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mbedtls/include/psa/crypto_sizes.h
Gilles Peskine f82088a5f4 Favor stdint.h types in example code
2019-07-15 11:16:18 +02:00

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/**
* \file psa/crypto_sizes.h
*
* \brief PSA cryptography module: Mbed TLS buffer size macros
*
* \note This file may not be included directly. Applications must
* include psa/crypto.h.
*
* This file contains the definitions of macros that are useful to
* compute buffer sizes. The signatures and semantics of these macros
* are standardized, but the definitions are not, because they depend on
* the available algorithms and, in some cases, on permitted tolerances
* on buffer sizes.
*
* In implementations with isolation between the application and the
* cryptography module, implementers should take care to ensure that
* the definitions that are exposed to applications match what the
* module implements.
*
* Macros that compute sizes whose values do not depend on the
* implementation are in crypto.h.
*/
/*
* Copyright (C) 2018, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#ifndef PSA_CRYPTO_SIZES_H
#define PSA_CRYPTO_SIZES_H
/* Include the Mbed TLS configuration file, the way Mbed TLS does it
* in each of its header files. */
#if !defined(MBEDTLS_CONFIG_FILE)
#include "../mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#define PSA_BITS_TO_BYTES(bits) (((bits) + 7) / 8)
#define PSA_BYTES_TO_BITS(bytes) ((bytes) * 8)
#define PSA_ROUND_UP_TO_MULTIPLE(block_size, length) \
(((length) + (block_size) - 1) / (block_size) * (block_size))
/** The size of the output of psa_hash_finish(), in bytes.
*
* This is also the hash size that psa_hash_verify() expects.
*
* \param alg A hash algorithm (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_HASH(\p alg) is true), or an HMAC algorithm
* (#PSA_ALG_HMAC(\c hash_alg) where \c hash_alg is a
* hash algorithm).
*
* \return The hash size for the specified hash algorithm.
* If the hash algorithm is not recognized, return 0.
* An implementation may return either 0 or the correct size
* for a hash algorithm that it recognizes, but does not support.
*/
#define PSA_HASH_SIZE(alg) \
( \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD2 ? 16 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD4 ? 16 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD5 ? 16 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_RIPEMD160 ? 20 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_1 ? 20 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_224 ? 28 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_256 ? 32 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_384 ? 48 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512 ? 64 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512_224 ? 28 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512_256 ? 32 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_224 ? 28 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_256 ? 32 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_384 ? 48 : \
PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_512 ? 64 : \
0)
/** \def PSA_HASH_MAX_SIZE
*
* Maximum size of a hash.
*
* This macro must expand to a compile-time constant integer. This value
* should be the maximum size of a hash supported by the implementation,
* in bytes, and must be no smaller than this maximum.
*/
/* Note: for HMAC-SHA-3, the block size is 144 bytes for HMAC-SHA3-226,
* 136 bytes for HMAC-SHA3-256, 104 bytes for SHA3-384, 72 bytes for
* HMAC-SHA3-512. */
#if defined(MBEDTLS_SHA512_C)
#define PSA_HASH_MAX_SIZE 64
#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 128
#else
#define PSA_HASH_MAX_SIZE 32
#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 64
#endif
/** \def PSA_MAC_MAX_SIZE
*
* Maximum size of a MAC.
*
* This macro must expand to a compile-time constant integer. This value
* should be the maximum size of a MAC supported by the implementation,
* in bytes, and must be no smaller than this maximum.
*/
/* All non-HMAC MACs have a maximum size that's smaller than the
* minimum possible value of PSA_HASH_MAX_SIZE in this implementation. */
/* Note that the encoding of truncated MAC algorithms limits this value
* to 64 bytes.
*/
#define PSA_MAC_MAX_SIZE PSA_HASH_MAX_SIZE
/** The tag size for an AEAD algorithm, in bytes.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
*
* \return The tag size for the specified algorithm.
* If the AEAD algorithm does not have an identified
* tag that can be distinguished from the rest of
* the ciphertext, return 0.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
#define PSA_AEAD_TAG_LENGTH(alg) \
(PSA_ALG_IS_AEAD(alg) ? \
(((alg) & PSA_ALG_AEAD_TAG_LENGTH_MASK) >> PSA_AEAD_TAG_LENGTH_OFFSET) : \
0)
/* The maximum size of an RSA key on this implementation, in bits.
* This is a vendor-specific macro.
