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8224 report required permissions when authorization fails #8314

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@ItamarYuran ItamarYuran commented Oct 28, 2024

Closes #(8224)

Change Description

The added code helps the user understand why they are not authorized to perform a certain action.

Background

Up until now in case a user had no permissions or was denied of some action, they would only get a 401 unauthorized message, making it hard to understand what is missing in order to perform that action.

The enhancement will report all denied actions in case there are any, or if there aren't any - report missing permissions.

Testing Details

Changes were not tested yet, no existing test got broken

Additional info

Screenshot 2024-10-28 at 13 59 02 Screenshot 2024-10-28 at 14 02 29

@ItamarYuran ItamarYuran linked an issue Oct 28, 2024 that may be closed by this pull request
@ItamarYuran ItamarYuran added the exclude-changelog PR description should not be included in next release changelog label Oct 28, 2024
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github-actions bot commented Oct 28, 2024

E2E Test Results - Quickstart

11 passed

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E2E Test Results - DynamoDB Local - Local Block Adapter

13 passed

@ItamarYuran ItamarYuran marked this pull request as draft October 28, 2024 12:53
@ItamarYuran ItamarYuran marked this pull request as ready for review October 29, 2024 12:11
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@arielshaqed arielshaqed left a comment

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Nice! Can you please show what outputs we can expect? Or is that in the next commit with tests etc.?

Comment on lines 1157 to 1161
deniedStr := "denied from:\n"
for _, statement := range n.Denied {
deniedStr += strings.Join(statement.Action, "\n")
}
return deniedStr
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  1. Not sure how this code can successfully format deniedStr if len(n.Denied) > 0. There will be no newline after the last row of the Action list on each statement.
  2. It will probably be easier to use strings.Builder. This is actually an io.Writer, so you can just write to it using the normal operations. Here's a playground.

allowed := CheckNeutral
hasPermission := false
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This var is used only in case permissions.NoteTypeNode. So please keep it in scope there: you could just put that entire case inside curly brackets, and that var in there. Or extract it to another func, or even go full OO and make each of these a method. Right now the code confuses me about what might happen with this variable in other cases.

@@ -1165,23 +1189,28 @@ func CheckPermissions(ctx context.Context, node permissions.Node, username strin

if stmt.Effect == model.StatementEffectDeny {
// this is a "Deny" and it takes precedence
return CheckDeny
perm.Denied = append(perm.Denied, stmt)
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This is confusing: I take perm as an input, now I modify it and return it. So I've changed my input, but also returned it as an output.

I think either make perm into an object, pass it by pointer, and keep state on it, or explicitly handle the lists.

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Was thinking the same, agree with @arielshaqed 100%

@ItamarYuran
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The current code returns:

  • All denied actions in a policy in case there are any
  • First missing permission in case there is no relevant denied action

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Thanks!

Final stretch: the actual message. The current message is too detailed and as a result needs too many lines. Let's start by playing safely and never report anything other than action names. Reporting an entire statement gives a wealth of information that might not visible to the user - such as permissions of other users.

@@ -234,7 +235,7 @@ func TestCreateRepo_Unauthorized(t *testing.T) {
})
require.NoError(t, err)
require.NotNil(t, resp.JSON401)
if resp.JSON401.Message != auth.ErrInsufficientPermissions.Error() {
if !strings.Contains(resp.JSON401.Message, auth.ErrInsufficientPermissions.Error()) {
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Can we test here (and below) that we got an expected value? Obviously doing so makes sense only after we finalize the message contents. So it is fine to open an issue to improve these checks in this test file.

},
},
username: "user1",
expected: "lacking permissions for:\nfs:CreateRepository",
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I would expect it to report both missing permissions. Reporting only one is fine, but then the message is surprising - it says "permissions" when it only ever means a single permissions.


if allowed != CheckAllow {
return &AuthorizationResponse{
Allowed: false,
Error: ErrInsufficientPermissions,
Error: fmt.Errorf("%w\n%s", ErrInsufficientPermissions, perm.String()),
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Looking at the results in the tests, I prefer without the newline, error messages are rarely >1 line.

Suggested change
Error: fmt.Errorf("%w\n%s", ErrInsufficientPermissions, perm.String()),
Error: fmt.Errorf("%w: %s", ErrInsufficientPermissions, perm.String()),

fmt.Fprintln(w, action)
}
}
return strings.TrimSpace(w.String())
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It is quite rare to need to TrimSpace on a string you created.

Comment on lines 1158 to 1164
fmt.Fprintln(w, "denied from:")
for _, statement := range n.Denied {
for _, action := range statement.Action {
fmt.Fprintln(w, action)
}
}
return strings.TrimSpace(w.String())
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I think you don't even need a strings.Builder here:

Suggested change
fmt.Fprintln(w, "denied from:")
for _, statement := range n.Denied {
for _, action := range statement.Action {
fmt.Fprintln(w, action)
}
}
return strings.TrimSpace(w.String())
return fmt.Sprintf("denied permission to %s", strings.Join(n.Denied, ", "))

The same of course in the next section.

}
return strings.TrimSpace(w.String())
}
return strings.TrimSpace(w.String())
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This returns "". If that is not helpful, please return some constant string like "not allowed".

Comment on lines 48 to 49
Denied []model.Statement
Unauthorized []permissions.Node
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These are a bit too informative IMO. Let's just keep the action name here? Otherwise I learn details of the policy including denied paths that I might not have known existed!

Suggested change
Denied []model.Statement
Unauthorized []permissions.Node
// Denied is a list of actions the user was denied for the attempt.
Denied []string
// Unauthorized is a list of actions the user did not have for the attempt.
Unauthorized []string

return strings.TrimSpace(w.String())
}

func CheckPermissions(ctx context.Context, node permissions.Node, username string, policies []*model.Policy, perm *NeededPermissions) CheckResult {
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nit: variable name perm is too generic.
Can you use something more explicit?
for example: audit, denyAudit, permAudit, history etc...
So that in the future when extending, debugging or just reading the code we can immediately understand what it is used for.

@@ -1165,23 +1189,28 @@ func CheckPermissions(ctx context.Context, node permissions.Node, username strin

if stmt.Effect == model.StatementEffectDeny {
// this is a "Deny" and it takes precedence
return CheckDeny
perm.Denied = append(perm.Denied, stmt)
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Was thinking the same, agree with @arielshaqed 100%

@@ -44,6 +44,11 @@ type AuthorizationResponse struct {
Error error
}

type NeededPermissions struct {
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rename, MissingPermissions or PermissionsAudit or DenyHistory w/e would be more appropriate?

@@ -895,8 +895,8 @@ func (s *AuthService) Authorize(ctx context.Context, req *auth.AuthorizationRequ
if err != nil {
return nil, err
}

allowed := auth.CheckPermissions(ctx, req.RequiredPermissions, req.Username, policies)
perm := &auth.NeededPermissions{}
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sorry, Im confused what are you doing with this variable?

@ItamarYuran ItamarYuran force-pushed the 8224-report-required-permissions-when-authorization-fails branch from 539918d to 704af7d Compare November 4, 2024 17:08
@ItamarYuran
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Thank you for your reviews!
These changes will return all denied permissions, only the ones that regard the request (not all permission in the policy)
Same goes for missing permissions, all missing one will return. In case of denied + missing permissions only denied ones return.

@ItamarYuran ItamarYuran force-pushed the 8224-report-required-permissions-when-authorization-fails branch from 972dc58 to 758d910 Compare November 5, 2024 14:02
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Report required permission(s) when authorization fails
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