/* 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 #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_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 in some fashion and should not be used outside of that * context. They require an additional data of length 11 (the standard TLS one * with the length omitted). They are also stateful, so a given |EVP_AEAD_CTX| * may only be used for one of seal or open, but not both. */ 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 in some fashion and should not be used outside of that * context. */ 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. */ 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|. */ 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_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); #if defined(__cplusplus) } /* extern C */ #endif #endif /* OPENSSL_HEADER_AEAD_H */