*
* Mbed TLS does not set a hard limit on the size of RSA keys: any key
* whose parameters fit in a bignum is accepted. However large keys can
* induce a large memory usage and long computation times. Unlike other
* auxiliary macros in this file and in crypto.h, which reflect how the
* library is configured, this macro defines how the library is
* configured. This implementation refuses to import or generate an
* RSA key whose size is larger than the value defined here.
*
* Note that an implementation may set different size limits for different
* operations, and does not need to accept all key sizes up to the limit. */
#define PSA_VENDOR_RSA_MAX_KEY_BITS 4096
/* The maximum size of an ECC key on this implementation, in bits.
* This is a vendor-specific macro. */
#if defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 521
#elif defined(MBEDTLS_ECP_DP_BP512R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 512
#elif defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 448
#elif defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 384
#elif defined(MBEDTLS_ECP_DP_BP384R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 384
#elif defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
#elif defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
#elif defined(MBEDTLS_ECP_DP_BP256R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
#elif defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 255
#elif defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 224
#elif defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 224
#elif defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 192
#elif defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED)
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 192
#else
#define PSA_VENDOR_ECC_MAX_CURVE_BITS 0
#endif
/** Bit size associated with an elliptic curve.
*
* \param curve An elliptic curve (value of type #psa_ecc_curve_t).
*
* \return The size associated with \p curve, in bits.
* This may be 0 if the implementation does not support
* the specified curve.
*/
#define PSA_ECC_CURVE_BITS(curve) \
((curve) == PSA_ECC_CURVE_SECT163K1 ? 163 : \
(curve) == PSA_ECC_CURVE_SECT163R1 ? 163 : \
(curve) == PSA_ECC_CURVE_SECT163R2 ? 163 : \
(curve) == PSA_ECC_CURVE_SECT193R1 ? 193 : \
(curve) == PSA_ECC_CURVE_SECT193R2 ? 193 : \
(curve) == PSA_ECC_CURVE_SECT233K1 ? 233 : \
(curve) == PSA_ECC_CURVE_SECT233R1 ? 233 : \
(curve) == PSA_ECC_CURVE_SECT239K1 ? 239 : \
(curve) == PSA_ECC_CURVE_SECT283K1 ? 283 : \
(curve) == PSA_ECC_CURVE_SECT283R1 ? 283 : \
(curve) == PSA_ECC_CURVE_SECT409K1 ? 409 : \
(curve) == PSA_ECC_CURVE_SECT409R1 ? 409 : \
(curve) == PSA_ECC_CURVE_SECT571K1 ? 571 : \
(curve) == PSA_ECC_CURVE_SECT571R1 ? 571 : \
(curve) == PSA_ECC_CURVE_SECP160K1 ? 160 : \
(curve) == PSA_ECC_CURVE_SECP160R1 ? 160 : \
(curve) == PSA_ECC_CURVE_SECP160R2 ? 160 : \
(curve) == PSA_ECC_CURVE_SECP192K1 ? 192 : \
(curve) == PSA_ECC_CURVE_SECP192R1 ? 192 : \
(curve) == PSA_ECC_CURVE_SECP224K1 ? 224 : \
(curve) == PSA_ECC_CURVE_SECP224R1 ? 224 : \
(curve) == PSA_ECC_CURVE_SECP256K1 ? 256 : \
(curve) == PSA_ECC_CURVE_SECP256R1 ? 256 : \
(curve) == PSA_ECC_CURVE_SECP384R1 ? 384 : \
(curve) == PSA_ECC_CURVE_SECP521R1 ? 521 : \
(curve) == PSA_ECC_CURVE_BRAINPOOL_P256R1 ? 256 : \
(curve) == PSA_ECC_CURVE_BRAINPOOL_P384R1 ? 384 : \
(curve) == PSA_ECC_CURVE_BRAINPOOL_P512R1 ? 512 : \
(curve) == PSA_ECC_CURVE_CURVE25519 ? 255 : \
(curve) == PSA_ECC_CURVE_CURVE448 ? 448 : \
0)
/** \def PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN
*
* This macro returns the maximum length of the PSK supported
* by the TLS-1.2 PSK-to-MS key derivation.
*
* Quoting RFC 4279, Sect 5.3:
* TLS implementations supporting these ciphersuites MUST support
* arbitrary PSK identities up to 128 octets in length, and arbitrary
* PSKs up to 64 octets in length. Supporting longer identities and
* keys is RECOMMENDED.
*
* Therefore, no implementation should define a value smaller than 64
* for #PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN.
