Author: Zbigniew Kurzynski zbigniew.kurzynski@intel.com
Created: May 8, 2020
Related documents:
With help of this guidebook you should be able to create both client and server certificates signed by a CA that can be used to authenticate user requests to an OpenBMC server. You will also learn how to enable and test the OpenBMC TLS authentication.
For a certificate to be marked as valid, it (and every certificate in the chain) has to meet these conditions:
KeyUsage contains required purpose digitalSignature and keyAgreement (see rfc 3280 4.2.1.3)ExtendedKeyUsage contains required purpose clientAuth for client certificate and serverAuth for server certificate (see rfc 3280 4.2.1.13)notBefore and notAfter fields have to contain valid timeIf you already have certificates you can skip to Enable TLS authentication or go to Verify certificates and check if they meet the above requirements.
To generate certificates with required parameters some modification must be made to the default openssl configuration file.
First create a new folder named ca and create a configuration file using the default configuration as a template (we do not want to change the original one). The location of the configuration file may vary depending on the operating system. For Ubuntu it is usually /usr/lib/ssl/openssl.cnf, but can also can be at /etc/ssl/openssl.cnf. For Cygwin it might be /etc/defaults/etc/pki/tls/openssl.cnf or /etc/pki/tls/openssl.cnf.
mkdir ~/ca cd ~/ca cp /usr/lib/ssl/openssl.cnf openssl-client.cnf
Then open the client ~/ca/openssl-client.cnf file in your favorite editor, for example vi.
vi ~/ca/openssl-client.cnf
Find the sections listed below and add or choose the presented values.
[ req ] req_extensions = v3_req [ usr_cert ] extendedKeyUsage = clientAuth [ v3_req ] extendedKeyUsage = clientAuth keyUsage = digitalSignature, keyAgreement
Now create a server configuration openssl-server.cnf by copying the client file
cp ~/ca/openssl-client.cnf openssl-server.cnf
and changing values presented in the sections listed below.
[ usr_cert ] extendedKeyUsage = serverAuth [ v3_req ] extendedKeyUsage = serverAuth
Create two additional configuration files myext-client.cnf and myext-server.cnf for the client and server certificates respectively. Without these files no extensions are added to the certificate.
cat << END > myext-client.cnf [ my_ext_section ] keyUsage = digitalSignature, keyAgreement extendedKeyUsage = clientAuth authorityKeyIdentifier = keyid END
cat << END > myext-server.cnf [ my_ext_section ] keyUsage = digitalSignature, keyAgreement extendedKeyUsage = serverAuth authorityKeyIdentifier = keyid END
First we need to create a private key to sign the CA certificate.
openssl genrsa -out CA-key.pem 2048
Now we can create a CA certificate, using the previously generated key. You will be prompted for information which will be incorporated into the certificate, such as Country, City, Company Name, etc.
openssl req -new -config openssl-client.cnf -key CA-key.pem -x509 -days 1000 -out CA-cert.pem
To create a client certificate, a signing request must be created first. For this another private key will be needed.
Generate a new key that will be used to sign the certificate signing request:
openssl genrsa -out client-key.pem 2048
Generate a certificate signing request.
You will be prompted for the same information as during CA generation, but provide the OpenBMC system user name for the CommonName attribute of this certificate. In this example, use root.
openssl req -new -config openssl-client.cnf -key client-key.pem -out signingReqClient.csr
Sign the certificate using your CA-cert.pem certificate with following command:
openssl x509 -req -extensions my_ext_section -extfile myext-client.cnf -days 365 -in signingReqClient.csr -CA CA-cert.pem -CAkey CA-key.pem -CAcreateserial -out client-cert.pem
The file client-cert.pem now contains a signed client certificate.
For convenience we will use the same CA generated in paragraph Create a new CA certificate, although a different one could be used.
Generate a new key that will be used to sign the server certificate signing request:
openssl genrsa -out server-key.pem 2048
Generate a certificate signing request. You will be prompted for the same information as during CA generation, but provide the fully qualified domain name of your OpenBMC server for the CommonName attribute of this certificate. In this example it will be bmc.example.com. A wildcard can be used to protect multiple host, for example a certificate configured for *.example.com will secure www.example.com, as well as mail.example.com, blog.example.com, and others.
openssl req -new -config openssl-server.cnf -key server-key.pem -out signingReqServer.csr
Sign the certificate using your CA-cert.pem certificate with following command:
openssl x509 -req -extensions my_ext_section -extfile myext-server.cnf -days 365 -in signingReqServer.csr -CA CA-cert.pem -CAkey CA-key.pem -CAcreateserial -out server-cert.pem
The file server-cert.pem now contains a signed server certificate.
