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TARGET_MBED_PSA_SRV/inc/psa/crypto_sizes.h
1 /**
2  * \file psa/crypto_sizes.h
3  *
4  * \brief PSA cryptography module: Mbed TLS buffer size macros
5  *
6  * \note This file may not be included directly. Applications must
7  * include psa/crypto.h.
8  *
9  * This file contains the definitions of macros that are useful to
10  * compute buffer sizes. The signatures and semantics of these macros
11  * are standardized, but the definitions are not, because they depend on
12  * the available algorithms and, in some cases, on permitted tolerances
13  * on buffer sizes.
14  *
15  * In implementations with isolation between the application and the
16  * cryptography module, implementers should take care to ensure that
17  * the definitions that are exposed to applications match what the
18  * module implements.
19  *
20  * Macros that compute sizes whose values do not depend on the
21  * implementation are in crypto.h.
22  */
23 /*
24  * Copyright (C) 2018, ARM Limited, All Rights Reserved
25  * SPDX-License-Identifier: Apache-2.0
26  *
27  * Licensed under the Apache License, Version 2.0 (the "License"); you may
28  * not use this file except in compliance with the License.
29  * You may obtain a copy of the License at
30  *
31  * http://www.apache.org/licenses/LICENSE-2.0
32  *
33  * Unless required by applicable law or agreed to in writing, software
34  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
35  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
36  * See the License for the specific language governing permissions and
37  * limitations under the License.
38  *
39  * This file is part of mbed TLS (https://tls.mbed.org)
40  */
41 
42 #ifndef PSA_CRYPTO_SIZES_H
43 #define PSA_CRYPTO_SIZES_H
44 
45 /* Include the Mbed TLS configuration file, the way Mbed TLS does it
46  * in each of its header files. */
47 #if !defined(MBEDTLS_CONFIG_FILE)
48 #include "mbedtls/config.h"
49 #else
50 #include MBEDTLS_CONFIG_FILE
51 #endif
52 
53 #define PSA_BITS_TO_BYTES(bits) (((bits) + 7) / 8)
54 #define PSA_BYTES_TO_BITS(bytes) ((bytes) * 8)
55 
56 #define PSA_ROUND_UP_TO_MULTIPLE(block_size, length) \
57  (((length) + (block_size) - 1) / (block_size) * (block_size))
58 
59 /** The size of the output of psa_hash_finish(), in bytes.
60  *
61  * This is also the hash size that psa_hash_verify() expects.
62  *
63  * \param alg A hash algorithm (\c PSA_ALG_XXX value such that
64  * #PSA_ALG_IS_HASH(\p alg) is true), or an HMAC algorithm
65  * (#PSA_ALG_HMAC(\c hash_alg) where \c hash_alg is a
66  * hash algorithm).
67  *
68  * \return The hash size for the specified hash algorithm.
69  * If the hash algorithm is not recognized, return 0.
70  * An implementation may return either 0 or the correct size
71  * for a hash algorithm that it recognizes, but does not support.
72  */
73 #define PSA_HASH_SIZE(alg) \
74  ( \
75  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD2 ? 16 : \
76  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD4 ? 16 : \
77  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_MD5 ? 16 : \
78  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_RIPEMD160 ? 20 : \
79  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_1 ? 20 : \
80  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_224 ? 28 : \
81  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_256 ? 32 : \
82  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_384 ? 48 : \
83  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512 ? 64 : \
84  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512_224 ? 28 : \
85  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA_512_256 ? 32 : \
86  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_224 ? 28 : \
87  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_256 ? 32 : \
88  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_384 ? 48 : \
89  PSA_ALG_HMAC_GET_HASH(alg) == PSA_ALG_SHA3_512 ? 64 : \
90  0)
91 
92 /** \def PSA_HASH_MAX_SIZE
93  *
94  * Maximum size of a hash.
95  *
96  * This macro must expand to a compile-time constant integer. This value
97  * should be the maximum size of a hash supported by the implementation,
98  * in bytes, and must be no smaller than this maximum.
99  */
100 /* Note: for HMAC-SHA-3, the block size is 144 bytes for HMAC-SHA3-226,
101  * 136 bytes for HMAC-SHA3-256, 104 bytes for SHA3-384, 72 bytes for
102  * HMAC-SHA3-512. */
103 #if defined(MBEDTLS_SHA512_C)
104 #define PSA_HASH_MAX_SIZE 64
105 #define PSA_HMAC_MAX_HASH_BLOCK_SIZE 128
106 #else
107 #define PSA_HASH_MAX_SIZE 32
108 #define PSA_HMAC_MAX_HASH_BLOCK_SIZE 64
109 #endif
110 
111 /** \def PSA_MAC_MAX_SIZE
112  *
113  * Maximum size of a MAC.
