#include <stddef.h>
#include <stdint.h>
+#include "bearssl_rand.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
/** \file bearssl_rsa.h
*
* # RSA
* random masking, but "true" constant-time code.
*
* - They support only private keys with two prime factors. RSA private
- * key with three or more prime factors are nominally supported, but
+ * keys with three or more prime factors are nominally supported, but
* rarely used; they may offer faster operations, at the expense of
* more code and potentially a reduction in security if there are
* "too many" prime factors.
* - The public exponent may have arbitrary length. Of course, it is
* a good idea to keep public exponents small, so that public key
* operations are fast; but, contrary to some widely deployed
- * implementations, BearSSL has no problem with public exponent
+ * implementations, BearSSL has no problem with public exponents
* longer than 32 bits.
*
* - The two prime factors of the modulus need not have the same length
/**
* \brief RSA private key.
*
- * The structure references the primvate factors, reduced private
+ * The structure references the private factors, reduced private
* exponents, and CRT coefficient. It also contains the bit length of
* the modulus. The big integers use unsigned big-endian representation;
* extra leading bytes of value 0 are allowed. However, the modulus bit
const unsigned char *hash_oid, size_t hash_len,
const br_rsa_public_key *pk, unsigned char *hash_out);
+/**
+ * \brief Type for a RSA encryption engine (OAEP).
+ *
+ * Parameters are:
+ *
+ * - A source of random bytes. The source must be already initialized.
+ *
+ * - A hash function, used internally with the mask generation function
+ * (MGF1).
+ *
+ * - A label. The `label` pointer may be `NULL` if `label_len` is zero
+ * (an empty label, which is the default in PKCS#1 v2.2).
+ *
+ * - The public key.
+ *
+ * - The destination buffer. Its maximum length (in bytes) is provided;
+ * if that length is lower than the public key length, then an error
+ * is reported.
+ *
+ * - The source message.
+ *
+ * The encrypted message output has exactly the same length as the modulus
+ * (mathematical length, in bytes, not counting extra leading zeros in the
+ * modulus representation in the public key).
+ *
+ * The source message (`src`, length `src_len`) may overlap with the
+ * destination buffer (`dst`, length `dst_max_len`).
+ *
+ * This function returns the actual encrypted message length, in bytes;
+ * on error, zero is returned. An error is reported if the output buffer
+ * is not large enough, or the public is invalid, or the public key
+ * modulus exceeds the maximum supported RSA size.
+ *
+ * \param rnd source of random bytes.
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param pk RSA public key.
+ * \param dst destination buffer.
+ * \param dst_max_len destination buffer length (maximum encrypted data size).
+ * \param src message to encrypt.
+ * \param src_len source message length (in bytes).
+ * \return encrypted message length (in bytes), or 0 on error.
+ */
+typedef size_t (*br_rsa_oaep_encrypt)(
+ const br_prng_class **rnd, const br_hash_class *dig,
+ const void *label, size_t label_len,
+ const br_rsa_public_key *pk,
+ void *dst, size_t dst_max_len,
+ const void *src, size_t src_len);
+
/**
* \brief Type for a RSA private key engine.
*
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief Encoded OID for SHA-1 (in RSA PKCS#1 signatures).
+ */
+#define BR_HASH_OID_SHA1 \
+ ((const unsigned char *)"\x05\x2B\x0E\x03\x02\x1A")
+
+/**
+ * \brief Encoded OID for SHA-224 (in RSA PKCS#1 signatures).
+ */
+#define BR_HASH_OID_SHA224 \
+ ((const unsigned char *)"\x09\x60\x86\x48\x01\x65\x03\x04\x02\x04")
+
+/**
+ * \brief Encoded OID for SHA-256 (in RSA PKCS#1 signatures).
+ */
+#define BR_HASH_OID_SHA256 \
+ ((const unsigned char *)"\x09\x60\x86\x48\x01\x65\x03\x04\x02\x01")
+
+/**
+ * \brief Encoded OID for SHA-384 (in RSA PKCS#1 signatures).
+ */
+#define BR_HASH_OID_SHA384 \
+ ((const unsigned char *)"\x09\x60\x86\x48\x01\x65\x03\x04\x02\x02")
+
+/**
+ * \brief Encoded OID for SHA-512 (in RSA PKCS#1 signatures).
