124 行
3.0 KiB
C
124 行
3.0 KiB
C
#include <stdio.h>
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#include <openssl/hmac.h>
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#include <openssl/sha.h>
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#include <gpgme.h>
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#include "base32.h"
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#include "otppass.h"
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unsigned char* extract_secret(const char* otpauth_url, size_t* decoded_len) {
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const char* secret_start = strstr(otpauth_url, "secret=");
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if (!secret_start) {
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fprintf(stderr, "OTPAuth URLの中に、シークレットを見つけられませんでした。\n");
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return NULL;
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}
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secret_start += 7;
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const char* secret_end = strchr(secret_start, '&');
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if (!secret_end) {
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if (secret_start[0] != '\0') {
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secret_end = secret_start + strlen(secret_start);
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} else {
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secret_end = secret_start;
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}
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}
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if (secret_end < secret_start) {
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fprintf(stderr, "不正なシークレットの距離。\n");
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return NULL;
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}
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size_t secret_len = secret_end - secret_start;
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char* secret_encoded = (char*)malloc(secret_len + 1);
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if (secret_encoded == NULL) {
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fprintf(stderr, "メモリの役割に失敗。\n");
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return NULL;
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}
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strncpy(secret_encoded, secret_start, secret_len);
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secret_encoded[secret_len] = '\0';
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unsigned char* secret_decoded = base32_decode(secret_encoded, decoded_len);
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free(secret_encoded);
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if (!secret_decoded) {
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fprintf(stderr, "BASE32の復号化に失敗。\n");
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return NULL;
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}
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return secret_decoded;
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}
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uint32_t generate_totp(const char *secret, uint64_t counter) {
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counter = htobe64(counter);
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unsigned char hash[SHA_DIGEST_LENGTH];
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HMAC(EVP_sha1(), secret, strlen(secret), (unsigned char *)&counter, sizeof(counter), hash, NULL);
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int offset = hash[SHA_DIGEST_LENGTH - 1] & 0x0F;
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uint32_t truncated_hash =
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(hash[offset] & 0x7F) << 24 |
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(hash[offset + 1] & 0xFF) << 16 |
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(hash[offset + 2] & 0xFF) << 8 |
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(hash[offset + 3] & 0xFF);
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return truncated_hash % 1000000;
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}
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void otppass(char* file) {
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gpgme_ctx_t ctx;
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gpgme_error_t err;
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gpgme_data_t in, out;
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size_t secret_len;
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gpgme_check_version(NULL);
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err = gpgme_new(&ctx);
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if (err) {
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fprintf(stderr, "GPGMEを創作に失敗\n");
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exit(1);
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}
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err = gpgme_data_new_from_file(&in, file, 1);
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if (err) {
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fprintf(stderr, "GPGファイルを読込に失敗\n");
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exit(1);
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}
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err = gpgme_data_new(&out);
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if (err) {
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fprintf(stderr, "GPGデータを読込に失敗\n");
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exit(1);
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}
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err = gpgme_op_decrypt(ctx, in, out);
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if (err) {
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fprintf(stderr, "GPGを復号化に失敗\n");
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exit(1);
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}
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char* secret = gpgme_data_release_and_get_mem(out, &secret_len);
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if (!secret) {
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fprintf(stderr, "GPGを受取に失敗\n");
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exit(1);
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}
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size_t decoded_len;
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unsigned char* secret_decoded = extract_secret(secret, &decoded_len);
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if (!secret_decoded) {
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fprintf(stderr, "シークレットの抽出またはデコードに失敗しました\n");
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free(secret);
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exit(1);
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}
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time_t current_time = time(NULL);
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uint64_t counter = current_time / 30;
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uint32_t otp = generate_totp((const char*)secret_decoded, counter);
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printf("%06d\n", otp);
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gpgme_data_release(in);
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gpgme_release(ctx);
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free(secret);
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free(secret_decoded);
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}
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