extkeys.c

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include "extkeys.h"

/**
 * Reads a line from file f and parses out the key and value from it.
 * The format of a line must match /^ *[A-Za-z0-9_] *[,=] *.+$/.
 * If a line ends in \r, the final \r is stripped.
 * The input file is assumed to have been opened with the 'b' flag.
 * The input file is assumed to contain only ASCII.
 *
 * A line cannot exceed 512 bytes in length.
 * Lines that are excessively long will be silently truncated.
 *
 * On success, *key and *value will be set to point to the key and value in
 * the input line, respectively.
 * *key and *value may also be NULL in case of empty lines.
 * On failure, *key and *value will be set to NULL.
 * End of file is considered failure.
 *
 * Because *key and *value will point to a static buffer, their contents must be
 * copied before calling this function again.
 * For the same reason, this function is not thread-safe.
 *
 * The key will be converted to lowercase.
 * An empty key is considered a parse error, but an empty value is returned as
 * success.
 *
 * This function assumes that the file can be trusted not to contain any NUL in
 * the contents.
 *
 * Whitespace (' ', ASCII 0x20, as well as '\t', ASCII 0x09) at the beginning of
 * the line, at the end of the line as well as around = (or ,) will be ignored.
 *
 * @param f the file to read
 * @param key pointer to change to point to the key
 * @param value pointer to change to point to the value
 * @return 0 on success,
 *         1 on end of file,
 *         -1 on parse error (line too long, line malformed)
 *         -2 on I/O error
 */
static int get_kv(FILE *f, char **key, char **value) {
#define SKIP_SPACE(p)   do {\
    for (; *p == ' ' || *p == '\t'; ++p)\
        ;\
} while(0);
    static char line[512];
    char *k, *v, *p, *end;

    *key = *value = NULL;

    errno = 0;
    if (fgets(line, (int)sizeof(line), f) == NULL) {
        if (feof(f))
            return 1;
        else
            return -2;
    }
    if (errno != 0)
        return -2;

    if (*line == '\n' || *line == '\r' || *line == '\0')
        return 0;

    /* Not finding \r or \n is not a problem.
     * The line might just be exactly 512 characters long, we have no way to
     * tell.
     * Additionally, it's possible that the last line of a file is not actually
     * a line (i.e., does not end in '\n'); we do want to handle those.
     */
    if ((p = strchr(line, '\r')) != NULL || (p = strchr(line, '\n')) != NULL) {
        end = p;
        *p = '\0';
    } else {
        end = line + strlen(line) + 1;
    }

    p = line;
    SKIP_SPACE(p);
    k = p;

    /* Validate key and convert to lower case. */
    for (; *p != ' ' && *p != ',' && *p != '\t' && *p != '='; ++p) {
        if (*p == '\0')
            return -1;

        if (*p >= 'A' && *p <= 'Z') {
            *p = 'a' + (*p - 'A');
            continue;
        }

        if (*p != '_' &&
                (*p < '0' && *p > '9') &&
                (*p < 'a' && *p > 'z'))
            return -1;
    }

    /* Bail if the final ++p put us at the end of string */
    if (*p == '\0')
        return -1;

    /* We should be at the end of key now and either whitespace or [,=]
     * follows.
     */
    if (*p == '=' || *p == ',') {
        *p++ = '\0';
    } else {
        *p++ = '\0';
        SKIP_SPACE(p);
        if (*p != '=' && *p != ',')
            return -1;
        *p++ = '\0';
    }

    /* Empty key is an error. */
    if (*k == '\0')
        return -1;

    SKIP_SPACE(p);
    v = p;

    /* Skip trailing whitespace */
    for (p = end - 1; *p == '\t' || *p == ' '; --p)
        ;

    *(p + 1) = '\0';

    *key = k;
    *value = v;

    return 0;
#undef SKIP_SPACE
}

static int ishex(char c) {
    if ('a' <= c && c <= 'f') return 1;
    if ('A' <= c && c <= 'F') return 1;
    if ('0' <= c && c <= '9') return 1;
    return 0;
}

static char hextoi(char c) {
    if ('a' <= c && c <= 'f') return c - 'a' + 0xA;
    if ('A' <= c && c <= 'F') return c - 'A' + 0xA;
    if ('0' <= c && c <= '9') return c - '0';
    return 0;
}

void parse_hex_key(unsigned char *key, const char *hex, unsigned int len) {
    if (strlen(hex) != 2 * len) {
        fprintf(stderr, "Key (%s) must be %"PRIu32" hex digits!\n", hex, 2 * len);
        exit(EXIT_FAILURE);
    }

    for (unsigned int i = 0; i < 2 * len; i++) {
        if (!ishex(hex[i])) {
            fprintf(stderr, "Key (%s) must be %"PRIu32" hex digits!\n", hex, 2 * len);
            exit(EXIT_FAILURE);
        }
    }

    memset(key, 0, len);

    for (unsigned int i = 0; i < 2 * len; i++) {
        char val = hextoi(hex[i]);
        if ((i & 1) == 0) {
            val <<= 4;
        }
        key[i >> 1] |= val;
    }
}

void extkeys_initialize_keyset(nca_keyset_t *keyset, FILE *f) {
    char *key, *value;
    int ret;
    
