On 16/10/2018 16:39, Dmitry wrote:
Hello!
I have a C++ programme, ECDSA key pair and some string to sign. The
programme generates signature and saves it into a file
(signature.bin). Then I check the validity of the signature via the
following command:
openssl dgst -verify ec_public.pem -signature signature.bin ToSign.txt
the problem is that *my programme sometimes generates wrong
signature*. 16 times out of 21 the signature produced is invalid and
the above command outputs:
Error Verifying Data
while in the remaining 5 occurrences it outputs:
Verified OK
Do you have any ideas of how it can be possible? What am I doing wrong?
Here is the programme:
SSL_library_init();
OPENSSL_config(nullptr);
SSL_load_error_strings();
OpenSSL_add_all_algorithms();
ERR_load_BIO_strings();
CRYPTO_set_id_callback(ThreadIdFunction);
CRYPTO_set_locking_callback(LockingFunction);
const TString pk = "-----BEGIN EC PRIVATE KEY-----\n"
"MHcCAQEEIG90zmo1o3NWNFa8wp2z4rdQXGSN8xAP/OATLpwlgi+1oAoGCCqGSM49\n"
"AwEHoUQDQgAE5TwpzBhjUWZoOf629GfwGG5WlRJD7TSuz+ZTHUaiK5mj2qgxBOPk\n"
"eqOrTYXsiPwnaWe23zHjIM8NOhAm1BiGgA==\n"
"-----END EC PRIVATE KEY-----\n";
const TString ToSign =
"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhdWQiOiJhc2RmIn0";
EVP_MD_CTX *Ctx = EVP_MD_CTX_create();
BIO * Bio = BIO_new_mem_buf(pk.data(), pk.size());
EVP_PKEY * EVPKey = PEM_read_bio_PrivateKey(Bio, nullptr, nullptr,
nullptr);
EVP_DigestSignInit(Ctx, nullptr, EVP_sha256(), nullptr, EVPKey);
EVP_DigestSignUpdate(Ctx, ToSign.data(), ToSign.size());
size_t SignatureLength;
EVP_DigestSignFinal(Ctx, nullptr, &SignatureLength);
TString Result;
^^^^^^^ You are treating binary data as a string.
Chances are the TString class will truncate at the first byte with
the value zero, and/or do some other text-specific thing that is bad
for binary data.
Result.resize(SignatureLength);
EVP_DigestSignFinal(Ctx, reinterpret_cast<unsigned char
*>(const_cast<char *>(Result.data())), &SignatureLength);
// Saving to file...
Enjoy
Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10
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