114  *
115  * This macro must expand to a compile-time constant integer. This value
116  * should be the maximum size of a MAC supported by the implementation,
117  * in bytes, and must be no smaller than this maximum.
118  */
119 /* All non-HMAC MACs have a maximum size that's smaller than the
120  * minimum possible value of PSA_HASH_MAX_SIZE in this implementation. */
121 /* Note that the encoding of truncated MAC algorithms limits this value
122  * to 64 bytes.
123  */
124 #define PSA_MAC_MAX_SIZE PSA_HASH_MAX_SIZE
125 
126 /** The tag size for an AEAD algorithm, in bytes.
127  *
128  * \param alg An AEAD algorithm
129  * (\c PSA_ALG_XXX value such that
130  * #PSA_ALG_IS_AEAD(\p alg) is true).
131  *
132  * \return The tag size for the specified algorithm.
133  * If the AEAD algorithm does not have an identified
134  * tag that can be distinguished from the rest of
135  * the ciphertext, return 0.
136  * If the AEAD algorithm is not recognized, return 0.
137  * An implementation may return either 0 or a
138  * correct size for an AEAD algorithm that it
139  * recognizes, but does not support.
140  */
141 #define PSA_AEAD_TAG_LENGTH(alg) \
142  (PSA_ALG_IS_AEAD(alg) ? \
143  (((alg) & PSA_ALG_AEAD_TAG_LENGTH_MASK) >> PSA_AEAD_TAG_LENGTH_OFFSET) : \
144  0)
145 
146 /* The maximum size of an RSA key on this implementation, in bits.
147  * This is a vendor-specific macro.
148  *
149  * Mbed TLS does not set a hard limit on the size of RSA keys: any key
150  * whose parameters fit in a bignum is accepted. However large keys can
151  * induce a large memory usage and long computation times. Unlike other
152  * auxiliary macros in this file and in crypto.h, which reflect how the
153  * library is configured, this macro defines how the library is
154  * configured. This implementation refuses to import or generate an
155  * RSA key whose size is larger than the value defined here.
156  *
157  * Note that an implementation may set different size limits for different
158  * operations, and does not need to accept all key sizes up to the limit. */
159 #define PSA_VENDOR_RSA_MAX_KEY_BITS 4096
160 
161 /* The maximum size of an ECC key on this implementation, in bits.
162  * This is a vendor-specific macro. */
163 #if defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED)
164 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 521
165 #elif defined(MBEDTLS_ECP_DP_BP512R1_ENABLED)
166 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 512
167 #elif defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
168 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 448
169 #elif defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
170 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 384
171 #elif defined(MBEDTLS_ECP_DP_BP384R1_ENABLED)
172 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 384
173 #elif defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
174 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
175 #elif defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
176 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
177 #elif defined(MBEDTLS_ECP_DP_BP256R1_ENABLED)
178 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 256
179 #elif defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
180 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 255
181 #elif defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)
182 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 224
183 #elif defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
184 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 224
185 #elif defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
186 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 192
187 #elif defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED)
188 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 192
189 #else
190 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 0
191 #endif
192 
193 /** \def PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN
194  *
195  * This macro returns the maximum length of the PSK supported
196  * by the TLS-1.2 PSK-to-MS key derivation.
197  *
198  * Quoting RFC 4279, Sect 5.3:
199  * TLS implementations supporting these ciphersuites MUST support
200  * arbitrary PSK identities up to 128 octets in length, and arbitrary
201  * PSKs up to 64 octets in length. Supporting longer identities and
202  * keys is RECOMMENDED.
203  *
204  * Therefore, no implementation should define a value smaller than 64
205  * for #PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN.
206  */
207 #define PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN 128
208 
209 /** The maximum size of a block cipher supported by the implementation. */
210 #define PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE 16
211 
212 /** The size of the output of psa_mac_sign_finish(), in bytes.
213  *
214  * This is also the MAC size that psa_mac_verify_finish() expects.
215  *
216  * \param key_type The type of the MAC key.
217  * \param key_bits The size of the MAC key in bits.
