Gaurav Aggarwal a9f64006ea Add support for const error description strings
Problem
-------
mbedtls_strerror is a utility function which converts an mbedTLS error code
into a human readable string. It requires the caller to allocate a buffer every
time an error code needs to be converted to a string. It is an overkill and a
waste of RAM for resource constrained microcontrollers - where the most common
use case is to use these strings for logging.

Solution
--------
The proposed commit adds two functions:

* const char * mbedtls_high_level_strerr( int error_code );
* const char * mbedtls_low_level_strerr( int error_code );

The above two functions convert the high level and low level parts of an mbedTLS
error code to human readable strings. They return a const pointer to an
unmodifiable string which is not supposed to be modified by the caller and only
to be used for logging purposes. The caller no longer needs to allocate a
buffer.

Backward Compatibility
----------------------
The proposed change is completely backward compatible as it does not change
the existing mbedtls_strerror function and ensures that it continues to behave
the same way.

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
2020-04-09 01:44:52 -07:00

161 lines
5.1 KiB
C

/**
* \file error.h
*
* \brief Error to string translation
*/
/*
* Copyright (C) 2006-2018, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#ifndef MBEDTLS_ERROR_H
#define MBEDTLS_ERROR_H
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include <stddef.h>
/**
* Error code layout.
*
* Currently we try to keep all error codes within the negative space of 16
* bits signed integers to support all platforms (-0x0001 - -0x7FFF). In
* addition we'd like to give two layers of information on the error if
* possible.
*
* For that purpose the error codes are segmented in the following manner:
*
* 16 bit error code bit-segmentation
*
* 1 bit - Unused (sign bit)
* 3 bits - High level module ID
* 5 bits - Module-dependent error code
* 7 bits - Low level module errors
*
* For historical reasons, low-level error codes are divided in even and odd,
* even codes were assigned first, and -1 is reserved for other errors.
*
* Low-level module errors (0x0002-0x007E, 0x0001-0x007F)
*
* Module Nr Codes assigned
* ERROR 2 0x006E 0x0001
* MPI 7 0x0002-0x0010
* GCM 3 0x0012-0x0014 0x0013-0x0013
* BLOWFISH 3 0x0016-0x0018 0x0017-0x0017
* THREADING 3 0x001A-0x001E
* AES 5 0x0020-0x0022 0x0021-0x0025
* CAMELLIA 3 0x0024-0x0026 0x0027-0x0027
* XTEA 2 0x0028-0x0028 0x0029-0x0029
* BASE64 2 0x002A-0x002C
* OID 1 0x002E-0x002E 0x000B-0x000B
* PADLOCK 1 0x0030-0x0030
* DES 2 0x0032-0x0032 0x0033-0x0033
* CTR_DBRG 4 0x0034-0x003A
* ENTROPY 3 0x003C-0x0040 0x003D-0x003F
* NET 13 0x0042-0x0052 0x0043-0x0049
* ARIA 4 0x0058-0x005E
* ASN1 7 0x0060-0x006C
* CMAC 1 0x007A-0x007A
* PBKDF2 1 0x007C-0x007C
* HMAC_DRBG 4 0x0003-0x0009
* CCM 3 0x000D-0x0011
* ARC4 1 0x0019-0x0019
* MD2 1 0x002B-0x002B
* MD4 1 0x002D-0x002D
* MD5 1 0x002F-0x002F
* RIPEMD160 1 0x0031-0x0031
* SHA1 1 0x0035-0x0035 0x0073-0x0073
* SHA256 1 0x0037-0x0037 0x0074-0x0074
* SHA512 1 0x0039-0x0039 0x0075-0x0075
* CHACHA20 3 0x0051-0x0055
* POLY1305 3 0x0057-0x005B
* CHACHAPOLY 2 0x0054-0x0056
* PLATFORM 2 0x0070-0x0072
*
* High-level module nr (3 bits - 0x0...-0x7...)
* Name ID Nr of Errors
* PEM 1 9
* PKCS#12 1 4 (Started from top)
* X509 2 20
* PKCS5 2 4 (Started from top)
* DHM 3 11
* PK 3 15 (Started from top)
* RSA 4 11
* ECP 4 10 (Started from top)
* MD 5 5
* HKDF 5 1 (Started from top)
* SSL 5 1 (Started from 0x5F00)
* CIPHER 6 8 (Started from 0x6080)
* SSL 6 24 (Started from top, plus 0x6000)
* SSL 7 32
*
* Module dependent error code (5 bits 0x.00.-0x.F8.)
*/
#ifdef __cplusplus
extern "C" {
#endif
#define MBEDTLS_ERR_ERROR_GENERIC_ERROR -0x0001 /**< Generic error */
#define MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED -0x006E /**< This is a bug in the library */
/**
* \brief Translate a mbed TLS error code into a string representation,
* Result is truncated if necessary and always includes a terminating
* null byte.
*
* \param errnum error code
* \param buffer buffer to place representation in
* \param buflen length of the buffer
*/
void mbedtls_strerror( int errnum, char *buffer, size_t buflen );
/**
* \brief Translate high level part of a mbed TLS error code into a string
* representation.
*
* This function returns a const pointer to an un-modifiable string. The caller
* must not try to modify the string use it only for logging purposes.
*
* \param error_code error code
*
* \return The string representation of the error code.
*/
const char * mbedtls_high_level_strerr( int error_code );
/**
* \brief Translate low level part of a mbed TLS error code into a string
* representation.
*
* This function returns a const pointer to an un-modifiable string. The caller
* must not try to modify the string and use it only for logging purposes.
*
* \param error_code error code
*
* \return The string representation of the error code.
*/
const char * mbedtls_low_level_strerr( int error_code );
#ifdef __cplusplus
}
#endif
#endif /* error.h */