diff options
Diffstat (limited to 'modexp.c')
| -rw-r--r-- | modexp.c | 243 |
1 files changed, 143 insertions, 100 deletions
@@ -43,7 +43,6 @@ #include <stdio.h> #include <stdint.h> -#include <assert.h> #include "hal.h" #include "hal_internal.h" @@ -60,173 +59,217 @@ void hal_modexp_set_debug(const int onoff) } /* - * Check a result, report on failure if debugging, pass failures up - * the chain. + * Get value of an ordinary register. */ -#define check(_expr_) \ - do { \ - hal_error_t _err = (_expr_); \ - if (_err != HAL_OK && debug) \ - printf("%s failed: %s\n", #_expr_, hal_error_string(_err)); \ - if (_err != HAL_OK) \ - return _err; \ - } while (0) +static hal_error_t inline get_register(const hal_core_t *core, + const hal_addr_t addr, + uint32_t &value) +{ + hal_error_t err; + uint8_t w[4]; + + if (value == NULL) + return HAL_ERROR_IMPOSSIBLE; + + if ((err = hal_io_read(core, addr, w, sizeof(w))) != HAL_OK) + return err; + + *value = (w[0] << 0) | (w[1] << 8) | (w[2] << 16) | (w[3] << 24); + + return HAL_OK; +} /* - * Set an ordinary register. + * Set value of an ordinary register. */ -static hal_error_t set_register(const hal_core_t *core, - const hal_addr_t addr, - uint32_t value) +static hal_error_t inline set_register(const hal_core_t *core, + const hal_addr_t addr, + const uint32_t value) { - uint8_t w[4]; - int i; - - for (i = 3; i >= 0; i--) { - w[i] = value & 0xFF; - value >>= 8; - } + const uint8_t w[4] = { + ((value >> 24) & 0xFF), + ((value >> 16) & 0xFF), + ((value >> 8) & 0xFF), + ((value >> 0) & 0xFF) + }; return hal_io_write(core, addr, w, sizeof(w)); } /* * Get value of a data buffer. We reverse the order of 32-bit words - * in the buffer during the transfer to match what the modexps6 core + * in the buffer during the transfer to match what the modexpa7 core * expects. */ -static hal_error_t get_buffer(const hal_core_t *core, - const hal_addr_t data_addr, - uint8_t *value, - const size_t length) +static inline hal_error_t get_buffer(const hal_core_t *core, + const hal_addr_t data_addr, + uint8_t *value, + const size_t length) { + hal_error_t err; size_t i; - assert(value != NULL && length % 4 == 0); + if (value == NULL || length % 4 != 0) + return HAL_ERROR_IMPOSSIBLE; for (i = 0; i < length; i += 4) - check(hal_io_read(core, data_addr + i/4, &value[length - 4 - i], 4)); + if ((err = hal_io_read(core, data_addr + i/4, &value[length - 4 - i], 4)) != HAL_OK) + return err; return HAL_OK; } /* * Set value of a data buffer. We reverse the order of 32-bit words - * in the buffer during the transfer to match what the modexps6 core + * in the buffer during the transfer to match what the modexpa7 core * expects. + * + * Do we need to zero the portion of the buffer we're not using + * explictly (that is, the portion between `length` and the value of + * the core's MODEXPA7_ADDR_BUFFER_BITS register)? We've gotten away + * without doing this so far, but the core doesn't take an explicit + * length parameter for the message itself, instead it assumes that + * the message is either as long as or twice as long as the exponent, + * depending on the setting of the CRT mode bit. Maybe initializing + * the core clears the excess bits so there's no issue? Dunno. Have + * never seen a problem with this yet, just dont' know why not. */ -static hal_error_t set_buffer(const hal_core_t *core, - const hal_addr_t data_addr, - const uint8_t * const value, - const size_t length) +static inline hal_error_t set_buffer(const hal_core_t *core, + const hal_addr_t data_addr, + const uint8_t * const value, + const size_t length) { + hal_error_t; size_t