To verify the signing request and both certificates you can use following commands.
openssl x509 -in CA-cert.pem -text -noout openssl x509 -in client-cert.pem -text -noout openssl x509 -in server-cert.pem -text -noout openssl req -in signingReqClient.csr -noout -text openssl req -in signingReqServer.csr -noout -text
Below are example listings that you can compare with your results. Pay special attention to attributes like:
Issuer in client-cert.pem, it must match to Subject in CA-cert.pem,client-cert.pem it should contain proper values,Public-Key length, it cannot be less than 2048 bits.Subject CN in client-cert.pem, it should match existing OpemBMC user name. In this example it is root.Subject CN in server-cert.pem, it should match OpemBMC host name. In this example it is **bmc.example.com **. (see rfc 3280 4.2.1.11 for name constraints)Below are fragments of generated certificates that you can compare with.
CA-cert.pem
Data:
Version: 3 (0x2)
Serial Number: 16242916899984461675 (0xe16a6edca3c34f6b)
Signature Algorithm: sha256WithRSAEncryption
Issuer: C=US, ST=California, L=San Francisco, O=Intel, CN=Test CA
Validity
Not Before: May 11 11:40:48 2020 GMT
Not After : Feb 5 11:40:48 2023 GMT
Subject: C=US, ST=California, L=San Francisco, O=Intel, CN=Test CA
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:d4:24:c1:1d:ac:85:8c:5b:42:e4:f8:a8:d8:7c:
...
55:83:8b:aa:ac:ac:6e:e3:01:2b:ce:f7:ee:87:21:
f9:2b
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Subject Key Identifier:
ED:FF:80:A7:F8:DA:99:7F:94:35:95:F0:92:74:1A:55:CD:DF:BA:FE
X509v3 Authority Key Identifier:
keyid:ED:FF:80:A7:F8:DA:99:7F:94:35:95:F0:92:74:1A:55:CD:DF:BA:FE
X509v3 Basic Constraints:
CA:TRUE
Signature Algorithm: sha256WithRSAEncryption
cc:8b:61:6a:55:60:2b:26:55:9f:a6:0c:42:b0:47:d4:ec:e0:
...
45:47:91:62:10:bd:3e:a8:da:98:33:65:cc:11:23:95:06:1b:
ee:d3:78:84
client-cert.pem
Data:
Version: 3 (0x2)
Serial Number: 10150871893861973895 (0x8cdf2434b223bf87)
Signature Algorithm: sha256WithRSAEncryption
Issuer: C=US, ST=California, L=San Francisco, O=Intel, CN=Test CA
Validity
Not Before: May 11 11:42:58 2020 GMT
Not After : May 11 11:42:58 2021 GMT
Subject: C=US, ST=California, L=San Francisco, O=Intel, CN=root
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:cf:d6:d0:a2:09:62:df:e9:a9:b1:e1:3d:7f:2f:
...
30:7b:48:dc:c5:2c:3f:a9:c0:d1:b6:04:d4:1a:c8:
8a:51
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage:
Digital Signature, Key Agreement
X509v3 Extended Key Usage:
TLS Web Client Authentication
X509v3 Authority Key Identifier:
keyid:ED:FF:80:A7:F8:DA:99:7F:94:35:95:F0:92:74:1A:55:CD:DF:BA:FE
Signature Algorithm: sha256WithRSAEncryption
7f:a4:57:f5:97:48:2a:c4:8e:d3:ef:d8:a1:c9:65:1b:20:fd:
...
25:cb:5e:0a:37:fb:a1:ab:b0:c4:62:fe:51:d3:1c:1b:fb:11:
56:57:4c:6a
server-cert.pem
Data:
Version: 3 (0x2)
Serial Number: 10622848005881387807 (0x936beffaa586db1f)
Signature Algorithm: sha256WithRSAEncryption
Issuer: C=US, ST=z, L=z, O=z, OU=z, CN=bmc.example.com
Validity
Not Before: May 22 13:46:02 2020 GMT
Not After : May 22 13:46:02 2021 GMT
Subject: C=US, ST=z, L=z, O=z, OU=z, CN=bmc.example.com
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:d9:34:9c:da:83:c6:eb:af:8f:e8:11:56:2a:59:
...