*/
#define PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN 128
/** \def PSA_ASYMMETRIC_SIGNATURE_MAX_SIZE
*
* Maximum size of an asymmetric signature.
*
* This macro must expand to a compile-time constant integer. This value
* should be the maximum size of a MAC supported by the implementation,
* in bytes, and must be no smaller than this maximum.
*/
#define PSA_ASYMMETRIC_SIGNATURE_MAX_SIZE \
PSA_BITS_TO_BYTES( \
PSA_VENDOR_RSA_MAX_KEY_BITS > PSA_VENDOR_ECC_MAX_CURVE_BITS ? \
PSA_VENDOR_RSA_MAX_KEY_BITS : \
PSA_VENDOR_ECC_MAX_CURVE_BITS \
)
/** The maximum size of a block cipher supported by the implementation. */
#define PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE 16
/** The size of the output of psa_mac_sign_finish(), in bytes.
*
* This is also the MAC size that psa_mac_verify_finish() expects.
*
* \param key_type The type of the MAC key.
* \param key_bits The size of the MAC key in bits.
* \param alg A MAC algorithm (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_MAC(\p alg) is true).
*
* \return The MAC size for the specified algorithm with
* the specified key parameters.
* \return 0 if the MAC algorithm is not recognized.
* \return Either 0 or the correct size for a MAC algorithm that
* the implementation recognizes, but does not support.
* \return Unspecified if the key parameters are not consistent
* with the algorithm.
*/
#define PSA_MAC_FINAL_SIZE(key_type, key_bits, alg) \
((alg) & PSA_ALG_MAC_TRUNCATION_MASK ? PSA_MAC_TRUNCATED_LENGTH(alg) : \
PSA_ALG_IS_HMAC(alg) ? PSA_HASH_SIZE(PSA_ALG_HMAC_GET_HASH(alg)) : \
PSA_ALG_IS_BLOCK_CIPHER_MAC(alg) ? PSA_BLOCK_CIPHER_BLOCK_SIZE(key_type) : \
((void)(key_type), (void)(key_bits), 0))
/** The maximum size of the output of psa_aead_encrypt(), in bytes.
*
* If the size of the ciphertext buffer is at least this large, it is
* guaranteed that psa_aead_encrypt() will not fail due to an
* insufficient buffer size. Depending on the algorithm, the actual size of
* the ciphertext may be smaller.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
* \param plaintext_length Size of the plaintext in bytes.
*
* \return The AEAD ciphertext size for the specified
* algorithm.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
#define PSA_AEAD_ENCRYPT_OUTPUT_SIZE(alg, plaintext_length) \
(PSA_AEAD_TAG_LENGTH(alg) != 0 ? \
(plaintext_length) + PSA_AEAD_TAG_LENGTH(alg) : \
0)
/** The maximum size of the output of psa_aead_decrypt(), in bytes.
*
* If the size of the plaintext buffer is at least this large, it is
* guaranteed that psa_aead_decrypt() will not fail due to an
* insufficient buffer size. Depending on the algorithm, the actual size of
* the plaintext may be smaller.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
* \param ciphertext_length Size of the plaintext in bytes.
*
* \return The AEAD ciphertext size for the specified
* algorithm.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
#define PSA_AEAD_DECRYPT_OUTPUT_SIZE(alg, ciphertext_length) \
(PSA_AEAD_TAG_LENGTH(alg) != 0 ? \
(ciphertext_length) - PSA_AEAD_TAG_LENGTH(alg) : \
0)
/** A sufficient output buffer size for psa_aead_update().
*
* If the size of the output buffer is at least this large, it is
* guaranteed that psa_aead_update() will not fail due to an
* insufficient buffer size. The actual size of the output may be smaller
* in any given call.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
* \param input_length Size of the input in bytes.
*
* \return A sufficient output buffer size for the specified
* algorithm.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
/* For all the AEAD modes defined in this specification, it is possible
* to emit output without delay. However, hardware may not always be
* capable of this. So for modes based on a block cipher, allow the
* implementation to delay the output until it has a full block. */
#define PSA_AEAD_UPDATE_OUTPUT_SIZE(alg, input_length) \
(PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
PSA_ROUND_UP_TO_MULTIPLE(PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE, (input_length)) : \
(input_length))
/** A sufficient ciphertext buffer size for psa_aead_finish().
