#include <stddef.h>
#include <stdint.h>
+#include "bearssl_hash.h"
+#include "bearssl_rand.h"
+
#ifdef __cplusplus
extern "C" {
#endif
* 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 signature verification engine (PSS).
+ *
+ * Parameters are:
+ *
+ * - The signature itself. The provided array is NOT modified.
+ *
+ * - The hash function which was used to hash the message.
+ *
+ * - The hash function to use with MGF1 within the PSS padding. This
+ * is not necessarily the same hash function as the one which was
+ * used to hash the signed message.
+ *
+ * - The hashed message (as an array of bytes).
+ *
+ * - The PSS salt length (in bytes).
+ *
+ * - The public key.
+ *
+ * **Constraints:**
+ *
+ * - Hash message length MUST be no more than 64 bytes.
+ *
+ * Note that, contrary to PKCS#1 v1.5 signature, the hash value of the
+ * signed data cannot be extracted from the signature; it must be
+ * provided to the verification function.
+ *
+ * This function verifies that the signature length (`xlen`) matches the
+ * modulus length (this function returns 0 on mismatch). If the modulus
+ * size exceeds the maximum supported RSA size, then the function also
+ * returns 0.
+ *
+ * Returned value is 1 on success, 0 on error.
+ *
+ * Implementations of this type need not be constant-time.
+ *
+ * \param x signature buffer.
+ * \param xlen signature length (in bytes).
+ * \param hf_data hash function applied on the message.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hash value of the signed message.
+ * \param salt_len PSS salt length (in bytes).
+ * \param pk RSA public key.
+ * \return 1 on success, 0 on error.
+ */
+typedef uint32_t (*br_rsa_pss_vrfy)(const unsigned char *x, size_t xlen,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const void *hash, size_t salt_len, const br_rsa_public_key *pk);
+
/**
* \brief Type for a RSA encryption engine (OAEP).
*
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief Type for a RSA signature generation engine (PSS).
+ *
+ * Parameters are:
+ *
+ * - An initialized PRNG for salt generation. If the salt length is
+ * zero (`salt_len` parameter), then the PRNG is optional (this is
+ * not the typical case, as the security proof of RSA/PSS is
+ * tighter when a non-empty salt is used).
+ *
+ * - The hash function which was used to hash the message.
+ *
+ * - The hash function to use with MGF1 within the PSS padding. This
+ * is not necessarily the same function as the one used to hash the
+ * message.
+ *
+ * - The hashed message.
+ *
+ * - The salt length, in bytes.
+ *
+ * - The RSA private key.
+ *
+ * - The output buffer, that receives the signature.
+ *
+ * Returned value is 1 on success, 0 on error. Error conditions include
+ * a too small modulus for the provided hash and salt lengths, or some
+ * invalid key parameters. The signature length is exactly
+ * `(sk->n_bitlen+7)/8` bytes.
+ *
+ * This function is expected to be constant-time with regards to the
+ * private key bytes (lengths of the modulus and the individual factors
+ * may leak, though) and to the hashed data.
+ *
+ * \param rng PRNG for salt generation (`NULL` if `salt_len` is zero).
+ * \param hf_data hash function used to hash the signed data.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hashed message.
+ * \param salt_len salt length (in bytes).
+ * \param sk RSA private key.
+ * \param x output buffer for the signature value.
+ * \return 1 on success, 0 on error.
+ */
+typedef uint32_t (*br_rsa_pss_sign)(const br_prng_class **rng,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const unsigned char *hash_value, size_t salt_len,
+ const br_rsa_private_key *sk, unsigned char *x);
+
/**
* \brief Encoded OID for SHA-1 (in RSA PKCS#1 signatures).
*/
const br_rsa_public_key *pk);
/**
- * \brief RSA signature verification engine "i32".
+ * \brief RSA signature verification engine "i32" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_vrfy
*
const unsigned char *hash_oid, size_t hash_len,
const br_rsa_public_key *pk, unsigned char *hash_out);
+/**
+ * \brief RSA signature verification engine "i32" (PSS signatures).
+ *
+ * \see br_rsa_pss_vrfy
+ *
+ * \param x signature buffer.
+ * \param xlen signature length (in bytes).
+ * \param hf_data hash function applied on the message.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hash value of the signed message.
+ * \param salt_len PSS salt length (in bytes).
+ * \param pk RSA public key.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i32_pss_vrfy(const unsigned char *x, size_t xlen,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const void *hash, size_t salt_len, const br_rsa_public_key *pk);
+
/**
* \brief RSA private key engine "i32".
*
const br_rsa_private_key *sk);
/**
- * \brief RSA signature generation engine "i32".
+ * \brief RSA signature generation engine "i32" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_sign
*
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief RSA signature generation engine "i32" (PSS signatures).