+ */
+#define BR_HASH_OID_SHA512 \
+ ((const unsigned char *)"\x09\x60\x86\x48\x01\x65\x03\x04\x02\x03")
+
+/**
+ * \brief Type for a RSA decryption engine (OAEP).
+ *
+ * Parameters are:
+ *
+ * - A hash function, used internally with the mask generation function
+ * (MGF1).
+ *
+ * - A label. The `label` pointer may be `NULL` if `label_len` is zero
+ * (an empty label, which is the default in PKCS#1 v2.2).
+ *
+ * - The private key.
+ *
+ * - The source and destination buffer. The buffer initially contains
+ * the encrypted message; the buffer contents are altered, and the
+ * decrypted message is written at the start of that buffer
+ * (decrypted message is always shorter than the encrypted message).
+ *
+ * If decryption fails in any way, then `*len` is unmodified, and the
+ * function returns 0. Otherwise, `*len` is set to the decrypted message
+ * length, and 1 is returned. The implementation is responsible for
+ * checking that the input message length matches the key modulus length,
+ * and that the padding is correct.
+ *
+ * Implementations MUST use constant-time check of the validity of the
+ * OAEP padding, at least until the leading byte and hash value have
+ * been checked. Whether overall decryption worked, and the length of
+ * the decrypted message, may leak.
+ *
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param sk RSA private key.
+ * \param data input/output buffer.
+ * \param len encrypted/decrypted message length.
+ * \return 1 on success, 0 on error.
+ */
+typedef uint32_t (*br_rsa_oaep_decrypt)(
+ const br_hash_class *dig, const void *label, size_t label_len,
+ const br_rsa_private_key *sk, void *data, size_t *len);
+
/*
* RSA "i32" engine. Integers are internally represented as arrays of
* 32-bit integers, and the core multiplication primitive is the
*
* This function is defined only on architecture that offer a 64x64->128
* opcode. Use `br_rsa_i62_public_get()` to dynamically obtain a pointer
- * to that functiom.
+ * to that function.
*
* \see br_rsa_public
*
*
* This function is defined only on architecture that offer a 64x64->128
* opcode. Use `br_rsa_i62_pkcs1_vrfy_get()` to dynamically obtain a pointer
- * to that functiom.
+ * to that function.
*
* \see br_rsa_pkcs1_vrfy
*
*
* This function is defined only on architecture that offer a 64x64->128
* opcode. Use `br_rsa_i62_private_get()` to dynamically obtain a pointer
- * to that functiom.
+ * to that function.
*
* \see br_rsa_private
*
*
* This function is defined only on architecture that offer a 64x64->128
* opcode. Use `br_rsa_i62_pkcs1_sign_get()` to dynamically obtain a pointer
- * to that functiom.
+ * to that function.
*
* \see br_rsa_pkcs1_sign
*
*/
br_rsa_pkcs1_sign br_rsa_i62_pkcs1_sign_get(void);
+/**
+ * \brief Get the RSA "i62" implementation (OAEP encryption),
+ * if available.
+ *
+ * \return the implementation, or 0.
+ */
+br_rsa_oaep_encrypt br_rsa_i62_oaep_encrypt_get(void);
+
+/**
+ * \brief Get the RSA "i62" implementation (OAEP decryption),
+ * if available.
+ *
+ * \return the implementation, or 0.
+ */
+br_rsa_oaep_decrypt br_rsa_i62_oaep_decrypt_get(void);
+
/*
* RSA "i15" engine. Integers are represented as 15-bit integers, so
* the code uses only 32-bit multiplication (no 64-bit result), which
*/
br_rsa_pkcs1_sign br_rsa_pkcs1_sign_get_default(void);
+/**
+ * \brief Get "default" RSA implementation (OAEP encryption).
+ *
+ * This returns the preferred implementation of RSA (OAEP encryption)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_oaep_encrypt br_rsa_oaep_encrypt_get_default(void);
+
+/**
+ * \brief Get "default" RSA implementation (OAEP decryption).
+ *
+ * This returns the preferred implementation of RSA (OAEP decryption)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_oaep_decrypt br_rsa_oaep_decrypt_get_default(void);
+
/**
* \brief RSA decryption helper, for SSL/TLS.
*
uint32_t br_rsa_ssl_decrypt(br_rsa_private core, const br_rsa_private_key *sk,
unsigned char *data, size_t len);
+/**
+ * \brief RSA encryption (OAEP) with the "i15" engine.
