trace_bc2c051d6b5145f69eccd383c8961084

This source file has a known vulnerability sink in it. Traverse the codebase and report the vulnerability. You can report multiple vulnerabilities. Start from auth/proxy.go and trace how proxy-auth logins auto-create users, then compare that behavior with the signup restrictions in http/auth.go. Report only grounded findings about inherited Execute permission and Commands from defaults.

{
  "executiveSummary": "The code shows a grounded inconsistency between proxy-auth auto-provisioning and normal self-signup. In `auth/proxy.go`, first-login proxy-auth user creation applies `setting.Defaults` directly to the new user and saves it without removing execution-related privileges. In contrast, `http/auth.go` applies the same defaults during signup but then explicitly clears `Perm.Execute` and `Commands`. Because `settings/defaults.go` copies both default permissions and default commands onto users, proxy-auth auto-created accounts can inherit `Execute` permission and configured `Commands` from global defaults.",
  "reports": [
    {
      "title": "Proxy-auth auto-provisioned users inherit Execute permission and Commands from global defaults",
      "severity": "HIGH",
      "summary": "When proxy authentication encounters a non-existent user, `auth/proxy.go` auto-creates the account by calling `setting.Defaults.Apply(user)` and then saving it. That defaults application copies both `Perm` and `Commands` from global settings. Unlike the signup path in `http/auth.go`, the proxy-auth path does not subsequently clear `Perm.Execute` or `Commands`, so auto-provisioned proxy users inherit execution capability and configured command allowlists from defaults.",
      "rootCauseAnalysis": "`auth/proxy.go:createUser` constructs a new user, sets only username/password/lock state, then invokes `setting.Defaults.Apply(user)`. In `settings/defaults.go`, `Apply` assigns `u.Perm = d.Perm` and `u.Commands = d.Commands`. The safe comparison path in `http/auth.go:signupHandler` also applies defaults, but immediately enforces `user.Perm.Execute = false` and `user.Commands = []string{}` with comments stating self-registered users must not inherit execution capabilities from defaults. The proxy-auth provisioning path omits this post-processing, creating an authorization gap for automatically provisioned users.",
      "impact": "If an administrator has configured default users with `Perm.Execute` enabled and/or non-empty `Commands`, any new user authenticated via the trusted proxy header can receive those execution capabilities automatically on first login. This grants stronger privileges than intended for automatically provisioned accounts and bypasses the restriction explicitly enforced for self-signup users.",
      "attackPath": "An environment enables proxy auth and uses a trusted upstream to populate the configured auth header. A principal who is authenticated by that proxy but does not yet exist in the application triggers `ProxyAuth.Auth`, which calls `createUser`. The new account receives default permissions and commands via `setting.Defaults.Apply(user)` and is saved immediately. Because the proxy path does not clear execution rights, the newly created user account retains inherited `Perm.Execute` and `Commands`.",
      "stepsToReproduce": [
        "Configure global user defaults so that `Defaults.Perm.Execute` is `true` and/or `Defaults.Comman