# Step by step to generate sample self-signed X.509 certificate chain and sign data with PKCS7 structure

This readme demonstrates how to generate 3-layer X.509 certificate chain (RootCA
-> IntermediateCA -> SigningCert) with OpenSSL commands, and user MUST set a
UNIQUE Subject Name ("Common Name") on these three different certificates.

## How to generate a self-signed X.509 certificate chain via OPENSSL

### Set OPENSSL environment

NOTE: Below steps are required for Windows. Linux may already have the OPENSSL
environment correctly.

```cmd
set OPENSSL_HOME=c:\home\openssl\openssl-[version]
set OPENSSL_CONF=%OPENSSL_HOME%\apps\openssl.cnf
```

When a user uses OpenSSL (req or ca command) to generate the certificates,
OpenSSL will use the openssl.cnf file as the configuration data (can use
"-config path/to/openssl.cnf" to describe the specific config file).

The user need check the openssl.cnf file, to find your CA path setting, e.g.
check if the path exists in [ CA_default ] section.

```inf
[ CA_default ]
    dir = ./demoCA              # Where everything is kept
```

You may need the following steps for initialization:

```cmd
rd ./demoCA /S/Q
mkdir ./demoCA
echo.>./demoCA/index.txt
echo 01 > ./demoCA/serial
mkdir ./demoCA/newcerts
```

OpenSSL will apply the options from the specified sections in openssl.cnf when
creating certificates or certificate signing requests. Make sure your
configuration in `openssl.cnf` is correct and rational for certificate
constraints. The following sample sections were used when generating test
certificates in this readme.

``` inf
[ req ]
default_bits        = 2048
default_keyfile     = privkey.pem
distinguished_name  = req_distinguished_name
attributes          = req_attributes
x509_extensions     = v3_ca       # The extensions to add to the self signed cert
...
[ v3_ca ]
# Extensions for a typical Root CA.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid:always,issuer
basicConstraints = critical,CA:true
keyUsage = critical, digitalSignature, cRLSign, keyCertSign
...
[ v3_intermediate_ca ]
# Extensions for a typical intermediate CA.
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true
keyUsage = critical, digitalSignature, cRLSign, keyCertSign
...
[ usr_cert ]
# Extensions for user end certificates.
basicConstraints = CA:FALSE
nsCertType = client, email
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
keyUsage = critical, nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage = clientAuth, emailProtection
...
```

### Generate the certificate chain

NOTE: User MUST set a UNIQUE "Common Name" on the different certificate

1) Generate the Root Pair:

    * Generate a root key:

        ```cmd
        openssl genrsa -aes256 -out TestRoot.key 2048
        ```

    * Generate a self-signed root certificate:

        ```cmd
        openssl req -extensions v3_ca -new -x509 -days 3650 -key TestRoot.key -out TestRoot.crt
        openssl x509 -in TestRoot.crt -out TestRoot.cer -outform DER
        openssl x509 -inform DER -in TestRoot.cer -outform PEM -out TestRoot.pub.pem
        ```

2) Generate the Intermediate Pair:

    * Generate the intermediate key:

        ```cmd
        openssl genrsa -aes256 -out TestSub.key 2048
        ```

    * Generate the intermediate certificate:

        ```cmd
        openssl req -new -days 3650 -key TestSub.key -out TestSub.csr
        openssl ca -extensions v3_intermediate_ca -in TestSub.csr -days 3650 -out TestSub.crt -cert TestRoot.crt -keyfile TestRoot.key
        openssl x509 -in TestSub.crt -out TestSub.cer -outform DER
        openssl x509 -inform DER -in TestSub.cer -outform PEM -out TestSub.pub.pem
        ```

3) Generate User Key Pair for Data Signing:

    * Generate User key:

        ```cmd
        openssl genrsa -aes256 -out TestCert.key 2048
        ```

    * Generate User certificate:

        ```cmd
        openssl req -new -days 3650 -key TestCert.key -out TestCert.csr
        openssl ca -extensions usr_cert -in TestCert.csr -days 3650 -out TestCert.crt -cert TestSub.crt -keyfile TestSub.key
        openssl x509 -in TestCert.crt -out TestCert.cer -outform DER
        openssl x509 -inform DER -in TestCert.cer -outform PEM -out TestCert.pub.pem
        ```

    * Convert Key and Certificate for signing
        Password is removed with -nodes flag for convenience in this sample.

        ```cmd
        openssl pkcs12 -export -out TestCert.pfx -inkey TestCert.key -in TestCert.crt
        openssl pkcs12 -in TestCert.pfx -nodes -out TestCert.pem
        ```

## Verify Data Signing & Verification with new X.509 Certificate Chain

1) Sign a Binary File to generate a detached PKCS7 signature:

    ```cmd
    openssl smime -sign -binary -signer TestCert.pem -outform DER -md sha256 -certfile TestSub.pub.pem -out test.bin.p7 -in test.bin
    ```

2) Verify PKCS7 Signature of a Binary File:

    ```cmd
    openssl smime -verify -inform DER -in test.bin.p7 -content test.bin -CAfile TestRoot.pub.pem -out test.org.bin
    ```

## Generate DSC PCD include files for Certificate

The `BinToPcd` utility can be used to convert the binary Certificate file to a
text file can be included from a DSC file to set a PCD to the contents of the
Certificate file.

The following 2 PCDs can be set to the PKCS7 Certificate value.  The first one
supports a single certificate.  The second one supports multiple certificate
values using the XDR format.

* `gEfiSecurityPkgTokenSpaceGuid.PcdPkcs7CertBuffer`
* `gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr`

### Generate DSC PCD include files

```cmd
BinToPcd.py -i TestRoot.cer -p gEfiSecurityPkgTokenSpaceGuid.PcdPkcs7CertBuffer -o TestRoot.cer.gEfiSecurityPkgTokenSpaceGuid.PcdPkcs7CertBuffer.inc
BinToPcd.py -i TestRoot.cer -p gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr -x -o TestRoot.cer.gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr.inc
```

These files can be used in `!include` statements in DSC file PCD sections.  For
example:

* Platform scoped fixed at build PCD section

    ```edk2_dsc
    [PcdsFixedAtBuild]
    !include BaseTools/Source/Python/Pkcs7Sign/TestRoot.cer.gEfiSecurityPkgTokenSpaceGuid.PcdPkcs7CertBuffer.inc
    ```

* Platform scoped patchable in module PCD section

    ```edk2_dsc
    [PcdsPatchableInModule]
    !include BaseTools/Source/Python/Pkcs7Sign/TestRoot.cer.gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr.inc
    ```

* Module scoped fixed at build PCD section

    ```edk2_dsc
    [Components]
    FmpDevicePkg/FmpDxe/FmpDxe.inf {
        <PcdsFixedAtBuild>
        !include BaseTools/Source/Python/Pkcs7Sign/TestRoot.cer.gFmpDevicePkgTokenSpaceGuid.PcdFmpDevicePkcs7CertBufferXdr.inc
    }
    ```