Linus Torvalds Interview for LinuxFR

tbassetto wrote: post #4

Almost all browsers will show a warning about the certificate… Link without https : http://linuxfr.org/nodes/85904/comments/1230981

Off-topic, but does anyone know why browsers go crazy about self signed certs?

It's not as good as one signed by an ostensibly trusted CA, but it's strictly better than plain HTTP (no sniffing, harder MITM, etc) - so why not present it to the user the same way that plain HTTP is?

The conspiracy theorist in me wonders if trusted CAs 'lobby' browser vendors to make it so?

Re: Linus Torvalds Interview for LinuxFR

#6

Post by wazoox » Wed, May 04, 2011, 10:21 AM UTC

smanek wrote: post #5

tbassetto wrote: post #4

Almost all browsers will show a warning about the certificate… Link without https : http://linuxfr.org/nodes/85904/comments/1230981

Off-topic, but does anyone know why browsers go crazy about self signed certs? It's not as good as one signed by an ostensibly trusted CA, but it's strictly better than plain HTTP (no sniffing, harder MITM, etc) - so why not present it to the user the same way that plain HTTP is? The conspiracy theorist in me wonders if trusted CAs 'lobby' browser vendors to make it so?

It's explained on the Wikipedia entry : http://en.wikipedia.org/wiki/Self-signed_certificate

Basically, self-signed certificates can't be revoked in case of a security breach.

There's an excellent resume of the discussion of the subject at Mozilla : http://www.gerv.net/security/self-signed-certs/

Re: Linus Torvalds Interview for LinuxFR

#7

Post by pmjordan » Wed, May 04, 2011, 10:44 AM UTC

smanek wrote: post #5

tbassetto wrote: post #4

Almost all browsers will show a warning about the certificate… Link without https : http://linuxfr.org/nodes/85904/comments/1230981

Off-topic, but does anyone know why browsers go crazy about self signed certs? It's not as good as one signed by an ostensibly trusted CA, but it's strictly better than plain HTTP (no sniffing, harder MITM, etc) - so why not present it to the user the same way that plain HTTP is? The conspiracy theorist in me wonders if trusted CAs 'lobby' browser vendors to make it so?

Self-signed certificates don't prevent MITM attacks on connecting unless you've transmitted the certificate securely out-of-band and installed it in the client's browser. (which practically never happens with sites on the open internet) They only prevent tampering with the connection once it's established.

The browser should jump up and down when encountering such a certificate as it's exactly how an attempted MITM attack would look.

Re: Linus Torvalds Interview for LinuxFR

#8

Post by smanek » Wed, May 04, 2011, 10:50 AM UTC

wazoox wrote: post #6

smanek wrote: post #5

Earlier quoted context omitted.

Off-topic, but does anyone know why browsers go crazy about self signed certs? It's not as good as one signed by an ostensibly trusted CA, but it's strictly better than plain HTTP (no sniffing, harder MITM, etc) - so why not present it to the user the same way that plain HTTP is? The conspiracy theorist in me wonders if trusted CAs 'lobby' browser vendors to make it so?

It's explained on the Wikipedia entry : http://en.wikipedia.org/wiki/Self-signed_certificate Basically, self-signed certificates can't be revoked in case of a security breach. There's an excellent resume of the discussion of the subject at Mozilla : http://www.gerv.net/security/self-signed-certs/

Any attack I can think of that exploits that fact would work at least as easily on plain HTTP. And there are a large class of attacks that work on plain HTTP but not with a self signed cert.

Can you think of any counter examples? (Note: I'm a security noob - so I'm asking out of sincere curiosity).

Re: Linus Torvalds Interview for LinuxFR

#9

Post by wladimir » Wed, May 04, 2011, 10:55 AM UTC

smanek wrote: post #8

wazoox wrote: post #6

Earlier quoted context omitted.

It's explained on the Wikipedia entry : http://en.wikipedia.org/wiki/Self-signed_certificate Basically, self-signed certificates can't be revoked in case of a security breach. There's an excellent resume of the discussion of the subject at Mozilla : http://www.gerv.net/security/self-signed-certs/

Any attack I can think of that exploits that fact would work at least as easily on plain HTTP. And there are a large class of attacks that work on plain HTTP but not with a self signed cert. Can you think of any counter examples? (Note: I'm a security noob - so I'm asking out of sincere curiosity).

I don't think there is any doubt that even with a self-signed certificate, HTTPS is more secure than HTTP. At the least, it makes interception/sniffing/modification a bit harder. Security, after all, is about making attacks more difficult and costly.

Still there is good reason that browsers rub it in the users face when a site tries to use a self-signed certificate. The user has to be really really sure that this is expected (it is like the SSH "the remote host key has changed" warnings).

Re: Linus Torvalds Interview for LinuxFR

#10

Post by smanek » Wed, May 04, 2011, 10:59 AM UTC

pmjordan wrote: post #7

smanek wrote: post #5

Earlier quoted context omitted.

Off-topic, but does anyone know why browsers go crazy about self signed certs? It's not as good as one signed by an ostensibly trusted CA, but it's strictly better than plain HTTP (no sniffing, harder MITM, etc) - so why not present it to the user the same way that plain HTTP is? The conspiracy theorist in me wonders if trusted CAs 'lobby' browser vendors to make it so?

Self-signed certificates don't prevent MITM attacks on connecting unless you've transmitted the certificate securely out-of-band and installed it in the client's browser. (which practically never happens with sites on the open internet) They only prevent tampering with the connection once it's established. The browser should jump up and down when encountering such a certificate as it's exactly how an attempted MITM a…

Granted, it doesn't provide as much protection as a cert signed by a trusted CA - but it's still far more protection than plain HTTP, right? e.g, Firesheep wouldn't work

I don't know if browsers do this, but in principle they could even notify the user on certificate change, so the MITM would have to be on the first connection to a site.