HOWTO: Verify Debian ISO Downloads (from OS X)

gpg-verify-iso.txt

HOWTO: Verify Debian ISO Downloads (from OS X)


- Download the required ISO from http://www.debian.org/CD/. Also download the SHA512SUMS and SHA512SUMS.sign files. (of course MD5SUM etc. work fine, but as long as we're being paranoid, we might as well go all the way)

- Install GPGTools if needed https://www.gpgtools.org/


- Verify the signature on SHA512SUMS

You should see something like this the first time you run gpg --verify: 

  $ gpg --verify SHA512SUMS.sign 
  gpg: Signature made Sun May 13 05:01:57 2012 PDT using RSA key ID 6294BE9B
  gpg: requesting key 6294BE9B from hkp server keys.gnupg.net
  gpg: key 6294BE9B: public key "Debian CD signing key <debian-cd@lists.debian.org>" imported
  gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
  gpg: depth: 0  valid:   2  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 2u
  gpg: next trustdb check due at 2015-08-18
  gpg: Total number processed: 1
  gpg:               imported: 1  (RSA: 1)
  gpg: Good signature from "Debian CD signing key <debian-cd@lists.debian.org>"
  gpg: WARNING: This key is not certified with a trusted signature!
  gpg:          There is no indication that the signature belongs to the owner.
  Primary key fingerprint: DF9B 9C49 EAA9 2984 3258  9D76 DA87 E80D 6294 BE9B

Subsequent runs will look something like this:

  $ gpg --verify SHA512SUMS.sign 
  gpg: Signature made Sun May 13 05:01:57 2012 PDT using RSA key ID 6294BE9B 
  gpg: Good signature from "Debian CD signing key <debian-cd@lists.debian.org>"  
  gpg: WARNING: This key is not certified with a trusted signature!
  gpg:          There is no indication that the signature belongs to the owner.
  Primary key fingerprint: DF9B 9C49 EAA9 2984 3258  9D76 DA87 E80D 6294 BE9B    


To be extra safe, verify that the primary key fingerprint exists on this page: http://www.debian.org/CD/verify

- Find the SHA512SUM of the ISO(s)

  $ openssl dgst -sha512  ~/Downloads/debian-6.0.5-i386-netinst.iso
  SHA512(/Users/mds/Downloads/debian-6.0.5-i386-netinst.iso)= 536ce3de14ba537590e9794a8a053fcbf81f8063aaf690d766e1ef784c2609932f481a2079cf3982f87ef64354398eb36ec2d8d1c8d207c5723c1c66ffa3495b

Verify that the calculated hash is the same as the one in SHA512SUMS:

  $ grep $(openssl dgst -sha512  ~/Downloads/debian-6.0.5-i386-netinst.iso | cut -f 2 -d" ") SHA512SUMS  && echo OK ||   echo FAILED
  536ce3de14ba537590e9794a8a053fcbf81f8063aaf690d766e1ef784c2609932f481a2079cf3982f87ef64354398eb36ec2d8d1c8d207c5723c1c66ffa3495b  debian-6.0.5-i386-netinst.iso
  OK




See also:
http://www.debian.org/CD/verify, http://keyring.debian.org