218  * \param alg A MAC algorithm (\c PSA_ALG_XXX value such that
219  * #PSA_ALG_IS_MAC(\p alg) is true).
220  *
221  * \return The MAC size for the specified algorithm with
222  * the specified key parameters.
223  * \return 0 if the MAC algorithm is not recognized.
224  * \return Either 0 or the correct size for a MAC algorithm that
225  * the implementation recognizes, but does not support.
226  * \return Unspecified if the key parameters are not consistent
227  * with the algorithm.
228  */
229 #define PSA_MAC_FINAL_SIZE(key_type, key_bits, alg) \
230  ((alg) & PSA_ALG_MAC_TRUNCATION_MASK ? PSA_MAC_TRUNCATED_LENGTH(alg) : \
231  PSA_ALG_IS_HMAC(alg) ? PSA_HASH_SIZE(PSA_ALG_HMAC_GET_HASH(alg)) : \
232  PSA_ALG_IS_BLOCK_CIPHER_MAC(alg) ? PSA_BLOCK_CIPHER_BLOCK_SIZE(key_type) : \
233  ((void)(key_type), (void)(key_bits), 0))
234 
235 /** The maximum size of the output of psa_aead_encrypt(), in bytes.
236  *
237  * If the size of the ciphertext buffer is at least this large, it is
238  * guaranteed that psa_aead_encrypt() will not fail due to an
239  * insufficient buffer size. Depending on the algorithm, the actual size of
240  * the ciphertext may be smaller.
241  *
242  * \param alg An AEAD algorithm
243  * (\c PSA_ALG_XXX value such that
244  * #PSA_ALG_IS_AEAD(\p alg) is true).
245  * \param plaintext_length Size of the plaintext in bytes.
246  *
247  * \return The AEAD ciphertext size for the specified
248  * algorithm.
249  * If the AEAD algorithm is not recognized, return 0.
250  * An implementation may return either 0 or a
251  * correct size for an AEAD algorithm that it
252  * recognizes, but does not support.
253  */
254 #define PSA_AEAD_ENCRYPT_OUTPUT_SIZE(alg, plaintext_length) \
255  (PSA_AEAD_TAG_LENGTH(alg) != 0 ? \
256  (plaintext_length) + PSA_AEAD_TAG_LENGTH(alg) : \
257  0)
258 
259 /** The maximum size of the output of psa_aead_decrypt(), in bytes.
260  *
261  * If the size of the plaintext buffer is at least this large, it is
262  * guaranteed that psa_aead_decrypt() will not fail due to an
263  * insufficient buffer size. Depending on the algorithm, the actual size of
264  * the plaintext may be smaller.
265  *
266  * \param alg An AEAD algorithm
267  * (\c PSA_ALG_XXX value such that
268  * #PSA_ALG_IS_AEAD(\p alg) is true).
269  * \param ciphertext_length Size of the plaintext in bytes.
270  *
271  * \return The AEAD ciphertext size for the specified
272  * algorithm.
273  * If the AEAD algorithm is not recognized, return 0.
274  * An implementation may return either 0 or a
275  * correct size for an AEAD algorithm that it
276  * recognizes, but does not support.
277  */
278 #define PSA_AEAD_DECRYPT_OUTPUT_SIZE(alg, ciphertext_length) \
279  (PSA_AEAD_TAG_LENGTH(alg) != 0 ? \
280  (ciphertext_length) - PSA_AEAD_TAG_LENGTH(alg) : \
281  0)
282 
283 /** A sufficient output buffer size for psa_aead_update().
284  *
285  * If the size of the output buffer is at least this large, it is
286  * guaranteed that psa_aead_update() will not fail due to an
287  * insufficient buffer size. The actual size of the output may be smaller
288  * in any given call.
289  *
290  * \param alg An AEAD algorithm
291  * (\c PSA_ALG_XXX value such that
292  * #PSA_ALG_IS_AEAD(\p alg) is true).
293  * \param input_length Size of the input in bytes.
294  *
295  * \return A sufficient output buffer size for the specified
296  * algorithm.
297  * If the AEAD algorithm is not recognized, return 0.
298  * An implementation may return either 0 or a
299  * correct size for an AEAD algorithm that it
300  * recognizes, but does not support.
