Problem with decrypting using mbedtls on esp32

Question

I am trying to write function to decrypt rsa2048 with mbedtls/pk.h

I am trying to write function to decrypt rsa2048 with mbedtls/pk.h esp32 but on the site they wrote Store data to be decrypted and its length in variables. This tutorial stores the data in to_decrypt, and its length in to_decrypt_len: I idk what is the format of to_decrypt i tried to put encrypted with code upper buf but it didn't work. Tried co encode on rsa online sites into base64 and put into the program convert to unsigned char* It gaves to me error 0x4080 RSA - Bad input parameters to function code :

#include <Arduino.h>
#include "mbedtls/pk.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/platform.h"
#include "mbedtls/base64.h"

void rsa2048_encrypt(const char *text)
{

    // RNG (Random number generator init)
    int ret = 0;
    mbedtls_entropy_context entropy;
    mbedtls_entropy_init(&entropy);
    mbedtls_ctr_drbg_context ctr_drbg;
    const char *personalization = "mgkegneljgnjlwgnjefdcmeg12313123dsggsd";

    mbedtls_ctr_drbg_init(&ctr_drbg);

    ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
                                (const unsigned char *)personalization,
                                strlen(personalization));
    if (ret != 0)
    {
        // ERROR HANDLING CODE FOR YOUR APP
    }

    // Creating rsa context + Importing pub key
    ret = 0;
    mbedtls_pk_context pk;
    mbedtls_pk_init(&pk);

    /*
     * Read the RSA public key
     */
    const unsigned char *key = (const unsigned char *)"-----BEGIN PUBLIC KEY-----\n"
                                                      "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAmwukduTT4dMD+EXuho4L\n"
                                                      "zEg9pH7Bk4y6TPw9pQqiw4b5Qx3+KM+SFi2I4AncfkOcjtuMqtSPdNSgFb1DErQD\n"
                                                      "+I+yOS7ztuAVy6hO/oRpVKAJNVl385pC/Ah8aiZts6cY8kjs47Mw4ufFNwIH8hOy\n"
                                                      "6f1+e8chBgeKxOVJBNiWr2nsPhvvAERTunw/CTvWsBLakyGs+OJwOcYsr0m5iOJx\n"
                                                      "XfBUEYOQ68XDIUTTLKdYsUOFSESwtIsPgqytj+SRcA/STH8eQJigNQNj8Zexpi+3\n"
                                                      "ykDWAxbmHQ8UWma1vV//oM6xy3DI/SXxvPusjNbKxDg+q5/e3hWoaBVq3ti9/ZTe\n"
                                                      "kQIDAQAB\n"
                                                      "-----END PUBLIC KEY-----\n";

    if ((ret = mbedtls_pk_parse_public_key(&pk, key, strlen((const char *)key) + 1)) != 0)
    {

        printf(" failed\n  ! mbedtls_pk_parse_public_key returned -0x%04x\n", -ret);
    };
    // Encrypting data
    const unsigned char *to_encrypt = (const unsigned char *)text;
    size_t to_encrypt_len = strlen((const char *)to_encrypt);

    unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
    size_t olen = 0;

    /*
     * Calculate the RSA encryption of the data.
     */
    printf("\n  . Generating the encrypted value: \n");
    fflush(stdout);

    if ((ret = mbedtls_pk_encrypt(&pk, to_encrypt, to_encrypt_len,
                                  buf, &olen, sizeof(buf),
                                  mbedtls_ctr_drbg_random, &ctr_drbg)) != 0)
    {
        printf(" failed\n  ! mbedtls_pk_encrypt returned -0x%04x\n", -ret);
    }

    for (size_t i = 0; i < olen; i++)
    {
        mbedtls_printf("%02X%s", buf[i],
                       (i + 1) % 16 == 0 ? "\r\n" : " ");
    }

