Hello! Thank you for your reply. I am not looking for a bootloader at this point, although it is good to know about wolfBoot. The use case I am working on is 'secure boot'. Ensuring that only legitimate firmware is booted when the device is powered. I am the one working on this. Firmware update is also a legitimate use case for this.

I have had some luck [since my initial post on this forum] using the wolfSSL APIs but as of now, I am seeing a -229 (SIG_VERIFY_E) error upon calling wc_SignatureVerify(..).

The issue I see is quite similar to the one described here -
https://www.wolfssl.com/forums/topic891 … alues.html

Could you please tell me what the final resolution to the problem [that thomas.cornu reported] was? I haven't compared the bytes in the two hashes but I do see that the return value from wc_RsaSSL_Verify() call is 51 (vs. 32 for the hash it is being compared against).

Below is a close representation of what the code looks like....

    ret = wolfSSL_Init();
    if (ret != SSL_SUCCESS) {
            /*failed to initialize wolfSSL library*/
            while(1);
    }

    /* open and read DER-formatted cert into buffer */
    file = fopen("./cert.der", "rb");
    if (!file)
    {
        while(1); // error reading certificate file
    }

    derCertSz = fread(derCert, 1, sizeof(derCert), file);
    fclose(file);

    wolfSSL_X509_d2i(&certificate, derCert, derCertSz); //wolfSSL_X509_load_certificate_file(CERT_FILE, SSL_FILETYPE_ASN1);
    pubKeyTmp = wolfSSL_X509_get_pubkey(certificate);

    if (certificate != NULL) {
        wolfSSL_X509_free(certificate);
    } else {
        return 0;
    }

    /* initialize DecodedCert with DER cert */
    InitDecodedCert(&cert, derCert, derCertSz, 0);
    ret = ParseCert(&cert, RSA_PUBLICKEY_TYPE /*RSA_PUBLICKEY_TYPE*/, NO_VERIFY, 0);
    if (ret != 0)
    {
        while(1); // ParseCert failed
    }

    /* extract the public key from the cert */
    wc_InitRsaKey(&pubKey, NULL);
    ret = wc_RsaPublicKeyDecode((byte*)pubKeyTmp->pkey.ptr, &idx, &pubKey, pubKeyTmp->pkey_sz);

    if (ret != 0)
    {
        while(1); //  RsaPublicKeyDecode failed
    }

    /* Copy the binary into a buffer */
    appFilePtr = fopen("./app.bin", "rb");
    fseek(appFilePtr,0,SEEK_END);
    filelen = ftell(appFilePtr);
    rewind(appFilePtr);
    buffer = (char *)malloc((filelen)*sizeof(char));
    fread(buffer,1,filelen,appFilePtr);
    fclose(appFilePtr);

    /* Verify signature */
    ret = wc_SignatureVerify(WC_HASH_TYPE_SHA256, WC_SIGNATURE_TYPE_RSA, buffer, filelen, cert.signature,   cert.sigLength, &pubKey, sizeof(pubKey));
    if (ret == 0)
    {
        printf("PASS: %d", ret);
    }
    else{
        printf("FAIL: %d", ret);
    }

The result I see is - FAIL: -229

What might I need to do differently?

Hi agoswam,

You indicated the digest size is 51 which may be the source of the issue. You are passing WC_HASH_TYPE_SHA256 which has a digest of only 32-bytes not 51.

A SHA256 digest is 32-bytes long,
A SHA384 digest is 48-bytes long,
and
A SHA512 digest is 64-bytes long.

There are no digests that are 51 bytes long. Can you double check the digest length?

Warm Regards,

K

agoswam,

Can you tell us where the signature came from and how it was generated initially? If there is DER encoding in front of the signature is it possibly PKCS8 encoded? Can you try calling wc_GetPkcs8TraditionalOffset on the signature first and check the return code of that function? If wc_GetPkcs8TraditionalOffset returns a zero (success) can you try stripping off the PKCS8 header before verifying the signature?

If it is not a PKCS8 encoded signature do you know how it was encoded initially?

Warm Regards,

K