301  */
302 /* For all the AEAD modes defined in this specification, it is possible
303  * to emit output without delay. However, hardware may not always be
304  * capable of this. So for modes based on a block cipher, allow the
305  * implementation to delay the output until it has a full block. */
306 #define PSA_AEAD_UPDATE_OUTPUT_SIZE(alg, input_length) \
307  (PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
308  PSA_ROUND_UP_TO_MULTIPLE(PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE, (input_length)) : \
309  (input_length))
310 
311 /** A sufficient ciphertext buffer size for psa_aead_finish().
312  *
313  * If the size of the ciphertext buffer is at least this large, it is
314  * guaranteed that psa_aead_finish() will not fail due to an
315  * insufficient ciphertext buffer size. The actual size of the output may
316  * be smaller in any given call.
317  *
318  * \param alg An AEAD algorithm
319  * (\c PSA_ALG_XXX value such that
320  * #PSA_ALG_IS_AEAD(\p alg) is true).
321  *
322  * \return A sufficient ciphertext buffer size for the
323  * specified algorithm.
324  * If the AEAD algorithm is not recognized, return 0.
325  * An implementation may return either 0 or a
326  * correct size for an AEAD algorithm that it
327  * recognizes, but does not support.
328  */
329 #define PSA_AEAD_FINISH_OUTPUT_SIZE(alg) \
330  (PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
331  PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE : \
332  0)
333 
334 /** A sufficient plaintext buffer size for psa_aead_verify().
335  *
336  * If the size of the plaintext buffer is at least this large, it is
337  * guaranteed that psa_aead_verify() will not fail due to an
338  * insufficient plaintext buffer size. The actual size of the output may
339  * be smaller in any given call.
340  *
341  * \param alg An AEAD algorithm
342  * (\c PSA_ALG_XXX value such that
343  * #PSA_ALG_IS_AEAD(\p alg) is true).
344  *
345  * \return A sufficient plaintext buffer size for the
346  * specified algorithm.
347  * If the AEAD algorithm is not recognized, return 0.
348  * An implementation may return either 0 or a
349  * correct size for an AEAD algorithm that it
350  * recognizes, but does not support.
351  */
352 #define PSA_AEAD_VERIFY_OUTPUT_SIZE(alg) \
353  (PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) ? \
354  PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE : \
355  0)
356 
357 #define PSA_RSA_MINIMUM_PADDING_SIZE(alg) \
358  (PSA_ALG_IS_RSA_OAEP(alg) ? \
359  2 * PSA_HASH_SIZE(PSA_ALG_RSA_OAEP_GET_HASH(alg)) + 1 : \
360  11 /*PKCS#1v1.5*/)
361 
362 /**
363  * \brief ECDSA signature size for a given curve bit size
364  *
365  * \param curve_bits Curve size in bits.
366  * \return Signature size in bytes.
367  *
368  * \note This macro returns a compile-time constant if its argument is one.
369  */
370 #define PSA_ECDSA_SIGNATURE_SIZE(curve_bits) \
371  (PSA_BITS_TO_BYTES(curve_bits) * 2)
372 
373 /** Sufficient signature buffer size for psa_sign_hash().
374  *
375  * This macro returns a sufficient buffer size for a signature using a key
376  * of the specified type and size, with the specified algorithm.
377  * Note that the actual size of the signature may be smaller
378  * (some algorithms produce a variable-size signature).
379  *
380  * \warning This function may call its arguments multiple times or
381  * zero times, so you should not pass arguments that contain
382  * side effects.
383  *
384  * \param key_type An asymmetric key type (this may indifferently be a
385  * key pair type or a public key type).
386  * \param key_bits The size of the key in bits.
387  * \param alg The signature algorithm.
388  *
389  * \return If the parameters are valid and supported, return
390  * a buffer size in bytes that guarantees that
391  * psa_sign_hash() will not fail with
392  * #PSA_ERROR_BUFFER_TOO_SMALL.
393  * If the parameters are a valid combination that is not supported
394  * by the implementation, this macro shall return either a
395  * sensible size or 0.
396  * If the parameters are not valid, the
397  * return value is unspecified.
398  */
399 #define PSA_SIGN_OUTPUT_SIZE(key_type, key_bits, alg) \
400  (PSA_KEY_TYPE_IS_RSA(key_type) ? ((void)alg, PSA_BITS_TO_BYTES(key_bits)) : \
401  PSA_KEY_TYPE_IS_ECC(key_type) ? PSA_ECDSA_SIGNATURE_SIZE(key_bits) : \
402  ((void)alg, 0))
403 
404 #define PSA_VENDOR_ECDSA_SIGNATURE_MAX_SIZE \
405  PSA_ECDSA_SIGNATURE_SIZE(PSA_VENDOR_ECC_MAX_CURVE_BITS)
406 
407 /** \def PSA_SIGNATURE_MAX_SIZE
408  *
409  * Maximum size of an asymmetric signature.
