tpm2: CryptSym: fix AES output IV

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>

configure.ac

@@ -173,6 +173,7 @@ AS_IF([test "x$enable_use_openssl_functions" != "xno"], [
 	AC_CHECK_LIB([crypto], [EVP_des_ede3_cbc],, not_found=1)
 	AC_CHECK_LIB([crypto], [EVP_camellia_128_cbc],, not_found=1)
 	AC_CHECK_LIB([crypto], [DES_random_key],, not_found=1)
+	AC_CHECK_LIB([crypto], [EVP_CIPHER_CTX_iv],, not_found=1)
 	if test "x$not_found" = "x0"; then
 		use_openssl_functions_symmetric=1
 		use_openssl_functions_for="symmetric (AES, TDES) "

src/tpm2/crypto/openssl/CryptSym.c

@@ -532,6 +532,7 @@ 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)
@@ -596,6 +597,14 @@ 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);
@@ -637,6 +646,7 @@ 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
@@ -709,6 +719,15 @@ 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);