1421413 - add a preference to control the accepted signature algorithms for add-ons

Status: VERIFIED FIXED

(Core :: Security: PSM, enhancement, P1)

Description

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

For the great add-on signature changening, we'll eventually need a preference we can use to enable/disable COSE signature checking. In the meantime, it would also be useful to have a way to easily disable SHA-1 in add-on signatures (i.e. in the old PKCS#7 format). We can add an integer preference to control this policy.

Comment 1

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

Attachment: bug 1421413 - add a preference to control which add-on signature algorithms are valid

Review commit: https://reviewboard.mozilla.org/r/203682/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/203682/

Comment 2

[J.C. Jones [:jcj] (he/him)]

Comment on attachment 8932630 [details]
bug 1421413 - add a preference to control which add-on signature algorithms are valid

https://reviewboard.mozilla.org/r/203682/#review209204

::: security/manager/ssl/tests/unit/test_signed_apps.js:329
(Diff revision 1)
>                        Cr.NS_ERROR_SIGNED_JAR_UNSIGNED_ENTRY));
>  });
>  
> +add_test(function setPrefToDisableSHA1() {
> +  // Setting this to 1 means only PKCS#7 with SHA-256 is accepted.
> +  Services.prefs.setIntPref("security.signed_app_signatures.policy", 1);

Nit: Seems fragile to do it this way; why not push the pref for each test?

Comment 3

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

Comment on attachment 8932630 [details]
bug 1421413 - add a preference to control which add-on signature algorithms are valid

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/203682/diff/1-2/

Comment 4

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

Thanks! Here's try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=bb559992cf2d

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e0293c32f167
add a preference to control which add-on signature algorithms are valid r=jcj

Comment 6

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/e0293c32f167

Comment 7

[CosminB]

Attachment: Bug1421413.zip

This issue is verified as fixed on Firefox 59.0a1(20180112100121) under Wind 7 64-bit and Mac OS X 10.13.

The preference is displayed in about:config as security.signed_app_signatures.policy with the default value 2. (please see the attached screenshot)

Modifying the value to “0”, Firefox will accept SHA1 or SHA256 signatures.
Modifying the value to “1”, Firefox will accept only SHA256 signatures.

Please see the attached video.

Comment 8

[Franziskus Kiefer [:franziskus]]

With bug 1403844 the preference security.signed_app_signatures.policy changed [1]. The meaning of 0 and 1 remains the same but as you noted the default is 2 now (it is interpreted as binary 0b10).
So it would be good to test the default too, which should behave the same as "0", as well as 0b11 = "3", which should be behave the same as "1".

[1] https://searchfox.org/mozilla-central/rev/7476b71e0010ab3277b77cc0ae4d998c4b1d2b64/security/manager/ssl/security-prefs.js#81

Comment 9

[CosminB]

Attachment: Bug1421413Values.zip

I can confirm that:

With the default value “2”, Firefox will accept SHA1 or SHA256.
Modifying the value to “3”, Firefox will accept only SHA256.

Thanks for the help!

I also noticed that if you introduce a random number, for example “72” it will work as the default value “2” or if you use “83” it will work as the value “3”.

Is this expected?

Please see the attached videos.

Comment 10

[Franziskus Kiefer [:franziskus]]

> I also noticed that if you introduce a random number, for example “72” it will work as the default value “2” or if you use “83” it will work as the value “3”.

Yes this is expected. 72 = 0b1001000 is interpreted as 0b000, which says COSE disabled, ignore files, PKCS#7 must verify with SHA-1 and/or SHA-256 PKCS#7 allowed. 83 = 0b1010011 is interpreted as 0b011, which says COSE is verified if present, PKCS#7 must verify with SHA-256 PKCS#7 allowed.