_ Git - BearSSL/blob - inc/bearssl_rsa.h

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #ifndef BR_BEARSSL_RSA_H__
  26 #define BR_BEARSSL_RSA_H__
  27
  28 #include <stddef.h>
  29 #include <stdint.h>
  30
  31 /** \file bearssl_rsa.h
  32  *
  33  * # RSA
  34  *
  35  * This file documents the RSA implementations provided with BearSSL.
  36  * Note that the SSL engine accesses these implementations through a
  37  * configurable API, so it is possible to, for instance, run a SSL
  38  * server which uses a RSA engine which is not based on this code.
  39  *
  40  * ## Key Elements
  41  *
  42  * RSA public and private keys consist in lists of big integers. All
  43  * such integers are represented with big-endian unsigned notation:
  44  * first byte is the most significant, and the value is positive (so
  45  * there is no dedicated "sign bit"). Public and private key structures
  46  * thus contain, for each such integer, a pointer to the first value byte
  47  * (`unsigned char *`), and a length (`size_t`) which is the number of
  48  * relevant bytes. As a general rule, minimal-length encoding is not
  49  * enforced: values may have extra leading bytes of value 0.
  50  *
  51  * RSA public keys consist in two integers:
  52  *
  53  *   - the modulus (`n`);
  54  *   - the public exponent (`e`).
  55  *
  56  * RSA private keys, as defined in
  57  * [PKCS#1](https://tools.ietf.org/html/rfc3447), contain eight integers:
  58  *
  59  *   - the modulus (`n`);
  60  *   - the public exponent (`e`);
  61  *   - the private exponent (`d`);
  62  *   - the first prime factor (`p`);
  63  *   - the second prime factor (`q`);
  64  *   - the first reduced exponent (`dp`, which is `d` modulo `p-1`);
  65  *   - the second reduced exponent (`dq`, which is `d` modulo `q-1`);
  66  *   - the CRT coefficient (`iq`, the inverse of `q` modulo `p`).
  67  *
  68  * However, the implementations defined in BearSSL use only five of
  69  * these integers: `p`, `q`, `dp`, `dq` and `iq`.
  70  *
  71  * ## Security Features and Limitations
  72  *
  73  * The implementations contained in BearSSL have the following limitations
  74  * and features:
  75  *
  76  *   - They are constant-time. This means that the execution time and
  77  *     memory access pattern may depend on the _lengths_ of the private
  78  *     key components, but not on their value, nor on the value of
  79  *     the operand. Note that this property is not achieved through
  80  *     random masking, but "true" constant-time code.
  81  *
  82  *   - They support only private keys with two prime factors. RSA private
  83  *     key with three or more prime factors are nominally supported, but
  84  *     rarely used; they may offer faster operations, at the expense of
  85  *     more code and potentially a reduction in security if there are
  86  *     "too many" prime factors.
  87  *
  88  *   - The public exponent may have arbitrary length. Of course, it is
  89  *     a good idea to keep public exponents small, so that public key
  90  *     operations are fast; but, contrary to some widely deployed
  91  *     implementations, BearSSL has no problem with public exponent
  92  *     longer than 32 bits.
  93  *
  94  *   - The two prime factors of the modulus need not have the same length
  95  *     (but severely imbalanced factor lengths might reduce security).
  96  *     Similarly, there is no requirement that the first factor (`p`)
  97  *     be greater than the second factor (`q`).
  98  *
  99  *   - Prime factors and modulus must be smaller than a compile-time limit.
 100  *     This is made necessary by the use of fixed-size stack buffers, and
 101  *     the limit has been adjusted to keep stack usage under 2 kB for the
 102  *     RSA operations. Currently, the maximum modulus size is 4096 bits,
 103  *     and the maximum prime factor size is 2080 bits.
 104  *
 105  *   - The RSA functions themselves do not enforce lower size limits,
 106  *     except that which is absolutely necessary for the operation to
 107  *     mathematically make sense (e.g. a PKCS#1 v1.5 signature with
 108  *     SHA-1 requires a modulus of at least 361 bits). It is up to users
 109  *     of this code to enforce size limitations when appropriate (e.g.