i; - assert(value != NULL && length % 4 == 0); + if (value == NULL || length % 4 != 0) + return HAL_ERROR_IMPOSSIBLE; for (i = 0; i < length; i += 4) - check(hal_io_write(core, data_addr + i/4, &value[length - 4 - i], 4)); + if ((err = hal_io_write(core, data_addr + i/4, &value[length - 4 - i], 4)) != HAL_OK) + return err; return HAL_OK; } /* + * Check a result, report on failure if debugging, pass failures up + * the chain. + */ + +#define check(_expr_) \ + do { \ + hal_error_t _err = (_expr_); \ + if (_err != HAL_OK && debug) \ + hal_log(HAL_LOG_WARN, "%s failed: %s\n", #_expr_, hal_error_string(_err)); \ + if (_err != HAL_OK) { \ + hal_core_free(core); \ + return _err; \ + } \ + } while (0) + +/* * Run one modexp operation. */ hal_error_t hal_modexp(hal_core_t *core, - const uint8_t * const msg, const size_t msg_len, /* Message */ - const uint8_t * const exp, const size_t exp_len, /* Exponent */ - const uint8_t * const mod, const size_t mod_len, /* Modulus */ - uint8_t *result, const size_t result_len) + const int precalc_done, + const uint8_t * const msg, const size_t msg_len, /* Message */ + const uint8_t * const exp, const size_t exp_len, /* Exponent */ + const uint8_t * const mod, const size_t mod_len, /* Modulus */ + uint8_t *result, const size_t result_len, /* Result of exponentiation */ + uint8_t *coeff, const size_t coeff_len, /* Modulus coefficient (r/w) */ + uint8_t *mont, const size_t mont_len) /* Montgomery factor (r/w)*/ { hal_error_t err; /* - * All pointers must be set, neither message nor exponent may be - * longer than modulus, result buffer must not be shorter than - * modulus, and all input lengths must be a multiple of four. - * - * The multiple-of-four restriction is a pain, but the rest of the - * HAL code currently enforces the same restriction, and allowing - * arbitrary lengths would require some tedious shuffling to deal - * with alignment issues, so it's not worth trying to fix only here. + * All pointers must be set, exponent may not be longer than + * modulus, message may not be longer than twice the modulus (CRT + * mode), result buffer must not be shorter than modulus, and all + * input lengths must be a multiple of four bytes (the core is all + * about 32-bit words). */ - if (msg == NULL || exp == NULL || mod == NULL || result == NULL || - msg_len > mod_len || exp_len > mod_len || result_len < mod_len || - ((msg_len | exp_len | mod_len) & 3) != 0) + if (mod == NULL || + msg == NULL || msg_len > mod_len * 2 || + exp == NULL || exp_len > mod_len || + result == NULL || result_len < mod_len || + coeff == NULL || coeff_len != mod_len || + mont == NULL || mont_len != mod_len || + ((msg_len | exp_len | mod_len | coeff_len | mont_len) & 3) != 0) return HAL_ERROR_BAD_ARGUMENTS; - if (((err = hal_core_alloc(MODEXPS6_NAME, &core)) == HAL_ERROR_CORE_NOT_FOUND) && - ((err = hal_core_alloc(MODEXPA7_NAME, &core)) != HAL_OK)) - return err; + /* + * Gonna need to think about running two modexpa7 cores in parallel + * in CRT mode for full speed signature. + */ -#undef check -#define check(_expr_) \ - do { \ - hal_error_t _err = (_expr_); \ - if (_err != HAL_OK && debug) \ - printf("%s failed: %s\n", #_expr_, hal_error_string(_err)); \ - if (_err != HAL_OK) { \ - hal_core_free(core); \ - return _err; \ - } \ - } while (0) + if (((err = hal_core_alloc(MODEXPA7_NAME, &core)) != HAL_OK)) + return err; /* - * We probably ought to take the mode (fast vs constant-time) as an - * argument, but for the moment we just guess that really short - * exponent means we're using the public key and can use fast mode, - * really short