/* Copyright (c) 2014, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#ifndef OPENSSL_HEADER_AEAD_H
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#define OPENSSL_HEADER_AEAD_H
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#include <openssl/base.h>
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#if defined(__cplusplus)
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extern "C" {
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#endif
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// Authenticated Encryption with Additional Data.
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//
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// AEAD couples confidentiality and integrity in a single primitive. AEAD
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// algorithms take a key and then can seal and open individual messages. Each
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// message has a unique, per-message nonce and, optionally, additional data
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// which is authenticated but not included in the ciphertext.
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//
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// The |EVP_AEAD_CTX_init| function initialises an |EVP_AEAD_CTX| structure and
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// performs any precomputation needed to use |aead| with |key|. The length of
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// the key, |key_len|, is given in bytes.
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//
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// The |tag_len| argument contains the length of the tags, in bytes, and allows
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// for the processing of truncated authenticators. A zero value indicates that
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// the default tag length should be used and this is defined as
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// |EVP_AEAD_DEFAULT_TAG_LENGTH| in order to make the code clear. Using
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// truncated tags increases an attacker's chance of creating a valid forgery.
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// Be aware that the attacker's chance may increase more than exponentially as
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// would naively be expected.
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//
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// When no longer needed, the initialised |EVP_AEAD_CTX| structure must be
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// passed to |EVP_AEAD_CTX_cleanup|, which will deallocate any memory used.
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//
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// With an |EVP_AEAD_CTX| in hand, one can seal and open messages. These
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// operations are intended to meet the standard notions of privacy and
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// authenticity for authenticated encryption. For formal definitions see
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// Bellare and Namprempre, "Authenticated encryption: relations among notions
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// and analysis of the generic composition paradigm," Lecture Notes in Computer
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// Science B<1976> (2000), 531–545,
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// http://www-cse.ucsd.edu/~mihir/papers/oem.html.
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//
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// When sealing messages, a nonce must be given. The length of the nonce is
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// fixed by the AEAD in use and is returned by |EVP_AEAD_nonce_length|. *The
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// nonce must be unique for all messages with the same key*. This is critically
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// important - nonce reuse may completely undermine the security of the AEAD.
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// Nonces may be predictable and public, so long as they are unique. Uniqueness
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// may be achieved with a simple counter or, if large enough, may be generated
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// randomly. The nonce must be passed into the "open" operation by the receiver
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// so must either be implicit (e.g. a counter), or must be transmitted along
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// with the sealed message.
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//
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// The "seal" and "open" operations are atomic - an entire message must be
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// encrypted or decrypted in a single call. Large messages may have to be split
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// up in order to accommodate this. When doing so, be mindful of the need not to
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// repeat nonces and the possibility that an attacker could duplicate, reorder
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// or drop message chunks. For example, using a single key for a given (large)
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// message and sealing chunks with nonces counting from zero would be secure as
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// long as the number of chunks was securely transmitted. (Otherwise an
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// attacker could truncate the message by dropping chunks from the end.)
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//
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// The number of chunks could be transmitted by prefixing it to the plaintext,
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// for example. This also assumes that no other message would ever use the same
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// key otherwise the rule that nonces must be unique for a given key would be
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// violated.
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//
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// The "seal" and "open" operations also permit additional data to be
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// authenticated via the |ad| parameter. This data is not included in the
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// ciphertext and must be identical for both the "seal" and "open" call. This
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// permits implicit context to be authenticated but may be empty if not needed.
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//
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// The "seal" and "open" operations may work in-place if the |out| and |in|
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// arguments are equal. Otherwise, if |out| and |in| alias, input data may be
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// overwritten before it is read. This situation will cause an error.
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//
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// The "seal" and "open" operations return one on success and zero on error.
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// AEAD algorithms.
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// EVP_aead_aes_128_gcm is AES-128 in Galois Counter Mode.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm(void);
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// EVP_aead_aes_256_gcm is AES-256 in Galois Counter Mode.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm(void);
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// EVP_aead_chacha20_poly1305 is the AEAD built from ChaCha20 and
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// Poly1305 as described in RFC 7539.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305(void);
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// EVP_aead_aes_128_ctr_hmac_sha256 is AES-128 in CTR mode with HMAC-SHA256 for
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// authentication. The nonce is 12 bytes; the bottom 32-bits are used as the
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// block counter, thus the maximum plaintext size is 64GB.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void);
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// EVP_aead_aes_256_ctr_hmac_sha256 is AES-256 in CTR mode with HMAC-SHA256 for
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// authentication. See |EVP_aead_aes_128_ctr_hmac_sha256| for details.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void);
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// EVP_aead_aes_128_gcm_siv is AES-128 in GCM-SIV mode. See
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// https://tools.ietf.org/html/draft-irtf-cfrg-gcmsiv-02
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void);
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// EVP_aead_aes_256_gcm_siv is AES-256 in GCM-SIV mode. See
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// https://tools.ietf.org/html/draft-irtf-cfrg-gcmsiv-02
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void);
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// EVP_has_aes_hardware returns one if we enable hardware support for fast and
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// constant-time AES-GCM.
