/* * Copyright (C) 2019 sysmocom -s.f.m.c. GmbH, Author: Kevin Redon * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #include #include #include "utils.h" #include "iso7816_3.h" /*! Table of clock rate conversion integer F indexed by Fi. * \note Fi is indicated in TA1, but the same table is used for F and Fn during PPS * ISO/IEC 7816-3:2006(E) table 7 */ const uint16_t iso7816_3_fi_table[16] = { 372, 372, 558, 744, 1116, 1488, 1860, 0, 0, 512, 768, 1024, 1536, 2048, 0, 0 }; /*! Table of maximum clock frequency f_max in Hz indexed by Fi. * ISO/IEC 7816-3:2006(E) table 7 * \note f_max is indicated in TA1, but the same table is used for F and Fn during PPS */ const uint32_t iso7816_3_fmax_table[16] = { 4000000, 5000000, 6000000, 8000000, 12000000, 16000000, 20000000, 0, 0, 5000000, 7500000, 10000000, 15000000, 20000000, 0, 0 }; /*! Table encoding the baud rate adjust integer D indexed by Di. * ISO/IEC 7816-3:2006(E) table 8 * \note Di is indicated in TA1, but the same table is used for D and Dn during PPS */ const uint8_t iso7816_3_di_table[16] = { 0, 1, 2, 4, 8, 16, 32, 64, 12, 20, 0, 0, 0, 0, 0, 0, }; /* All values are based on the Elementary Time Unit (ETU), defined in ISO/IEC 7816-3 section 7.1 * this is the time required to transmit a bit, and is calculated as follows: * 1 ETU = (F / D) x (1 / f) * where: * - F is the clock rate conversion integer * - D is the baud rate adjustment factor * - f is the clock frequency * * The possible F, f(max), and D values are defined in ISO/IEC 7816-3 table 7 and 8 * - the initial value for F (after reset) is Fd = 372 * - the initial value for D (after reset) is Dd = 1 * - the initial maximum frequency f(max) is 5 MHz * * The card must measure the ETU based on the clock signal provided by the reader * one ETU (e.g. 1 bit) takes F/D clock cycles, which the card must count * * The card can indicate an alternative set of supported values Fi (with corresponding f(max)) and * Di for higher baud rate in TA1 in the ATR (see ISO/IEC 7816-3 section 8.3) * * These values are selected according to ISO/IEC 7816-3 section 6.3.1: * - card in specific mode: they are enforced if TA2 is present (the reader can deactivate the card * if it does not support these values) * - card in negotiable mode: * -- they can be selected by the reader using the Protocol and Parameters Selection (PPS) procedure * -- the first offered protocol and default values are used when no PPS is started * * PPS is done with Fd and Dd (see ISO/IEC 7816-3 section 9) the reader can propose any F and D * values between from Fd to Fi, and from Dd to Di (Fi and Di are indicated in TA1) the in PPS * agreed values F and D are called Fn and Dn and are applied after a successful exchange, * corresponding to PPS1_Response bit 5 * * The F and D values must be provided to the SAM3S USART peripheral (after reset and PPS) */ /*! Verify if the clock rate conversion integer F value is valid. * \param[in] f F value to be validated * \return if F value is valid * \note only values in ISO/IEC 7816-3:2006(E) table 7 are valid */ bool iso7816_3_valid_f(uint16_t f) { if (0 == f) { return false; } uint8_t i = 0; for (i = 0; i < ARRAY_SIZE(iso7816_3_fi_table) && iso7816_3_fi_table[i] != f; i++); return (i < ARRAY_SIZE(iso7816_3_fi_table) && iso7816_3_fi_table[i] == f); } /*! Verify if the baud rate adjustment factor D value is valid. * \param[in] d D value to be validated * \return if D value is valid * \note only values in ISO/IEC 7816-3:2006(E) table 8 are valid */ bool iso7816_3_valid_d(uint8_t d) { if (0 == d) { return false; } uint8_t i = 0; for (i = 0; i < ARRAY_SIZE(iso7816_3_di_table) && iso7816_3_di_table[i] != d; i++); return (i < ARRAY_SIZE(iso7816_3_di_table) && iso7816_3_di_table[i] == d); } /* The ETU is not only used to define the baud rate, but also the Waiting Time (WT) (see ISO/IEC * 7816-3 section 8.1) * * when exceeding WT without card response, the reader flags the card as unresponsive, and resets it * this can be used by the card to indicate errors or unsupported operations if the card requires * more time to respond, it shall send a procedure byte to restart WT WT is calculated as follows * (for T=0, see ISO/IEC 7816-3 section 10.2): WT = WI x 960 x (Fi / f(max)) where * - WI is encoded in TC2 in the ATR (10 if absent) * - WI does not depend on D/Di (used for the ETU) * - after reset WT is 9600 ETU * - WI (e.g. the new WT) is applied when T=0 is used (after 6.3.1), even if Fi is not Fn (this WT * extension is important to know for the reader so to have the right timeout) */ /*! Calculate Waiting Time (WT) in units of ETU. * \param[in] wi Waiting Integer * \param[in] fi clock rate conversion integer Fi value * \param[in] di baud rate adjustment factor Di value * \param[in] f clock rate conversion integer F value * \param[in] d baud rate adjustment factor D value * \return Waiting Time WT, in ETU, or < 0 on error (see code for return codes) * \note this should happen after reset and T=0 protocol select (through PPS or implicit) * ISO/IEC 7816-3:2006(E) section 8.1 and 10.2 */ int32_t iso7816_3_calculate_wt(uint8_t wi, uint16_t fi, uint8_t di, uint16_t f, uint8_t d) { /* sanity checks */ if (0 == wi) return -1; if (!iso7816_3_valid_f(fi)) return -2; if (!iso7816_3_valid_d(di)) return -3; if (!iso7816_3_valid_f(f)) return -4; if (!iso7816_3_valid_d(d)) return -5; if (f > fi) return -6; if (d > di) return -7; /* see 7816-3 Section 10.2 */ return wi * 960UL * (fi/f) * (di/d); // calculate timeout value in ETU }