messages are Miller-Rabin tests and can also use - * fast mode, all other cases are something to do with the private - * key and therefore must use constant-time mode. - * - * Unclear whether it's worth trying to figure out exactly how long - * the operands are: assuming a multiple of eight is safe, but makes - * a bit more work for the core; checking to see how many bits are - * really set leaves the core sitting idle while the main CPU does - * these checks. No way to know which is faster without testing; - * take simple approach for the moment. + * Now that we have the core, check operand length against what it + * says it can handle. */ - /* Select mode (1 = fast, 0 = safe) */ - check(set_register(core, MODEXPS6_ADDR_MODE, (exp_len <= 4 || msg_len <= 4))); + uint32_t operand_max; + check(get_register(core, MODEXPA7_ADDR_BUFFER_BITS, &operand_max)); + operand_max /= 8; - /* Set modulus size in bits */ - check(set_register(core, MODEXPS6_ADDR_MODULUS_WIDTH, mod_len * 8)); + if (msg_len > operand_max || exp_len > operand_max || mod_len > operand_max || + (coeff != NULL && coeff_len > operand_max) || + (mont != NULL && mont_len > operand_max)) { + hal_core_free(core); + return HAL_ERROR_BAD_ARGUMENTS; + } - /* Write new modulus */ - check(set_buffer(core, MODEXPS6_ADDR_MODULUS, mod, mod_len)); + /* Set modulus */ - /* Pre-calcuate speed-up coefficient */ - check(hal_io_init(core)); + check(set_register(core, MODEXPA7_ADDR_MODULUS_BITS, mod_len * 8)); + check(set_buffer(core, MODEXPA7_ADDR_MODULUS, mod, mod_len)); - /* Wait for calculation to complete */ - check(hal_io_wait_ready(core)); + /* + * Calculate modulus-dependent speedup factors if needed. Buffer + * space is always caller's problem (because caller almost certainly + * wants to stash these values in the keystore anyway). Calculation + * is edge-triggered by "init" bit going from zero to one. + */ - /* Write new message */ - check(set_buffer(core, MODEXPS6_ADDR_MESSAGE, msg, msg_len)); + if (!precalc_done) { + check(hal_io_zero(core)); + check(hal_io_init(core)); + check(hal_io_wait_ready(core)); + check(get_buffer(core, MODEXPA7_ADDR_MODULUS_COEFF_OUT, coeff, coeff_len)); + check(get_buffer(core, MODEXPA7_ADDR_MONTGOMERY_FACTOR_OUT, mont, mont_len)); + } - /* Set new exponent length in bits */ - check(set_register(core, MODEXPS6_ADDR_EXPONENT_WIDTH, exp_len * 8)); + /* Load modulus-dependent speedup factors (even if we just calculated them) */ + check(set_buffer(core, MODEXPA7_ADDR_MODULUS_COEFF_IN, coeff, coeff_len)); + check(set_buffer(core, MODEXPA7_ADDR_MONTGOMERY_FACTOR_IN, mont, mont_len)); - /* Set new exponent */ - check(set_buffer(core, MODEXPS6_ADDR_EXPONENT, exp, exp_len)); + /* Select CRT mode if and only if message is longer than exponent */ + check(set_register(core, MODEXPA7_ADDR_MODE, + (msg_len > mod_len + ? MODEXPA7_MODE_CRT + : MODEXPA7_MODE_PLAIN))); - /* Start calculation */ - check(hal_io_next(core)); + /* Set message and exponent */ + check(set_buffer(core, MODEXPA7_ADDR_MESSAGE, msg, msg_len)); + check(set_buffer(core, MODEXPA7_ADDR_EXPONENT, exp, exp_len)); + check(set_register(core, MODEXPA7_ADDR_EXPONENT_BITS, exp_len * 8)); - /* Wait for result */ + /* Edge-trigger the "next" bit to start calculation, then wait for the result */ + check(hal_io_zero(core)); + check(hal_io_next(core)); check(hal_io_wait_valid(core)); - /* Extract result */ - check(get_buffer(core, MODEXPS6_ADDR_RESULT, result, mod_len)); - + /* Extract result, clean up, then done */ + check(get_buffer(core, MODEXPA7_ADDR_RESULT, result, mod_len)); hal_core_free(core); return HAL_OK; } |