4 ms·

As long as verification happens independently, and the keys are obtained from trusted sources, there is nothing wrong in downloading Ubuntu over http. It appea

As long as verification happens independently, and the keys are obtained from trusted sources, there is nothing wrong in downloading Ubuntu over http. It appears this to be the case, see "How to verify Ubuntu download" tutorial that provides detailed steps: https://tutorials.ubuntu.com/tutorial/tutorial-how-to-verify-ubuntu#0 https://tutorials.ubuntu.com/tutorial/tutorial-how-to-verify... (If you plan to install an Operating System, then I believe some homework is in order -- you cannot expect the OS developers to spoon-feed you trivial security aspects that are expected to be a skill-set that you, the operating system installer, or System Administrator, do possess).

vvanders 8y ago
> 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]
yjftsjthsd-h 8y ago
> As long as verification happens independently, and the keys are obtained from trusted sources, there is nothing wrong in downloading Ubuntu over http. In the abstract, this is true. In practice, however, the checksums are always downloaded from the same page as the OS and usually over the same (unencrypted) connection from the same servers.
- bigiain 8y ago
  Yeah, but the checksums are GPG signed, so you can't change the ISO and then create a valid signature for the new checksum without also having the GPG private key matching the public key you use to check the signature. Having said that, it seems keyserver.ubuntu.com is happy enough to allow connections via http instead of https, so there's a valid avenue to serve up a bogus public key... That's a much smaller window of opportunity since if you're already a Ubuntu user you'll have a pre-existing copy of ubuntu-archive-keyring.gpg already, rather than trying to download a possibly mitm-ed public key at the same time as you download the ISO. But I must admit I boggled a little bit when I saw that keyserver.ubuntu.com happily server their public key over http instead of just https...
stouset 8y ago
> If you plan to install an Operating System, then I believe some homework is in order -- you cannot expect the OS developers to spoon-feed you trivial security aspects that are expected to be a skill-set that you, the operating system installer, or System Administrator, do possess If you plan to publish an operating system, you should take effort to reduce this homework as much as is humanly possible. For every step where a user is expected to—but not explicitly required to—perform extra work to ensure their own security, the overwhelming majority of users will not take these extra steps. Arguing that they "should" gets us nowhere.
- SmellyGeekBoy 8y ago
  Indeed, and adding these extra verification steps just feeds the "Linux is too complicated for ordinary people" crowd.

vvanders 8y ago

> 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]

yjftsjthsd-h 8y ago

> As long as verification happens independently, and the keys are obtained from trusted sources, there is nothing wrong in downloading Ubuntu over http. In the abstract, this is true. In practice, however, the checksums are always downloaded from the same page as the OS and usually over the same (unencrypted) connection from the same servers.

bigiain 8y ago
Yeah, but the checksums are GPG signed, so you can't change the ISO and then create a valid signature for the new checksum without also having the GPG private key matching the public key you use to check the signature. Having said that, it seems keyserver.ubuntu.com is happy enough to allow connections via http instead of https, so there's a valid avenue to serve up a bogus public key... That's a much smaller window of opportunity since if you're already a Ubuntu user you'll have a pre-existing copy of ubuntu-archive-keyring.gpg already, rather than trying to download a possibly mitm-ed public key at the same time as you download the ISO. But I must admit I boggled a little bit when I saw that keyserver.ubuntu.com happily server their public key over http instead of just https...

stouset 8y ago

> If you plan to install an Operating System, then I believe some homework is in order -- you cannot expect the OS developers to spoon-feed you trivial security aspects that are expected to be a skill-set that you, the operating system installer, or System Administrator, do possess If you plan to publish an operating system, you should take effort to reduce this homework as much as is humanly possible. For every step where a user is expected to—but not explicitly required to—perform extra work to ensure their own security, the overwhelming majority of users will not take these extra steps. Arguing that they "should" gets us nowhere.

SmellyGeekBoy 8y ago
Indeed, and adding these extra verification steps just feeds the "Linux is too complicated for ordinary people" crowd.