 110  *     the X.509 validation engine, by default, rejects RSA keys of
 111  *     less than 1017 bits).
 112  *
 113  *   - Within the size constraints expressed above, arbitrary bit lengths
 114  *     are supported. There is no requirement that prime factors or
 115  *     modulus have a size multiple of 8 or 16.
 116  *
 117  *   - When verifying PKCS#1 v1.5 signatures, both variants of the hash
 118  *     function identifying header (with and without the ASN.1 NULL) are
 119  *     supported. When producing such signatures, the variant with the
 120  *     ASN.1 NULL is used.
 121  *
 122  * ## Implementations
 123  *
 124  * Three RSA implementations are included:
 125  *
 126  *   - The **i32** implementation internally represents big integers
 127  *     as arrays of 32-bit integers. It is perfunctory and portable,
 128  *     but not very efficient.
 129  *
 130  *   - The **i31** implementation uses 32-bit integers, each containing
 131  *     31 bits worth of integer data. The i31 implementation is somewhat
 132  *     faster than the i32 implementation (the reduced integer size makes
 133  *     carry propagation easier) for a similar code footprint, but uses
 134  *     very slightly larger stack buffers (about 4% bigger).
 135  *
 136  *   - The **i62** implementation is similar to the i31 implementation,
 137  *     except that it internally leverages the 64x64->128 multiplication
 138  *     opcode. This implementation is available only on architectures
 139  *     where such an opcode exists. It is much faster than i31.
 140  *
 141  *   - The **i15** implementation uses 16-bit integers, each containing
 142  *     15 bits worth of integer data. Multiplication results fit on
 143  *     32 bits, so this won't use the "widening" multiplication routine
 144  *     on ARM Cortex M0/M0+, for much better performance and constant-time
 145  *     execution.
 146  */
 147
 148 /**
 149  * \brief RSA public key.
 150  *
 151  * The structure references the modulus and the public exponent. Both
 152  * integers use unsigned big-endian representation; extra leading bytes
 153  * of value 0 are allowed.
 154  */
 155 typedef struct {
 156         /** \brief Modulus. */
 157         unsigned char *n;
 158         /** \brief Modulus length (in bytes). */
 159         size_t nlen;
 160         /** \brief Public exponent. */
 161         unsigned char *e;
 162         /** \brief Public exponent length (in bytes). */
 163         size_t elen;
 164 } br_rsa_public_key;
 165
 166 /**
 167  * \brief RSA private key.
 168  *
 169  * The structure references the primvate factors, reduced private
 170  * exponents, and CRT coefficient. It also contains the bit length of
 171  * the modulus. The big integers use unsigned big-endian representation;
 172  * extra leading bytes of value 0 are allowed. However, the modulus bit
 173  * length (`n_bitlen`) MUST be exact.
 174  */
 175 typedef struct {
 176         /** \brief Modulus bit length (in bits, exact value). */
 177         uint32_t n_bitlen;
 178         /** \brief First prime factor. */
 179         unsigned char *p;
 180         /** \brief First prime factor length (in bytes). */
 181         size_t plen;
 182         /** \brief Second prime factor. */
 183         unsigned char *q;
 184         /** \brief Second prime factor length (in bytes). */
 185         size_t qlen;
 186         /** \brief First reduced private exponent. */
 187         unsigned char *dp;
 188         /** \brief First reduced private exponent length (in bytes). */
 189         size_t dplen;
 190         /** \brief Second reduced private exponent. */
 191         unsigned char *dq;
 192         /** \brief Second reduced private exponent length (in bytes). */
 193         size_t dqlen;
 194         /** \brief CRT coefficient. */
 195         unsigned char *iq;
 196         /** \brief CRT coefficient length (in bytes). */
 197         size_t iqlen;
 198 } br_rsa_private_key;
 199
 200 /**
 201  * \brief Type for a RSA public key engine.
 202  *
 203  * The public key engine performs the modular exponentiation of the
 204  * provided value with the public exponent. The value is modified in
 205  * place.