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OPENSSL_EXPORT int EVP_has_aes_hardware(void);
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// Utility functions.
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// EVP_AEAD_key_length returns the length, in bytes, of the keys used by
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// |aead|.
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OPENSSL_EXPORT size_t EVP_AEAD_key_length(const EVP_AEAD *aead);
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// EVP_AEAD_nonce_length returns the length, in bytes, of the per-message nonce
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// for |aead|.
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OPENSSL_EXPORT size_t EVP_AEAD_nonce_length(const EVP_AEAD *aead);
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// EVP_AEAD_max_overhead returns the maximum number of additional bytes added
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// by the act of sealing data with |aead|.
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OPENSSL_EXPORT size_t EVP_AEAD_max_overhead(const EVP_AEAD *aead);
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// EVP_AEAD_max_tag_len returns the maximum tag length when using |aead|. This
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// is the largest value that can be passed as |tag_len| to
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// |EVP_AEAD_CTX_init|.
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OPENSSL_EXPORT size_t EVP_AEAD_max_tag_len(const EVP_AEAD *aead);
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// AEAD operations.
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// An EVP_AEAD_CTX represents an AEAD algorithm configured with a specific key
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// and message-independent IV.
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typedef struct evp_aead_ctx_st {
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const EVP_AEAD *aead;
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// aead_state is an opaque pointer to whatever state the AEAD needs to
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// maintain.
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void *aead_state;
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// tag_len may contain the actual length of the authentication tag if it is
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// known at initialization time.
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uint8_t tag_len;
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} EVP_AEAD_CTX;
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// EVP_AEAD_MAX_KEY_LENGTH contains the maximum key length used by
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// any AEAD defined in this header.
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#define EVP_AEAD_MAX_KEY_LENGTH 80
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// EVP_AEAD_MAX_NONCE_LENGTH contains the maximum nonce length used by
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// any AEAD defined in this header.
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#define EVP_AEAD_MAX_NONCE_LENGTH 16
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// EVP_AEAD_MAX_OVERHEAD contains the maximum overhead used by any AEAD
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// defined in this header.
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#define EVP_AEAD_MAX_OVERHEAD 64
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// EVP_AEAD_DEFAULT_TAG_LENGTH is a magic value that can be passed to
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// EVP_AEAD_CTX_init to indicate that the default tag length for an AEAD should
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// be used.
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#define EVP_AEAD_DEFAULT_TAG_LENGTH 0
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// EVP_AEAD_CTX_zero sets an uninitialized |ctx| to the zero state. It must be
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// initialized with |EVP_AEAD_CTX_init| before use. It is safe, but not
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// necessary, to call |EVP_AEAD_CTX_cleanup| in this state. This may be used for
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// more uniform cleanup of |EVP_AEAD_CTX|.
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OPENSSL_EXPORT void EVP_AEAD_CTX_zero(EVP_AEAD_CTX *ctx);
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// EVP_AEAD_CTX_new allocates an |EVP_AEAD_CTX|, calls |EVP_AEAD_CTX_init| and
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// returns the |EVP_AEAD_CTX|, or NULL on error.
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OPENSSL_EXPORT EVP_AEAD_CTX *EVP_AEAD_CTX_new(const EVP_AEAD *aead,
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const uint8_t *key,
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size_t key_len, size_t tag_len);
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// EVP_AEAD_CTX_free calls |EVP_AEAD_CTX_cleanup| and |OPENSSL_free| on
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// |ctx|.
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OPENSSL_EXPORT void EVP_AEAD_CTX_free(EVP_AEAD_CTX *ctx);
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// EVP_AEAD_CTX_init initializes |ctx| for the given AEAD algorithm. The |impl|
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// argument is ignored and should be NULL. Authentication tags may be truncated
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// by passing a size as |tag_len|. A |tag_len| of zero indicates the default
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// tag length and this is defined as EVP_AEAD_DEFAULT_TAG_LENGTH for
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// readability.
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//
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// Returns 1 on success. Otherwise returns 0 and pushes to the error stack. In
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// the error case, you do not need to call |EVP_AEAD_CTX_cleanup|, but it's
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// harmless to do so.
