OpenSSL 1.0.2k EVP_PKEY decryption failing
Richard Levitte
richard at levitte.org
Tue Mar 28 18:11:27 UTC 2023
You have this:
> OPENSSL_free(encrypted);
just a few lines above this:
> //When I call the below, I gey EVP_PKEY_decrypt error:040A1079:rsa routines:RSA_padding_check_PKCS1_OAEP_mgf1:oaep decoding error
> decrypte(encrypted, encryptedLen);
I would suspect that things will work better if you move the
OPENSSL_free() call to happen after the decode() call.
Cheers,
Richard
On Tue, 28 Mar 2023 18:34:51 +0200,
Viken Kondakji wrote:
>
> Hello,
>
> I am new to openssl.
>
> My objective is to encrypt data using RSA public key, with SHA-256 as hash function and MGF1 as mask generating function.
> To do that, I am using the EVP_PKEY API.
> I seem to be able to encrypt, but when I try to decrypt, I fail, with
> EVP_PKEY_decrypt error:040A1079:rsa routines:RSA_padding_check_PKCS1_OAEP_mgf1:oaep decoding error
>
> My environ:
> $ openssl version -a
> OpenSSL 1.0.2k-fips 26 Jan 2017
> built on: reproducible build, date unspecified
> platform: linux-x86_64
> options: bn(64,64) md2(int) rc4(16x,int) des(idx,cisc,16,int) idea(int) blowfish(idx)
> compiler: gcc -I. -I.. -I../include -fPIC -DOPENSSL_PIC -DZLIB -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DKRB5_MIT -m64 -DL_ENDIAN -Wall -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -Wa,--noexecstack -DPURIFY -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPE
> NSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DRC4_ASM -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM -DWHIRLPOOL_ASM -DGHASH_ASM -DECP_NISTZ256_ASM
> OPENSSLDIR: "/etc/pki/tls"
> engines: dynamic
>
> Code snippet is below.
>
> My issue is, after encryption (assuming what I'm doing is correct), how to I go about decrypting using the EVP_PKEY API and the associated RSA private key?
> Can someone guide me please?
>
> Thanks
> Viken Kondakji
>
>
>
> /* =============================Code Used============================================ */
> int decrypte(unsigned char*, size_t);
>
> void getError(std::array<char,120>& error) {
> ERR_load_crypto_strings();
> ERR_error_string_n(ERR_get_error(), error.data(), error.size());
> }
>
> int padding = RSA_PKCS1_OAEP_PADDING;
>
> EVP_PKEY * createEvpKeyFromFile(const char* theFile, bool publicKey) {
> std::array<char, 120> error;
>
> BIO *bioFile = BIO_new(BIO_s_file());
> if (!BIO_read_filename(bioFile, theFile))
> {
> BIO_free(bioFile);
> getError(error);
> throw std::runtime_error(std::string("Failed to read the file ") +
> theFile + " " + std::string(error.data()));
> }
>
> EVP_PKEY *evpKey= nullptr;
> evpKey = publicKey ? PEM_read_bio_PUBKEY(bioFile, NULL, NULL, NULL)
> : PEM_read_bio_PrivateKey(bioFile, NULL, NULL, NULL);
> BIO_free(bioFile);
> if(!evpKey)
> {
> getError(error);
> throw std::runtime_error(std::string("Failed to create EVP_KEY from the file ")
> + theFile + ' ' + std::string(error.data()));
> }
> return evpKey;
> }
>
> int main(int argc, char* argv[])
> {
> unsigned char plainText[] = "Hello World! Nice to meet you. How are you?";
>
> EVP_PKEY * evpKey = createEvpKeyFromFile("public2048bitsKey.pem", 1);
>
> std::array<char, 120> error;
>
> EVP_PKEY_CTX* ctx = EVP_PKEY_CTX_new(evpKey, NULL);
> if (nullptr == ctx)
> {
> getError(error);
> throw std::runtime_error(std::string("Failed in EVP_PKEY_CTX_new ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_encrypt_init(ctx) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_encrypt_init ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_OAEP_PADDING) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_padding ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_oaep_md(ctx, EVP_sha256()) <=0 )
