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mbedtls/include/psa/crypto_sizes.h
Gilles Peskine e1f2d7d1ac Document and check the consistency of truncated MAC encodings 
Add comments noting that the maximum length of a MAC must fit in
PSA_ALG_MAC_TRUNCATION_MASK. Add a unit test that verifies that the
maximum MAC size fits.
2018-10-17 13:54:47 +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
/** \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 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
/** \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(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(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(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 ? \
(plaintext_length) - PSA_AEAD_TAG_LENGTH(alg) : \
0)
/** Safe signature buffer size for psa_asymmetric_sign().
*
* This macro returns a safe 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 either 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))
/** Safe output buffer size for psa_asymmetric_encrypt().
*
* This macro returns a safe 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 either 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)
/** Safe output buffer size for psa_asymmetric_decrypt().
*
* This macro returns a safe 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 either 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.
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING } -- contains RSAPublicKey
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters NULL }
* RSAPublicKey ::= SEQUENCE {
* modulus INTEGER, -- n
* publicExponent INTEGER } -- e
*
* - 3 * 4 bytes of SEQUENCE overhead;
* - 1 + 1 + 9 bytes of algorithm (RSA OID);
* - 2 bytes of NULL;
* - 4 bytes of BIT STRING 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) + 36)
/* 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_KEYPAIR_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_KEYPAIR_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.
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING } -- contains ECPoint
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters OBJECT IDENTIFIER } -- namedCurve
* ECPoint ::= ...
* -- first 8 bits: 0x04;
* -- then x_P as an n-bit string, big endian;
* -- then y_P as a n-bit string, big endian,
* -- where n is the order of the curve.
*
* - 2 * 4 bytes of SEQUENCE overhead;
* - 1 + 1 + 7 bytes of algorithm (id-ecPublicKey OID);
* - 1 + 1 + 12 bytes of namedCurve OID;
* - 4 bytes of BIT STRING overhead;
* - 1 byte + 2 * point size in ECPoint.
*/
#define PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(key_bits) \
(2 * PSA_BITS_TO_BYTES(key_bits) + 36)
/* Maximum size of the export encoding of an ECC key pair.
*
* ECPrivateKey ::= SEQUENCE {
* version INTEGER, -- must be 1
* privateKey OCTET STRING,
* -- `ceiling(log2(n)/8)`-byte string, big endian,
* -- where n is the order of the curve.
* parameters [0] IMPLICIT ECParameters {{ NamedCurve }},
* publicKey [1] IMPLICIT BIT STRING
* }
*
* - 4 bytes of SEQUENCE overhead;
* - 1 * point size in privateKey
* - 1 + 1 + 12 bytes of namedCurve OID;
* - 4 bytes of BIT STRING overhead;
* - public key as for #PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE.
*/
#define PSA_KEY_EXPORT_ECC_KEYPAIR_MAX_SIZE(key_bits) \
(3 * PSA_BITS_TO_BYTES(key_bits) + 56)
/** Safe 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_type_t key_type;
* size_t key_bits;
* psa_status_t status;
* status = psa_get_key_information(key, &key_type, &key_bits);
* if (status != PSA_SUCCESS) handle_error(...);
* size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(key_type, key_bits);
* unsigned char *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_KEYPAIR
* to convert a key pair type to the corresponding public key type.
* \code{c}
* psa_key_type_t key_type;
* size_t key_bits;
* psa_status_t status;
* status = psa_get_key_information(key, &key_type, &key_bits);
* if (status != PSA_SUCCESS) handle_error(...);
* psa_key_type_t public_key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEYPAIR(key_type);
* size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(public_key_type, key_bits);
* unsigned char *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 either 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_KEYPAIR ? PSA_KEY_EXPORT_RSA_KEYPAIR_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_KEYPAIR ? PSA_KEY_EXPORT_DSA_KEYPAIR_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_KEYPAIR(key_type) ? PSA_KEY_EXPORT_ECC_KEYPAIR_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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