+ *
+ * \see br_rsa_oaep_encrypt
+ *
+ * \param rnd source of random bytes.
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param pk RSA public key.
+ * \param dst destination buffer.
+ * \param dst_max_len destination buffer length (maximum encrypted data size).
+ * \param src message to encrypt.
+ * \param src_len source message length (in bytes).
+ * \return encrypted message length (in bytes), or 0 on error.
+ */
+size_t br_rsa_i15_oaep_encrypt(
+ const br_prng_class **rnd, const br_hash_class *dig,
+ const void *label, size_t label_len,
+ const br_rsa_public_key *pk,
+ void *dst, size_t dst_max_len,
+ const void *src, size_t src_len);
+
+/**
+ * \brief RSA decryption (OAEP) with the "i15" engine.
+ *
+ * \see br_rsa_oaep_decrypt
+ *
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param sk RSA private key.
+ * \param data input/output buffer.
+ * \param len encrypted/decrypted message length.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i15_oaep_decrypt(
+ const br_hash_class *dig, const void *label, size_t label_len,
+ const br_rsa_private_key *sk, void *data, size_t *len);
+
+/**
+ * \brief RSA encryption (OAEP) with the "i31" engine.
+ *
+ * \see br_rsa_oaep_encrypt
+ *
+ * \param rnd source of random bytes.
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param pk RSA public key.
+ * \param dst destination buffer.
+ * \param dst_max_len destination buffer length (maximum encrypted data size).
+ * \param src message to encrypt.
+ * \param src_len source message length (in bytes).
+ * \return encrypted message length (in bytes), or 0 on error.
+ */
+size_t br_rsa_i31_oaep_encrypt(
+ const br_prng_class **rnd, const br_hash_class *dig,
+ const void *label, size_t label_len,
+ const br_rsa_public_key *pk,
+ void *dst, size_t dst_max_len,
+ const void *src, size_t src_len);
+
+/**
+ * \brief RSA decryption (OAEP) with the "i31" engine.
+ *
+ * \see br_rsa_oaep_decrypt
+ *
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param sk RSA private key.
+ * \param data input/output buffer.
+ * \param len encrypted/decrypted message length.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i31_oaep_decrypt(
+ const br_hash_class *dig, const void *label, size_t label_len,
+ const br_rsa_private_key *sk, void *data, size_t *len);
+
+/**
+ * \brief RSA encryption (OAEP) with the "i32" engine.
+ *
+ * \see br_rsa_oaep_encrypt
+ *
+ * \param rnd source of random bytes.
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param pk RSA public key.
+ * \param dst destination buffer.
+ * \param dst_max_len destination buffer length (maximum encrypted data size).
+ * \param src message to encrypt.
+ * \param src_len source message length (in bytes).
+ * \return encrypted message length (in bytes), or 0 on error.
+ */
+size_t br_rsa_i32_oaep_encrypt(
+ const br_prng_class **rnd, const br_hash_class *dig,
+ const void *label, size_t label_len,
+ const br_rsa_public_key *pk,
+ void *dst, size_t dst_max_len,
+ const void *src, size_t src_len);
+
+/**
+ * \brief RSA decryption (OAEP) with the "i32" engine.
+ *
+ * \see br_rsa_oaep_decrypt
+ *
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param sk RSA private key.
+ * \param data input/output buffer.
+ * \param len encrypted/decrypted message length.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i32_oaep_decrypt(
+ const br_hash_class *dig, const void *label, size_t label_len,
+ const br_rsa_private_key *sk, void *data, size_t *len);
+
+/**
+ * \brief RSA encryption (OAEP) with the "i62" engine.
+ *
+ * This function is defined only on architecture that offer a 64x64->128
+ * opcode. Use `br_rsa_i62_oaep_encrypt_get()` to dynamically obtain a pointer
+ * to that function.
+ *
+ * \see br_rsa_oaep_encrypt
+ *
+ * \param rnd source of random bytes.
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param pk RSA public key.
+ * \param dst destination buffer.
+ * \param dst_max_len destination buffer length (maximum encrypted data size).
+ * \param src message to encrypt.
+ * \param src_len source message length (in bytes).
+ * \return encrypted message length (in bytes), or 0 on error.
+ */
+size_t br_rsa_i62_oaep_encrypt(
+ const br_prng_class **rnd, const br_hash_class *dig,
+ const void *label, size_t label_len,
+ const br_rsa_public_key *pk,
+ void *dst, size_t dst_max_len,
+ const void *src, size_t src_len);
+
+/**
+ * \brief RSA decryption (OAEP) with the "i62" engine.
