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+/**
+ * \file chachapoly.h
+ *
+ * \brief   This file contains the AEAD-ChaCha20-Poly1305 definitions and
+ *          functions.
+ *
+ *          ChaCha20-Poly1305 is an algorithm for Authenticated Encryption
+ *          with Associated Data (AEAD) that can be used to encrypt and
+ *          authenticate data. It is based on ChaCha20 and Poly1305 by Daniel
+ *          Bernstein and was standardized in RFC 7539.
+ *
+ * \author Daniel King <damaki.gh@gmail.com>
+ */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#ifndef MBEDTLS_CHACHAPOLY_H
+#define MBEDTLS_CHACHAPOLY_H
+#include "mbedtls/private_access.h"
+
+#include "mbedtls/build_info.h"
+
+/* for shared error codes */
+#include "mbedtls/poly1305.h"
+
+/** The requested operation is not permitted in the current state. */
+#define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE            -0x0054
+/** Authenticated decryption failed: data was not authentic. */
+#define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED          -0x0056
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+    MBEDTLS_CHACHAPOLY_ENCRYPT,     /**< The mode value for performing encryption. */
+    MBEDTLS_CHACHAPOLY_DECRYPT      /**< The mode value for performing decryption. */
+}
+mbedtls_chachapoly_mode_t;
+
+#if !defined(MBEDTLS_CHACHAPOLY_ALT)
+
+#include "mbedtls/chacha20.h"
+
+typedef struct mbedtls_chachapoly_context {
+    mbedtls_chacha20_context MBEDTLS_PRIVATE(chacha20_ctx);  /**< The ChaCha20 context. */
+    mbedtls_poly1305_context MBEDTLS_PRIVATE(poly1305_ctx);  /**< The Poly1305 context. */
+    uint64_t MBEDTLS_PRIVATE(aad_len);                       /**< The length (bytes) of the Additional Authenticated Data. */
+    uint64_t MBEDTLS_PRIVATE(ciphertext_len);                /**< The length (bytes) of the ciphertext. */
+    int MBEDTLS_PRIVATE(state);                              /**< The current state of the context. */
+    mbedtls_chachapoly_mode_t MBEDTLS_PRIVATE(mode);         /**< Cipher mode (encrypt or decrypt). */
+}
+mbedtls_chachapoly_context;
+
+#else /* !MBEDTLS_CHACHAPOLY_ALT */
+#include "chachapoly_alt.h"
+#endif /* !MBEDTLS_CHACHAPOLY_ALT */
+
+/**
+ * \brief           This function initializes the specified ChaCha20-Poly1305 context.
+ *
+ *                  It must be the first API called before using
+ *                  the context. It must be followed by a call to
+ *                  \c mbedtls_chachapoly_setkey() before any operation can be
+ *                  done, and to \c mbedtls_chachapoly_free() once all
+ *                  operations with that context have been finished.
+ *
+ *                  In order to encrypt or decrypt full messages at once, for
+ *                  each message you should make a single call to
+ *                  \c mbedtls_chachapoly_crypt_and_tag() or
+ *                  \c mbedtls_chachapoly_auth_decrypt().
+ *
+ *                  In order to encrypt messages piecewise, for each
+ *                  message you should make a call to
+ *                  \c mbedtls_chachapoly_starts(), then 0 or more calls to
+ *                  \c mbedtls_chachapoly_update_aad(), then 0 or more calls to
+ *                  \c mbedtls_chachapoly_update(), then one call to
+ *                  \c mbedtls_chachapoly_finish().
+ *
+ * \warning         Decryption with the piecewise API is discouraged! Always
+ *                  use \c mbedtls_chachapoly_auth_decrypt() when possible!
+ *
+ *                  If however this is not possible because the data is too
+ *                  large to fit in memory, you need to:
+ *
+ *                  - call \c mbedtls_chachapoly_starts() and (if needed)
+ *                  \c mbedtls_chachapoly_update_aad() as above,
+ *                  - call \c mbedtls_chachapoly_update() multiple times and
+ *                  ensure its output (the plaintext) is NOT used in any other
+ *                  way than placing it in temporary storage at this point,
+ *                  - call \c mbedtls_chachapoly_finish() to compute the
+ *                  authentication tag and compared it in constant time to the
+ *                  tag received with the ciphertext.
+ *
+ *                  If the tags are not equal, you must immediately discard
+ *                  all previous outputs of \c mbedtls_chachapoly_update(),
+ *                  otherwise you can now safely use the plaintext.
+ *
+ * \param ctx       The ChachaPoly context to initialize. Must not be \c NULL.
+ */
+void mbedtls_chachapoly_init(mbedtls_chachapoly_context *ctx);
+
+/**
+ * \brief           This function releases and clears the specified
+ *                  ChaCha20-Poly1305 context.