*
* If the size of the ciphertext buffer is at least this large, it is
* guaranteed that psa_aead_finish() will not fail due to an
* insufficient ciphertext buffer size. The actual size of the output may
* be smaller in any given call.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
*
* \return A sufficient ciphertext buffer size for the
* specified algorithm.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
#define PSA_AEAD_FINISH_OUTPUT_SIZE(alg) \
(PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE : \
0)
/** A sufficient plaintext buffer size for psa_aead_verify().
*
* If the size of the plaintext buffer is at least this large, it is
* guaranteed that psa_aead_verify() will not fail due to an
* insufficient plaintext buffer size. The actual size of the output may
* be smaller in any given call.
*
* \param alg An AEAD algorithm
* (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_AEAD(\p alg) is true).
*
* \return A sufficient plaintext buffer size for the
* specified algorithm.
* If the AEAD algorithm is not recognized, return 0.
* An implementation may return either 0 or a
* correct size for an AEAD algorithm that it
* recognizes, but does not support.
*/
#define PSA_AEAD_VERIFY_OUTPUT_SIZE(alg) \
(PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE : \
0)
#define PSA_RSA_MINIMUM_PADDING_SIZE(alg) \
(PSA_ALG_IS_RSA_OAEP(alg) ? \
2 * PSA_HASH_SIZE(PSA_ALG_RSA_OAEP_GET_HASH(alg)) + 1 : \
11 /*PKCS#1v1.5*/)
/**
* \brief ECDSA signature size for a given curve bit size
*
* \param curve_bits Curve size in bits.
* \return Signature size in bytes.
*
* \note This macro returns a compile-time constant if its argument is one.
*/
#define PSA_ECDSA_SIGNATURE_SIZE(curve_bits) \
(PSA_BITS_TO_BYTES(curve_bits) * 2)
/** Sufficient signature buffer size for psa_asymmetric_sign().
*
* This macro returns a sufficient buffer size for a signature using a key
* of the specified type and size, with the specified algorithm.
* Note that the actual size of the signature may be smaller
* (some algorithms produce a variable-size signature).
*
* \warning This function may call its arguments multiple times or
* zero times, so you should not pass arguments that contain
* side effects.
*
* \param key_type An asymmetric key type (this may indifferently be a
* key pair type or a public key type).
* \param key_bits The size of the key in bits.
* \param alg The signature algorithm.
*
* \return If the parameters are valid and supported, return
* a buffer size in bytes that guarantees that
* psa_asymmetric_sign() will not fail with
* #PSA_ERROR_BUFFER_TOO_SMALL.
* If the parameters are a valid combination that is not supported
* by the implementation, this macro shall return either a
* sensible size or 0.
* If the parameters are not valid, the
* return value is unspecified.
*/
#define PSA_ASYMMETRIC_SIGN_OUTPUT_SIZE(key_type, key_bits, alg) \
(PSA_KEY_TYPE_IS_RSA(key_type) ? ((void)alg, PSA_BITS_TO_BYTES(key_bits)) : \
PSA_KEY_TYPE_IS_ECC(key_type) ? PSA_ECDSA_SIGNATURE_SIZE(key_bits) : \
((void)alg, 0))
/** Sufficient output buffer size for psa_asymmetric_encrypt().
*
* This macro returns a sufficient buffer size for a ciphertext produced using
* a key of the specified type and size, with the specified algorithm.
* Note that the actual size of the ciphertext may be smaller, depending
* on the algorithm.
*
* \warning This function may call its arguments multiple times or
* zero times, so you should not pass arguments that contain
* side effects.
*
* \param key_type An asymmetric key type (this may indifferently be a
* key pair type or a public key type).
* \param key_bits The size of the key in bits.
* \param alg The signature algorithm.
*
* \return If the parameters are valid and supported, return
* a buffer size in bytes that guarantees that
* psa_asymmetric_encrypt() will not fail with
* #PSA_ERROR_BUFFER_TOO_SMALL.
* If the parameters are a valid combination that is not supported
* by the implementation, this macro shall return either a
* sensible size or 0.
* If the parameters are not valid, the
* return value is unspecified.
*/
#define PSA_ASYMMETRIC_ENCRYPT_OUTPUT_SIZE(key_type, key_bits, alg) \
(PSA_KEY_TYPE_IS_RSA(key_type) ? \
((void)alg, PSA_BITS_TO_BYTES(key_bits)) : \
0)
/** Sufficient output buffer size for psa_asymmetric_decrypt().
*
* This macro returns a sufficient buffer size for a ciphertext produced using
* a key of the specified type and size, with the specified algorithm.