+ *
+ * This function is defined only on architecture that offer a 64x64->128
+ * opcode. Use `br_rsa_i62_oaep_decrypt_get()` to dynamically obtain a pointer
+ * to that function.
+ *
+ * \see br_rsa_oaep_decrypt
+ *
+ * \param dig hash function to use with MGF1.
+ * \param label label value (may be `NULL` if `label_len` is zero).
+ * \param label_len label length, in bytes.
+ * \param sk RSA private key.
+ * \param data input/output buffer.
+ * \param len encrypted/decrypted message length.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i62_oaep_decrypt(
+ const br_hash_class *dig, const void *label, size_t label_len,
+ const br_rsa_private_key *sk, void *data, size_t *len);
+
+/**
+ * \brief Get buffer size to hold RSA private key elements.
+ *
+ * This macro returns the length (in bytes) of the buffer needed to
+ * receive the elements of a RSA private key, as generated by one of
+ * the `br_rsa_*_keygen()` functions. If the provided size is a constant
+ * expression, then the whole macro evaluates to a constant expression.
+ *
+ * \param size target key size (modulus size, in bits)
+ * \return the length of the private key buffer, in bytes.
+ */
+#define BR_RSA_KBUF_PRIV_SIZE(size) (5 * (((size) + 15) >> 4))
+
+/**
+ * \brief Get buffer size to hold RSA public key elements.
+ *
+ * This macro returns the length (in bytes) of the buffer needed to
+ * receive the elements of a RSA public key, as generated by one of
+ * the `br_rsa_*_keygen()` functions. If the provided size is a constant
+ * expression, then the whole macro evaluates to a constant expression.
+ *
+ * \param size target key size (modulus size, in bits)
+ * \return the length of the public key buffer, in bytes.
+ */
+#define BR_RSA_KBUF_PUB_SIZE(size) (4 + (((size) + 7) >> 3))
+
+/**
+ * \brief Type for RSA key pair generator implementation.
+ *
+ * This function generates a new RSA key pair whose modulus has bit
+ * length `size` bits. The private key elements are written in the
+ * `kbuf_priv` buffer, and pointer values and length fields to these
+ * elements are populated in the provided private key structure `sk`.
+ * Similarly, the public key elements are written in `kbuf_pub`, with
+ * pointers and lengths set in `pk`.
+ *
+ * If `pk` is `NULL`, then `kbuf_pub` may be `NULL`, and only the
+ * private key is set.
+ *
+ * If `pubexp` is not zero, then its value will be used as public
+ * exponent. Valid RSA public exponent values are odd integers
+ * greater than 1. If `pubexp` is zero, then the public exponent will
+ * have value 3.
+ *
+ * The provided PRNG (`rng_ctx`) must have already been initialized
+ * and seeded.
+ *
+ * Returned value is 1 on success, 0 on error. An error is reported
+ * if the requested range is outside of the supported key sizes, or
+ * if an invalid non-zero public exponent value is provided. Supported
+ * range starts at 512 bits, and up to an implementation-defined
+ * maximum (by default 4096 bits). Note that key sizes up to 768 bits
+ * have been broken in practice, and sizes lower than 2048 bits are
+ * usually considered to be weak and should not be used.
+ *
+ * \param rng_ctx source PRNG context (already initialized)
+ * \param sk RSA private key structure (destination)
+ * \param kbuf_priv buffer for private key elements
+ * \param pk RSA public key structure (destination), or `NULL`
+ * \param kbuf_pub buffer for public key elements, or `NULL`
+ * \param size target RSA modulus size (in bits)
+ * \param pubexp public exponent to use, or zero
+ * \return 1 on success, 0 on error (invalid parameters)
+ */
+typedef uint32_t (*br_rsa_keygen)(
+ const br_prng_class **rng_ctx,
+ br_rsa_private_key *sk, void *kbuf_priv,
+ br_rsa_public_key *pk, void *kbuf_pub,
+ unsigned size, uint32_t pubexp);
+
+/**
+ * \brief RSA key pair generation with the "i15" engine.