    mbedtls_pk_free(&pk);
    mbedtls_entropy_free(&entropy);
    mbedtls_ctr_drbg_free(&ctr_drbg);
}
void decrypt_test()
{
    const unsigned char *private_key = (const unsigned char *)"-----BEGIN RSA PRIVATE KEY-----\n"
                                                              "MIIEogIBAAKCAQEAmwukduTT4dMD+EXuho4LzEg9pH7Bk4y6TPw9pQqiw4b5Qx3+\n"
                                                              "KM+SFi2I4AncfkOcjtuMqtSPdNSgFb1DErQD+I+yOS7ztuAVy6hO/oRpVKAJNVl3\n"
                                                              "85pC/Ah8aiZts6cY8kjs47Mw4ufFNwIH8hOy6f1+e8chBgeKxOVJBNiWr2nsPhvv\n"
                                                              "AERTunw/CTvWsBLakyGs+OJwOcYsr0m5iOJxXfBUEYOQ68XDIUTTLKdYsUOFSESw\n"
                                                              "tIsPgqytj+SRcA/STH8eQJigNQNj8Zexpi+3ykDWAxbmHQ8UWma1vV//oM6xy3DI\n"
                                                              "/SXxvPusjNbKxDg+q5/e3hWoaBVq3ti9/ZTekQIDAQABAoIBADXzji5FICnDuOzq\n"
                                                              "wL6XrSlPtguIhCmo3acuWvEUS2EIlbIyPJ/M4wPOooN7Svuw4Uigw0kqoCTCXFZU\n"
                                                              "PoPCmmMi9ZyKZwoq3cq5bYuJXfGxoqKq2F+vPUHgXhK9/ox2R+r/T1dIomlCx1CF\n"
                                                              "52foTOi5agr+VtJ3S2WKd6c1CvJMuRRoIX9vI49L+NdA9FUcA4Ge2rJZPu7zd/Xj\n"
                                                              "VvqtIH63Y/4z+S5YqnBgYjk7xWf3f9ybrkdi9fiRNt9wq4LOet+OSiQXWyuX+ppL\n"
                                                              "im6Sl3O8XkaDWAFo8dUWkZf+6RpABxFnUy45CWZGs7W8MpVwykXdpxcn9iJ7jIaR\n"
                                                              "9dcmUgECgYEA3aAWxuiX081mFIdmQEpKkp1JFbZOoZpIzBXNx/M05FGkz8QPL7G3\n"
                                                              "9h8A8UCbTFG+cAM1vjMUPzWXbsytE8VC4qjGy+1RBDltBt5/XX4VECVDIwjTdmc0\n"
                                                              "RPfJ2vKkAFYPHjyQijQCZxAPM0E/IFGKnTP4Dt+rITxkYvoouFiR2eECgYEAsxfq\n"
                                                              "qk2d8K62DQPURHvNmFnct+QAlIF9i/XHGcLNvnzEASiIsZ75TiXUc0xIxY2/ewo4\n"
                                                              "CMbNUG98xiW0Q5pdyKFQ3qnhNNTKPCK1T4qqKarDU2pSXFC2afkCSBbfO7qWblRD\n"
                                                              "PMJJ7SG8fAeIWbqKVzPgSfwRw4xY+iEe7SvoerECgYAEIQhrmkfB3XDKbx9bkUbE\n"
                                                              "ZoPHEMd0QVCb5MgZspFIs7CzYj66L8ByqG83D3IVQOygX57vtTnqV5BDszKCTMmL\n"
                                                              "OYPCpuA8iOlcGGcdEc1IqLkQfQibix6xLkCngJ/HldLgSFaVDJUC4Iy38r4/VuWT\n"
                                                              "OjWj6Uzh6KMiKPD7RkMpYQKBgH2BSjM0l3U+ilfOkie39tlISDQaNQndQQUfJPr5\n"
                                                              "mENgnd8N79VBygYo3pw6HllLP5/TBneoEePHbVJSw+QIPqbF3a1csXTblinUTOlE\n"
                                                              "DIGMqLtBLByDd4IGPcIVPTVXSephZIkkwrfKR5NHmBcBcccwlIJkgnJeXVBUe57L\n"
                                                              "gWzRAoGAAmLnPNkIT5Nruqy7EdEeb90W0VA/7/CaESvZKUkAHUy4bIqwFSGGJz1Q\n"
                                                              "oKUx8cuK4tz79mHsjzlJoCSLUvI5Fpfz+CS9uvA15QBIHU+5G37Ga5WsuBTww+lx\n"
                                                              "XC6IQ356/xfs4CmAVD1xjhEuBjANSs8lgHMAQPGngU5EVaE1hPw=\n"
                                                              "-----END RSA PRIVATE KEY-----";

