2.29.0