der_cert_to_pem_cert function of ssl module in Python

Function Name:

DER_cert_to_PEM_cert

Function Signature:

DER_cert_to_PEM_cert(DER_cert_bytes)

Parameters:

DER_cert_bytes – The digital certificate of a secure machine (client or server) in DER Format.

Overview:

DER is a binary encoding format in which the contents of a X.509 digital certificate are stored.
PEM is a base64 encoding format that encodes the binary DER using ASCII values A-Z, a-z, 0-9, +, / and =.
Each character in a PEM data represents 6 bits of information from the binary data.
To encode three bytes of data PEM encoding takes four sextets (i.e, the six bit units).
The PEM format has header, data and footer parts. Each line of data consists of 64 characters followed by the platform specific whitespace character.
The method DER_cert_to_PEM_cert() converts a X.509 digital certificate in DER format to PEM format.

Converting a digital certificate from DER format to PEM format using ssl module of Python

Example:

# Example Python program that converts a digital certificate

# from DER format to PEM format

import socket

import ssl

import platform

import os

# Function to get the certificate of a host in DER foramt

def getDERCertificate(hostname, port):

# Create a streaming socket

connection = socket.socket(socket.AF_INET, socket.SOCK_STREAM);

# Create a secure socket

secureConnection = securityContext.wrap_socket(connection,

server_hostname=hostname);

# Connect to host

secureConnection.connect((hostname, port));

# Get the certificate from the host

cert = secureConnection.getpeercert(binary_form=True);

return cert;

# Create an SSL context

securityContext = ssl.SSLContext();

securityContext.verify_mode = ssl.CERT_REQUIRED;

securityContext.check_hostname = True;

securityContext.load_default_certs();

# Check for OS X platform

if platform.system().lower() == 'darwin':

import certifi

securityContext.load_verify_locations(

cafile=os.path.relpath(certifi.where()),

capath=None,

cadata=None);

# Get the certificate in DER format

cert_DER = getDERCertificate("example.org", 443);

print("Certificate in DER format:");

print(cert_DER);

# Convert the certificate to PEM format

cert_PEM = ssl.DER_cert_to_PEM_cert(cert_DER);

print("Certificate in PEM format:");

print(cert_PEM);

Output:

Certificate in DER format:

