| /* 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_aes_128_gcm is AES-128 in Galois Counter Mode. */ |
| const EVP_AEAD *EVP_aead_aes_128_gcm(void); |
| |
| /* EVP_aes_256_gcm is AES-256 in Galois Counter Mode. */ |
| const EVP_AEAD *EVP_aead_aes_256_gcm(void); |
| |
| /* EVP_aead_chacha20_poly1305 is an AEAD built from ChaCha20 and Poly1305. */ |
| const EVP_AEAD *EVP_aead_chacha20_poly1305(); |
| |
| |
| /* 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. */ |
| |
| /* EVP_aead_rc4_md5_tls uses RC4 and HMAC(MD5) in MAC-then-encrypt mode. Unlike |
| * a standard AEAD, this is stateful as the RC4 state is carried from operation |
| * to operation. */ |
| const EVP_AEAD *EVP_aead_rc4_md5_tls(); |
| |
| |
| /* Utility functions. */ |
| |
| /* EVP_AEAD_key_length returns the length, in bytes, of the keys used by |
| * |aead|. */ |
| 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|. */ |
| 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|. */ |
| 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|. */ |
| 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_OVERHEAD contains the maximum overhead used by any AEAD |
| * defined in this header. */ |
| #define EVP_AEAD_MAX_OVERHEAD 16 |
| |
| /* 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_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. */ |
| 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_cleanup frees any data allocated by |ctx|. */ |
| 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|. */ |
| 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|. */ |
| 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 */ |