ACL rules and categories in Redis - Step-by-Step Execution

Concept Flow - ACL rules and categories

Start: User connects

↓

Check ACL Categories

↓

Match Command Category?

No→Deny Command

Yes↓

Check Specific ACL Rules

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Allow or Deny Command

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Execute Command or Return Error

When a user sends a command, Redis checks if the command's category is allowed by ACL categories, then checks specific ACL rules to allow or deny execution.

Execution Sample

Redis

ACL SETUSER alice on >password ~* -@dangerous +@all
AUTH alice password
SET key value

Defines user 'alice' with all commands allowed except dangerous ones, then runs a SET command to see if allowed.

Execution Table

Step	Action	Input/Condition	Result	Notes
1	User 'alice' connects	User 'alice'	User profile loaded	ACL rules for 'alice' active
2	Check command category	Command: SET (category: @write)	Category @write allowed?	Yes, +@all includes @write
3	Check specific ACL rules	Is @dangerous category allowed?	No, -@dangerous denies it	SET is not in @dangerous, so allowed
4	Allow or deny command	All checks passed	Command allowed	SET command executed
5	Execute command	SET key value	Key set in database	Command success response sent

💡 Command allowed because user 'alice' has +@all and -@dangerous, and SET is not dangerous

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
User ACL Categories	none	+@all	+@all and -@dangerous	+@all and -@dangerous	+@all and -@dangerous
Command Category	none	@write	@write	@write	@write
Command Allowed?	unknown	true (category allowed)	true (not denied by specific rules)	true	true

Key Moments - 3 Insights

Why does the command get allowed even though -@dangerous is set?

Because the SET command belongs to the @write category, not @dangerous. The user has +@all which includes @write, so the command is allowed (see execution_table rows 2 and 3).

What happens if a command belongs to a denied category?

If the command's category matches a denied ACL category (like -@dangerous), the command is denied immediately (see execution_table row 3).

How do ACL categories simplify permission management?

ACL categories group commands by type, so you can allow or deny many commands at once instead of listing each command individually (see concept_flow and variable_tracker).

Visual Quiz - 3 Questions

Look at the execution_table, what is the command category checked at step 2?

A @write

B @dangerous

C @read

D @admin

💡 Hint

Check the 'Command Category' column in execution_table row 2

At which step does the system decide if the command is allowed or denied?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Allow or deny command' action in execution_table

If the user had -@write instead of +@all, what would happen to the SET command?

A Command allowed

B Command category changes

C Command denied

D User disconnected

💡 Hint

Refer to variable_tracker 'User ACL Categories' and execution_table logic for category checks

Concept Snapshot

ACL rules control which commands a user can run.
Categories group commands (e.g., @write, @read).
Users get +category to allow, -category to deny.
Commands checked first by category, then specific rules.
If denied, command is rejected immediately.
Simplifies managing many commands at once.

Full Transcript

When a Redis user connects, the system loads their ACL rules including allowed and denied command categories. When the user sends a command, Redis checks the command's category against the user's allowed categories. If the category is allowed, Redis then checks if any specific deny rules apply. If no denies match, the command is allowed and executed. For example, a user with +@all and -@dangerous can run all commands except those in the dangerous category. The SET command belongs to @write, which is allowed, so it runs successfully. This process helps manage permissions efficiently by grouping commands into categories.