410  *
411  * This macro must expand to a compile-time constant integer. This value
412  * should be the maximum size of a signature supported by the implementation,
413  * in bytes, and must be no smaller than this maximum.
414  */
415 #define PSA_SIGNATURE_MAX_SIZE \
416  (PSA_BITS_TO_BYTES(PSA_VENDOR_RSA_MAX_KEY_BITS) > PSA_VENDOR_ECDSA_SIGNATURE_MAX_SIZE ? \
417  PSA_BITS_TO_BYTES(PSA_VENDOR_RSA_MAX_KEY_BITS) : \
418  PSA_VENDOR_ECDSA_SIGNATURE_MAX_SIZE)
419 
420 /** Sufficient output buffer size for psa_asymmetric_encrypt().
421  *
422  * This macro returns a sufficient buffer size for a ciphertext produced using
423  * a key of the specified type and size, with the specified algorithm.
424  * Note that the actual size of the ciphertext may be smaller, depending
425  * on the algorithm.
426  *
427  * \warning This function may call its arguments multiple times or
428  * zero times, so you should not pass arguments that contain
429  * side effects.
430  *
431  * \param key_type An asymmetric key type (this may indifferently be a
432  * key pair type or a public key type).
433  * \param key_bits The size of the key in bits.
434  * \param alg The signature algorithm.
435  *
436  * \return If the parameters are valid and supported, return
437  * a buffer size in bytes that guarantees that
438  * psa_asymmetric_encrypt() will not fail with
439  * #PSA_ERROR_BUFFER_TOO_SMALL.
440  * If the parameters are a valid combination that is not supported
441  * by the implementation, this macro shall return either a
442  * sensible size or 0.
443  * If the parameters are not valid, the
444  * return value is unspecified.
445  */
446 #define PSA_ASYMMETRIC_ENCRYPT_OUTPUT_SIZE(key_type, key_bits, alg) \
447  (PSA_KEY_TYPE_IS_RSA(key_type) ? \
448  ((void)alg, PSA_BITS_TO_BYTES(key_bits)) : \
449  0)
450 
451 /** Sufficient output buffer size for psa_asymmetric_decrypt().
452  *
453  * This macro returns a sufficient buffer size for a ciphertext produced using
454  * a key of the specified type and size, with the specified algorithm.
455  * Note that the actual size of the ciphertext may be smaller, depending
456  * on the algorithm.
457  *
458  * \warning This function may call its arguments multiple times or
459  * zero times, so you should not pass arguments that contain
460  * side effects.
461  *
462  * \param key_type An asymmetric key type (this may indifferently be a
463  * key pair type or a public key type).
464  * \param key_bits The size of the key in bits.
465  * \param alg The signature algorithm.
466  *
467  * \return If the parameters are valid and supported, return
468  * a buffer size in bytes that guarantees that
469  * psa_asymmetric_decrypt() will not fail with
470  * #PSA_ERROR_BUFFER_TOO_SMALL.
471  * If the parameters are a valid combination that is not supported
472  * by the implementation, this macro shall return either a
473  * sensible size or 0.
474  * If the parameters are not valid, the
475  * return value is unspecified.
476  */
477 #define PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE(key_type, key_bits, alg) \
478  (PSA_KEY_TYPE_IS_RSA(key_type) ? \
479  PSA_BITS_TO_BYTES(key_bits) - PSA_RSA_MINIMUM_PADDING_SIZE(alg) : \
480  0)
481 
482 /* Maximum size of the ASN.1 encoding of an INTEGER with the specified
483  * number of bits.
484  *
485  * This definition assumes that bits <= 2^19 - 9 so that the length field
486  * is at most 3 bytes. The length of the encoding is the length of the
487  * bit string padded to a whole number of bytes plus:
488  * - 1 type byte;
489  * - 1 to 3 length bytes;
490  * - 0 to 1 bytes of leading 0 due to the sign bit.
491  */
492 #define PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(bits) \
493  ((bits) / 8 + 5)
494 
495 /* Maximum size of the export encoding of an RSA public key.
