Add SGX enclave signing with OpenSSL engine

[svenkata9]

Signed-off-by: Sankaranarayanan Venkatasubramanian sankaranarayanan.venkatasubramanian@intel.com

This adds a plugin gramine-sgx-ossl-sign to core Gramine. This plugin
allows to sign SGX enclaves with private keys stored in a HSM using OpenSSL engine.

See also gramineproject/gsc#139 for additional discussions.

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This change is 

[dimakuv]

Reviewed 1 of 2 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 12 unresolved discussions, not enough approvals from maintainers (2 more required), not enough approvals from different teams (2 more required, approved so far: ), "fixup! " found in commit messages' one-liners (waiting on @svenkata9)

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Integrations/openssl/engine-sign/gramine-sgx-ossl-sign line 20 at r2 (raw file):

def sign_with_ossl_engine(data, engine, key):
    """Signs *data* using *key* from OpenSSL *engine*

Please add a dot at the end.

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Integrations/openssl/engine-sign/gramine-sgx-ossl-sign line 26 at r2 (raw file):

    Suitable to be used as a callback to :py:func:`graminelibos.Sigstruct.sign()`. This function
    requires that a valid OpenSSL engine is installed/enabled, the user has access to the engine and
    a 3072-bit RSA key created in the engine that is enabled for signing. 

Please remove trailing whitespace.

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Integrations/openssl/engine-sign/gramine-sgx-ossl-sign line 54 at r2 (raw file):

    signature_int = int.from_bytes(signature, byteorder='big')

    return exponent_int, modulus_int, signature_int

The code looks reasonable, though I have no experience with OpenSSL Engine API. But from quick googling, looks legit.

As far as this was tested (and it was, by Intel), I'm fine with this implementation.

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Integrations/openssl/engine-sign/README.md line 1 at r2 (raw file):

# Enclave signing with a HSM using OpenSSL engine

an HSM

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Integrations/openssl/engine-sign/README.md line 7 at r2 (raw file):

deployments, you should use a key secured in a Hardware Security Module (HSM).

This directory contains the plugin to Gramine tools and templates that enable

and templates? I think you should just delete these two words.

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Integrations/openssl/engine-sign/README.md line 7 at r2 (raw file):

deployments, you should use a key secured in a Hardware Security Module (HSM).

This directory contains the plugin to Gramine tools and templates that enable

enable -> enables

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Integrations/openssl/engine-sign/README.md line 8 at r2 (raw file):

This directory contains the plugin to Gramine tools and templates that enable
support for production signing of SGX enclaves using keys from a HSM accessible

an HSM

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Integrations/openssl/engine-sign/README.md line 9 at r2 (raw file):

This directory contains the plugin to Gramine tools and templates that enable
support for production signing of SGX enclaves using keys from a HSM accessible
using OpenSSL engine.

Could you give a link to OpenSSL engine description? This one looks the most official: https://www.openssl.org/docs/man1.1.1/man1/openssl-engine.html

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Integrations/openssl/engine-sign/README.md line 13 at r2 (raw file):

## Prerequisites for SGX enclave signing

- OpenSSL engine-based access available for the HSM.

I can't parse this sentence. What does it mean exactly?

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Integrations/openssl/engine-sign/README.md line 15 at r2 (raw file):

- OpenSSL engine-based access available for the HSM.
- 3072-bit RSA private key with a public exponent 3 created in this HSM. Please
  note that only Managed HSM supports setting public exponent.

Please note that only Managed HSM ... -- remnant from Azure KeyVault? This sentence should be removed.

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Integrations/openssl/engine-sign/README.md line 16 at r2 (raw file):

- 3072-bit RSA private key with a public exponent 3 created in this HSM. Please
  note that only Managed HSM supports setting public exponent.
- Tools installed and the user is authenticated to access to the HSM.

Which tools? Is there something more specific that could be said? Or maybe a link to some tutorial which explains how a hardware HSM can be used with OpenSSL Engine?

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Integrations/openssl/engine-sign/README.md line 20 at r2 (raw file):

## Running

The command to sign the enclave with a HSM using OpenSSL engine looks like this:

with an HSM

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Integrations/openssl/engine-sign/README.md line 29 at r2 (raw file):

where `sgx_sign_key` is the name of the RSA private key created in the HSM
accessible through the engine `openssl_engine`.

Please remove this empty line.

[svenkata9]

Reviewable status: all files reviewed, 12 unresolved discussions, not enough approvals from maintainers (2 more required), not enough approvals from different teams (2 more required, approved so far: ), "fixup! " found in commit messages' one-liners (waiting on @dimakuv)

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Integrations/openssl/engine-sign/README.md line 7 at r2 (raw file):

Previously, dimakuv (Dmitrii Kuvaiskii) wrote…

and templates? I think you should just delete these two words.

I should have mentioned it. There is this PR in GSC (gramineproject/gsc#112) that enables --template option for signing (with HSMs or user preferred way). I wanted to avoid two PRs (once now and to update readme later), hence added the wording. I have the templates ready and once the template PR gets merged into GSC repo and the ossl engine sign gets merged to contrib, I will just add the templates in a new PR without having to update the readme.

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Integrations/openssl/engine-sign/README.md line 7 at r2 (raw file):

Previously, dimakuv (Dmitrii Kuvaiskii) wrote…

enable -> enables

with templates, and so enables is valid. (please see comment above)

[dimakuv]

Reviewable status: all files reviewed, 11 unresolved discussions, not enough approvals from maintainers (2 more required), not enough approvals from different teams (2 more required, approved so far: ), "fixup! " found in commit messages' one-liners (waiting on @svenkata9)

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Integrations/openssl/engine-sign/README.md line 7 at r2 (raw file):

Previously, svenkata9 (Sankaranarayanan Venkatasubramanian) wrote…

I should have mentioned it. There is this PR in GSC (gramineproject/gsc#112) that enables --template option for signing (with HSMs or user preferred way). I wanted to avoid two PRs (once now and to update readme later), hence added the wording. I have the templates ready and once the template PR gets merged into GSC repo and the ossl engine sign gets merged to contrib, I will just add the templates in a new PR without having to update the readme.

Ok, but please also take my comments in #20 into account (I requested to modify the wording slightly).