Adding this prefix to digest_info_der is required if you are using
RSA_PKCS1_PADDING for signature padding. It is just binary representation of
ASN.1 encoded values for "SHA1WithRSA" signing algorithm, so if you are not
using RSA_PKCS1_PADDING padding for signature then it looks like you don't need
this prefix.
----- Original Message -----
> 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 3:36:23 AM
> Subject: Re: [TrouSerS-users] Verifying a signature using public key
> from X509 certificate
> 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.
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> > > > > > > > _______________________________________________
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > > TrouSerS-users mailing list
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > > [email protected]
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > > https://lists.sourceforge.net/lists/listinfo/trousers-users
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > ------------------------------------------------------------------------------
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > Transform Data into Opportunity.
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> > >
> >
>
> > > > > > > http://makebettercode.com/inteldaal-eval
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > _______________________________________________
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > TrouSerS-users mailing list
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > [email protected]
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > > https://lists.sourceforge.net/lists/listinfo/trousers-users
> > > > > >
> > > > >
> > > >
> > >
> >
>
> > > > > > ------------------------------------------------------------------------------
> > > > >
> > > >
> > >
> >
>
> > > > > > Transform Data into Opportunity.
> > > > >
> > > >
> > >
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> > > > > > Accelerate data analysis in your applications with
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> > > > > > _______________________________________________
> > > > >
> > > >
> > >
> >
>
> > > > > > TrouSerS-users mailing list
> > > > >
> > > >
> > >
> >
>
> > > > > > [email protected]
> > > > >
> > > >
> > >
> >
>
> > > > > > https://lists.sourceforge.net/lists/listinfo/trousers-users
> > > > >
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> > >
> >
>
> > > > > ------------------------------------------------------------------------------
> > > >
> > >
> >
>
> > > > > Transform Data into Opportunity.
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> > > > > _______________________________________________
> > > >
> > >
> >
>
> > > > > TrouSerS-users mailing list
> > > >
> > >
> >
>
> > > > > [email protected]
> > > >
> > >
> >
>
> > > > > https://lists.sourceforge.net/lists/listinfo/trousers-users
> > > >
> > >
> >
>
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