* Note that the actual size of the ciphertext may be smaller, depending
* on the algorithm.
*
* \warning This function may call its arguments multiple times or
* zero times, so you should not pass arguments that contain
* side effects.
*
* \param key_type An asymmetric key type (this may indifferently be a
* key pair type or a public key type).
* \param key_bits The size of the key in bits.
* \param alg The signature algorithm.
*
* \return If the parameters are valid and supported, return
* a buffer size in bytes that guarantees that
* psa_asymmetric_decrypt() will not fail with
* #PSA_ERROR_BUFFER_TOO_SMALL.
* If the parameters are a valid combination that is not supported
* by the implementation, this macro shall return either a
* sensible size or 0.
* If the parameters are not valid, the
* return value is unspecified.
*/
#define PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE(key_type, key_bits, alg) \
(PSA_KEY_TYPE_IS_RSA(key_type) ? \
PSA_BITS_TO_BYTES(key_bits) - PSA_RSA_MINIMUM_PADDING_SIZE(alg) : \
0)
/* Maximum size of the ASN.1 encoding of an INTEGER with the specified
* number of bits.
*
* This definition assumes that bits <= 2^19 - 9 so that the length field
* is at most 3 bytes. The length of the encoding is the length of the
* bit string padded to a whole number of bytes plus:
* - 1 type byte;
* - 1 to 3 length bytes;
* - 0 to 1 bytes of leading 0 due to the sign bit.
*/
#define PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(bits) \
((bits) / 8 + 5)
/* Maximum size of the export encoding of an RSA public key.
* Assumes that the public exponent is less than 2^32.
*
* RSAPublicKey ::= SEQUENCE {
* modulus INTEGER, -- n
* publicExponent INTEGER } -- e
*
* - 4 bytes of SEQUENCE overhead;
* - n : INTEGER;
* - 7 bytes for the public exponent.
*/
#define PSA_KEY_EXPORT_RSA_PUBLIC_KEY_MAX_SIZE(key_bits) \
(PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) + 11)
/* Maximum size of the export encoding of an RSA key pair.
* Assumes thatthe public exponent is less than 2^32 and that the size
* difference between the two primes is at most 1 bit.
*
* RSAPrivateKey ::= SEQUENCE {
* version Version, -- 0
* modulus INTEGER, -- N-bit
* publicExponent INTEGER, -- 32-bit
* privateExponent INTEGER, -- N-bit
* prime1 INTEGER, -- N/2-bit
* prime2 INTEGER, -- N/2-bit
* exponent1 INTEGER, -- N/2-bit
* exponent2 INTEGER, -- N/2-bit
* coefficient INTEGER, -- N/2-bit
* }
*
* - 4 bytes of SEQUENCE overhead;
* - 3 bytes of version;
* - 7 half-size INTEGERs plus 2 full-size INTEGERs,
* overapproximated as 9 half-size INTEGERS;
* - 7 bytes for the public exponent.
*/
#define PSA_KEY_EXPORT_RSA_KEY_PAIR_MAX_SIZE(key_bits) \
(9 * PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE((key_bits) / 2 + 1) + 14)
/* Maximum size of the export encoding of a DSA public key.
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING } -- contains DSAPublicKey
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters Dss-Parms } -- SEQUENCE of 3 INTEGERs
* DSAPublicKey ::= INTEGER -- public key, Y
*
* - 3 * 4 bytes of SEQUENCE overhead;
* - 1 + 1 + 7 bytes of algorithm (DSA OID);
* - 4 bytes of BIT STRING overhead;
* - 3 full-size INTEGERs (p, g, y);
* - 1 + 1 + 32 bytes for 1 sub-size INTEGER (q <= 256 bits).
*/
#define PSA_KEY_EXPORT_DSA_PUBLIC_KEY_MAX_SIZE(key_bits) \
(PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) * 3 + 59)
/* Maximum size of the export encoding of a DSA key pair.
*
* DSAPrivateKey ::= SEQUENCE {
* version Version, -- 0
* prime INTEGER, -- p
* subprime INTEGER, -- q
* generator INTEGER, -- g
* public INTEGER, -- y
* private INTEGER, -- x
* }
*
* - 4 bytes of SEQUENCE overhead;
* - 3 bytes of version;
* - 3 full-size INTEGERs (p, g, y);
* - 2 * (1 + 1 + 32) bytes for 2 sub-size INTEGERs (q, x <= 256 bits).
