124 lines
4.7 KiB
C
124 lines
4.7 KiB
C
/*
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* Copyright (C) 2019 sysmocom -s.f.m.c. GmbH, Author: Kevin Redon <kredon@sysmocom.de>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <stdint.h>
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#include <stddef.h>
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#include <osmocom/core/utils.h>
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#include "iso7816_3.h"
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const uint16_t iso7816_3_fi_table[16] = {
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372, 372, 558, 744, 1116, 1488, 1860, 0,
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0, 512, 768, 1024, 1536, 2048, 0, 0
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};
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const uint32_t iso7816_3_fmax_table[16] = {
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4000000, 5000000, 6000000, 8000000, 12000000, 16000000, 20000000, 0,
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0, 5000000, 7500000, 10000000, 15000000, 20000000, 0, 0
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};
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const uint8_t iso7816_3_di_table[16] = {
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0, 1, 2, 4, 8, 16, 32, 64,
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12, 20, 0, 0, 0, 0, 0, 0,
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};
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/* all values are based on the Elementary Time Unit (ETU), defined in ISO/IEC 7816-3 section 7.1
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* this is the time required to transmit a bit, and is calculated as follows: 1 ETU = (F / D) x (1 / f) where:
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* - F is the clock rate conversion integer
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* - D is the baud rate adjustment factor
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* - f is the clock frequency
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* the possible F, f(max), and D values are defined in ISO/IEC 7816-3 table 7 and 8
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* - the initial value for F (after reset) is Fd = 372
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* - the initial value for D (after reset) is Dd = 1
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* - the initial maximum frequency f(max) is 5 MHz
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* the card must measure the ETU based on the clock signal provided by the reader
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* one ETU (e.g. 1 bit) takes F/D clock cycles, which the card must count
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*
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* 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)
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* these values are selected according to ISO/IEC 7816-3 section 6.3.1:
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* - card in specific mode: they are enforced if TA2 is present (the reader can deactivate the card if it does not support these values)
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* - card in negotiable mode:
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* -- they can be selected by the reader using the Protocol and Parameters Selection (PPS) procedure
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* -- the first offered protocol and default values are used when no PPS is started
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*
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* PPS is done with Fd and Dd (see ISO/IEC 7816-3 section 9)
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* 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)
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* 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
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*
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* the F and D values must be provided to the SAM3S USART peripheral (after reset and PPS)
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*/
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bool iso7816_3_valid_f(uint16_t f)
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{
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if (0 == f) {
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return false;
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}
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uint8_t i = 0;
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for (i = 0; i < ARRAY_SIZE(iso7816_3_fi_table) && iso7816_3_fi_table[i] != f; i++);
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return (i < ARRAY_SIZE(iso7816_3_fi_table) && iso7816_3_fi_table[i] == f);
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}
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bool iso7816_3_valid_d(uint8_t d)
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{
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if (0 == d) {
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return false;
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}
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uint8_t i = 0;
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for (i = 0; i < ARRAY_SIZE(iso7816_3_di_table) && iso7816_3_di_table[i] != d; i++);
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return (i < ARRAY_SIZE(iso7816_3_di_table) && iso7816_3_di_table[i] == d);
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}
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/*
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* 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)
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* when exceeding WT without card response, the reader flags the card as unresponsive, and resets it
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* this can be used by the card to indicate errors or unsupported operations
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* if the card requires more time to respond, it shall send a procedure byte to restart WT
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* 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
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* - WI is encoded in TC2 in the ATR (10 if absent)
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* - WI does not depend on D/Di (used for the ETU)
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* - after reset WT is 9600 ETU
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* - 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)
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*/
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int32_t iso7816_3_calculate_wt(uint8_t wi, uint16_t fi, uint8_t di, uint16_t f, uint8_t d)
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{
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// sanity checks
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if (0 == wi) {
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return -1;
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}
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if (!iso7816_3_valid_f(fi)) {
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return -2;
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}
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if (!iso7816_3_valid_d(di)) {
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return -3;
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}
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if (!iso7816_3_valid_f(f)) {
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return -4;
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}
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if (!iso7816_3_valid_d(d)) {
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return -5;
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}
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if (f > fi) {
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return -6;
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}
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if (d > di) {
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return -7;
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}
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return wi * 960UL * (fi/f) * (di/d); // calculate timeout value in ETU
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}
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