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_oaep_md ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_mgf1_md(ctx, EVP_sha256()) <=0 )
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_mgf1_md ") + std::string(error.data()));
> }
>
> // Determine encryption buffer length
> size_t encryptedLen {};
> if (EVP_PKEY_encrypt(ctx, NULL, &encryptedLen, plainText, sizeof(plainText)) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("Determine encryption length ") + std::string(error.data()));
> }
> std::cout << "bytes needed to encrypt = " << encryptedLen << '\n';
> unsigned char* encrypted = (unsigned char*) OPENSSL_malloc(encryptedLen);
> if (!encrypted)
> {
> throw std::runtime_error("OPENSSL_malloc failure");
> }
>
> if (EVP_PKEY_encrypt(ctx, encrypted, &encryptedLen, plainText, sizeof(plainText)) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_encrypt failed ") + std::string(error.data()));
> }
>
> int base64LenNeeded = std::ceil(encryptedLen/3.0) * 4;
> std::cout << "base64LenNeeded = " << base64LenNeeded << '\n';
>
> unsigned char base64Encoded[8196];
> size_t base64EncodedLength = EVP_EncodeBlock(base64Encoded, (unsigned char *)encrypted, encryptedLen);
> std::cout << "base64EncodedLength = " << base64EncodedLength << '\n';
> std::cout << "base64Encoded\n" << base64Encoded << '\n';
>
> OPENSSL_free(encrypted);
>
> EVP_PKEY_CTX_free(ctx);
>
> /* encryption seems to be fine. Let's check our work and attempt to decrypt... */
>
> //When I call the below, I gey EVP_PKEY_decrypt error:040A1079:rsa routines:RSA_padding_check_PKCS1_OAEP_mgf1:oaep decoding error
> decrypte(encrypted, encryptedLen);
> return 0;
> }
>
> int decrypte(unsigned char* encrypted, size_t encryptedLen) {
> EVP_PKEY * evpKey = createEvpKeyFromFile("private2048bitsKey.pem", 0);
>
> std::array<char, 120> error;
>
> EVP_PKEY_CTX* ctx = EVP_PKEY_CTX_new(evpKey, NULL);
> if (nullptr == ctx)
> {
> getError(error);
> throw std::runtime_error(std::string("Failed in EVP_PKEY_CTX_new ") + std::string(error.data()));
> }
>
> // initializes a public key algorithm context
> if (EVP_PKEY_decrypt_init(ctx) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_decrypt_init ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_OAEP_PADDING) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_padding ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_oaep_md(ctx, EVP_sha256()) <=0 )
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_oaep_md ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_CTX_set_rsa_mgf1_md(ctx, EVP_sha256()) <=0 )
> {
> getError(error);
> throw std::runtime_error(std::string("EVP_PKEY_CTX_set_rsa_mgf1_md ") + std::string(error.data()));
> }
>
> // determine buffer length
> size_t outLen {};
> size_t privateKeyLen = strlen((const char*)privateKey);
> if (EVP_PKEY_decrypt(ctx, NULL, &outLen, privateKey, privateKeyLen) <= 0)
> {
> getError(error);
> throw std::runtime_error(std::string("determine buffer length in decrypt ") + std::string(error.data()));
> }
> std::cout << "outLen = " << outLen << '\n';
> unsigned char* out = (unsigned char*)OPENSSL_malloc(outLen);
> if(!out)
> {
> throw std::runtime_error(std::string("malloc failed in decrypt ") + std::string(error.data()));
> }
>
> if (EVP_PKEY_decrypt(ctx, out, &outLen, encrypted, encryptedLen) <= 0 ) /* I fail in this call */
> {
> getError(error);
> std::ostringstream os;
> os << "at line #" << __LINE__ << "...EVP_PKEY_decrypt " << error.data();
> throw std::runtime_error(os.str());
> }
>
> return 0;
> }
>
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