 206  *
 207  * The value length (`xlen`) is verified to have _exactly_ the same
 208  * length as the modulus (actual modulus length, without extra leading
 209  * zeros in the modulus representation in memory). If the length does
 210  * not match, then this function returns 0 and `x[]` is unmodified.
 211  *
 212  * It `xlen` is correct, then `x[]` is modified. Returned value is 1
 213  * on success, 0 on error. Error conditions include an oversized `x[]`
 214  * (the array has the same length as the modulus, but the numerical value
 215  * is not lower than the modulus) and an invalid modulus (e.g. an even
 216  * integer). If an error is reported, then the new contents of `x[]` are
 217  * unspecified.
 218  *
 219  * \param x      operand to exponentiate.
 220  * \param xlen   length of the operand (in bytes).
 221  * \param pk     RSA public key.
 222  * \return  1 on success, 0 on error.
 223  */
 224 typedef uint32_t (*br_rsa_public)(unsigned char *x, size_t xlen,
 225         const br_rsa_public_key *pk);
 226
 227 /**
 228  * \brief Type for a RSA signature verification engine (PKCS#1 v1.5).
 229  *
 230  * Parameters are:
 231  *
 232  *   - The signature itself. The provided array is NOT modified.
 233  *
 234  *   - The encoded OID for the hash function. The provided array must begin
 235  *     with a single byte that contains the length of the OID value (in
 236  *     bytes), followed by exactly that many bytes. This parameter may
 237  *     also be `NULL`, in which case the raw hash value should be used
 238  *     with the PKCS#1 v1.5 "type 1" padding (as used in SSL/TLS up
 239  *     to TLS-1.1, with a 36-byte hash value).
 240  *
 241  *   - The hash output length, in bytes.
 242  *
 243  *   - The public key.
 244  *
 245  *   - An output buffer for the hash value. The caller must still compare
 246  *     it with the hash of the data over which the signature is computed.
 247  *
 248  * **Constraints:**
 249  *
 250  *   - Hash length MUST be no more than 64 bytes.
 251  *
 252  *   - OID value length MUST be no more than 32 bytes (i.e. `hash_oid[0]`
 253  *     must have a value in the 0..32 range, inclusive).
 254  *
 255  * This function verifies that the signature length (`xlen`) matches the
 256  * modulus length (this function returns 0 on mismatch). If the modulus
 257  * size exceeds the maximum supported RSA size, then the function also
 258  * returns 0.
 259  *
 260  * Returned value is 1 on success, 0 on error.
 261  *
 262  * Implementations of this type need not be constant-time.
 263  *
 264  * \param x          signature buffer.
 265  * \param xlen       signature length (in bytes).
 266  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 267  * \param hash_len   expected hash value length (in bytes).
 268  * \param pk         RSA public key.
 269  * \param hash_out   output buffer for the hash value.
 270  * \return  1 on success, 0 on error.
 271  */
 272 typedef uint32_t (*br_rsa_pkcs1_vrfy)(const unsigned char *x, size_t xlen,
 273         const unsigned char *hash_oid, size_t hash_len,
 274         const br_rsa_public_key *pk, unsigned char *hash_out);
 275
 276 /**
 277  * \brief Type for a RSA private key engine.
 278  *
 279  * The `x[]` buffer is modified in place, and its length is inferred from
 280  * the modulus length (`x[]` is assumed to have a length of
 281  * `(sk->n_bitlen+7)/8` bytes).
 282  *
 283  * Returned value is 1 on success, 0 on error.
 284  *
 285  * \param x    operand to exponentiate.
 286  * \param sk   RSA private key.
 287  * \return  1 on success, 0 on error.
 288  */
 289 typedef uint32_t (*br_rsa_private)(unsigned char *x,
 290         const br_rsa_private_key *sk);
 291
 292 /**
 293  * \brief Type for a RSA signature generation engine (PKCS#1 v1.5).