+ *
+ * \see br_rsa_pss_sign
+ *
+ * \param rng PRNG for salt generation (`NULL` if `salt_len` is zero).
+ * \param hf_data hash function used to hash the signed data.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hashed message.
+ * \param salt_len salt length (in bytes).
+ * \param sk RSA private key.
+ * \param x output buffer for the signature value.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i32_pss_sign(const br_prng_class **rng,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const unsigned char *hash_value, size_t salt_len,
+ const br_rsa_private_key *sk, unsigned char *x);
+
/*
* RSA "i31" engine. Similar to i32, but only 31 bits are used per 32-bit
* word. This uses slightly more stack space (about 4% more) and code
const br_rsa_public_key *pk);
/**
- * \brief RSA signature verification engine "i31".
+ * \brief RSA signature verification engine "i31" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_vrfy
*
const unsigned char *hash_oid, size_t hash_len,
const br_rsa_public_key *pk, unsigned char *hash_out);
+/**
+ * \brief RSA signature verification engine "i31" (PSS signatures).
+ *
+ * \see br_rsa_pss_vrfy
+ *
+ * \param x signature buffer.
+ * \param xlen signature length (in bytes).
+ * \param hf_data hash function applied on the message.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hash value of the signed message.
+ * \param salt_len PSS salt length (in bytes).
+ * \param pk RSA public key.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i31_pss_vrfy(const unsigned char *x, size_t xlen,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const void *hash, size_t salt_len, const br_rsa_public_key *pk);
+
/**
* \brief RSA private key engine "i31".
*
const br_rsa_private_key *sk);
/**
- * \brief RSA signature generation engine "i31".
+ * \brief RSA signature generation engine "i31" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_sign
*
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief RSA signature generation engine "i31" (PSS signatures).
+ *
+ * \see br_rsa_pss_sign
+ *
+ * \param rng PRNG for salt generation (`NULL` if `salt_len` is zero).
+ * \param hf_data hash function used to hash the signed data.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hashed message.
+ * \param salt_len salt length (in bytes).
+ * \param sk RSA private key.
+ * \param x output buffer for the signature value.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i31_pss_sign(const br_prng_class **rng,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const unsigned char *hash_value, size_t salt_len,
+ const br_rsa_private_key *sk, unsigned char *x);
+
/*
* RSA "i62" engine. Similar to i31, but internal multiplication use
* 64x64->128 multiplications. This is available only on architecture
const br_rsa_public_key *pk);
/**
- * \brief RSA signature verification engine "i62".
+ * \brief RSA signature verification engine "i62" (PKCS#1 v1.5 signatures).
*
* 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
const unsigned char *hash_oid, size_t hash_len,
const br_rsa_public_key *pk, unsigned char *hash_out);
+/**
+ * \brief RSA signature verification engine "i62" (PSS signatures).
+ *
+ * This function is defined only on architecture that offer a 64x64->128
+ * opcode. Use `br_rsa_i62_pss_vrfy_get()` to dynamically obtain a pointer
+ * to that function.
+ *
+ * \see br_rsa_pss_vrfy
+ *
+ * \param x signature buffer.
+ * \param xlen signature length (in bytes).
+ * \param hf_data hash function applied on the message.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hash value of the signed message.
+ * \param salt_len PSS salt length (in bytes).
+ * \param pk RSA public key.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i62_pss_vrfy(const unsigned char *x, size_t xlen,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const void *hash, size_t salt_len, const br_rsa_public_key *pk);
+
/**
* \brief RSA private key engine "i62".
*
const br_rsa_private_key *sk);
/**
- * \brief RSA signature generation engine "i62".
+ * \brief RSA signature generation engine "i62" (PKCS#1 v1.5 signatures).
*
* 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
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief RSA signature generation engine "i62" (PSS signatures).
+ *
+ * This function is defined only on architecture that offer a 64x64->128
+ * opcode. Use `br_rsa_i62_pss_sign_get()` to dynamically obtain a pointer
+ * to that function.
+ *
+ * \see br_rsa_pss_sign
+ *
+ * \param rng PRNG for salt generation (`NULL` if `salt_len` is zero).
+ * \param hf_data hash function used to hash the signed data.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hashed message.
+ * \param salt_len salt length (in bytes).
+ * \param sk RSA private key.
+ * \param x output buffer for the signature value.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i62_pss_sign(const br_prng_class **rng,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const unsigned char *hash_value, size_t salt_len,
+ const br_rsa_private_key *sk, unsigned char *x);
+
/**
* \brief Get the RSA "i62" implementation (public key operations),
* if available.
br_rsa_public br_rsa_i62_public_get(void);
/**
- * \brief Get the RSA "i62" implementation (PKCS#1 signature verification),
+ * \brief Get the RSA "i62" implementation (PKCS#1 v1.5 signature verification),
* if available.