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OPENSSL_EXPORT int EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead,
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const uint8_t *key, size_t key_len,
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size_t tag_len, ENGINE *impl);
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// EVP_AEAD_CTX_cleanup frees any data allocated by |ctx|. It is a no-op to
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// call |EVP_AEAD_CTX_cleanup| on a |EVP_AEAD_CTX| that has been |memset| to
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// all zeros.
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OPENSSL_EXPORT void EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx);
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// EVP_AEAD_CTX_seal encrypts and authenticates |in_len| bytes from |in| and
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// authenticates |ad_len| bytes from |ad| and writes the result to |out|. It
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// returns one on success and zero otherwise.
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//
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// This function may be called concurrently with itself or any other seal/open
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// function on the same |EVP_AEAD_CTX|.
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//
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// At most |max_out_len| bytes are written to |out| and, in order to ensure
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// success, |max_out_len| should be |in_len| plus the result of
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// |EVP_AEAD_max_overhead|. On successful return, |*out_len| is set to the
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// actual number of bytes written.
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//
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// The length of |nonce|, |nonce_len|, must be equal to the result of
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// |EVP_AEAD_nonce_length| for this AEAD.
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//
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// |EVP_AEAD_CTX_seal| never results in a partial output. If |max_out_len| is
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// insufficient, zero will be returned. If any error occurs, |out| will be
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// filled with zero bytes and |*out_len| set to zero.
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//
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// If |in| and |out| alias then |out| must be == |in|.
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OPENSSL_EXPORT int EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
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size_t *out_len, size_t max_out_len,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *in, size_t in_len,
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const uint8_t *ad, size_t ad_len);
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// EVP_AEAD_CTX_open authenticates |in_len| bytes from |in| and |ad_len| bytes
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// from |ad| and decrypts at most |in_len| bytes into |out|. It returns one on
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// success and zero otherwise.
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//
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// This function may be called concurrently with itself or any other seal/open
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// function on the same |EVP_AEAD_CTX|.
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//
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// At most |in_len| bytes are written to |out|. In order to ensure success,
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// |max_out_len| should be at least |in_len|. On successful return, |*out_len|
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// is set to the the actual number of bytes written.
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//
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// The length of |nonce|, |nonce_len|, must be equal to the result of
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// |EVP_AEAD_nonce_length| for this AEAD.
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//
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// |EVP_AEAD_CTX_open| never results in a partial output. If |max_out_len| is
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// insufficient, zero will be returned. If any error occurs, |out| will be
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// filled with zero bytes and |*out_len| set to zero.
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//
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// If |in| and |out| alias then |out| must be == |in|.
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OPENSSL_EXPORT int EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
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size_t *out_len, size_t max_out_len,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *in, size_t in_len,
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const uint8_t *ad, size_t ad_len);
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// EVP_AEAD_CTX_seal_scatter encrypts and authenticates |in_len| bytes from |in|
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// and authenticates |ad_len| bytes from |ad|. It writes |in_len| bytes of
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// ciphertext to |out| and the authentication tag to |out_tag|. It returns one
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// on success and zero otherwise.
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//
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// This function may be called concurrently with itself or any other seal/open
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// function on the same |EVP_AEAD_CTX|.
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//
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// Exactly |in_len| bytes are written to |out|, and up to
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// |EVP_AEAD_max_overhead+extra_in_len| bytes to |out_tag|. On successful
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// return, |*out_tag_len| is set to the actual number of bytes written to
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// |out_tag|.
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//
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// |extra_in| may point to an additional plaintext input buffer if the cipher
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// supports it. If present, |extra_in_len| additional bytes of plaintext are
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// encrypted and authenticated, and the ciphertext is written (before the tag)
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// to |out_tag|. |max_out_tag_len| must be sized to allow for the additional
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// |extra_in_len| bytes.
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//
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// The length of |nonce|, |nonce_len|, must be equal to the result of
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// |EVP_AEAD_nonce_length| for this AEAD.
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//
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// |EVP_AEAD_CTX_seal_scatter| never results in a partial output. If
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// |max_out_tag_len| is insufficient, zero will be returned. If any error
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// occurs, |out| and |out_tag| will be filled with zero bytes and |*out_tag_len|
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// set to zero.
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//
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// If |in| and |out| alias then |out| must be == |in|. |out_tag| may not alias
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// any other argument.
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OPENSSL_EXPORT int EVP_AEAD_CTX_seal_scatter(
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const EVP_AEAD_CTX *ctx, uint8_t *out,
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uint8_t *out_tag, size_t *out_tag_len, size_t max_out_tag_len,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *in, size_t in_len,
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const uint8_t *extra_in, size_t extra_in_len,
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const uint8_t *ad, size_t ad_len);
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// EVP_AEAD_CTX_open_gather decrypts and authenticates |in_len| bytes from |in|
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// and authenticates |ad_len| bytes from |ad| using |in_tag_len| bytes of
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// authentication tag from |in_tag|. If successful, it writes |in_len| bytes of
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// plaintext to |out|. It returns one on success and zero otherwise.
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//
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// This function may be called concurrently with itself or any other seal/open
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// function on the same |EVP_AEAD_CTX|.
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//
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// The length of |nonce|, |nonce_len|, must be equal to the result of
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// |EVP_AEAD_nonce_length| for this AEAD.
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//
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// |EVP_AEAD_CTX_open_gather| never results in a partial output. If any error
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// occurs, |out| will be filled with zero bytes.
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//
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// If |in| and |out| alias then |out| must be == |in|.
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OPENSSL_EXPORT int EVP_AEAD_CTX_open_gather(
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const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce,
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size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag,
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size_t in_tag_len, const uint8_t *ad, size_t ad_len);
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// EVP_AEAD_CTX_aead returns the underlying AEAD for |ctx|, or NULL if one has
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// not been set.
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OPENSSL_EXPORT const EVP_AEAD *EVP_AEAD_CTX_aead(const EVP_AEAD_CTX *ctx);
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// TLS-specific AEAD algorithms.
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//
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// These AEAD primitives do not meet the definition of generic AEADs. They are
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// all specific to TLS and should not be used outside of that context. They must
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// be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful, and may
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// not be used concurrently. Any nonces are used as IVs, so they must be
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// unpredictable. They only accept an |ad| parameter of length 11 (the standard
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// TLS one with length omitted).
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha256_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha256_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha384_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_null_sha1_tls(void);
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// EVP_aead_aes_128_gcm_tls12 is AES-128 in Galois Counter Mode using the TLS
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// 1.2 nonce construction.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_tls12(void);
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// EVP_aead_aes_256_gcm_tls12 is AES-256 in Galois Counter Mode using the TLS
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// 1.2 nonce construction.
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_tls12(void);
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// SSLv3-specific AEAD algorithms.
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//
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// These AEAD primitives do not meet the definition of generic AEADs. They are
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// all specific to SSLv3 and should not be used outside of that context. They
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// must be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful,
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// and may not be used concurrently. They only accept an |ad| parameter of
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// length 9 (the standard TLS one with length and version omitted).
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_ssl3(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_ssl3(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_ssl3(void);
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OPENSSL_EXPORT const EVP_AEAD *EVP_aead_null_sha1_ssl3(void);
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// Obscure functions.
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// evp_aead_direction_t denotes the direction of an AEAD operation.
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enum evp_aead_direction_t {
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evp_aead_open,
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evp_aead_seal,
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};
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// EVP_AEAD_CTX_init_with_direction calls |EVP_AEAD_CTX_init| for normal
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// AEADs. For TLS-specific and SSL3-specific AEADs, it initializes |ctx| for a
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// given direction.
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OPENSSL_EXPORT int EVP_AEAD_CTX_init_with_direction(
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EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, const uint8_t *key, size_t key_len,
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size_t tag_len, enum evp_aead_direction_t dir);
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// EVP_AEAD_CTX_get_iv sets |*out_len| to the length of the IV for |ctx| and
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// sets |*out_iv| to point to that many bytes of the current IV. This is only
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// meaningful for AEADs with implicit IVs (i.e. CBC mode in SSLv3 and TLS 1.0).
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//
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// It returns one on success or zero on error.
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OPENSSL_EXPORT int EVP_AEAD_CTX_get_iv(const EVP_AEAD_CTX *ctx,
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const uint8_t **out_iv, size_t *out_len);
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// EVP_AEAD_CTX_tag_len computes the exact byte length of the tag written by
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// |EVP_AEAD_CTX_seal_scatter| and writes it to |*out_tag_len|. It returns one
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// on success or zero on error. |in_len| and |extra_in_len| must equal the
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// arguments of the same names passed to |EVP_AEAD_CTX_seal_scatter|.
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OPENSSL_EXPORT int EVP_AEAD_CTX_tag_len(const EVP_AEAD_CTX *ctx,
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size_t *out_tag_len,
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const size_t in_len,
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const size_t extra_in_len);
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#if defined(__cplusplus)
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} // extern C
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#if !defined(BORINGSSL_NO_CXX)
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extern "C++" {
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namespace bssl {
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using ScopedEVP_AEAD_CTX =
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internal::StackAllocated<EVP_AEAD_CTX, void, EVP_AEAD_CTX_zero,
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EVP_AEAD_CTX_cleanup>;
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BORINGSSL_MAKE_DELETER(EVP_AEAD_CTX, EVP_AEAD_CTX_free)
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} // namespace bssl
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} // extern C++
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#endif
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#endif
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#endif // OPENSSL_HEADER_AEAD_H
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