 294  *
 295  * Parameters are:
 296  *
 297  *   - The encoded OID for the hash function. The provided array must begin
 298  *     with a single byte that contains the length of the OID value (in
 299  *     bytes), followed by exactly that many bytes. This parameter may
 300  *     also be `NULL`, in which case the raw hash value should be used
 301  *     with the PKCS#1 v1.5 "type 1" padding (as used in SSL/TLS up
 302  *     to TLS-1.1, with a 36-byte hash value).
 303  *
 304  *   - The hash value computes over the data to sign (its length is
 305  *     expressed in bytes).
 306  *
 307  *   - The RSA private key.
 308  *
 309  *   - The output buffer, that receives the signature.
 310  *
 311  * Returned value is 1 on success, 0 on error. Error conditions include
 312  * a too small modulus for the provided hash OID and value, or some
 313  * invalid key parameters. The signature length is exactly
 314  * `(sk->n_bitlen+7)/8` bytes.
 315  *
 316  * This function is expected to be constant-time with regards to the
 317  * private key bytes (lengths of the modulus and the individual factors
 318  * may leak, though) and to the hashed data.
 319  *
 320  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 321  * \param hash       hash value.
 322  * \param hash_len   hash value length (in bytes).
 323  * \param sk         RSA private key.
 324  * \param x          output buffer for the signature value.
 325  * \return  1 on success, 0 on error.
 326  */
 327 typedef uint32_t (*br_rsa_pkcs1_sign)(const unsigned char *hash_oid,
 328         const unsigned char *hash, size_t hash_len,
 329         const br_rsa_private_key *sk, unsigned char *x);
 330
 331 /*
 332  * RSA "i32" engine. Integers are internally represented as arrays of
 333  * 32-bit integers, and the core multiplication primitive is the
 334  * 32x32->64 multiplication.
 335  */
 336
 337 /**
 338  * \brief RSA public key engine "i32".
 339  *
 340  * \see br_rsa_public
 341  *
 342  * \param x      operand to exponentiate.
 343  * \param xlen   length of the operand (in bytes).
 344  * \param pk     RSA public key.
 345  * \return  1 on success, 0 on error.
 346  */
 347 uint32_t br_rsa_i32_public(unsigned char *x, size_t xlen,
 348         const br_rsa_public_key *pk);
 349
 350 /**
 351  * \brief RSA signature verification engine "i32".
 352  *
 353  * \see br_rsa_pkcs1_vrfy
 354  *
 355  * \param x          signature buffer.
 356  * \param xlen       signature length (in bytes).
 357  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 358  * \param hash_len   expected hash value length (in bytes).
 359  * \param pk         RSA public key.
 360  * \param hash_out   output buffer for the hash value.
 361  * \return  1 on success, 0 on error.
 362  */
 363 uint32_t br_rsa_i32_pkcs1_vrfy(const unsigned char *x, size_t xlen,
 364         const unsigned char *hash_oid, size_t hash_len,
 365         const br_rsa_public_key *pk, unsigned char *hash_out);
 366
 367 /**
 368  * \brief RSA private key engine "i32".
 369  *
 370  * \see br_rsa_private
 371  *
 372  * \param x    operand to exponentiate.
 373  * \param sk   RSA private key.
 374  * \return  1 on success, 0 on error.
 375  */
 376 uint32_t br_rsa_i32_private(unsigned char *x,
 377         const br_rsa_private_key *sk);
 378
 379 /**
 380  * \brief RSA signature generation engine "i32".
 381  *
 382  * \see br_rsa_pkcs1_sign
 383  *
 384  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 385  * \param hash       hash value.
 386  * \param hash_len   hash value length (in bytes).
 387  * \param sk         RSA private key.
 388  * \param x          output buffer for the hash value.
 389  * \return  1 on success, 0 on error.
 390  */
 391 uint32_t br_rsa_i32_pkcs1_sign(const unsigned char *hash_oid,
 392         const unsigned char *hash, size_t hash_len,
 393         const br_rsa_private_key *sk, unsigned char *x);
 394
 395 /*
 396  * RSA "i31" engine. Similar to i32, but only 31 bits are used per 32-bit
 397  * word. This uses slightly more stack space (about 4% more) and code
 398  * space, but it quite faster.
