Authentication mechanisms in MongoDB - Step-by-Step Execution

Concept Flow - Authentication mechanisms

Client sends credentials

↓

MongoDB receives request

↓

Check authentication method

↓

Verify credentials

↓

Grant access

↓

Respond to client

The client sends credentials, MongoDB checks the authentication method, verifies credentials, and either grants or denies access.

Execution Sample

MongoDB

db.runCommand({authenticate: 1, user: 'alice', pwd: 'pass123', mechanism: 'SCRAM-SHA-256'})

This command authenticates user 'alice' with password 'pass123' using SCRAM-SHA-256 mechanism.

Execution Table

Step	Action	Input	Check	Result	Next Step
1	Receive auth request	{user: 'alice', pwd: 'pass123', mechanism: 'SCRAM-SHA-256'}	N/A	Request accepted	Check mechanism
2	Check mechanism	SCRAM-SHA-256	Is mechanism supported?	Yes	Verify credentials
3	Verify credentials	user: alice, pwd: pass123	Does password match stored hash?	Yes	Grant access
4	Grant access	N/A	N/A	Access granted	Respond to client
5	Respond to client	N/A	N/A	Success message sent	End
6	If failure at any step	N/A	N/A	Access denied	Respond with error

💡 Authentication ends after success or failure response sent to client.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
credentials	{}	{user: 'alice', pwd: 'pass123', mechanism: 'SCRAM-SHA-256'}	{user: 'alice', pwd: 'pass123', mechanism: 'SCRAM-SHA-256'}	{user: 'alice', pwd: 'pass123', mechanism: 'SCRAM-SHA-256'}	Used for verification
mechanism_supported	false	false	true	true	true
credentials_valid	false	false	false	true	true
access_granted	false	false	false	true	true

Key Moments - 3 Insights

Why does MongoDB check the authentication mechanism before verifying credentials?

Because the mechanism determines how credentials are verified. If the mechanism is unsupported, MongoDB denies access immediately (see execution_table step 2).

What happens if the password does not match the stored hash?

MongoDB denies access and sends an error response to the client, stopping the authentication process (see execution_table step 6).

Can authentication succeed if the mechanism is correct but the password is wrong?

No, both mechanism support and correct credentials are required for access (see execution_table steps 2 and 3).

Visual Quiz - 3 Questions

Look at the execution_table, what is the result after step 2?

A Mechanism unsupported

B Credentials verified

C Mechanism supported

D Access granted

💡 Hint

Check the 'Result' column in execution_table row for step 2.

At which step does MongoDB decide to grant access?

A Step 3

B Step 4

C Step 1

D Step 5

💡 Hint

Look for the step labeled 'Grant access' in execution_table.

If the password is incorrect, which step in the execution_table shows the outcome?

A Step 6

B Step 2

C Step 3

D Step 5

💡 Hint

Check the step that handles failure in execution_table.

Concept Snapshot

Authentication in MongoDB:
- Client sends credentials with chosen mechanism.
- MongoDB checks if mechanism is supported.
- Credentials are verified against stored data.
- Access granted if valid, denied if not.
- Common mechanisms: SCRAM-SHA-1, SCRAM-SHA-256.
- Always secure credentials during transmission.

Full Transcript

Authentication mechanisms in MongoDB start when the client sends credentials including username, password, and the authentication mechanism. MongoDB first checks if the mechanism is supported. If supported, it verifies the credentials by comparing the password with the stored hash. If the credentials match, MongoDB grants access and responds with success. If any check fails, access is denied and an error is sent. This process ensures only authorized users can access the database.