    while ((ret = get_kv(f, &key, &value)) != 1 && ret != -2) {
        if (ret == 0) {
            if (key == NULL || value == NULL) {
                continue;
            }
            int matched_key = 0;
            if (strcmp(key, "aes_kek_generation_source") == 0) {
                parse_hex_key(keyset->aes_kek_generation_source, value, sizeof(keyset->aes_kek_generation_source));
                matched_key = 1;
            } else if (strcmp(key, "aes_key_generation_source") == 0) {
                parse_hex_key(keyset->aes_key_generation_source, value, sizeof(keyset->aes_key_generation_source));            
                matched_key = 1;
            } else if (strcmp(key, "key_area_key_application_source") == 0) {
                parse_hex_key(keyset->key_area_key_application_source, value, sizeof(keyset->key_area_key_application_source));
                matched_key = 1;
            } else if (strcmp(key, "key_area_key_ocean_source") == 0) {
                parse_hex_key(keyset->key_area_key_ocean_source, value, sizeof(keyset->key_area_key_ocean_source));
                matched_key = 1;
            } else if (strcmp(key, "key_area_key_system_source") == 0) {
                parse_hex_key(keyset->key_area_key_system_source, value, sizeof(keyset->key_area_key_system_source));
                matched_key = 1;
            } else if (strcmp(key, "titlekek_source") == 0) {
                parse_hex_key(keyset->titlekek_source, value, sizeof(keyset->titlekek_source));
                matched_key = 1;
            } else if (strcmp(key, "header_kek_source") == 0) {
                parse_hex_key(keyset->header_kek_source, value, sizeof(keyset->header_kek_source));
                matched_key = 1;
            } else if (strcmp(key, "header_key_source") == 0) {
                parse_hex_key(keyset->encrypted_header_key, value, sizeof(keyset->encrypted_header_key));
                matched_key = 1;
            } else if (strcmp(key, "header_key") == 0) {
                parse_hex_key(keyset->header_key, value, sizeof(keyset->header_key));
                matched_key = 1;
            } else if (strcmp(key, "encrypted_header_key") == 0) {
                parse_hex_key(keyset->encrypted_header_key, value, sizeof(keyset->encrypted_header_key));
                matched_key = 1;
            } else if (strcmp(key, "package2_key_source") == 0) {
                parse_hex_key(keyset->package2_key_source, value, sizeof(keyset->package2_key_source));
                matched_key = 1;
            } else if (strcmp(key, "sd_card_kek_source") == 0) {
                parse_hex_key(keyset->sd_card_kek_source, value, sizeof(keyset->sd_card_kek_source));
                matched_key = 1;
            } else if (strcmp(key, "sd_card_nca_key_source") == 0) {
                parse_hex_key(keyset->sd_card_key_sources[1], value, sizeof(keyset->sd_card_key_sources[1]));
                matched_key = 1;
            } else if (strcmp(key, "sd_card_save_key_source") == 0) {
                parse_hex_key(keyset->sd_card_key_sources[0], value, sizeof(keyset->sd_card_key_sources[0]));
                matched_key = 1;
            } else if (strcmp(key, "master_key_source") == 0) {
                parse_hex_key(keyset->master_key_source, value, sizeof(keyset->master_key_source));
                matched_key = 1;
            } else if (strcmp(key, "keyblob_mac_key_source") == 0) {
                parse_hex_key(keyset->keyblob_mac_key_source, value, sizeof(keyset->keyblob_mac_key_source));
                matched_key = 1;
            } else if (strcmp(key, "secure_boot_key") == 0) {
                parse_hex_key(keyset->secure_boot_key, value, sizeof(keyset->secure_boot_key));
                matched_key = 1;
            } else if (strcmp(key, "tsec_key") == 0) {
                parse_hex_key(keyset->tsec_key, value, sizeof(keyset->tsec_key));
                matched_key = 1;
            } else {
                char test_name[0x100];
                memset(test_name, 0, sizeof(100));
                for (unsigned int i = 0; i < 0x20 && !matched_key; i++) {
                    snprintf(test_name, sizeof(test_name), "keyblob_key_source_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->keyblob_key_sources[i], value, sizeof(keyset->keyblob_key_sources[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "keyblob_key_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->keyblob_keys[i], value, sizeof(keyset->keyblob_keys[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "keyblob_mac_key_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->keyblob_mac_keys[i], value, sizeof(keyset->keyblob_mac_keys[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "encrypted_keyblob_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->encrypted_keyblobs[i], value, sizeof(keyset->encrypted_keyblobs[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "keyblob_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->keyblobs[i], value, sizeof(keyset->keyblobs[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "master_key_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->master_keys[i], value, sizeof(keyset->master_keys[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "package1_key_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->package1_keys[i], value, sizeof(keyset->package1_keys[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "package2_key_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->package2_keys[i], value, sizeof(keyset->package2_keys[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "titlekek_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->titlekeks[i], value, sizeof(keyset->titlekeks[i]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "key_area_key_application_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->key_area_keys[i][0], value, sizeof(keyset->key_area_keys[i][0]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "key_area_key_ocean_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->key_area_keys[i][1], value, sizeof(keyset->key_area_keys[i][1]));
                        matched_key = 1;
                        break;
                    }
                    
                    snprintf(test_name, sizeof(test_name), "key_area_key_system_%02"PRIx32, i);
                    if (strcmp(key, test_name) == 0) {
                        parse_hex_key(keyset->key_area_keys[i][2], value, sizeof(keyset->key_area_keys[i][2]));
                        matched_key = 1;
                        break;
                    }
                }
            }
            if (!matched_key) {
                fprintf(stderr, "[WARN]: Failed to match key \"%s\", (value \"%s\")\n", key, value);
            }
        }
    }
}