+ *
+ * \param ctx       The ChachaPoly context to clear. This may be \c NULL, in which
+ *                  case this function is a no-op.
+ */
+void mbedtls_chachapoly_free(mbedtls_chachapoly_context *ctx);
+
+/**
+ * \brief           This function sets the ChaCha20-Poly1305
+ *                  symmetric encryption key.
+ *
+ * \param ctx       The ChaCha20-Poly1305 context to which the key should be
+ *                  bound. This must be initialized.
+ * \param key       The \c 256 Bit (\c 32 Bytes) key.
+ *
+ * \return          \c 0 on success.
+ * \return          A negative error code on failure.
+ */
+int mbedtls_chachapoly_setkey(mbedtls_chachapoly_context *ctx,
+                              const unsigned char key[32]);
+
+/**
+ * \brief           This function starts a ChaCha20-Poly1305 encryption or
+ *                  decryption operation.
+ *
+ * \warning         You must never use the same nonce twice with the same key.
+ *                  This would void any confidentiality and authenticity
+ *                  guarantees for the messages encrypted with the same nonce
+ *                  and key.
+ *
+ * \note            If the context is being used for AAD only (no data to
+ *                  encrypt or decrypt) then \p mode can be set to any value.
+ *
+ * \warning         Decryption with the piecewise API is discouraged, see the
+ *                  warning on \c mbedtls_chachapoly_init().
+ *
+ * \param ctx       The ChaCha20-Poly1305 context. This must be initialized
+ *                  and bound to a key.
+ * \param nonce     The nonce/IV to use for the message.
+ *                  This must be a readable buffer of length \c 12 Bytes.
+ * \param mode      The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or
+ *                  #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).
+ *
+ * \return          \c 0 on success.
+ * \return          A negative error code on failure.
+ */
+int mbedtls_chachapoly_starts(mbedtls_chachapoly_context *ctx,
+                              const unsigned char nonce[12],
+                              mbedtls_chachapoly_mode_t mode);
+
+/**
+ * \brief           This function feeds additional data to be authenticated
+ *                  into an ongoing ChaCha20-Poly1305 operation.
+ *
+ *                  The Additional Authenticated Data (AAD), also called
+ *                  Associated Data (AD) is only authenticated but not
+ *                  encrypted nor included in the encrypted output. It is
+ *                  usually transmitted separately from the ciphertext or
+ *                  computed locally by each party.
+ *
+ * \note            This function is called before data is encrypted/decrypted.
+ *                  I.e. call this function to process the AAD before calling
+ *                  \c mbedtls_chachapoly_update().
+ *
+ *                  You may call this function multiple times to process
+ *                  an arbitrary amount of AAD. It is permitted to call
+ *                  this function 0 times, if no AAD is used.
+ *
+ *                  This function cannot be called any more if data has
+ *                  been processed by \c mbedtls_chachapoly_update(),
+ *                  or if the context has been finished.
+ *
+ * \warning         Decryption with the piecewise API is discouraged, see the
+ *                  warning on \c mbedtls_chachapoly_init().
+ *
+ * \param ctx       The ChaCha20-Poly1305 context. This must be initialized
+ *                  and bound to a key.
+ * \param aad_len   The length in Bytes of the AAD. The length has no
+ *                  restrictions.
+ * \param aad       Buffer containing the AAD.
+ *                  This pointer can be \c NULL if `aad_len == 0`.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA
+ *                  if \p ctx or \p aad are NULL.
+ * \return          #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
+ *                  if the operations has not been started or has been
+ *                  finished, or if the AAD has been finished.
+ */
+int mbedtls_chachapoly_update_aad(mbedtls_chachapoly_context *ctx,
+                                  const unsigned char *aad,
+                                  size_t aad_len);
+
+/**
+ * \brief           Thus function feeds data to be encrypted or decrypted
+ *                  into an on-going ChaCha20-Poly1305
+ *                  operation.
+ *
+ *                  The direction (encryption or decryption) depends on the
+ *                  mode that was given when calling
+ *                  \c mbedtls_chachapoly_starts().
+ *
+ *                  You may call this function multiple times to process
+ *                  an arbitrary amount of data. It is permitted to call
+ *                  this function 0 times, if no data is to be encrypted
+ *                  or decrypted.
+ *
+ * \warning         Decryption with the piecewise API is discouraged, see the
+ *                  warning on \c mbedtls_chachapoly_init().
+ *
+ * \param ctx       The ChaCha20-Poly1305 context to use. This must be initialized.
+ * \param len       The length (in bytes) of the data to encrypt or decrypt.
+ * \param input     The buffer containing the data to encrypt or decrypt.
+ *                  This pointer can be \c NULL if `len == 0`.
+ * \param output    The buffer to where the encrypted or decrypted data is
+ *                  written. This must be able to hold \p len bytes.