496  * Assumes that the public exponent is less than 2^32.
497  *
498  * RSAPublicKey ::= SEQUENCE {
499  * modulus INTEGER, -- n
500  * publicExponent INTEGER } -- e
501  *
502  * - 4 bytes of SEQUENCE overhead;
503  * - n : INTEGER;
504  * - 7 bytes for the public exponent.
505  */
506 #define PSA_KEY_EXPORT_RSA_PUBLIC_KEY_MAX_SIZE(key_bits) \
507  (PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) + 11)
508 
509 /* Maximum size of the export encoding of an RSA key pair.
510  * Assumes thatthe public exponent is less than 2^32 and that the size
511  * difference between the two primes is at most 1 bit.
512  *
513  * RSAPrivateKey ::= SEQUENCE {
514  * version Version, -- 0
515  * modulus INTEGER, -- N-bit
516  * publicExponent INTEGER, -- 32-bit
517  * privateExponent INTEGER, -- N-bit
518  * prime1 INTEGER, -- N/2-bit
519  * prime2 INTEGER, -- N/2-bit
520  * exponent1 INTEGER, -- N/2-bit
521  * exponent2 INTEGER, -- N/2-bit
522  * coefficient INTEGER, -- N/2-bit
523  * }
524  *
525  * - 4 bytes of SEQUENCE overhead;
526  * - 3 bytes of version;
527  * - 7 half-size INTEGERs plus 2 full-size INTEGERs,
528  * overapproximated as 9 half-size INTEGERS;
529  * - 7 bytes for the public exponent.
530  */
531 #define PSA_KEY_EXPORT_RSA_KEY_PAIR_MAX_SIZE(key_bits) \
532  (9 * PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE((key_bits) / 2 + 1) + 14)
533 
534 /* Maximum size of the export encoding of a DSA public key.
535  *
536  * SubjectPublicKeyInfo ::= SEQUENCE {
537  * algorithm AlgorithmIdentifier,
538  * subjectPublicKey BIT STRING } -- contains DSAPublicKey
539  * AlgorithmIdentifier ::= SEQUENCE {
540  * algorithm OBJECT IDENTIFIER,
541  * parameters Dss-Parms } -- SEQUENCE of 3 INTEGERs
542  * DSAPublicKey ::= INTEGER -- public key, Y
543  *
544  * - 3 * 4 bytes of SEQUENCE overhead;
545  * - 1 + 1 + 7 bytes of algorithm (DSA OID);
546  * - 4 bytes of BIT STRING overhead;
547  * - 3 full-size INTEGERs (p, g, y);
548  * - 1 + 1 + 32 bytes for 1 sub-size INTEGER (q <= 256 bits).
549  */
550 #define PSA_KEY_EXPORT_DSA_PUBLIC_KEY_MAX_SIZE(key_bits) \
551  (PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) * 3 + 59)
552 
553 /* Maximum size of the export encoding of a DSA key pair.
554  *
555  * DSAPrivateKey ::= SEQUENCE {
556  * version Version, -- 0
557  * prime INTEGER, -- p
558  * subprime INTEGER, -- q
559  * generator INTEGER, -- g
560  * public INTEGER, -- y
561  * private INTEGER, -- x
562  * }
563  *
564  * - 4 bytes of SEQUENCE overhead;
565  * - 3 bytes of version;
566  * - 3 full-size INTEGERs (p, g, y);
567  * - 2 * (1 + 1 + 32) bytes for 2 sub-size INTEGERs (q, x <= 256 bits).
568  */
569 #define PSA_KEY_EXPORT_DSA_KEY_PAIR_MAX_SIZE(key_bits) \
570  (PSA_KEY_EXPORT_ASN1_INTEGER_MAX_SIZE(key_bits) * 3 + 75)
571 
572 /* Maximum size of the export encoding of an ECC public key.
573  *
574  * The representation of an ECC public key is:
575  * - The byte 0x04;
576  * - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
577  * - `y_P` as a `ceiling(m/8)`-byte string, big-endian;
578  * - where m is the bit size associated with the curve.
579  *
580  * - 1 byte + 2 * point size.
581  */
582 #define PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(key_bits) \
583  (2 * PSA_BITS_TO_BYTES(key_bits) + 1)
584 
585 /* Maximum size of the export encoding of an ECC key pair.
586  *
587  * An ECC key pair is represented by the secret value.
