/* rsa_raw_test.c — 验证 weapi 需要的 textbook RSA（无 padding 模幂）
 * 用 mbedtls_rsa_public() 对固定 16 字节消息做 c = m^e mod n，
 * 输出定长 256 hex（与模数等长）。宿主用 Python pow(m,e,n) 交叉校验。
 * 编译(mipsel): .tools/zig-mipsel-cc -O2 -static -Ivendor/mbedtls/include rsa_raw_test.c \
 *               out/mbedtls/mipsel/libmbedcrypto.a -o out/rsa_raw_test
 */
#include <stdio.h>
#include <string.h>
#include "mbedtls/rsa.h"
#include "mbedtls/pk.h"
#include "mbedtls/base64.h"

/* PUBLIC_KEY_DER_B64 (PKCS#8 / SubjectPublicKeyInfo, 1024-bit RSA) */
static const char *PEM_DER_B64 =
 "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDgtQn2JZ34ZC28NWYpAUd98iZ37BUrX/aKzmFbt7clFSs6sXqHauqKWqdtLkF2KexO40H1YTX8z2lSgBBOAxLsvaklV8k4cBFK9snQXE9/DDaFt6Rr7iVZMldczhC0JNgTz+SHXT6CBHuX3e9SdB1Ua44oncaTWz7OBGLbCiK45wIDAQAB";

int main(void) {
    unsigned char der[512], *buf = der; size_t der_len = sizeof der;
    /* 解码 base64 DER */
    if (mbedtls_base64_decode(der, sizeof der, &der_len, (const unsigned char*)PEM_DER_B64, strlen(PEM_DER_B64)) != 0) {
        printf("base64 decode fail\n"); return 1;
    }
    /* 解析公钥 */
    mbedtls_pk_context pk; mbedtls_pk_init(&pk);
    if (mbedtls_pk_parse_public_key(&pk, der, der_len) != 0) {
        printf("pk parse fail\n"); return 1;
    }
    mbedtls_rsa_context *rsa = mbedtls_pk_rsa(pk);
    int keylen = mbedtls_rsa_get_len(rsa);
    printf("rsa len=%d (bytes)\n", keylen);

    /* 固定 16 字节明文(weapi 的 secret_key)，右对齐到 keylen 后做 raw 模幂 */
    unsigned char secret[16];
    for (int i = 0; i < 16; i++) secret[i] = (unsigned char)(0x41 + i);  /* 测试向量 */
    unsigned char input[256], output[256];
    memset(input, 0, sizeof input);
    memcpy(input + keylen - 16, secret, 16);
    int rc = mbedtls_rsa_public(rsa, input, output);  /* 无 padding 纯模幂 */
    if (rc != 0) { printf("rsa_public fail %d\n", rc); return 1; }
    printf("secret = ");
    for (int i = 0; i < 16; i++) printf("%02X", secret[i]);
    printf("\nCT = ");
    for (int i = 0; i < keylen; i++) printf("%02X", output[i]);
    printf("\n");

    mbedtls_pk_free(&pk);
    return 0;
}