I posted this on https://stackoverflow.com/questions/78604338/why-do-i-get-the-following-error-wrong-signature-length-when-i-try-to-validate
I'm writing an c++ program LicenseValidator -> https://github.com/christiangda/LicenseValidator <https://github.com/christiangda/LicenseValidator> to validate a hypothetical program license using OpenSSL 3.1 Library <https://wiki.openssl.org/index.php/OpenSSL_3.0>, and when I tried to validate the licensed content I got the following error: Failed to verify license 008C1AF901000000:error:02000077:rsa routines:ossl_rsa_verify:wrong signature length:crypto/rsa/rsa_sign.c:338: 008C1AF901000000:error:1C880004:Provider routines:rsa_verify:RSA lib:providers/implementations/signature/rsa_sig.c:785: I would appreciate any help or guidance on what I am doing wrong. I am not at all an expert in the c/c++ programming language and this is the first time I have tried to use the OpenSSL library. Of course, I've used GitHub Copilot, gemini, and chatgpt to write and understand the repository code. The chalenge is about the examples I found on internet, the majority of them are about OpenSSL v1 and the v3 is very different, so was hard to understand the migration. The README.md <https://github.com/christiangda/LicenseValidator/blob/main/README.md> file has the instructions to create all the necessary keys, etc, references I used and the instructions to compile it using cmake. The core function is LicenseValidator/src/License.cpp <https://github.com/christiangda/LicenseValidator/blob/82f5501ab2e5bf2d91dc4298245b36fde2efd66b/src/License.cpp#L79> : bool verifyLicense(const unsigned char *licenseContent, const unsigned char *licenseSignature, const std::string pubkey){ EVP_PKEY *pkey = loadRsaPemPubKey(pubkey); if (pkey == NULL) { std::cerr << "Failed to load public key" << std::endl; ERR_print_errors_fp(stdout); return false; } EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new(pkey, NULL); if (ctx == NULL) { std::cerr << "Failed to create EVP_PKEY_CTX" << std::endl; EVP_PKEY_free(pkey); ERR_print_errors_fp(stdout); return false; } if (EVP_PKEY_verify_init(ctx) <= 0) { std::cerr << "Failed to initialize EVP_PKEY_CTX" << std::endl; EVP_PKEY_CTX_free(ctx); EVP_PKEY_free(pkey); ERR_print_errors_fp(stdout); return false; } // PKCS1 padding scheme if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) { std::cerr << "Failed to set RSA padding" << std::endl; EVP_PKEY_CTX_free(ctx); EVP_PKEY_free(pkey); ERR_print_errors_fp(stdout); return false; } // SHA256 digest if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) { std::cerr << "Failed to set signature MD" << std::endl; EVP_PKEY_CTX_free(ctx); EVP_PKEY_free(pkey); ERR_print_errors_fp(stdout); return false; } if (EVP_PKEY_verify(ctx, licenseSignature, sizeof(licenseSignature), licenseContent, sizeof(licenseContent)) <= 0) { std::cerr << "Failed to verify license" << std::endl; EVP_PKEY_CTX_free(ctx); EVP_PKEY_free(pkey); ERR_print_errors_fp(stdout); return false; } EVP_PKEY_CTX_free(ctx); EVP_PKEY_free(pkey); return true; } Some guidance about how to solve the error I got. -- Saludos, Christian