b'0\x82\x07@0\x82\x06(\xa0\x03\x02\x01\x02\x02\x10\x0f\xd0x\xddH\xf1\xa2\xbdM\x0f+\xa9k`8\xfe0\r\x06\t*\x86H\x86\xf7\r\x01\x01\x0b\x05\x000M1\x0b0\t\x06\x03U\x04\x06\x13\x02US1\x150\x13\x06\x03U\x04\n\x13\x0cDigiCert Inc1\'0%\x06\x03U\x04\x03\x13\x1eDigiCert SHA2 Secure Server CA0\x1e\x17\r181128000000Z\x17\r201202120000Z0\x81\xa51\x0b0\t\x06\x03U\x04\x06\x13\x02US1\x130\x11\x06\x03U\x04\x08\x13\nCalifornia1\x140\x12\x06\x03U\x04\x07\x13\x0bLos Angeles1<0:\x06\x03U\x04\n\x133Internet Corporation for Assigned Names and Numbers1\x130\x11\x06\x03U\x04\x0b\x13\nTechnology1\x180\x16\x06\x03U\x04\x03\x13\x0fwww.example.org0\x82\x01"0\r\x06\t*\x86H\x86\xf7\r\x01\x01\x01\x05\x00\x03\x82\x01\x0f\x000\x82\x01\n\x02\x82\x01\x01\x00\xd0\xf0\x12t\xa0\x96 r\x08e\x19\x12Z]J\xd0:\x8cf\x8f\xa0)+\xa7\xdb\xd5\xac\x0c\xcf\xa5q\x92\x15B\x15\xb0\x07\x92v1u\xd7\'\x8eMPju\xd1{S^\'\xaa\xed\xeb\xa4`:\xf2\x8eE\x18kE3\\\x85\x11\xaa \x12\xfe`\xac\x9dLE\x8f\xdd\xd3\x0e>w\x0f\t\xc2\x85e4\xc7"\xfbt\x13\xb9B\x9f\xf7!\xf6\xf0\x9cDtm\xc9\xdf\xb3\x1f\x8f`\xb7q\x11\x06\x90cA\x9d\x8f4{$IF\xac\xf2\xf0\x8d\x0bH\xf4\xd3\x92\x1a\xf7\xa2E\xee\xcc\xe5\xd7\x83\x7f.\x82\xbdq\xdd(\x19X3n\x11\xa1:\xa0jr`\x92\x01Y\x9fc\x17zIB{\x9c?\xdb\xd3\x05\xe8\xcc\x87~\xf8\xaa\xfc\x9d\xd1\x05P\xabu\xb1\x1e\xba \xcb\x89\xd4ml7\x82(L\xc5?|\xc1\x10\xf5\xa0\xa5fkSS\xc9\xdb\xed\x85\xc3m\x05\xf8d\xa7\xc9\x0e\xeb\x8f\xe1\xc4\xb1\xeb-h\x0e\x15?\xe5\xe2\xdc\xfc!d-\xeei+\x04x\xdbwe\xcbT\xf9\x02\x03\x01\x00\x01\xa3\x82\x03\xc10\x82\x03\xbd0\x1f\x06\x03U\x1d#\x04\x180\x16\x80\x14\x0f\x80a\x1c\x821a\xd5/(\xe7\x8dF8\xb4,\xe1\xc6\xd9\xe20\x1d\x06\x03U\x1d\x0e\x04\x16\x04\x14f\x98b\x02\xe0\t\x91\xa7\xd9\xe36\xfbv\xc6\xb0\xbf\xa1m\xa7\xbe0\x81\x81\x06\x03U\x1d\x11\x04z0x\x82\x0fwww.example.org\x82\x0bexample.com\x82\x0bexample.edu\x82\x0bexample.net\x82\x0bexample.org\x82\x0fwww.example.com\x82\x0fwww.example.edu\x82\x0fwww.example.net0\x0e\x06\x03U\x1d\x0f\x01\x01\xff\x04\x04\x03\x02\x05\xa00\x1d\x06\x03U\x1d%\x04\x160\x14\x06\x08+\x06\x01\x05\x05\x07\x03\x01\x06\x08+\x06\x01\x05\x05\x07\x03\x020k\x06\x03U\x1d\x1f\x04d0b0/\xa0-\xa0+\x86)http://crl3.digicert.com/ssca-sha2-g6.crl0/\xa0-\xa0+\x86)http://crl4.digicert.com/ssca-sha2-g6.crl0L\x06\x03U\x1d \x04E0C07\x06\t`\x86H\x01\x86\xfdl\x01\x010*0(\x06\x08+\x06\x01\x05\x05\x07\x02\x01\x16\x1chttps://www.digicert.com/CPS0\x08\x06\x06g\x81\x0c\x01\x02\x020|\x06\x08+\x06\x01\x05\x05\x07\x01\x01\x04p0n0$\x06\x08+\x06\x01\x05\x05\x070\x01\x86\x18http://ocsp.digicert.com0F\x06\x08+\x06\x01\x05\x05\x070\x02\x86:http://cacerts.digicert.com/DigiCertSHA2SecureServerCA.crt0\x0c\x06\x03U\x1d\x13\x01\x01\xff\x04\x020\x000\x82\x01\x7f\x06\n+\x06\x01\x04\x01\xd6y\x02\x04\x02\x04\x82\x01o\x04\x82\x01k\x01i\x00w\x00\xa4\xb9\t\x90\xb4\x18X\x14\x87\xbb\x13\xa2\xccgp\n<5\x98\x04\xf9\x1b\xdf\xb8\xe3w\xcd\x0e\xc8\r\xdc\x10\x00\x00\x01g\\1\x95F\x00\x00\x04\x03\x00H0F\x02!\x00\x84d\x81\xb7!\x1d\xfa\x1aH\xf5v\xaeK\xe8F\x86W\'\x17\xb0{\xe9;\xb7JWBl\xa2\x84\xc4l\x02!\x00\xbb\x93\xb5\xfe0\xc4d\xe4\x16L|nXSW\xee\xec\x7f\xaaEO\xbf\x0eF\x8e\xfep\xfd\xfd\x8eBB\x00v\x00\x87u\xbf\xe7Y|\xf8\x8cC\x99_\xbd\xf3n\xffV\x8dGV6\xffJ\xb5`\xc1\xb4\xea\xff^\xa0\x83\x0f\x00\x00\x01g\\1\x96\x15\x00\x00\x04\x03\x00G0E\x02 o\xaaw\xd2\x1c\xa7\x94\xc0c-.\xb3\x86\xddA\x8b@\x8a\x1a/\x7f\xaef\xc1\x93_s\x1fH\x93P\x11\x02!\x00\xd2\xf9\x9dH\x86\x05\x1e\xa0\x97D%\x0b<\xea\xce\xfa+\x19|\x81\xff\'{\x9e\xdbX\xb6\xdc\xe8\xf0JN\x00v\x00oSv\xac1\xf01\x19\xd8\x99\x00\xa4Q\x15\xffw\x15\x1c\x11\xd9\x02\xc1\x00)\x06\x8d\xb2\x08\x9a7\xd9\x13\x00\x00\x01g\\1\x96\x9c\x00\x00\x04\x03\x00G0E\x02!\x00\xe4y\xfbC\x84\x8e\xca\xa1\xe4O\xe9\x03\xb0z\xbb\x92\xee\xf3D;\x8c\xec\xfe\x14\r}\x9f\xb7c)\x9f-\x02 MwZ\xdcI\x01J\xf4h\x04\x85a\x9f\xd7\x8d \x0c1\xfa\xc1\xd3\xf4q\n[\xd6V\xcb=,r\x8c0\r\x06\t*\x86H\x86\xf7\r\x01\x01\x0b\x05\x00\x03\x82\x01\x01\x00sp\x85\xef@A\xa7jC\xd5x\x9c{UH\xe6\xbck\x99\x86\xba\xfb\r\x03\x8bx\xfe\x11\xf0)\xa0\x0c\xcdi\x14\x0b\xc6\x04x\xb2\xce\xf0\x87\xd5\x01\x9d\xc4Yzq\xfe\xf0n\x9e\xc1\xa0\xb0\x91-\x1f\xea=U\xc53\x05\x0c\xcd\xc15\x18\xb0jhfL\xbfV!\xda[\xd9H\xb9\x8c5!\x91]\xdcu\xd7zF,"\'\xa6o\xd3:\x17\xeb\xbe\xbd\x13\xc5\x12&s\xc0]\xa35\x89j\xfb\'\xd4\xdd\xaatt.7\xe5\x01;\xa6\xd00\xb0\x83\xd0\xa1\xc4u!\x85\xb2\xe5\xfag\x000\xa2\xbcS\x83M\xbf\xd6\xa8\x83\xbb\xbc\xd6\xed\x1c\xb3\x1e\xf1X\x03\x82\x00\x8e\x9c\xef\x90\xf2\x1a_\xa2\xa3\x06\xda]\xbe\x9f\xda]\xa6\xe6/\xdeX\x80\x18\xd3\xf1b{\xa6\xa3\x9f\xae\xa8irc\x81e\xae\x82\x83\xa3\xb5\x97\x8a\x9b Q\xff\x1a?a@\x1eH\xd0k8\xf9\xe1\xfa\x17\xd8wJ\x88\xe6=6$O\xef\n\xb9\x9fp\xf3\x83\'\xf8\xcf*\x05u\x10\xa1\x8a\n\x80\x88\xcd'

