** Description changed:

  From https://gitlab.com/apparmor/apparmor/-/merge_requests/1803:
  
-     In AppArmor policy, unix addresses must start with @, and when
- trying to use alternations {.,.}, the parser would confuse that with an
- invalid variable, rightfully so. The problem is that this was supported
- in previous versions of the parser, so in order to not regress behavior,
- we are accepting such strings.
+     In AppArmor policy, abstract unix addresses must start with @. When 
trying to use alternations {.,.} at the start of an abstract address name, the 
@ and the alternation {.,.} would form an invalid variable name @{.,.}. 
AppArmor 5
+ added stricter checking around variables, and the addition checks catches 
this as the @ followed by an alternation as an invalid variable.
  
- In AppArmor 4.x, a rule of the form
+ Unfortunately this combination was supported in previous versions of the
+ parser, and in use in snapd policy, so in order to not regress behavior,
+ we are accepting such strings, using the previous behavior.
+ 
+ Specifically in AppArmor 4.x, a rule of the form
  
  unix connect peer=(addr="@{alt1,alt2}-test"),
  
  would parse as a literal @ followed by either alt1 or alt2, with
- abstract socket addresses having to start with @. However, @{var} is
- also the syntax used to specify variables, and stricter checking for
- variables led to the above erroring as an invalid variable. While the
- proper syntax should be escaping the @ with \@{alt1,alt2}, existing
- policy relies on the previous behavior, so it should be restored into
- AppArmor 5.x.
+ abstract socket addresses having to start with @.
+ 
+ Restore this behavior in AppArmor 5 by allowing it to detect the invalid
+ variable and treat it as an @ followed by an alternation.

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https://bugs.launchpad.net/bugs/2126450

Title:
  AppArmor Unix socket rules need to be able to support addr=@{a,b}
  variable usage

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