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/* Copyright (c) 2014, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#ifndef OPENSSL_HEADER_AEAD_H
#define OPENSSL_HEADER_AEAD_H
#include <openssl/base.h>
#if defined(__cplusplus)
extern "C" {
#endif
/* Authenticated Encryption with Additional Data.
*
* AEAD couples confidentiality and integrity in a single primtive. AEAD
* algorithms take a key and then can seal and open individual messages. Each
* message has a unique, per-message nonce and, optionally, additional data
* which is authenticated but not included in the ciphertext.
*
* The |EVP_AEAD_CTX_init| function initialises an |EVP_AEAD_CTX| structure and
* performs any precomputation needed to use |aead| with |key|. The length of
* the key, |key_len|, is given in bytes.
*
* The |tag_len| argument contains the length of the tags, in bytes, and allows
* for the processing of truncated authenticators. A zero value indicates that
* the default tag length should be used and this is defined as
* |EVP_AEAD_DEFAULT_TAG_LENGTH| in order to make the code clear. Using
* truncated tags increases an attacker's chance of creating a valid forgery.
* Be aware that the attacker's chance may increase more than exponentially as
* would naively be expected.
*
* When no longer needed, the initialised |EVP_AEAD_CTX| structure must be
* passed to |EVP_AEAD_CTX_cleanup|, which will deallocate any memory used.
*
* With an |EVP_AEAD_CTX| in hand, one can seal and open messages. These
* operations are intended to meet the standard notions of privacy and
* authenticity for authenticated encryption. For formal definitions see
* Bellare and Namprempre, "Authenticated encryption: relations among notions
* and analysis of the generic composition paradigm," Lecture Notes in Computer
* Science B<1976> (2000), 531–545,
* http://www-cse.ucsd.edu/~mihir/papers/oem.html.
*
* When sealing messages, a nonce must be given. The length of the nonce is
* fixed by the AEAD in use and is returned by |EVP_AEAD_nonce_length|. *The
* nonce must be unique for all messages with the same key*. This is critically
* important - nonce reuse may completely undermine the security of the AEAD.
* Nonces may be predictable and public, so long as they are unique. Uniqueness
* may be achieved with a simple counter or, if large enough, may be generated
* randomly. The nonce must be passed into the "open" operation by the receiver
* so must either be implicit (e.g. a counter), or must be transmitted along
* with the sealed message.
*
* The "seal" and "open" operations are atomic - an entire message must be
* encrypted or decrypted in a single call. Large messages may have to be split
* up in order to accomodate this. When doing so, be mindful of the need not to
* repeat nonces and the possibility that an attacker could duplicate, reorder
* or drop message chunks. For example, using a single key for a given (large)
* message and sealing chunks with nonces counting from zero would be secure as
* long as the number of chunks was securely transmitted. (Otherwise an
* attacker could truncate the message by dropping chunks from the end.)
*
* The number of chunks could be transmitted by prefixing it to the plaintext,
* for example. This also assumes that no other message would ever use the same
* key otherwise the rule that nonces must be unique for a given key would be
* violated.
*
* The "seal" and "open" operations also permit additional data to be
* authenticated via the |ad| parameter. This data is not included in the
* ciphertext and must be identical for both the "seal" and "open" call. This
* permits implicit context to be authenticated but may be empty if not needed.
*
* The "seal" and "open" operations may work in-place if the |out| and |in|
* arguments are equal. They may also be used to shift the data left inside the
* same buffer if |out| is less than |in|. However, |out| may not point inside
* the input data otherwise the input may be overwritten before it has been
* read. This situation will cause an error.
*
* The "seal" and "open" operations return one on success and zero on error. */
/* AEAD algorithms. */
/* EVP_aead_aes_128_gcm is AES-128 in Galois Counter Mode. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm(void);
/* EVP_aead_aes_256_gcm is AES-256 in Galois Counter Mode. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm(void);
/* EVP_aead_chacha20_poly1305 is an AEAD built from ChaCha20 and Poly1305. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305(void);
/* EVP_aead_aes_128_key_wrap is AES-128 Key Wrap mode. This should never be
* used except to interoperate with existing systems that use this mode.
