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> and the keys are obtained from trusted sources Isn't that a little hard if the verification keys(from that link) are served over HTTP[1][2]? [1] http://rele

> and the keys are obtained from trusted sources Isn't that a little hard if the verification keys(from that link) are served over HTTP[1][2]? [1] http://releases.ubuntu.com/18.04/SHA256SUMS.gpg http://releases.ubuntu.com/18.04/SHA256SUMS.gpg [2] http://releases.ubuntu.com/?_ga=2.21478331.1690774166.1548124147-631293260.1548124147 http://releases.ubuntu.com/?_ga=2.21478331.1690774166.154812...

whydoyoucare 8y ago
The Ubuntu verification tutorial (see my previous post) points to keyserver.ubuntu.com.
- bigiain 8y ago
  Hmmm, I just had a look there. keyserver.ubuntu.com is available over http as well as https, which means it's probably susceptible to a downgrade attack if you're mitming it - which would let you serve a bogus public key and therefore generate apparently valid signatures for the hash for a modified ISO. That's not good...
  - cordonbleu 8y ago
    its happened in variant form already, this is why habits of complacency should be kept in check. remember this ? V https://www.theregister.co.uk/2016/02/21/linux_mint_hacked_malwareinfected_isos_linked_from_official_site/ https://www.theregister.co.uk/2016/02/21/linux_mint_hacked_m...
bigiain 8y ago
Those are GPG signed SHA hashes. Sure anyone MITMing the http connection could change them, but for them too be valid signatures for the theoretically-modified ISO you've ended up with, they either need the correct GPG private key to generate that new signature, or they need to convince you to accept a bogus public key for ubuntu-archive-keyring.gpg
- vvanders 8y ago
  Or they could serve all this over HTTPS where that process would happen automatically when you download. As another poster noted the keyserver in that link will work over http so you're still susceptible to a possible downgrade attack. Given how easy it is to get a LE cert these days it's making me question what other security decision Ubuntu is making that I'm not aware of or have the expertise to evaluate.
  - bigiain 8y ago
    Heh. I think that "other poster" may also have been me... With regards to LE certs, I discussed elsewhere here the problems faced by the apt developers that make the obvious "just install a LE cert!" answer not actually workable for them - they rely heavily of volunteer run mirrors and local proxies. I don't know what Ubuntu's ISO download "server" really is underneath, it's possible they've got similar problems, where either they pay for all the bandwidth themselves, or they let people assume that an ssl secured connection to "ubuntu-mirror.usyd.edu.au" or "ubuntu-mirror.evilhacker.ru" is for some reason "safer" than an http connection...
- deleted 8y ago
  [deleted]

whydoyoucare 8y ago

The Ubuntu verification tutorial (see my previous post) points to keyserver.ubuntu.com.

bigiain 8y ago
Hmmm, I just had a look there. keyserver.ubuntu.com is available over http as well as https, which means it's probably susceptible to a downgrade attack if you're mitming it - which would let you serve a bogus public key and therefore generate apparently valid signatures for the hash for a modified ISO. That's not good...
- cordonbleu 8y ago
  its happened in variant form already, this is why habits of complacency should be kept in check. remember this ? V https://www.theregister.co.uk/2016/02/21/linux_mint_hacked_malwareinfected_isos_linked_from_official_site/ https://www.theregister.co.uk/2016/02/21/linux_mint_hacked_m...

bigiain 8y ago

Those are GPG signed SHA hashes. Sure anyone MITMing the http connection could change them, but for them too be valid signatures for the theoretically-modified ISO you've ended up with, they either need the correct GPG private key to generate that new signature, or they need to convince you to accept a bogus public key for ubuntu-archive-keyring.gpg

vvanders 8y ago
Or they could serve all this over HTTPS where that process would happen automatically when you download. As another poster noted the keyserver in that link will work over http so you're still susceptible to a possible downgrade attack. Given how easy it is to get a LE cert these days it's making me question what other security decision Ubuntu is making that I'm not aware of or have the expertise to evaluate.
- bigiain 8y ago
  Heh. I think that "other poster" may also have been me... With regards to LE certs, I discussed elsewhere here the problems faced by the apt developers that make the obvious "just install a LE cert!" answer not actually workable for them - they rely heavily of volunteer run mirrors and local proxies. I don't know what Ubuntu's ISO download "server" really is underneath, it's possible they've got similar problems, where either they pay for all the bandwidth themselves, or they let people assume that an ssl secured connection to "ubuntu-mirror.usyd.edu.au" or "ubuntu-mirror.evilhacker.ru" is for some reason "safer" than an http connection...
deleted 8y ago
[deleted]