Package: www.debian.org
Version: None
Severity: Wishlist
Here is a first
draft of a rewrite I did for the above mentioned URL in the bug
report. I felt it included not nearly enough useful information.
Please correct me if this is wrong and otherwise, feel free to
replace the existing page with my edit. Any suggestions etc you
might... uh... suggest, to make it better, please also let me know
and feel free to include those too. I’ve both attached it and
posted it below for posterity:
Official releases of Debian CDs come with signed checksum files;
look for them alongside the images in the iso-cd, jigdo-dvd, iso-hybrid etc. directories (if you can’t find the files, you can right click
the download link for various Debian images and remove the text at
the end of the link specific to your download; aka to see the list of
files for the net install on the amd64 architecture, left clicking
the link gives you https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.4.0-amd64-netinst.iso – remove the section after “iso-cd”). These allow you to check
that the images you download are correct. First of all, the checksum
can be used to check that the CDs have not been corrupted during
download. Secondly, the signatures on the checksum files allow you to
confirm that the files are the ones officially released by the Debian
CD / Debian Live team and have not been tampered with.
To validate the contents of a CD image, just be sure to use the
appropriate checksum tool. Cryptographically strong checksum
algorithms (SHA256 and SHA512) are available for every releases; you
should use the tools sha256sum or sha512sum to work with these.
To ensure that the checksums files themselves are correct, use
GnuPG to verify them against the accompanying signature files (e.g. SHA512SUMS.sign). The keys used for
these signatures are all in the Debian
GPG keyring and the best way to check them is to use that keyring
to validate via the web of trust. To make life easier for users, here
are the fingerprints for the keys that have been used for releases in
recent years:
pub 4096R/64E6EA7D 2009-10-03
Key fingerprint = 1046 0DAD 7616 5AD8 1FBC 0CE9 9880 21A9 64E6 EA7D
uid Debian CD signing key <debian-cd@lists.debian.org>
pub 4096R/6294BE9B 2011-01-05
Key fingerprint = DF9B 9C49 EAA9 2984 3258 9D76 DA87 E80D 6294 BE9B
uid Debian CD signing key <debian-cd@lists.debian.org>
sub 4096R/11CD9819 2011-01-05
pub 4096R/09EA8AC3 2014-04-15
Key fingerprint = F41D 3034 2F35 4669 5F65 C669 4246 8F40 09EA 8AC3
uid Debian Testing CDs Automatic Signing Key <debian-cd@lists.debian.org>
sub 4096R/6BD05CFB 2014-04-15
In more explicit terms, here is a more step by step breakdown of how
one actually does this:
1. Download all the relevant files – the SUMS file, the
signature, and the iso you want to download – to a single directory
(so as an example if we wanted to use SHA512, it would be SHA512SUMS,
SHA512SUMS.sign and the actual .iso file itself.
2. To verify the image against tampering (there are a few
different methods of doing this, we choose the following arbitrarily,
and we also choose SHA512, it can be done with less but this is
cryptographically stronger): “sha512sum path.to.iso >
verify.txt” “diff q
verify.txt SHA512SUMS” (without
quotes). If all checks
out, no output should be given and we can move on to the next step.
Else, re-download the image and try again.
3. To
verify the signature: “gpg –verify SHA512SUMS.sign SHA512SUMS”. You may get an output
like:
gpg: Signature made Mon 25 Jan 2016 05:08:46 AEDT using RSA key ID 6294BE9Bgpg: Can't check signature: public key not found
So:
“gpg –keyserver
keyring.debian.org –recv-keys 6294BE9B”,
And then run it again: “gpg
–verify SHA512SUMS.sign SHA512SUMS”. You may get an output like
the following:
gpg: Signature made Mon 25 Jan 2016 05:08:46 AEDT using RSA key ID 6294BE9Bgpg: 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
4. Verify this fingerprint is legitimate using one of the codes
(fingerprints) located above. This document will change to reflect
what the Debian project uses.
Attachment:
verifyimage.odt
Description: application/vnd.oasis.opendocument.text