 399  */
 400
 401 /**
 402  * \brief RSA public key engine "i31".
 403  *
 404  * \see br_rsa_public
 405  *
 406  * \param x      operand to exponentiate.
 407  * \param xlen   length of the operand (in bytes).
 408  * \param pk     RSA public key.
 409  * \return  1 on success, 0 on error.
 410  */
 411 uint32_t br_rsa_i31_public(unsigned char *x, size_t xlen,
 412         const br_rsa_public_key *pk);
 413
 414 /**
 415  * \brief RSA signature verification engine "i31".
 416  *
 417  * \see br_rsa_pkcs1_vrfy
 418  *
 419  * \param x          signature buffer.
 420  * \param xlen       signature length (in bytes).
 421  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 422  * \param hash_len   expected hash value length (in bytes).
 423  * \param pk         RSA public key.
 424  * \param hash_out   output buffer for the hash value.
 425  * \return  1 on success, 0 on error.
 426  */
 427 uint32_t br_rsa_i31_pkcs1_vrfy(const unsigned char *x, size_t xlen,
 428         const unsigned char *hash_oid, size_t hash_len,
 429         const br_rsa_public_key *pk, unsigned char *hash_out);
 430
 431 /**
 432  * \brief RSA private key engine "i31".
 433  *
 434  * \see br_rsa_private
 435  *
 436  * \param x    operand to exponentiate.
 437  * \param sk   RSA private key.
 438  * \return  1 on success, 0 on error.
 439  */
 440 uint32_t br_rsa_i31_private(unsigned char *x,
 441         const br_rsa_private_key *sk);
 442
 443 /**
 444  * \brief RSA signature generation engine "i31".
 445  *
 446  * \see br_rsa_pkcs1_sign
 447  *
 448  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 449  * \param hash       hash value.
 450  * \param hash_len   hash value length (in bytes).
 451  * \param sk         RSA private key.
 452  * \param x          output buffer for the hash value.
 453  * \return  1 on success, 0 on error.
 454  */
 455 uint32_t br_rsa_i31_pkcs1_sign(const unsigned char *hash_oid,
 456         const unsigned char *hash, size_t hash_len,
 457         const br_rsa_private_key *sk, unsigned char *x);
 458
 459 /*
 460  * RSA "i62" engine. Similar to i31, but internal multiplication use
 461  * 64x64->128 multiplications. This is available only on architecture
 462  * that offer such an opcode.
 463  */
 464
 465 /**
 466  * \brief RSA public key engine "i62".
 467  *
 468  * This function is defined only on architecture that offer a 64x64->128
 469  * opcode. Use `br_rsa_i62_public_get()` to dynamically obtain a pointer
 470  * to that functiom.
 471  *
 472  * \see br_rsa_public
 473  *
 474  * \param x      operand to exponentiate.
 475  * \param xlen   length of the operand (in bytes).
 476  * \param pk     RSA public key.
 477  * \return  1 on success, 0 on error.
 478  */
 479 uint32_t br_rsa_i62_public(unsigned char *x, size_t xlen,
 480         const br_rsa_public_key *pk);
 481
 482 /**
 483  * \brief RSA signature verification engine "i62".
 484  *
 485  * This function is defined only on architecture that offer a 64x64->128
 486  * opcode. Use `br_rsa_i62_pkcs1_vrfy_get()` to dynamically obtain a pointer
 487  * to that functiom.
 488  *
 489  * \see br_rsa_pkcs1_vrfy
 490  *
 491  * \param x          signature buffer.
 492  * \param xlen       signature length (in bytes).
 493  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 494  * \param hash_len   expected hash value length (in bytes).
 495  * \param pk         RSA public key.
 496  * \param hash_out   output buffer for the hash value.
 497  * \return  1 on success, 0 on error.