92:60:09:fc:f9:66:82:d0:27:03:44:2f:9d:6d:c0:
a5:6d
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage:
Digital Signature, Key Agreement
X509v3 Extended Key Usage:
TLS Web Server Authentication
X509v3 Authority Key Identifier:
keyid:5B:1D:0E:76:CC:54:B8:BF:AE:46:10:43:6F:79:0B:CA:14:5C:E0:90
Signature Algorithm: sha256WithRSAEncryption
bf:41:e2:2f:87:44:25:d8:54:9c:4e:dc:cc:b3:f9:af:5a:a3:
...
ef:0f:90:a6
The CA certificate can be installed via Redfish Service. The file CA-cert.pem can not be uploaded directly but must be sent embedded in a valid JSON string, which requires \, ", and control characters must be escaped. This means all content is placed in a single string on a single line by encoding the line endings as \n. The command below prepares a whole POST body and puts it into a file named: install_ca.json.
cat << END > install_ca.json
{
"CertificateString":"$(cat CA-cert.pem | sed -n -e '1h;1!H;${x;s/\n/\\n/g;p;}')",
"CertificateType": "PEM"
}
END
To install the CA certificate on the OpenBMC server post the content of install_ca.json with this command:
Where ${bmc} should be bmc.example.com. It is convenient to export it as an environment variable.
curl --user root:0penBmc -d @install_ca.json -k -H "Content-Type: application/json" -X POST https://${bmc}/redfish/v1/Managers/bmc/Truststore/Certificates
Credentials root:0penBmc can be replaced with any system user name and password of your choice but with proper access rights to resources used here.
After successful certificate installation you should get positive HTTP response and a new certificate should be available under this resource collection.
curl --user root:0penBmc -k https://${bmc}/redfish/v1/Managers/bmc/Truststore/Certificates
An auto-generated self-signed server certificate is already present on OpenBMC by default. To use the certificate signed by our CA it must be replaced. Additionally we must upload to OpenBMC the private key that was used to sign the server certificate. A proper message mody can be prepared the with this command:
cat << END > replace_cert.json
{
"CertificateString":"$(cat server-key.pem server-cert.pem | sed -n -e '1h;1!H;${x;s/\n/\\n/g;p;}')",
"CertificateUri":
{
"@odata.id": "/redfish/v1/Managers/bmc/NetworkProtocol/HTTPS/Certificates/1"
},
"CertificateType": "PEM"
}
END
To replace the server certificate on the OpenBMC server post the content of replace_cert.json with this command:
curl --user root:0penBmc -d @replace_cert.json -k -H "Content-Type: application/json" -X POST https://${bmc}/redfish/v1/CertificateService/Actions/CertificateService.ReplaceCertificate/
To check current state of the TLS authentication method use this command:
curl --user root:0penBmc -k https://${bmc}/redfish/v1/AccountService
and verify that the attribute Oem->OpenBMC->AuthMethods->TLS is set to true.
To enable TLS authentication use this command:
curl --user root:0penBmc -k -X PATCH -H "ContentType:application/json" --data '{"Oem": {"OpenBMC": {"AuthMethods": { "TLS": true} } } }' https://${bmc}/redfish/v1/AccountService
To disable TLS authentication use this command:
curl --user root:0penBmc -k -X PATCH -H "ContentType:application/json" --data '{"Oem": {"OpenBMC": {"AuthMethods": { "TLS": false} } } }' https://${bmc}/redfish/v1/AccountService
Other authentication methods like basic authentication can be enabled or disabled as well using the same mechanism. All supported authentication methods are available under attribute Oem->OpenBMC->AuthMethods of the /redfish/v1/AccountService resource.
If TLS is enabled, valid CA certificate was uploaded and the server certificate was replaced it should be possible to execute curl requests using only client certificate, key, and CA like below.
curl --cert client-cert.pem --key client-key.pem -vvv --cacert CA-cert.pem https://${bmc}/redfish/v1/SessionService/Sessions
Invalid date and time on OpenBMC,
Testing Redfish resources, like https://${bmc}/redfish/v1 which are always available without any authentication will always result with success, even when TLS is disabled or certificates are invalid.
Certificates do not meet the requirements. See paragraphs Verify certificates.
Attempting to load the same certificate twice will end up with an error.
Not having phosphor-bmcweb-cert-config in the build.