Add new mbedtls_pkcs5_pbe2_ext function

Add new mbedtls_pkcs5_pbe2_ext function to replace old
function with possible security issues.

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>

include/mbedtls/pkcs5.h

@@ -95,6 +95,50 @@ int mbedtls_pkcs5_pbes2(const mbedtls_asn1_buf *pbe_params, int mode,
                         const unsigned char *data, size_t datalen,
                         unsigned char *output);
 
+#if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
+
+/**
+ * \brief          PKCS#5 PBES2 function
+ *
+ * \warning        When decrypting:
+ *                 - This function validates the CBC padding and returns
+ *                   #MBEDTLS_ERR_PKCS5_PASSWORD_MISMATCH if the padding is
+ *                   invalid. Note that this can help active adversaries
+ *                   attempting to brute-forcing the password. Note also that
+ *                   there is no guarantee that an invalid password will be
+ *                   detected (the chances of a valid padding with a random
+ *                   password are about 1/255).
+ *
+ * \param pbe_params the ASN.1 algorithm parameters
+ * \param mode       either MBEDTLS_PKCS5_DECRYPT or MBEDTLS_PKCS5_ENCRYPT
+ * \param pwd        password to use when generating key
+ * \param pwdlen     length of password
+ * \param data       data to process
+ * \param datalen    length of data
+ * \param output     Output buffer.
+ *                   On success, it contains the decrypted data, possibly
+ *                   followed by the CBC padding.
+ *                   On failure, the content is indetermidate.
+ *                   For decryption, there must be enough room for \p datalen
+ *                   bytes.
+ *                   For encryption, there must be enough room for
+ *                   \p datalen + 1 bytes, rounded up to the block size of
+ *                   the block cipher identified by \p pbe_params.
+ * \param output_size size of output buffer.
+ *                    This must be big enough to accommodate for output plus
+ *                    padding data.
+ * \param output_len length of actual data written to the output buffer.
+ *
+ * \returns        0 on success, or a MBEDTLS_ERR_XXX code if verification fails.
+ */
+int mbedtls_pkcs5_pbes2_ext(const mbedtls_asn1_buf *pbe_params, int mode,
+                            const unsigned char *pwd,  size_t pwdlen,
+                            const unsigned char *data, size_t datalen,
+                            unsigned char *output, size_t output_size,
+                            size_t *output_len);
+
+#endif /* MBEDTLS_CIPHER_PADDING_PKCS7 */
+
 #endif /* MBEDTLS_ASN1_PARSE_C */
 
 /**