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mighq
Asked: 2012-07-14 03:02:38 +0800 CST

extracting raw ASN.1 parts from X.509 certificate

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I'd like to extract raw hex ASN.1 data from X.509 certificate. I know, that I can do this by using DER format and hexdumping it.

I'm interested in particular parts like "subject", "issuer" and their raw hex ASN1 data.

openssl x509

1 Answers

  1. Determine offset of interesting part by using (number in first column):

    openssl x509 -in crt.pem -outform der | openssl asn1parse -inform der -i

    For example, if "subject" entry is at offset 119. Dump raw data of that substructure:

    openssl x509 -in crt.pem -outform der | openssl asn1parse -inform der -i -strparse 119 -noout -out subject.raw

    Now print raw hex data:

    cat subject.raw | od --address-radix=n --format=x1 | tr -d ' \n'

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