Improve CCM documentation
- Rephrase function/parameter/enum/define/error descriptions into full and
clear sentences.
- Make sure to adhering to the Arm writing guidelines.
- Fix missing/incorrect Doxygen tags.
- Standardize terminology used within the file.
- Fix iv_len values per the standard.
GitHub PR: #1305
diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index 1459eb8..5a9ee4a 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -1,10 +1,19 @@
/**
* \file ccm.h
*
- * \brief Counter with CBC-MAC (CCM) for 128-bit block ciphers
+ * \brief CCM combines Counter mode encryption with CBC-MAC authentication
+ * for 128-bit block ciphers.
+ *
+ * Input to CCM includes the following elements:
+ * <ul><li>Payload - data that is both authenticated and encrypted.</li>
+ * <li>Associated data (Adata) - data that is authenticated but not
+ * encrypted, For example, a header.</li>
+ * <li>Nonce - A unique value that is assigned to the payload and the
+ * associated data.</li></ul>
+ *
*/
/*
- * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ * Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -19,16 +28,17 @@
* 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)
+ * This file is part of Mbed TLS (https://tls.mbed.org)
*/
+
#ifndef MBEDTLS_CCM_H
#define MBEDTLS_CCM_H
#include "cipher.h"
-#define MBEDTLS_ERR_CCM_BAD_INPUT -0x000D /**< Bad input parameters to function. */
-#define MBEDTLS_ERR_CCM_AUTH_FAILED -0x000F /**< Authenticated decryption failed. */
-#define MBEDTLS_ERR_CCM_HW_ACCEL_FAILED -0x0011 /**< CCM hardware accelerator failed. */
+#define MBEDTLS_ERR_CCM_BAD_INPUT -0x000D /**< Bad input parameters to the function. */
+#define MBEDTLS_ERR_CCM_AUTH_FAILED -0x000F /**< Authenticated decryption failed. */
+#define MBEDTLS_ERR_CCM_HW_ACCEL_FAILED -0x0011 /**< CCM hardware accelerator failed. */
#if !defined(MBEDTLS_CCM_ALT)
// Regular implementation
@@ -39,31 +49,33 @@
#endif
/**
- * \brief CCM context structure
+ * \brief The CCM context-type definition. The CCM context is passed
+ * to the APIs called.
*/
typedef struct {
- mbedtls_cipher_context_t cipher_ctx; /*!< cipher context used */
+ mbedtls_cipher_context_t cipher_ctx; /*!< The cipher context used. */
}
mbedtls_ccm_context;
/**
- * \brief Initialize CCM context (just makes references valid)
- * Makes the context ready for mbedtls_ccm_setkey() or
- * mbedtls_ccm_free().
+ * \brief This function initializes the specified CCM context,
+ * to make references valid, and prepare the context
+ * for mbedtls_ccm_setkey() or mbedtls_ccm_free().
*
- * \param ctx CCM context to initialize
+ * \param ctx The CCM context to initialize.
*/
void mbedtls_ccm_init( mbedtls_ccm_context *ctx );
/**
- * \brief CCM initialization (encryption and decryption)
+ * \brief This function initializes the CCM context set in the
+ * \p ctx parameter and sets the encryption key.
*
- * \param ctx CCM context to be initialized
- * \param cipher cipher to use (a 128-bit block cipher)
- * \param key encryption key
- * \param keybits key size in bits (must be acceptable by the cipher)
+ * \param ctx The CCM context to initialize.
+ * \param cipher The 128-bit block cipher to use.
+ * \param key The encryption key.
+ * \param keybits The key size in bits. This must be acceptable by the cipher.
*
- * \return 0 if successful, or a cipher specific error code
+ * \return \c 0 on success, or a cipher-specific error code.
*/
int mbedtls_ccm_setkey( mbedtls_ccm_context *ctx,
mbedtls_cipher_id_t cipher,
@@ -71,36 +83,37 @@
unsigned int keybits );
/**
- * \brief Free a CCM context and underlying cipher sub-context
+ * \brief This function releases and clears the specified CCM context
+ * and underlying cipher sub-context.
*
- * \param ctx CCM context to free
+ * \param ctx The CCM context to clear.
*/
void mbedtls_ccm_free( mbedtls_ccm_context *ctx );
/**
- * \brief CCM buffer encryption
+ * \brief This function encrypts a buffer using CCM.