*/
#define PSA_KEY_EXPORT_DSA_KEY_PAIR_MAX_SIZE(key_bits) \
(PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) * 3 + 75)
/* Maximum size of the export encoding of an ECC public key.
*
* The representation of an ECC public key is:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian;
* - where m is the bit size associated with the curve.
*
* - 1 byte + 2 * point size.
*/
#define PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(key_bits) \
(2 * PSA_BITS_TO_BYTES(key_bits) + 1)
/* Maximum size of the export encoding of an ECC key pair.
*
* An ECC key pair is represented by the secret value.
*/
#define PSA_KEY_EXPORT_ECC_KEY_PAIR_MAX_SIZE(key_bits) \
(PSA_BITS_TO_BYTES(key_bits))
/** Sufficient output buffer size for psa_export_key() or psa_export_public_key().
*
* This macro returns a compile-time constant if its arguments are
* compile-time constants.
*
* \warning This function may call its arguments multiple times or
* zero times, so you should not pass arguments that contain
* side effects.
*
* The following code illustrates how to allocate enough memory to export
* a key by querying the key type and size at runtime.
* \code{c}
* psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
* psa_status_t status;
* status = psa_get_key_attributes(key, &attributes);
* if (status != PSA_SUCCESS) handle_error(...);
* psa_key_type_t key_type = psa_get_key_type(&attributes);
* size_t key_bits = psa_get_key_bits(&attributes);
* size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(key_type, key_bits);
* psa_reset_key_attributes(&attributes);
* uint8_t *buffer = malloc(buffer_size);
* if (buffer == NULL) handle_error(...);
* size_t buffer_length;
* status = psa_export_key(key, buffer, buffer_size, &buffer_length);
* if (status != PSA_SUCCESS) handle_error(...);
* \endcode
*
* For psa_export_public_key(), calculate the buffer size from the
* public key type. You can use the macro #PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR
* to convert a key pair type to the corresponding public key type.
* \code{c}
* psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
* psa_status_t status;
* status = psa_get_key_attributes(key, &attributes);
* if (status != PSA_SUCCESS) handle_error(...);
* psa_key_type_t key_type = psa_get_key_type(&attributes);
* psa_key_type_t public_key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR(key_type);
* size_t key_bits = psa_get_key_bits(&attributes);
* size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(public_key_type, key_bits);
* psa_reset_key_attributes(&attributes);
* uint8_t *buffer = malloc(buffer_size);
* if (buffer == NULL) handle_error(...);
* size_t buffer_length;
* status = psa_export_public_key(key, buffer, buffer_size, &buffer_length);
* if (status != PSA_SUCCESS) handle_error(...);
* \endcode
*
* \param key_type A supported key type.
* \param key_bits The size of the key in bits.
*
* \return If the parameters are valid and supported, return
* a buffer size in bytes that guarantees that
* psa_asymmetric_sign() will not fail with
* #PSA_ERROR_BUFFER_TOO_SMALL.
* If the parameters are a valid combination that is not supported
* by the implementation, this macro shall return either a
* sensible size or 0.
* If the parameters are not valid, the
* return value is unspecified.
*/
#define PSA_KEY_EXPORT_MAX_SIZE(key_type, key_bits) \
(PSA_KEY_TYPE_IS_UNSTRUCTURED(key_type) ? PSA_BITS_TO_BYTES(key_bits) : \
(key_type) == PSA_KEY_TYPE_RSA_KEY_PAIR ? PSA_KEY_EXPORT_RSA_KEY_PAIR_MAX_SIZE(key_bits) : \
(key_type) == PSA_KEY_TYPE_RSA_PUBLIC_KEY ? PSA_KEY_EXPORT_RSA_PUBLIC_KEY_MAX_SIZE(key_bits) : \
(key_type) == PSA_KEY_TYPE_DSA_KEY_PAIR ? PSA_KEY_EXPORT_DSA_KEY_PAIR_MAX_SIZE(key_bits) : \
(key_type) == PSA_KEY_TYPE_DSA_PUBLIC_KEY ? PSA_KEY_EXPORT_DSA_PUBLIC_KEY_MAX_SIZE(key_bits) : \
PSA_KEY_TYPE_IS_ECC_KEY_PAIR(key_type) ? PSA_KEY_EXPORT_ECC_KEY_PAIR_MAX_SIZE(key_bits) : \
PSA_KEY_TYPE_IS_ECC_PUBLIC_KEY(key_type) ? PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(key_bits) : \
0)
#endif /* PSA_CRYPTO_SIZES_H */
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