*
* If the nonce is empty then the default nonce will be used, otherwise it must
* be eight bytes long. The input must be a multiple of eight bytes long. No
* additional data can be given to this mode. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_key_wrap(void);
/* EVP_aead_aes_256_key_wrap is AES-256 in Key Wrap mode. This should never be
* used except to interoperate with existing systems that use this mode.
*
* See |EVP_aead_aes_128_key_wrap| for details. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_key_wrap(void);
/* EVP_aead_aes_128_ctr_hmac_sha256 is AES-128 in CTR mode with HMAC-SHA256 for
* authentication. The nonce is 12 bytes; the bottom 32-bits are used as the
* block counter, thus the maximum plaintext size is 64GB. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void);
/* EVP_aead_aes_128_ctr_hmac_sha256 is AES-256 in CTR mode with HMAC-SHA256 for
* authentication. See |EVP_aead_aes_128_ctr_hmac_sha256| for details. */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void);
/* EVP_has_aes_hardware returns one if we enable hardware support for fast and
* constant-time AES-GCM. */
OPENSSL_EXPORT int EVP_has_aes_hardware(void);
/* TLS-specific AEAD algorithms.
*
* These AEAD primitives do not meet the definition of generic AEADs. They are
* all specific to TLS and should not be used outside of that context. They must
* be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful, and may
* not be used concurrently. Any nonces are used as IVs, so they must be
* unpredictable. They only accept an |ad| parameter of length 11 (the standard
* TLS one with length omitted). */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_rc4_md5_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_rc4_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha256_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha256_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha384_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void);
/* SSLv3-specific AEAD algorithms.
*
* These AEAD primitives do not meet the definition of generic AEADs. They are
* all specific to SSLv3 and should not be used outside of that context. They
* must be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful,
* and may not be used concurrently. They only accept an |ad| parameter of
* length 9 (the standard TLS one with length and version omitted). */
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_rc4_md5_ssl3(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_rc4_sha1_ssl3(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_ssl3(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_ssl3(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_ssl3(void);
/* Utility functions. */
/* EVP_AEAD_key_length returns the length, in bytes, of the keys used by
* |aead|. */
OPENSSL_EXPORT size_t EVP_AEAD_key_length(const EVP_AEAD *aead);
/* EVP_AEAD_nonce_length returns the length, in bytes, of the per-message nonce
* for |aead|. */
OPENSSL_EXPORT size_t EVP_AEAD_nonce_length(const EVP_AEAD *aead);
/* EVP_AEAD_max_overhead returns the maximum number of additional bytes added
* by the act of sealing data with |aead|. */
OPENSSL_EXPORT size_t EVP_AEAD_max_overhead(const EVP_AEAD *aead);
/* EVP_AEAD_max_tag_len returns the maximum tag length when using |aead|. This
* is the largest value that can be passed as |tag_len| to
* |EVP_AEAD_CTX_init|. */
OPENSSL_EXPORT size_t EVP_AEAD_max_tag_len(const EVP_AEAD *aead);
/* AEAD operations. */
/* An EVP_AEAD_CTX represents an AEAD algorithm configured with a specific key
* and message-independent IV. */
typedef struct evp_aead_ctx_st {
const EVP_AEAD *aead;
/* aead_state is an opaque pointer to whatever state the AEAD needs to
* maintain. */
void *aead_state;
} EVP_AEAD_CTX;
/* EVP_AEAD_MAX_KEY_LENGTH contains the maximum key length used by
* any AEAD defined in this header. */
#define EVP_AEAD_MAX_KEY_LENGTH 80
/* EVP_AEAD_MAX_NONCE_LENGTH contains the maximum nonce length used by
* any AEAD defined in this header. */
#define EVP_AEAD_MAX_NONCE_LENGTH 16
/* EVP_AEAD_MAX_OVERHEAD contains the maximum overhead used by any AEAD
* defined in this header. */
#define EVP_AEAD_MAX_OVERHEAD 64
/* EVP_AEAD_DEFAULT_TAG_LENGTH is a magic value that can be passed to
* EVP_AEAD_CTX_init to indicate that the default tag length for an AEAD should
* be used. */
#define EVP_AEAD_DEFAULT_TAG_LENGTH 0
/* evp_aead_direction_t denotes the direction of an AEAD operation. */
enum evp_aead_direction_t {
evp_aead_open,
evp_aead_seal,
};
/* EVP_AEAD_CTX_init initializes |ctx| for the given AEAD algorithm from |impl|.