*
- * \param ctx CCM context
- * \param length length of the input data in bytes
- * \param iv nonce (initialization vector)
- * \param iv_len length of IV in bytes
- * must be 2, 3, 4, 5, 6, 7 or 8
- * \param add additional data
- * \param add_len length of additional data in bytes
- * must be less than 2^16 - 2^8
- * \param input buffer holding the input data
- * \param output buffer for holding the output data
- * must be at least 'length' bytes wide
- * \param tag buffer for holding the tag
- * \param tag_len length of the tag to generate in bytes
- * must be 4, 6, 8, 10, 14 or 16
+ * \param ctx The CCM context to use for encryption.
+ * \param length The length of the input data in Bytes.
+ * \param iv Initialization vector (nonce).
+ * \param iv_len The length of the IV in Bytes: 7, 8, 9, 10, 11, 12, or 13.
+ * \param add The additional data field.
+ * \param add_len The length of additional data in Bytes.
+ * Must be less than 2^16 - 2^8.
+ * \param input The buffer holding the input data.
+ * \param output The buffer holding the output data.
+ * Must be at least \p length Bytes wide.
+ * \param tag The buffer holding the tag.
+ * \param tag_len The length of the tag to generate in Bytes:
+ * 4, 6, 8, 10, 14 or 16.
*
- * \note The tag is written to a separate buffer. To get the tag
- * concatenated with the output as in the CCM spec, use
- * tag = output + length and make sure the output buffer is
- * at least length + tag_len wide.
+ * \note The tag is written to a separate buffer. To concatenate
+ * the \p tag with the \p output, as done in <em>RFC-3610:
+ * Counter with CBC-MAC (CCM)</em>, use
+ * \p tag = \p output + \p length, and make sure that the
+ * output buffer is at least \p length + \p tag_len wide.
*
- * \return 0 if successful
+ * \return \c 0 on success.
*/
int mbedtls_ccm_encrypt_and_tag( mbedtls_ccm_context *ctx, size_t length,
const unsigned char *iv, size_t iv_len,
@@ -109,21 +122,22 @@
unsigned char *tag, size_t tag_len );
/**
- * \brief CCM buffer authenticated decryption
+ * \brief This function performs a CCM authenticated decryption of a
+ * buffer.
*
- * \param ctx CCM context
- * \param length length of the input data
- * \param iv initialization vector
- * \param iv_len length of IV
- * \param add additional data
- * \param add_len length of additional data
- * \param input buffer holding the input data
- * \param output buffer for holding the output data
- * \param tag buffer holding the tag
- * \param tag_len length of the tag
+ * \param ctx The CCM context to use for decryption.
+ * \param length The length of the input data in Bytes.
+ * \param iv Initialization vector.
+ * \param iv_len The length of the IV in Bytes: 7, 8, 9, 10, 11, 12, or 13.
+ * \param add The additional data field.
+ * \param add_len The length of additional data in Bytes.
+ * \param input The buffer holding the input data.
+ * \param output The buffer holding the output data.
+ * \param tag The buffer holding the tag.
+ * \param tag_len The length of the tag in Bytes.
*
- * \return 0 if successful and authenticated,
- * MBEDTLS_ERR_CCM_AUTH_FAILED if tag does not match
+ * \return 0 if successful and authenticated, or
+ * #MBEDTLS_ERR_CCM_AUTH_FAILED if the tag does not match.
*/
int mbedtls_ccm_auth_decrypt( mbedtls_ccm_context *ctx, size_t length,
const unsigned char *iv, size_t iv_len,
@@ -135,9 +149,9 @@
}
#endif
-#else /* !MBEDTLS_CCM_ALT */
+#else /* MBEDTLS_CCM_ALT */
#include "ccm_alt.h"
-#endif /* !MBEDTLS_CCM_ALT */
+#endif /* MBEDTLS_CCM_ALT */
#ifdef __cplusplus
extern "C" {
@@ -145,9 +159,9 @@
#if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
/**
- * \brief Checkup routine
+ * \brief The CCM checkup routine.
*
- * \return 0 if successful, or 1 if the test failed
+ * \return \c 0 on success, or \c 1 on failure.
*/
int mbedtls_ccm_self_test( int verbose );
#endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */