Alright, i got the verification function to work after changing
guint8 digest_info_der[35] = {0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b,
0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14};
SHA1 (data, data_len, &digest_info_der[15]);
to
guint8 digest_info_der[20];
SHA1 (data, data_len, &digest_info_der[0]);
However, now i am faced with another issue. Is there a way to use
the Tspi_Data_Bind function using the public key from the certificate?
On Fri, Mar 11, 2016 at 4:22 PM, Dmitri Toubelis <
[email protected]> wrote:
> That is the entire purpose of this code - to validate signatures created
> with TPM on a host that does not have TSS libraries installed. Just make
> sure that you use consistent padding.
>
> ------------------------------
>
> *From: *"eye two are" <[email protected]>
> *To: *"Dmitri Toubelis" <[email protected]>
> *Cc: *"Ken Goldman" <[email protected]>,
> [email protected], "David Challener" <
> [email protected]>
> *Sent: *Friday, March 11, 2016 12:24:06 AM
>
> *Subject: *Re: [TrouSerS-users] Verifying a signature using public key
> from X509 certificate
>
> Will it work even if i use Tspi_Hash_Sign to sign my message?
>
> On Fri, Mar 11, 2016 at 12:47 PM, Dmitri Toubelis <
> [email protected]> wrote:
>
>> Same thing - you just extract public key from the certificate and use it
>> to verify signature. You don't need TPM to validate signature and you don't
>> even need TSS - everything can be done in OpenSSL. The key thing to keep in
>> mind is that "verify" == "decrypt_with_public_key" . Here is working
>> example:
>>
>> gboolean
>> ak_crypto_verify_sha1_with_rsa (RSA *rsa, gpointer data, gsize data_len,
>> gpointer sig, gsize sig_len)
>> {
>> g_return_val_if_fail (rsa != NULL, FALSE);
>> g_return_val_if_fail (data != NULL, FALSE);
>> g_return_val_if_fail (data_len > 0, FALSE);
>> g_return_val_if_fail (sig != NULL, FALSE);
>> g_return_val_if_fail (sig_len == 256, FALSE);
>>
>> gboolean ret = FALSE;
>>
>> gsize msg_buf_size = 512;
>> gchar msg_buf[msg_buf_size];
>>
>> /* calculated digest of the provided data */
>> guint8 digest_info_der[35] = {0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
>> 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14};
>> SHA1 (data, data_len, &digest_info_der[15]);
>>
>> /* decrypt signature and remove PKCS#1 v1.5 padding */
>> guint8 digest[256];
>> gsize digest_size = RSA_public_decrypt (sig_len, sig, digest, rsa,
>> RSA_PKCS1_PADDING);
>> if (digest_size == -1) {
>> ERR_error_string_n (ERR_get_error (), msg_buf, sizeof (msg_buf));
>> g_critical (G_STRLOC ": %s", msg_buf);
>> goto done;
>> }
>>
>> if (digest_size == sizeof(digest_info_der) && memcmp
>> (digest_info_der, digest, digest_size) == 0) {
>> ret = TRUE;
>> }
>>
>> done:
>>
>> return ret;
>> }
>>
>> ------------------------------
>>
>> *From: *"eye two are" <[email protected]>
>> *To: *"David Challener" <[email protected]>
>> *Cc: *"Ken Goldman" <[email protected]>,
>> [email protected]
>> *Sent: *Thursday, March 10, 2016 11:27:30 PM
>> *Subject: *Re: [TrouSerS-users] Verifying a signature using public key
>> from X509 certificate
>>
>>
>> I am not trying to verify the certificate though. I am trying to verify a
>> message that was signed using the tpm with the private key generated for
>> the certificate. Is that possible? If so what are the steps required to
>> verify the message using the certificate?
>>
>> On Wed, Mar 9, 2016 at 11:19 AM, David Challener <
>> [email protected]> wrote:
>>
>>> Actually TPM 1.2 *does* verify signatures - but it requires owner auth.
>>> You use one of those CMK commands to do it.
>>> And you *can* load in the public key without loading in the private key
>>> to do it. I have some code around somewhere... I will try to find it
>>> tomorrow....
>>>
>>> On Tue, Mar 8, 2016 at 6:29 PM, Tadd Seiff <[email protected]> wrote:
>>>
>>>> TPM 1.2 doesn't verify signatures, but TSS 1.2 does.
>>>>
>>>> Trousers does all of the verification in software via openssl, it's not
>>>> using the hardware, so this does make sense.
>>>>
>>>> That said, do you even need to load the key? Maybe you can just
>>>> leverage the software? As long as the key you are using meets the PKCSv1.5
>>>> criteria.
>>>>
>>>> To address why your key won't load: I'm not sure you can just
>>>> arbitrarily create keys and load them, the key must be in the SRK
>>>> hierarchy. In other words, the TPM creates keys and TELLS YOU the RSA pub
>>>> key, no the other way around.
>>>>
>>>> -Tadd
>>>>
>>>>
>>>> On Tue, Mar 8, 2016 at 2:43 PM Ken Goldman <[email protected]> wrote:
>>>>
>>>>> On 3/8/2016 3:24 AM, eye two are wrote:
>>>>> > I am trying to verify a signature using a public key from an X509
>>>>> > certificate generated with the tpm engine.
>>>>> >
>>>>>
>>>>> I'm not a trousers expert, but I will note that:
>>>>>
>>>>> 1 - TPM 1.2 cannot do signature verification.
>>>>>
>>>>> 2- With TPM 1.2, one cannot load a key unless you have both the public
>>>>> and (wrapped) private part.
>>>>>
>>>>> Could #2 be related to your problem?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> Transform Data into Opportunity.
>>>>> Accelerate data analysis in your applications with
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>>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------------------
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>>>>
>>>
>>>
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>>
>>
>> ------------------------------------------------------------------------------
>> Transform Data into Opportunity.
>> Accelerate data analysis in your applications with
>> Intel Data Analytics Acceleration Library.
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>>
>>
>
>
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