* The |impl| argument may be NULL to choose the default implementation.
* Authentication tags may be truncated by passing a size as |tag_len|. A
* |tag_len| of zero indicates the default tag length and this is defined as
* EVP_AEAD_DEFAULT_TAG_LENGTH for readability.
*
* Returns 1 on success. Otherwise returns 0 and pushes to the error stack. In
* the error case, you do not need to call |EVP_AEAD_CTX_cleanup|, but it's
* harmless to do so. */
OPENSSL_EXPORT int EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead,
const uint8_t *key, size_t key_len,
size_t tag_len, ENGINE *impl);
/* EVP_AEAD_CTX_init_with_direction calls |EVP_AEAD_CTX_init| for normal
* AEADs. For TLS-specific and SSL3-specific AEADs, it initializes |ctx| for a
* given direction. */
OPENSSL_EXPORT int EVP_AEAD_CTX_init_with_direction(
EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, const uint8_t *key, size_t key_len,
size_t tag_len, enum evp_aead_direction_t dir);
/* EVP_AEAD_CTX_cleanup frees any data allocated by |ctx|. It is a no-op to
* call |EVP_AEAD_CTX_cleanup| on a |EVP_AEAD_CTX| that has been |memset| to
* all zeros. */
OPENSSL_EXPORT void EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx);
/* EVP_AEAD_CTX_seal encrypts and authenticates |in_len| bytes from |in| and
* authenticates |ad_len| bytes from |ad| and writes the result to |out|. It
* returns one on success and zero otherwise.
*
* This function may be called (with the same |EVP_AEAD_CTX|) concurrently with
* itself or |EVP_AEAD_CTX_open|.
*
* At most |max_out_len| bytes are written to |out| and, in order to ensure
* success, |max_out_len| should be |in_len| plus the result of
* |EVP_AEAD_max_overhead|. On successful return, |*out_len| is set to the
* actual number of bytes written.
*
* The length of |nonce|, |nonce_len|, must be equal to the result of
* |EVP_AEAD_nonce_length| for this AEAD.
*
* |EVP_AEAD_CTX_seal| never results in a partial output. If |max_out_len| is
* insufficient, zero will be returned. (In this case, |*out_len| is set to
* zero.)
*
* If |in| and |out| alias then |out| must be <= |in|. */
OPENSSL_EXPORT int EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
size_t *out_len, size_t max_out_len,
const uint8_t *nonce, size_t nonce_len,
const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len);
/* EVP_AEAD_CTX_open authenticates |in_len| bytes from |in| and |ad_len| bytes
* from |ad| and decrypts at most |in_len| bytes into |out|. It returns one on
* success and zero otherwise.
*
* This function may be called (with the same |EVP_AEAD_CTX|) concurrently with
* itself or |EVP_AEAD_CTX_seal|.
*
* At most |in_len| bytes are written to |out|. In order to ensure success,
* |max_out_len| should be at least |in_len|. On successful return, |*out_len|
* is set to the the actual number of bytes written.
*
* The length of |nonce|, |nonce_len|, must be equal to the result of
* |EVP_AEAD_nonce_length| for this AEAD.
*
* |EVP_AEAD_CTX_open| never results in a partial output. If |max_out_len| is
* insufficient, zero will be returned. (In this case, |*out_len| is set to
* zero.)
*
* If |in| and |out| alias then |out| must be <= |in|. */
OPENSSL_EXPORT int EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
size_t *out_len, size_t max_out_len,
const uint8_t *nonce, size_t nonce_len,
const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len);
/* Obscure functions. */
/* EVP_AEAD_CTX_get_rc4_state sets |*out_key| to point to an RC4 key structure.
* It returns one on success or zero if |ctx| doesn't have an RC4 key. */
OPENSSL_EXPORT int EVP_AEAD_CTX_get_rc4_state(const EVP_AEAD_CTX *ctx,
const RC4_KEY **out_key);
#if defined(__cplusplus)
} /* extern C */
#endif
#endif /* OPENSSL_HEADER_AEAD_H */