+ *                  This pointer can be \c NULL if `len == 0`.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
+ *                  if the operation has not been started or has been
+ *                  finished.
+ * \return          Another negative error code on other kinds of failure.
+ */
+int mbedtls_chachapoly_update(mbedtls_chachapoly_context *ctx,
+                              size_t len,
+                              const unsigned char *input,
+                              unsigned char *output);
+
+/**
+ * \brief           This function finished the ChaCha20-Poly1305 operation and
+ *                  generates the MAC (authentication tag).
+ *
+ * \param ctx       The ChaCha20-Poly1305 context to use. This must be initialized.
+ * \param mac       The buffer to where the 128-bit (16 bytes) MAC is written.
+ *
+ * \warning         Decryption with the piecewise API is discouraged, see the
+ *                  warning on \c mbedtls_chachapoly_init().
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
+ *                  if the operation has not been started or has been
+ *                  finished.
+ * \return          Another negative error code on other kinds of failure.
+ */
+int mbedtls_chachapoly_finish(mbedtls_chachapoly_context *ctx,
+                              unsigned char mac[16]);
+
+/**
+ * \brief           This function performs a complete ChaCha20-Poly1305
+ *                  authenticated encryption with the previously-set key.
+ *
+ * \note            Before using this function, you must set the key with
+ *                  \c mbedtls_chachapoly_setkey().
+ *
+ * \warning         You must never use the same nonce twice with the same key.
+ *                  This would void any confidentiality and authenticity
+ *                  guarantees for the messages encrypted with the same nonce
+ *                  and key.
+ *
+ * \param ctx       The ChaCha20-Poly1305 context to use (holds the key).
+ *                  This must be initialized.
+ * \param length    The length (in bytes) of the data to encrypt or decrypt.
+ * \param nonce     The 96-bit (12 bytes) nonce/IV to use.
+ * \param aad       The buffer containing the additional authenticated
+ *                  data (AAD). This pointer can be \c NULL if `aad_len == 0`.
+ * \param aad_len   The length (in bytes) of the AAD data to process.
+ * \param input     The buffer containing the data to encrypt or decrypt.
+ *                  This pointer can be \c NULL if `ilen == 0`.
+ * \param output    The buffer to where the encrypted or decrypted data
+ *                  is written. This pointer can be \c NULL if `ilen == 0`.
+ * \param tag       The buffer to where the computed 128-bit (16 bytes) MAC
+ *                  is written. This must not be \c NULL.
+ *
+ * \return          \c 0 on success.
+ * \return          A negative error code on failure.
+ */
+int mbedtls_chachapoly_encrypt_and_tag(mbedtls_chachapoly_context *ctx,
+                                       size_t length,
+                                       const unsigned char nonce[12],
+                                       const unsigned char *aad,
+                                       size_t aad_len,
+                                       const unsigned char *input,
+                                       unsigned char *output,
+                                       unsigned char tag[16]);
+
+/**
+ * \brief           This function performs a complete ChaCha20-Poly1305
+ *                  authenticated decryption with the previously-set key.
+ *
+ * \note            Before using this function, you must set the key with
+ *                  \c mbedtls_chachapoly_setkey().
+ *
+ * \param ctx       The ChaCha20-Poly1305 context to use (holds the key).
+ * \param length    The length (in Bytes) of the data to decrypt.
+ * \param nonce     The \c 96 Bit (\c 12 bytes) nonce/IV to use.
+ * \param aad       The buffer containing the additional authenticated data (AAD).
+ *                  This pointer can be \c NULL if `aad_len == 0`.
+ * \param aad_len   The length (in bytes) of the AAD data to process.
+ * \param tag       The buffer holding the authentication tag.
+ *                  This must be a readable buffer of length \c 16 Bytes.
+ * \param input     The buffer containing the data to decrypt.
+ *                  This pointer can be \c NULL if `ilen == 0`.
+ * \param output    The buffer to where the decrypted data is written.
+ *                  This pointer can be \c NULL if `ilen == 0`.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED
+ *                  if the data was not authentic.
+ * \return          Another negative error code on other kinds of failure.
+ */
+int mbedtls_chachapoly_auth_decrypt(mbedtls_chachapoly_context *ctx,
+                                    size_t length,
+                                    const unsigned char nonce[12],
+                                    const unsigned char *aad,
+                                    size_t aad_len,
+                                    const unsigned char tag[16],
+                                    const unsigned char *input,
+                                    unsigned char *output);
+
+#if defined(MBEDTLS_SELF_TEST)
+/**
+ * \brief           The ChaCha20-Poly1305 checkup routine.
+ *
+ * \return          \c 0 on success.
+ * \return          \c 1 on failure.
+ */
+int mbedtls_chachapoly_self_test(int verbose);
+#endif /* MBEDTLS_SELF_TEST */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MBEDTLS_CHACHAPOLY_H */