    // RNG (Random number generator init)
    int ret = 0;
    mbedtls_entropy_context entropy;
    mbedtls_entropy_init(&entropy);
    mbedtls_ctr_drbg_context ctr_drbg;
    const char *personalization = "mgkegneljgnjlwgnjefdcmeg12313123dsggsd";

    mbedtls_ctr_drbg_init(&ctr_drbg);

    ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
                                (const unsigned char *)personalization,
                                strlen(personalization));
    if (ret != 0)
    {
        // ERROR HANDLING CODE FOR YOUR APP
    }
    ret = 0;
    mbedtls_pk_context pk;

    mbedtls_pk_init(&pk);

    /*
     * Read the RSA privatekey
     */
    if ((ret = mbedtls_pk_parse_key(&pk, private_key, strlen((const char *)private_key) + 1, NULL, 0)) != 0)
    {
        printf(" failed\n  ! mbedtls_pk_parse_keyfile returned -0x%04x\n", -ret);
    }

    unsigned char result[MBEDTLS_MPI_MAX_SIZE];
    size_t olen = 0;

    /*
     * Calculate the RSA encryption of the data.
     */

    printf("\n  . Generating the decrypted value");
    fflush(stdout);
    const char *text = "fnianPxs/09bx75ufVLWPeFF9kbGEIL3+TQqW2+ZoeMpdvVnkifFToAii92ODVBPOL0RzQPfxlJcN/nVY3K5fWNSGHM8TTwTgCqvUc0ia5L5YHI1YSgDKzx2QPZlu7tEd06sjW7txRacnhilRfjFPp0CYeLwxYVBlPmKIE7oqQHrc8sal3X9NSqgwO7+03TBeH3beNanMCqQBRk9t+Z80XApEBMcZQHZ0lb+Z0C6DOuY0elH/fOp1SGlXuzf+tgcv7+TzL5uVVFCBNyMonTwMEp+zbLjX2Ck1IHhp8JXi3ovVi8HNcKCOQx/fxX1qTSt2NulHTwP2urCQSZbGjnYuw==";
    const unsigned char *to_decrypt = (unsigned char *)text;
    if ((ret = mbedtls_pk_decrypt(&pk, to_decrypt, (strlen(text) * 4) - 1, result, &olen, sizeof(result),
                                  mbedtls_ctr_drbg_random, &ctr_drbg)) != 0)
    {
        printf(" failed\n  ! mbedtls_pk_decrypt returned -0x%04x\n", -ret);
    }
}

So what I do wrong ?

First issue I see is that you are not passing the correct size to mbedtls_pk_decrypt `(strlen(text) * 4) - 1` why do you have `*4`? — user20716902, Jan 26 '23 at 14:40
Please select one language tag. This looks like C, so unless I'm mistaken you should remove the C++ tag. — wohlstad, Jan 26 '23 at 14:43
when i wrote `sizeof (text)` It gives me 4 byte so i decide to write 4 — Resent, Jan 26 '23 at 14:52
I can't understand size of what they want, or they want size of array , or len string — Resent, Jan 26 '23 at 14:53

Problem with decrypting using mbedtls on esp32

0 Answers0