588  */
589 #define PSA_KEY_EXPORT_ECC_KEY_PAIR_MAX_SIZE(key_bits) \
590  (PSA_BITS_TO_BYTES(key_bits))
591 
592 /** Sufficient output buffer size for psa_export_key() or psa_export_public_key().
593  *
594  * This macro returns a compile-time constant if its arguments are
595  * compile-time constants.
596  *
597  * \warning This function may call its arguments multiple times or
598  * zero times, so you should not pass arguments that contain
599  * side effects.
600  *
601  * The following code illustrates how to allocate enough memory to export
602  * a key by querying the key type and size at runtime.
603  * \code{c}
604  * psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
605  * psa_status_t status;
606  * status = psa_get_key_attributes(key, &attributes);
607  * if (status != PSA_SUCCESS) handle_error(...);
608  * psa_key_type_t key_type = psa_get_key_type(&attributes);
609  * size_t key_bits = psa_get_key_bits(&attributes);
610  * size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(key_type, key_bits);
611  * psa_reset_key_attributes(&attributes);
612  * uint8_t *buffer = malloc(buffer_size);
613  * if (buffer == NULL) handle_error(...);
614  * size_t buffer_length;
615  * status = psa_export_key(key, buffer, buffer_size, &buffer_length);
616  * if (status != PSA_SUCCESS) handle_error(...);
617  * \endcode
618  *
619  * For psa_export_public_key(), calculate the buffer size from the
620  * public key type. You can use the macro #PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR
621  * to convert a key pair type to the corresponding public key type.
622  * \code{c}
623  * psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
624  * psa_status_t status;
625  * status = psa_get_key_attributes(key, &attributes);
626  * if (status != PSA_SUCCESS) handle_error(...);
627  * psa_key_type_t key_type = psa_get_key_type(&attributes);
628  * psa_key_type_t public_key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR(key_type);
629  * size_t key_bits = psa_get_key_bits(&attributes);
630  * size_t buffer_size = PSA_KEY_EXPORT_MAX_SIZE(public_key_type, key_bits);
631  * psa_reset_key_attributes(&attributes);
632  * uint8_t *buffer = malloc(buffer_size);
633  * if (buffer == NULL) handle_error(...);
634  * size_t buffer_length;
635  * status = psa_export_public_key(key, buffer, buffer_size, &buffer_length);
636  * if (status != PSA_SUCCESS) handle_error(...);
637  * \endcode
638  *
639  * \param key_type A supported key type.
640  * \param key_bits The size of the key in bits.
641  *
642  * \return If the parameters are valid and supported, return
643  * a buffer size in bytes that guarantees that
644  * psa_sign_hash() will not fail with
645  * #PSA_ERROR_BUFFER_TOO_SMALL.
646  * If the parameters are a valid combination that is not supported
647  * by the implementation, this macro shall return either a
648  * sensible size or 0.
649  * If the parameters are not valid, the
650  * return value is unspecified.
651  */
652 #define PSA_KEY_EXPORT_MAX_SIZE(key_type, key_bits) \
653  (PSA_KEY_TYPE_IS_UNSTRUCTURED(key_type) ? PSA_BITS_TO_BYTES(key_bits) : \
654  (key_type) == PSA_KEY_TYPE_RSA_KEY_PAIR ? PSA_KEY_EXPORT_RSA_KEY_PAIR_MAX_SIZE(key_bits) : \
655  (key_type) == PSA_KEY_TYPE_RSA_PUBLIC_KEY ? PSA_KEY_EXPORT_RSA_PUBLIC_KEY_MAX_SIZE(key_bits) : \
656  (key_type) == PSA_KEY_TYPE_DSA_KEY_PAIR ? PSA_KEY_EXPORT_DSA_KEY_PAIR_MAX_SIZE(key_bits) : \
657  (key_type) == PSA_KEY_TYPE_DSA_PUBLIC_KEY ? PSA_KEY_EXPORT_DSA_PUBLIC_KEY_MAX_SIZE(key_bits) : \
658  PSA_KEY_TYPE_IS_ECC_KEY_PAIR(key_type) ? PSA_KEY_EXPORT_ECC_KEY_PAIR_MAX_SIZE(key_bits) : \
659  PSA_KEY_TYPE_IS_ECC_PUBLIC_KEY(key_type) ? PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(key_bits) : \
660  0)
661 
662 #endif /* PSA_CRYPTO_SIZES_H */
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