Chilkat2-Python

Duplicate openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

See more OpenSSL Examples

Demonstrates how to duplicate this OpenSSL command:

openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

This command creates 2 files:

1. mydomain.csr: this is the file to send to DigiCert or Let's Encrypt (or any other CA)
2. mydomain.pem: this is the private key of the domain.

The second file is needed to pair with the certificate that will later be received from the CA.

Chilkat2-Python

import sys
import chilkat2

success = False

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

rsa = chilkat2.Rsa()

# Generate a 2048-bit key.  Chilkat RSA supports
# key sizes ranging from 512 bits to 8192 bits.
privKey = chilkat2.PrivateKey()
success = rsa.GenKey(2048,privKey)
if (success == False):
    print(rsa.LastErrorText)
    sys.exit()

rsa.UsePrivateKey(privKey)

# Save the private key to unencrypted PKCS8 PEM
success = privKey.SavePkcs8PemFile("mydomain.pem")

# (alternatively) Save the private key to encrypted PKCS8 PEM
success = privKey.SavePkcs8EncryptedPemFile("myPassword","mydomain_enc.pem")

# We'll need the private key's modulus for the CSR.
# The modulus is not something that needs to be protected.  Most people don't realize
# that a public key is actually just a subset of the private key.  The public parts of
# an RSA private key are the modulus and exponent.  The exponent is always 65537.
privKeyXml = chilkat2.Xml()
success = privKeyXml.LoadXml(privKey.GetXml())

# Get the modulus in base64 format:
keyModulus = privKeyXml.GetChildContent("Modulus")

# --------------------------------------------------------------------------------
# Now build the CSR using Chilkat's ASN.1 API.
# The keyModulus will be embedded within the ASN.1.

# A new ASN.1 object is automatically a SEQUENCE.
# Given that the CSR's root item is a SEQUENCE, we can use
# this as the root of our CSR.
asnRoot = chilkat2.Asn()

# Beneath the root, we have a SEQUENCE (the certificate request info), 
# another SEQUENCE (the algorithm identifier), and a BITSTRING (the signature data)

success = asnRoot.AppendSequence()
success = asnRoot.AppendSequence()

# ----------------------------------
# Build the Certificate Request Info
# ----------------------------------
# asnCertReqInfo is a CkAsn
asnCertReqInfo = asnRoot.GetSubItem(0)
success = asnCertReqInfo.AppendInt(0)

# Build the Subject part of the Certificate Request Info
# asnCertSubject is a CkAsn
asnCertSubject = asnCertReqInfo.AppendSequenceR()

# Add each subject part..
# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
# AppendSequence2 updates the internal reference to the newly appended SEQUENCE.
# The OID and printable string are added to the SEQUENCE.
success = asnTemp.AppendOid("2.5.4.6")
success = asnTemp.AppendString("printable","US")

# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
success = asnTemp.AppendOid("2.5.4.8")
success = asnTemp.AppendString("utf8","Utah")

# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
success = asnTemp.AppendOid("2.5.4.7")
success = asnTemp.AppendString("utf8","Lindon")

# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
success = asnTemp.AppendOid("2.5.4.10")
success = asnTemp.AppendString("utf8","DigiCert Inc.")

# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
success = asnTemp.AppendOid("2.5.4.11")
success = asnTemp.AppendString("utf8","DigiCert")

# asnTemp is a CkAsn
asnTemp = asnCertSubject.AppendSetR()
success = asnTemp.AppendSequence2()
success = asnTemp.AppendOid("2.5.4.3")
success = asnTemp.AppendString("utf8","example.digicert.com")

# Build the Public Key Info part of the Certificate Request Info
# asnPubKeyInfo is a CkAsn
asnPubKeyInfo = asnCertReqInfo.AppendSequenceR()

# asnPubKeyAlgId is a CkAsn
asnPubKeyAlgId = asnPubKeyInfo.AppendSequenceR()
success = asnPubKeyAlgId.AppendOid("1.2.840.113549.1.1.1")
success = asnPubKeyAlgId.AppendNull()

# The public key itself is a BIT STRING, but the bit string is composed of ASN.1
# for the RSA public key.  We'll first build the RSA ASN.1 for the public key
# (containing the 2048 bit modulus and exponent), and encoded it to DER, and then add
# the DER bytes as a BIT STRING (as a sub-item of asnPubKeyInfo)

# This is already a SEQUENCE..
asnRsaKey = chilkat2.Asn()

# The RSA modulus is a big integer.
success = asnRsaKey.AppendBigInt(keyModulus,"base64")
success = asnRsaKey.AppendInt(65537)

rsaKeyDerBase64 = asnRsaKey.GetEncodedDer("base64")

# Now add the RSA key DER as a BIT STRING.
success = asnPubKeyInfo.AppendBits(rsaKeyDerBase64,"base64")

# The last part of the certificate request info is an empty context-specific constructed item
# with a tag equal to 0.
success = asnCertReqInfo.AppendContextConstructed(0)

# Get the DER of the asnCertReqInfo.  
# This will be signed using the RSA private key.
bdDer = chilkat2.BinData()
success = asnCertReqInfo.WriteBd(bdDer)

# Add the signature to the ASN.1
bdSig = chilkat2.BinData()
success = rsa.SignBd(bdDer,"SHA1",bdSig)
success = asnRoot.AppendBits(bdSig.GetEncoded("base64"),"base64")

# ----------------------------------
# Finally, add the algorithm identifier, which is the 2nd sub-item under the root.
# ----------------------------------
# asnAlgId is a CkAsn
asnAlgId = asnRoot.GetSubItem(1)
success = asnAlgId.AppendOid("1.2.840.113549.1.1.5")
success = asnAlgId.AppendNull()

# Write the CSR to a DER encoded binary file:
success = asnRoot.WriteBinaryDer("qa_output/mydomain.csr")
if (success == False):
    print(asnRoot.LastErrorText)
    sys.exit()

# It is also possible to get the CSR in base64 format:
csrBase64 = asnRoot.GetEncodedDer("base64")

print("Base64 CSR:")
print(csrBase64)