+ *
+ * \see br_rsa_keygen
+ *
+ * \param rng_ctx source PRNG context (already initialized)
+ * \param sk RSA private key structure (destination)
+ * \param kbuf_priv buffer for private key elements
+ * \param pk RSA public key structure (destination), or `NULL`
+ * \param kbuf_pub buffer for public key elements, or `NULL`
+ * \param size target RSA modulus size (in bits)
+ * \param pubexp public exponent to use, or zero
+ * \return 1 on success, 0 on error (invalid parameters)
+ */
+uint32_t br_rsa_i15_keygen(
+ const br_prng_class **rng_ctx,
+ br_rsa_private_key *sk, void *kbuf_priv,
+ br_rsa_public_key *pk, void *kbuf_pub,
+ unsigned size, uint32_t pubexp);
+
+/**
+ * \brief RSA key pair generation with the "i31" engine.
+ *
+ * \see br_rsa_keygen
+ *
+ * \param rng_ctx source PRNG context (already initialized)
+ * \param sk RSA private key structure (destination)
+ * \param kbuf_priv buffer for private key elements
+ * \param pk RSA public key structure (destination), or `NULL`
+ * \param kbuf_pub buffer for public key elements, or `NULL`
+ * \param size target RSA modulus size (in bits)
+ * \param pubexp public exponent to use, or zero
+ * \return 1 on success, 0 on error (invalid parameters)
+ */
+uint32_t br_rsa_i31_keygen(
+ const br_prng_class **rng_ctx,
+ br_rsa_private_key *sk, void *kbuf_priv,
+ br_rsa_public_key *pk, void *kbuf_pub,
+ unsigned size, uint32_t pubexp);
+
+/**
+ * \brief RSA key pair generation with the "i62" engine.
+ *
+ * This function is defined only on architecture that offer a 64x64->128
+ * opcode. Use `br_rsa_i62_keygen_get()` to dynamically obtain a pointer
+ * to that function.
+ *
+ * \see br_rsa_keygen
+ *
+ * \param rng_ctx source PRNG context (already initialized)
+ * \param sk RSA private key structure (destination)
+ * \param kbuf_priv buffer for private key elements
+ * \param pk RSA public key structure (destination), or `NULL`
+ * \param kbuf_pub buffer for public key elements, or `NULL`
+ * \param size target RSA modulus size (in bits)
+ * \param pubexp public exponent to use, or zero
+ * \return 1 on success, 0 on error (invalid parameters)
+ */
+uint32_t br_rsa_i62_keygen(
+ const br_prng_class **rng_ctx,
+ br_rsa_private_key *sk, void *kbuf_priv,
+ br_rsa_public_key *pk, void *kbuf_pub,
+ unsigned size, uint32_t pubexp);
+
+/**
+ * \brief Get the RSA "i62" implementation (key pair generation),
+ * if available.
+ *
+ * \return the implementation, or 0.
+ */
+br_rsa_keygen br_rsa_i62_keygen_get(void);
+
+/**
+ * \brief Get "default" RSA implementation (key pair generation).
+ *
+ * This returns the preferred implementation of RSA (key pair generation)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_keygen br_rsa_keygen_get_default(void);
+
+/**
+ * \brief Type for a modulus computing function.
+ *
+ * Such a function computes the public modulus from the private key. The
+ * encoded modulus (unsigned big-endian) is written on `n`, and the size
+ * (in bytes) is returned. If `n` is `NULL`, then the size is returned but
+ * the modulus itself is not computed.
+ *
+ * If the key size exceeds an internal limit, 0 is returned.
+ *
+ * \param n destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \return the modulus length (in bytes), or 0.
+ */
+typedef size_t (*br_rsa_compute_modulus)(void *n, const br_rsa_private_key *sk);
+
+/**
+ * \brief Recompute RSA modulus ("i15" engine).
+ *
+ * \see br_rsa_compute_modulus
+ *
+ * \param n destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \return the modulus length (in bytes), or 0.
+ */
+size_t br_rsa_i15_compute_modulus(void *n, const br_rsa_private_key *sk);
+
+/**
+ * \brief Recompute RSA modulus ("i31" engine).
+ *
+ * \see br_rsa_compute_modulus
+ *
+ * \param n destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \return the modulus length (in bytes), or 0.
+ */
+size_t br_rsa_i31_compute_modulus(void *n, const br_rsa_private_key *sk);
+
+/**
+ * \brief Get "default" RSA implementation (recompute modulus).
+ *
+ * This returns the preferred implementation of RSA (recompute modulus)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_compute_modulus br_rsa_compute_modulus_get_default(void);
+
+/**
+ * \brief Type for a public exponent computing function.