 498  */
 499 uint32_t br_rsa_i62_pkcs1_vrfy(const unsigned char *x, size_t xlen,
 500         const unsigned char *hash_oid, size_t hash_len,
 501         const br_rsa_public_key *pk, unsigned char *hash_out);
 502
 503 /**
 504  * \brief RSA private key engine "i62".
 505  *
 506  * This function is defined only on architecture that offer a 64x64->128
 507  * opcode. Use `br_rsa_i62_private_get()` to dynamically obtain a pointer
 508  * to that functiom.
 509  *
 510  * \see br_rsa_private
 511  *
 512  * \param x    operand to exponentiate.
 513  * \param sk   RSA private key.
 514  * \return  1 on success, 0 on error.
 515  */
 516 uint32_t br_rsa_i62_private(unsigned char *x,
 517         const br_rsa_private_key *sk);
 518
 519 /**
 520  * \brief RSA signature generation engine "i62".
 521  *
 522  * This function is defined only on architecture that offer a 64x64->128
 523  * opcode. Use `br_rsa_i62_pkcs1_sign_get()` to dynamically obtain a pointer
 524  * to that functiom.
 525  *
 526  * \see br_rsa_pkcs1_sign
 527  *
 528  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 529  * \param hash       hash value.
 530  * \param hash_len   hash value length (in bytes).
 531  * \param sk         RSA private key.
 532  * \param x          output buffer for the hash value.
 533  * \return  1 on success, 0 on error.
 534  */
 535 uint32_t br_rsa_i62_pkcs1_sign(const unsigned char *hash_oid,
 536         const unsigned char *hash, size_t hash_len,
 537         const br_rsa_private_key *sk, unsigned char *x);
 538
 539 /**
 540  * \brief Get the RSA "i62" implementation (public key operations),
 541  * if available.
 542  *
 543  * \return  the implementation, or 0.
 544  */
 545 br_rsa_public br_rsa_i62_public_get(void);
 546
 547 /**
 548  * \brief Get the RSA "i62" implementation (PKCS#1 signature verification),
 549  * if available.
 550  *
 551  * \return  the implementation, or 0.
 552  */
 553 br_rsa_pkcs1_vrfy br_rsa_i62_pkcs1_vrfy_get(void);
 554
 555 /**
 556  * \brief Get the RSA "i62" implementation (private key operations),
 557  * if available.
 558  *
 559  * \return  the implementation, or 0.
 560  */
 561 br_rsa_private br_rsa_i62_private_get(void);
 562
 563 /**
 564  * \brief Get the RSA "i62" implementation (PKCS#1 signature generation),
 565  * if available.
 566  *
 567  * \return  the implementation, or 0.
 568  */
 569 br_rsa_pkcs1_sign br_rsa_i62_pkcs1_sign_get(void);
 570
 571 /*
 572  * RSA "i15" engine. Integers are represented as 15-bit integers, so
 573  * the code uses only 32-bit multiplication (no 64-bit result), which
 574  * is vastly faster (and constant-time) on the ARM Cortex M0/M0+.
 575  */
 576
 577 /**
 578  * \brief RSA public key engine "i15".
 579  *
 580  * \see br_rsa_public
 581  *
 582  * \param x      operand to exponentiate.
 583  * \param xlen   length of the operand (in bytes).
 584  * \param pk     RSA public key.
 585  * \return  1 on success, 0 on error.
 586  */
 587 uint32_t br_rsa_i15_public(unsigned char *x, size_t xlen,
 588         const br_rsa_public_key *pk);
 589
 590 /**
 591  * \brief RSA signature verification engine "i15".
 592  *
 593  * \see br_rsa_pkcs1_vrfy
 594  *
 595  * \param x          signature buffer.
 596  * \param xlen       signature length (in bytes).
 597  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 598  * \param hash_len   expected hash value length (in bytes).
 599  * \param pk         RSA public key.
 600  * \param hash_out   output buffer for the hash value.
 601  * \return  1 on success, 0 on error.
 602  */
 603 uint32_t br_rsa_i15_pkcs1_vrfy(const unsigned char *x, size_t xlen,
 604         const unsigned char *hash_oid, size_t hash_len,
 605         const br_rsa_public_key *pk, unsigned char *hash_out);
 606
 607 /**
 608  * \brief RSA private key engine "i15".