*
* \return the implementation, or 0.
*/
br_rsa_pkcs1_vrfy br_rsa_i62_pkcs1_vrfy_get(void);
+/**
+ * \brief Get the RSA "i62" implementation (PSS signature verification),
+ * if available.
+ *
+ * \return the implementation, or 0.
+ */
+br_rsa_pss_vrfy br_rsa_i62_pss_vrfy_get(void);
+
/**
* \brief Get the RSA "i62" implementation (private key operations),
* if available.
br_rsa_private br_rsa_i62_private_get(void);
/**
- * \brief Get the RSA "i62" implementation (PKCS#1 signature generation),
+ * \brief Get the RSA "i62" implementation (PKCS#1 v1.5 signature generation),
* if available.
*
* \return the implementation, or 0.
*/
br_rsa_pkcs1_sign br_rsa_i62_pkcs1_sign_get(void);
+/**
+ * \brief Get the RSA "i62" implementation (PSS signature generation),
+ * if available.
+ *
+ * \return the implementation, or 0.
+ */
+br_rsa_pss_sign br_rsa_i62_pss_sign_get(void);
+
/**
* \brief Get the RSA "i62" implementation (OAEP encryption),
* if available.
const br_rsa_public_key *pk);
/**
- * \brief RSA signature verification engine "i15".
+ * \brief RSA signature verification engine "i15" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_vrfy
*
const unsigned char *hash_oid, size_t hash_len,
const br_rsa_public_key *pk, unsigned char *hash_out);
+/**
+ * \brief RSA signature verification engine "i15" (PSS signatures).
+ *
+ * \see br_rsa_pss_vrfy
+ *
+ * \param x signature buffer.
+ * \param xlen signature length (in bytes).
+ * \param hf_data hash function applied on the message.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hash value of the signed message.
+ * \param salt_len PSS salt length (in bytes).
+ * \param pk RSA public key.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i15_pss_vrfy(const unsigned char *x, size_t xlen,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const void *hash, size_t salt_len, const br_rsa_public_key *pk);
+
/**
* \brief RSA private key engine "i15".
*
const br_rsa_private_key *sk);
/**
- * \brief RSA signature generation engine "i15".
+ * \brief RSA signature generation engine "i15" (PKCS#1 v1.5 signatures).
*
* \see br_rsa_pkcs1_sign
*
const unsigned char *hash, size_t hash_len,
const br_rsa_private_key *sk, unsigned char *x);
+/**
+ * \brief RSA signature generation engine "i15" (PSS signatures).
+ *
+ * \see br_rsa_pss_sign
+ *
+ * \param rng PRNG for salt generation (`NULL` if `salt_len` is zero).
+ * \param hf_data hash function used to hash the signed data.
+ * \param hf_mgf1 hash function to use with MGF1.
+ * \param hash hashed message.
+ * \param salt_len salt length (in bytes).
+ * \param sk RSA private key.
+ * \param x output buffer for the signature value.
+ * \return 1 on success, 0 on error.
+ */
+uint32_t br_rsa_i15_pss_sign(const br_prng_class **rng,
+ const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+ const unsigned char *hash_value, size_t salt_len,
+ const br_rsa_private_key *sk, unsigned char *x);
+
/**
* \brief Get "default" RSA implementation (public-key operations).
*
br_rsa_private br_rsa_private_get_default(void);
/**
- * \brief Get "default" RSA implementation (PKCS#1 signature verification).
+ * \brief Get "default" RSA implementation (PKCS#1 v1.5 signature verification).
*
* This returns the preferred implementation of RSA (signature verification)
* on the current system.
br_rsa_pkcs1_vrfy br_rsa_pkcs1_vrfy_get_default(void);
/**
- * \brief Get "default" RSA implementation (PKCS#1 signature generation).
+ * \brief Get "default" RSA implementation (PSS signature verification).
+ *
+ * This returns the preferred implementation of RSA (signature verification)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_pss_vrfy br_rsa_pss_vrfy_get_default(void);
+
+/**
+ * \brief Get "default" RSA implementation (PKCS#1 v1.5 signature generation).
*
* This returns the preferred implementation of RSA (signature generation)
* on the current system.
*/
br_rsa_pkcs1_sign br_rsa_pkcs1_sign_get_default(void);
+/**
+ * \brief Get "default" RSA implementation (PSS signature generation).
+ *
+ * This returns the preferred implementation of RSA (signature generation)
+ * on the current system.
+ *
+ * \return the default implementation.
+ */
+br_rsa_pss_sign br_rsa_pss_sign_get_default(void);
+
/**
* \brief Get "default" RSA implementation (OAEP encryption).
*
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
projects / BearSSL / blobdiff