Why Field and document level security in Elasticsearch? - Purpose & Use Cases

The Big Idea

What if you could share data safely without worrying about accidentally exposing secrets?

The Scenario

Imagine you have a big library of documents with sensitive information. You want to share some documents with your friends but hide certain pages or details they shouldn't see.

The Problem

Manually checking each document and removing sensitive parts before sharing is slow and easy to mess up. You might forget to hide something or accidentally share too much.

The Solution

Field and document level security lets you set rules so only allowed parts of documents or certain documents are visible to each user automatically. This keeps data safe without extra work.

Before vs After

✗ Before

search all documents; then manually remove sensitive fields from results

✓ After

use field and document level security rules to filter data automatically

What It Enables

This makes sharing data safe and easy, letting users see only what they are allowed to see without extra manual filtering.

Real Life Example

A company shares customer data with support staff but hides payment info using document and field level security, so staff can help without seeing sensitive details.

Key Takeaways

Manual filtering of sensitive data is slow and risky.

Field and document level security automates safe data access.

This protects privacy and simplifies data sharing.

Practice

1. What is the main purpose of field-level security in Elasticsearch?

easy

A. To restrict access to specific fields within documents

B. To encrypt the entire Elasticsearch index

C. To limit the number of documents returned in a query

D. To control user login credentials

Solution

1. Step 1: Understand field-level security concept

   Field-level security controls which fields in a document a user can see or query.

2. Step 2: Compare with other options

   Encryption and login control are unrelated to field-level security; limiting documents is document-level security.

3. Final Answer:

   To restrict access to specific fields within documents -> Option A

4. Quick Check:

   Field-level security = restrict fields [OK]

Hint: Field-level security hides fields, not whole documents [OK]

Common Mistakes:

• Confusing field-level with document-level security
• Thinking it encrypts data
• Assuming it controls user passwords

2. Which of the following is the correct syntax to define field-level security in an Elasticsearch role?

easy

A. "fields": ["title", "author"]

B. "field_security": { "deny": ["title", "author"] }

C. "field_security": { "grant": ["title", "author"] }

D. "field_access": { "allow": ["title", "author"] }

Solution

1. Step 1: Recall correct field-level security syntax

   Elasticsearch uses "field_security" with a "grant" array to specify allowed fields.

2. Step 2: Eliminate incorrect options

   "deny" is not valid here; "fields" and "field_access" are incorrect keys.

3. Final Answer:

   "field_security": { "grant": ["title", "author"] } -> Option C

4. Quick Check:

   Use "field_security" with "grant" for allowed fields [OK]

Hint: Use "field_security" with "grant" to allow fields [OK]

Common Mistakes:

• Using "deny" instead of "grant"
• Wrong key names like "fields" or "field_access"
• Confusing syntax with document-level security

3. Given this role definition snippet:

{
  "indices": [
    {
      "names": ["books"],
      "privileges": ["read"],
      "query": { "term": { "genre": "fiction" } },
      "field_security": { "grant": ["title", "author"] }
    }
  ]
}

What documents and fields will a user with this role see when querying the books index?

medium

A. All documents showing all fields

B. All documents showing only 'title' and 'author' fields

C. Only documents where genre is 'fiction' showing all fields

D. Only documents where genre is 'fiction' showing only 'title' and 'author' fields

Solution

1. Step 1: Analyze document-level security query

   The "query" limits documents to those with genre 'fiction'.

2. Step 2: Analyze field-level security grant

   Only "title" and "author" fields are visible due to "field_security".

3. Final Answer:

   Only documents where genre is 'fiction' showing only 'title' and 'author' fields -> Option D

4. Quick Check:

   Query filters docs + grant limits fields = Only documents where genre is 'fiction' showing only 'title' and 'author' fields [OK]

Hint: Query filters docs; field_security limits fields shown [OK]

Common Mistakes:

• Ignoring the query filter on documents
• Assuming all fields are visible
• Confusing document and field level restrictions

4. You defined this role snippet:

{
  "indices": [
    {
      "names": ["library"],
      "privileges": ["read"],
      "query": { "term": { "category": "science" } },
      "field_security": { "grant": ["title", "summary"] }
    }
  ]
}

But users report they see all documents and fields. What is the likely error?

medium

A. The query filter is incorrect or not applied properly

B. Field names in grant are misspelled

C. Privileges should include "write" to restrict fields

D. Role must include "manage" privilege for security to work

Solution

1. Step 1: Check query filter correctness

   If the query filter is malformed or ignored, document filtering won't happen.

2. Step 2: Verify field_security and privileges

   Field names look correct; "read" privilege is enough for filtering; "write" or "manage" not needed.

3. Final Answer:

   The query filter is incorrect or not applied properly -> Option A

4. Quick Check:

   Query filter controls docs; if ignored, all docs show [OK]

Hint: Check query syntax if document filtering fails [OK]

Common Mistakes:

• Assuming 'write' privilege needed for filtering
• Ignoring query filter syntax errors
• Thinking field names cause document filtering issues

5. You want to create a role that allows users to read only documents where status is active and see only the name and email fields. Which role definition snippet correctly implements this?

hard

A. {
"indices": [
{
"names": ["users"],
"privileges": ["read"],
"query": { "match": { "status": "active" } },
"field_security": { "deny": ["password"] }
}
]
}

B. {
"indices": [
{
"names": ["users"],
"privileges": ["read"],
"query": { "term": { "status": "active" } },
"field_security": { "grant": ["name", "email"] }
}
]
}

C. {
"indices": [
{
"names": ["users"],
"privileges": ["read"],
"query": { "term": { "status": "active" } },
"fields": ["name", "email"]
}
]
}

D. {
"indices": [
{
"names": ["users"],
"privileges": ["read"],
"query": { "term": { "status": "active" } }
}
]
}

Solution

1. Step 1: Verify document-level security query

   Using "term" query on "status" with "active" correctly filters documents.

2. Step 2: Verify field-level security syntax

   "field_security" with "grant" array specifying "name" and "email" fields is correct.

3. Step 3: Eliminate incorrect options

   { "indices": [ { "names": ["users"], "privileges": ["read"], "query": { "match": { "status": "active" } }, "field_security": { "deny": ["password"] } } ] } uses "deny" which is invalid; { "indices": [ { "names": ["users"], "privileges": ["read"], "query": { "term": { "status": "active" } }, "fields": ["name", "email"] } ] } uses wrong key "fields"; { "indices": [ { "names": ["users"], "privileges": ["read"], "query": { "term": { "status": "active" } } } ] } lacks field-level security.

4. Final Answer:

   Role with "query" term filter and "field_security" grant for "name" and "email" -> Option B

5. Quick Check:

   Use "query" for docs + "field_security" grant for fields [OK]

Hint: Use "query" for docs and "field_security" with "grant" for fields [OK]

Common Mistakes:

• Using "deny" instead of "grant" in field_security
• Using wrong keys like "fields" instead of "field_security"
• Omitting field-level security to restrict fields