Re: Provider: cannot sign with ed25519-like key

Hey Tomas,

I have a working provider that uses a ED25519 key and has the sign 
(OSSL_FUNC_SIGNATURE_DIGEST_SIGN) and verify 
(OSSL_FUNC_SIGNATURE_DIGEST_VERIFY) methods implemented to use the 
ed25519ph algorithm.

Difference between this POC and my current implementation is that I need 
a ED25519 key with a different OID, thus implementing the encoder and 
decoder myself.

Do you have any idea what the error message means in this regard?

 > error:030000A7:digital envelope routines::unknown max size

The key looks exactly the same when I compare the ASN1dump with a 
originally created ED25519 key. Maybe the decoder is wrong somewhere? 
Hope you have any hint.

Cheers,
Bernd

Am 06.08.24 um 09:26 schrieb Tomas Mraz:
> Hello Bernd,
> 
> the EdDSA implementation in the default provider currently does not
> support the streaming operation with Update, Update,..., Final. It
> could be supported for the prehash variant but currently this is not
> implemented.
> 
> Tomas Mraz, OpenSSL
> 
> On Tue, 2024-08-06 at 08:57 +0200, 'Bernd Ritter' via openssl-users
> wrote:
>> Hello everyone,
>>
>> I am writing a custom provider which uses a different OID for ED25519
>> but internally uses this cipher. I'm now stuck on the signing for
>> weeks.
>>
>> The private and public key look identical except for the OID when
>> compared to a ED25519-key created by the default provider. This is
>> the
>> logging output I see, when I run into the problem with
>>
>> The used md_ctx is built up in the
>> OSSL_FUNC_signature_digest_sign_init_fn. Shortened for readability:
>>
>> ####################################################################
>> static int digest_sign_init(void *ctx, const char *mdname, void
>> *provkey, const OSSL_PARAM *params)
>> {
>>     sig_ctx *sigctx = (sig_ctx*) ctx;
>>
>>     EVP_PKEY *pkey = (EVP_PKEY*) provkey;
>>     EVP_PKEY_CTX* pkey_ctx = EVP_PKEY_CTX_new_from_pkey(NULL, pkey,
>> "provider=default");
>>
>>     EVP_MD_CTX* dflt_md_ctx = EVP_MD_CTX_new();
>>     EVP_MD_CTX_set_pkey_ctx(dflt_md_ctx, pkey_ctx);
>>
>>     // These two are checked in their return code but omitted here
>>     EVP_DigestSignInit_ex(dflt_md_ctx, NULL, NULL, NULL, NULL, pkey,
>> params));
>>     EVP_PKEY_CTX_ctrl_str(pkey_ctx, "instance", "ed25519ph");
>>
>>     sigctx->md_ctx = dflt_md_ctx;
>>
>>     return 1;
>> }
>> ####################################################################
>>
>> The digest-sign function is implemented as
>> OSSL_FUNC_signature_digest_sign_update_fn digest_sign_update:
>>
>> ####################################################################
>> static int digest_sign_update(void *ctx, const unsigned char *data,
>> size_t datalen)
>> {
>>     DBG("%s - digest sign update. datalen=%lu\n", __FILE__, datalen);
>>     sig_ctx *sigctx = (sig_ctx*) ctx;
>>
>>     // Just to see if we have a valid key
>>     EVP_PKEY* pkey =
>> EVP_PKEY_CTX_get0_pkey(EVP_MD_CTX_get_pkey_ctx(sigctx->md_ctx));
>>     DBG("%s - Public Key Context: %s, size:%d\n", __FILE__,
>> EVP_PKEY_get0_description(pkey), EVP_PKEY_get_size(pkey));
>>
>>     const int rc = EVP_DigestSignUpdate(sigctx->md_ctx, data,
>> datalen);
>>     if (rc != 1) {
>>       DBG("%s - digest sign update failed rc=%d. %s\n", __FILE__, rc,
>> ERR_error_string(ERR_get_error(), NULL));
>>     }
>>
>>     return rc;
>> }
>> ####################################################################
>>
>> So this is now the resulting log messages:
>>
>> ####################################################################
>> operating switch: 12 (1=DIGEST, 2=CIPHER, 5=RAND, 10=KEYMGMT, 12=SIG,
>> 20=ENC, 21=DEC, 22=STOR)
>> /src/ed25519ph_sign_x509.c - d
>> /src/ed25519ph_sign_x509.c - digest sign update. datalen=29
>> /src/ed25519ph_sign_x509.c - Public Key Context: OpenSSL ED25519
>> implementation, size:64
>> /src/ed25519ph_sign_x509.c - digest sign update failed rc=0.
>> error:030000A7:digital envelope routines::unknown max size
>> Error signing raw input data
>> Public Key operation error
>> 804B6635217A0000:error:030C0101:digital envelope
>> routines:EVP_DigestSignUpdate:called a function you should not
>> call:crypto/evp/m_sigver.c:420:
>> ####################################################################
>>
>> What does "unknown max size" mean in this context? The (custom)
>> public
>> key can be worked on with EVP_PKEY_print_public so it seems correct-
>> (ish)?
>>
>> ####################################################################
>> ED25519 Public-Key:
>> pub:
>>       86:f1:df:8f:7c:d1:51:b1:8d:b8:bf:4c:d7:e3:28:
>>       b3:1c:d6:1a:66:2a:00:2b:e8:34:18:bb:c4:e8:82:
>>       f5:d1
>> ####################################################################
>>
>> Hope anyone can give me some hint or direction, as said above I am
>> trying to figure this out for some weeks now.
>>
>> This message has been posted to OpenSSL github discussion board as
>> well,
>> it has nicer formatting if you like:
>> https://github.com/openssl/openssl/discussions/25050
>>
>> All the best,
>> Bernd
>>
>> -- 
>> Bernd Ritter
>> Senior Linux Developer
>> Tel.: +49 175 534 4534
>> Mail: ritter-shG/GajIFYqbacvFa/[email protected]
>>
>> B1 Systems GmbH
>> Osterfeldstraße 7 / 85088 Vohburg / http://www.b1-systems.de
>> GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt, HRB
>> 3537
>>
> 

-- 
Bernd Ritter
Senior Linux Developer
Tel.: +49 175 534 4534
Mail: ritter-shG/GajIFYqbacvFa/[email protected]

B1 Systems GmbH
Osterfeldstraße 7 / 85088 Vohburg / http://www.b1-systems.de
GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt, HRB 3537

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