card_status.h

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/*
 * SPDX-License-Identifier: LGPL-3.0-or-later
 * Copyright (c) 2026 Cryptnox SA
 */

 
#ifndef CARD_STATUS_H
#define CARD_STATUS_H
 
#include <stddef.h>
#include <stdint.h>

#define CARD_SELECT_APDU  { 0x00U, 0xA4U, 0x04U, 0x00U, 0x07U, \
                            0xA0U, 0x00U, 0x00U, 0x10U, 0x00U, 0x01U, 0x12U }

#define CARD_FLAGS_OFF    5U

#define CARD_SELECT_MIN   8U
 
#define CARD_FLAG_PIN_SET  0x40U   
#define CARD_FLAG_SEEDED   0x20U   

typedef enum {
    CARD_READY = 0,   
    CARD_UNKNOWN,     
    CARD_NO_PIN,      
    CARD_NO_KEY       
} card_state_t;

static inline card_state_t card_state(const uint8_t *r, size_t n)
{
    if ((r == NULL) || (n < CARD_SELECT_MIN)) { return CARD_UNKNOWN; }
    /* Not 0x9000 means the applet did not answer this SELECT, so there is no
     * layout below to trust. */
    if ((r[n - 2U] != 0x90U) || (r[n - 1U] != 0x00U)) { return CARD_UNKNOWN; }
    /* A card type whose flags byte we have not been told about could have
     * anything in bit 6, and reading it wrong here would refuse a card that
     * works. 'B' is Basic, 'N' is NFT; both carry these two flags. */
    if ((r[0] != (uint8_t)'B') && (r[0] != (uint8_t)'N')) { return CARD_UNKNOWN; }
 
    const uint8_t flags = r[CARD_FLAGS_OFF];
    if ((flags & CARD_FLAG_PIN_SET) == 0U) { return CARD_NO_PIN; }
    if ((flags & CARD_FLAG_SEEDED)  == 0U) { return CARD_NO_KEY; }
    return CARD_READY;
}

static inline const char *card_state_text(card_state_t s)
{
    switch (s) {
        case CARD_NO_PIN: return "Card not set up - initialise it first";
        case CARD_NO_KEY: return "Card has no key - load a seed first";
        default:          return NULL;
    }
}
 
#endif /* CARD_STATUS_H */