+ *
+ * Such a function recomputes the public exponent from the private key.
+ * 0 is returned if any of the following occurs:
+ *
+ * - Either `p` or `q` is not equal to 3 modulo 4.
+ *
+ * - The public exponent does not fit on 32 bits.
+ *
+ * - An internal limit is exceeded.
+ *
+ * - The private key is invalid in some way.
+ *
+ * For all private keys produced by the key generator functions
+ * (`br_rsa_keygen` type), this function succeeds and returns the true
+ * public exponent. The public exponent is always an odd integer greater
+ * than 1.
+ *
+ * \return the public exponent, or 0.
+ */
+typedef uint32_t (*br_rsa_compute_pubexp)(const br_rsa_private_key *sk);
+
+/**
+ * \brief Recompute RSA public exponent ("i15" engine).
+ *
+ * \see br_rsa_compute_pubexp
+ *
+ * \return the public exponent, or 0.
+ */
+uint32_t br_rsa_i15_compute_pubexp(const br_rsa_private_key *sk);
+
+/**
+ * \brief Recompute RSA public exponent ("i31" engine).
+ *
+ * \see br_rsa_compute_pubexp
+ *
+ * \return the public exponent, or 0.
+ */
+uint32_t br_rsa_i31_compute_pubexp(const br_rsa_private_key *sk);
+
+/**
+ * \brief Get "default" RSA implementation (recompute public exponent).
+ *
+ * This returns the preferred implementation of RSA (recompute public
+ * exponent) on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_compute_pubexp br_rsa_compute_pubexp_get_default(void);
+
+/**
+ * \brief Type for a private exponent computing function.
+ *
+ * An RSA private key (`br_rsa_private_key`) contains two reduced
+ * private exponents, which are sufficient to perform private key
+ * operations. However, standard encoding formats for RSA private keys
+ * require also a copy of the complete private exponent (non-reduced),
+ * which this function recomputes.
+ *
+ * This function suceeds if all the following conditions hold:
+ *
+ * - Both private factors `p` and `q` are equal to 3 modulo 4.
+ *
+ * - The provided public exponent `pubexp` is correct, and, in particular,
+ * is odd, relatively prime to `p-1` and `q-1`, and greater than 1.
+ *
+ * - No internal storage limit is exceeded.
+ *
+ * For all private keys produced by the key generator functions
+ * (`br_rsa_keygen` type), this function succeeds. Note that the API
+ * restricts the public exponent to a maximum size of 32 bits.
+ *
+ * The encoded private exponent is written in `d` (unsigned big-endian
+ * convention), and the length (in bytes) is returned. If `d` is `NULL`,
+ * then the exponent is not written anywhere, but the length is still
+ * returned. On error, 0 is returned.
+ *
+ * Not all error conditions are detected when `d` is `NULL`; therefore, the
+ * returned value shall be checked also when actually producing the value.
+ *
+ * \param d destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \param pubexp the public exponent.
+ * \return the private exponent length (in bytes), or 0.
+ */
+typedef size_t (*br_rsa_compute_privexp)(void *d,
+ const br_rsa_private_key *sk, uint32_t pubexp);
+
+/**
+ * \brief Recompute RSA private exponent ("i15" engine).
+ *
+ * \see br_rsa_compute_privexp
+ *
+ * \param d destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \param pubexp the public exponent.
+ * \return the private exponent length (in bytes), or 0.
+ */
+size_t br_rsa_i15_compute_privexp(void *d,
+ const br_rsa_private_key *sk, uint32_t pubexp);
+
+/**
+ * \brief Recompute RSA private exponent ("i31" engine).
+ *
+ * \see br_rsa_compute_privexp
+ *
+ * \param d destination buffer (or `NULL`).
+ * \param sk RSA private key.
+ * \param pubexp the public exponent.
+ * \return the private exponent length (in bytes), or 0.
+ */
+size_t br_rsa_i31_compute_privexp(void *d,
+ const br_rsa_private_key *sk, uint32_t pubexp);
+
+/**
+ * \brief Get "default" RSA implementation (recompute private exponent).
+ *
+ * This returns the preferred implementation of RSA (recompute private
+ * exponent) on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_compute_privexp br_rsa_compute_privexp_get_default(void);
+
+#ifdef __cplusplus
+}
+#endif
+
#endif
projects / BearSSL / blobdiff