Certificate in PEM format:

-----BEGIN CERTIFICATE-----

MIIHQDCCBiigAwIBAgIQD9B43Ujxor1NDyupa2A4/jANBgkqhkiG9w0BAQsFADBN

MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMScwJQYDVQQDEx5E

aWdpQ2VydCBTSEEyIFNlY3VyZSBTZXJ2ZXIgQ0EwHhcNMTgxMTI4MDAwMDAwWhcN

MjAxMjAyMTIwMDAwWjCBpTELMAkGA1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3Ju

aWExFDASBgNVBAcTC0xvcyBBbmdlbGVzMTwwOgYDVQQKEzNJbnRlcm5ldCBDb3Jw

b3JhdGlvbiBmb3IgQXNzaWduZWQgTmFtZXMgYW5kIE51bWJlcnMxEzARBgNVBAsT

ClRlY2hub2xvZ3kxGDAWBgNVBAMTD3d3dy5leGFtcGxlLm9yZzCCASIwDQYJKoZI

hvcNAQEBBQADggEPADCCAQoCggEBANDwEnSgliByCGUZElpdStA6jGaPoCkrp9vV

rAzPpXGSFUIVsAeSdjF11yeOTVBqddF7U14nqu3rpGA68o5FGGtFM1yFEaogEv5g

rJ1MRY/d0w4+dw8JwoVlNMci+3QTuUKf9yH28JxEdG3J37Mfj2C3cREGkGNBnY80

eyRJRqzy8I0LSPTTkhr3okXuzOXXg38ugr1x3SgZWDNuEaE6oGpyYJIBWZ9jF3pJ

QnucP9vTBejMh374qvyd0QVQq3WxHrogy4nUbWw3gihMxT98wRD1oKVma1NTydvt

hcNtBfhkp8kO64/hxLHrLWgOFT/l4tz8IWQt7mkrBHjbd2XLVPkCAwEAAaOCA8Ew

ggO9MB8GA1UdIwQYMBaAFA+AYRyCMWHVLyjnjUY4tCzhxtniMB0GA1UdDgQWBBRm

mGIC4AmRp9njNvt2xrC/oW2nvjCBgQYDVR0RBHoweIIPd3d3LmV4YW1wbGUub3Jn

ggtleGFtcGxlLmNvbYILZXhhbXBsZS5lZHWCC2V4YW1wbGUubmV0ggtleGFtcGxl

Lm9yZ4IPd3d3LmV4YW1wbGUuY29tgg93d3cuZXhhbXBsZS5lZHWCD3d3dy5leGFt

cGxlLm5ldDAOBgNVHQ8BAf8EBAMCBaAwHQYDVR0lBBYwFAYIKwYBBQUHAwEGCCsG

AQUFBwMCMGsGA1UdHwRkMGIwL6AtoCuGKWh0dHA6Ly9jcmwzLmRpZ2ljZXJ0LmNv

bS9zc2NhLXNoYTItZzYuY3JsMC+gLaArhilodHRwOi8vY3JsNC5kaWdpY2VydC5j

b20vc3NjYS1zaGEyLWc2LmNybDBMBgNVHSAERTBDMDcGCWCGSAGG/WwBATAqMCgG

CCsGAQUFBwIBFhxodHRwczovL3d3dy5kaWdpY2VydC5jb20vQ1BTMAgGBmeBDAEC

AjB8BggrBgEFBQcBAQRwMG4wJAYIKwYBBQUHMAGGGGh0dHA6Ly9vY3NwLmRpZ2lj

ZXJ0LmNvbTBGBggrBgEFBQcwAoY6aHR0cDovL2NhY2VydHMuZGlnaWNlcnQuY29t

L0RpZ2lDZXJ0U0hBMlNlY3VyZVNlcnZlckNBLmNydDAMBgNVHRMBAf8EAjAAMIIB

fwYKKwYBBAHWeQIEAgSCAW8EggFrAWkAdwCkuQmQtBhYFIe7E6LMZ3AKPDWYBPkb

37jjd80OyA3cEAAAAWdcMZVGAAAEAwBIMEYCIQCEZIG3IR36Gkj1dq5L6EaGVycX

sHvpO7dKV0JsooTEbAIhALuTtf4wxGTkFkx8blhTV+7sf6pFT78ORo7+cP39jkJC

AHYAh3W/51l8+IxDmV+9827/Vo1HVjb/SrVgwbTq/16ggw8AAAFnXDGWFQAABAMA

RzBFAiBvqnfSHKeUwGMtLrOG3UGLQIoaL3+uZsGTX3MfSJNQEQIhANL5nUiGBR6g

l0QlCzzqzvorGXyB/yd7nttYttzo8EpOAHYAb1N2rDHwMRnYmQCkURX/dxUcEdkC

wQApBo2yCJo32RMAAAFnXDGWnAAABAMARzBFAiEA5Hn7Q4SOyqHkT+kDsHq7ku7z

RDuM7P4UDX2ft2Mpny0CIE13WtxJAUr0aASFYZ/XjSAMMfrB0/RxClvWVss9LHKM

MA0GCSqGSIb3DQEBCwUAA4IBAQBzcIXvQEGnakPVeJx7VUjmvGuZhrr7DQOLeP4R

8CmgDM1pFAvGBHiyzvCH1QGdxFl6cf7wbp7BoLCRLR/qPVXFMwUMzcE1GLBqaGZM

v1Yh2lvZSLmMNSGRXdx113pGLCInpm/TOhfrvr0TxRImc8BdozWJavsn1N2qdHQu

N+UBO6bQMLCD0KHEdSGFsuX6ZwAworxTg02/1qiDu7zW7RyzHvFYA4IAjpzvkPIa

X6KjBtpdvp/aXabmL95YgBjT8WJ7pqOfrqhpcmOBZa6Cg6O1l4qbIFH/Gj9hQB5I

0Gs4+eH6F9h3SojmPTYkT+8KuZ9w84Mn+M8qBXUQoYoKgIjN

-----END CERTIFICATE-----