 609  *
 610  * \see br_rsa_private
 611  *
 612  * \param x    operand to exponentiate.
 613  * \param sk   RSA private key.
 614  * \return  1 on success, 0 on error.
 615  */
 616 uint32_t br_rsa_i15_private(unsigned char *x,
 617         const br_rsa_private_key *sk);
 618
 619 /**
 620  * \brief RSA signature generation engine "i15".
 621  *
 622  * \see br_rsa_pkcs1_sign
 623  *
 624  * \param hash_oid   encoded hash algorithm OID (or `NULL`).
 625  * \param hash       hash value.
 626  * \param hash_len   hash value length (in bytes).
 627  * \param sk         RSA private key.
 628  * \param x          output buffer for the hash value.
 629  * \return  1 on success, 0 on error.
 630  */
 631 uint32_t br_rsa_i15_pkcs1_sign(const unsigned char *hash_oid,
 632         const unsigned char *hash, size_t hash_len,
 633         const br_rsa_private_key *sk, unsigned char *x);
 634
 635 /**
 636  * \brief Get "default" RSA implementation (public-key operations).
 637  *
 638  * This returns the preferred implementation of RSA (public-key operations)
 639  * on the current system.
 640  *
 641  * \return  the default implementation.
 642  */
 643 br_rsa_public br_rsa_public_get_default(void);
 644
 645 /**
 646  * \brief Get "default" RSA implementation (private-key operations).
 647  *
 648  * This returns the preferred implementation of RSA (private-key operations)
 649  * on the current system.
 650  *
 651  * \return  the default implementation.
 652  */
 653 br_rsa_private br_rsa_private_get_default(void);
 654
 655 /**
 656  * \brief Get "default" RSA implementation (PKCS#1 signature verification).
 657  *
 658  * This returns the preferred implementation of RSA (signature verification)
 659  * on the current system.
 660  *
 661  * \return  the default implementation.
 662  */
 663 br_rsa_pkcs1_vrfy br_rsa_pkcs1_vrfy_get_default(void);
 664
 665 /**
 666  * \brief Get "default" RSA implementation (PKCS#1 signature generation).
 667  *
 668  * This returns the preferred implementation of RSA (signature generation)
 669  * on the current system.
 670  *
 671  * \return  the default implementation.
 672  */
 673 br_rsa_pkcs1_sign br_rsa_pkcs1_sign_get_default(void);
 674
 675 /**
 676  * \brief RSA decryption helper, for SSL/TLS.
 677  *
 678  * This function performs the RSA decryption for a RSA-based key exchange
 679  * in a SSL/TLS server. The provided RSA engine is used. The `data`
 680  * parameter points to the value to decrypt, of length `len` bytes. On
 681  * success, the 48-byte pre-master secret is copied into `data`, starting
 682  * at the first byte of that buffer; on error, the contents of `data`
 683  * become indeterminate.
 684  *
 685  * This function first checks that the provided value length (`len`) is
 686  * not lower than 59 bytes, and matches the RSA modulus length; if neither
 687  * of this property is met, then this function returns 0 and the buffer
 688  * is unmodified.
 689  *
 690  * Otherwise, decryption and then padding verification are performed, both
 691  * in constant-time. A decryption error, or a bad padding, or an
 692  * incorrect decrypted value length are reported with a returned value of
 693  * 0; on success, 1 is returned. The caller (SSL server engine) is supposed
 694  * to proceed with a random pre-master secret in case of error.
 695  *
 696  * \param core   RSA private key engine.
 697  * \param sk     RSA private key.
 698  * \param data   input/output buffer.
 699  * \param len    length (in bytes) of the data to decrypt.
 700  * \return  1 on success, 0 on error.
 701  */
 702 uint32_t br_rsa_ssl_decrypt(br_rsa_private core, const br_rsa_private_key *sk,
 703         unsigned char *data, size_t len);
 704
 705 #endif