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@anicet
Last active January 20, 2023 16:20
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PKeyRSAConverter: RSAKeyValue .NET XML to RSA PEM (and RSA PEM to RSAKeyValue .NET XML)
require 'openssl'
require 'base64'
require 'rexml/document'
class PKeyRSAConverter
def initialize(from_pem: nil, from_xml: nil)
@from_pem = from_pem
@from_xml = from_xml
end
def to_xml
xml = '<RSAKeyValue>'
xml += "<Modulus>#{xml_base64(xml_pkey.n)}</Modulus>"
xml += "<Exponent>#{xml_base64(xml_pkey.e)}</Exponent>"
xml += '</RSAKeyValue>'
xml
end
def to_pem
pem_key.to_pem
end
private
def pem_key
exponent = xml_find_exponent.to_s
modulus = xml_find_modulus.to_s
key = OpenSSL::PKey::RSA.new
key.set_key(pem_base64(modulus), pem_base64(exponent), nil)
key
end
def xml_find_modulus
REXML::XPath.match(xml_document.root, '//RSAKeyValue/Modulus/text()')[0]
end
def xml_find_exponent
REXML::XPath.match(xml_document.root, '//RSAKeyValue/Exponent/text()')[0]
end
def xml_document
@xml_document ||= REXML::Document.new(@from_xml.to_s)
end
def pem_base64(string)
Base64.urlsafe_decode64(string).bytes.inject(0) { |a, e| (a << 8) | e }
end
def xml_pkey
@xml_pkey ||= OpenSSL::PKey::RSA.new(@from_pem)
end
def xml_base64(int)
Base64.encode64([int.to_s(16).downcase].pack('H*')).split("\n").join
end
end
# Example
rsa_xml = '<RSAKeyValue><Modulus>lg6UHw38R0kv2eoSxE0X42j/1CSY9pf/HGk+V5lNM2BqRORSWbJk+53x4QaxpfucuChUXf3NOtd6DiEh5pawCw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>'
rsa_pem = "-----BEGIN PUBLIC KEY-----\nMFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJYOlB8N/EdJL9nqEsRNF+No/9QkmPaX\n/xxpPleZTTNgakTkUlmyZPud8eEGsaX7nLgoVF39zTrXeg4hIeaWsAsCAwEAAQ==\n-----END PUBLIC KEY-----\n"
puts 'Convert PEM to XML'
to_xml = PKeyRSAConverter.new(from_pem: rsa_pem).to_xml
puts to_xml == rsa_xml
puts 'Convert XML to PEM'
to_pem = PKeyRSAConverter.new(from_xml: rsa_xml).to_pem
puts rsa_pem == to_pem
@anicet
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anicet commented Feb 25, 2022

I have no idea why I did this @xiaoronglv, but thanks !
Code updated.

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