Host identity SCEP rate limit.

[getvictor]

Fixes #30989

Checklist for submitter

• Added/updated automated tests
  • Where appropriate, automated tests simulate multiple hosts and test for host isolation (updates to one hosts's records do not affect another.)

Summary by CodeRabbit

• New Features

  • Added rate limiting to SCEP certificate enrollment, returning a "Too Many Requests" (HTTP 429) response if hosts request certificates too frequently.

• Bug Fixes

  • Improved error handling for rate-limited SCEP requests, providing clear feedback when rate limits are exceeded.

• Tests

  • Introduced integration tests to verify SCEP rate limiting behavior.

• Chores

  • Enhanced internal configuration handling for SCEP certificate management.

[coderabbitai]

📝 Walkthrough

Walkthrough

This change adds a rate limit to the SCEP certificate enrollment endpoint, ensuring hosts cannot request certificates too frequently. It introduces a cooldown period, stores certificate creation timestamps, updates error handling to return HTTP 429 on rate limiting, and includes integration tests to verify correct behavior.

Changes

File(s)	Change Summary
ee/server/service/hostidentity/depot/depot.go	Added cooldown-based rate limiting to certificate storage; depot struct and constructor updated for config usage.
ee/server/service/hostidentity/scep.go	Introduced RateLimitError type; PKIOperation returns HTTP 429 on rate limiting.
ee/server/service/hostidentity/types/host_identity_certificates.go	Added CreatedAt timestamp field to HostIdentityCertificate struct.
server/datastore/mysql/host_identity_scep.go	Modified SQL to select created_at for certificates.
server/datastore/mysql/mysql.go	NewHostIdentitySCEPDepot now takes FleetConfig pointer as argument.
cmd/fleet/serve.go	Passes FleetConfig pointer to NewHostIdentitySCEPDepot.
ee/server/integrationtest/hostidentity/scep_rate_limit_test.go	New integration test verifying SCEP rate limiting per host.
ee/server/integrationtest/hostidentity/suite.go	Added SetUpSuiteWithConfig to allow test config mutation; passes config to depot constructor.

Sequence Diagram(s)

sequenceDiagram
    participant Host as Host
    participant SCEP as SCEP Endpoint
    participant Depot as HostIdentitySCEPDepot
    participant DB as Database

    Host->>SCEP: Request SCEP certificate (CSR)
    SCEP->>Depot: Store certificate for host
    Depot->>DB: Check for existing certificate by host
    DB-->>Depot: Return existing certificate (with CreatedAt)
    Depot-->>SCEP: Return error if within cooldown, else proceed
    alt Within cooldown
        SCEP-->>Host: HTTP 429 Too Many Requests
    else Not within cooldown
        Depot->>DB: Store new certificate
        SCEP-->>Host: Return issued certificate
    end

Loading

Possibly related PRs

• fleetdm/fleet#30589: Implements the SCEP endpoint for host identity, including the creation of the SCEP service, depot, and related datastore methods. This work is directly related as it provides the foundation for the rate limiting feature.

---

📜 Recent review details

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Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 50f18ea and 9fae641.

📒 Files selected for processing (8)

• cmd/fleet/serve.go (1 hunks)
• ee/server/integrationtest/hostidentity/scep_rate_limit_test.go (1 hunks)
• ee/server/integrationtest/hostidentity/suite.go (2 hunks)
• ee/server/service/hostidentity/depot/depot.go (3 hunks)
• ee/server/service/hostidentity/scep.go (3 hunks)
• ee/server/service/hostidentity/types/host_identity_certificates.go (1 hunks)
• server/datastore/mysql/host_identity_scep.go (1 hunks)
• server/datastore/mysql/mysql.go (1 hunks)

🧰 Additional context used

🧠 Learnings (7)

server/datastore/mysql/host_identity_scep.go (2)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: server/datastore/mysql/schema.sql:501-517
Timestamp: 2025-07-07T22:21:15.748Z
Learning: In the host_identity_scep_certificates table schema, the VARBINARY(100) size for public_key_raw, the nullable host_id without a foreign key constraint, and the use of plain DATETIME instead of DATETIME(6) are intentional design decisions, not issues to be addressed.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

cmd/fleet/serve.go (4)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:108-111
Timestamp: 2025-07-08T16:12:48.797Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the SCEP depot interface methods like Put() do not accept context parameters, and the common_mysql.WithRetryTxx callback function type TxFn only receives a transaction parameter, not a context. Therefore, using context.Background() in tx.ExecContext calls within the transaction callback is the correct approach.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:115-115
Timestamp: 2025-07-08T16:11:49.555Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the error from result.RowsAffected() is intentionally ignored because the information is only used for logging purposes, not for critical program logic.

Learnt from: getvictor
PR: fleetdm/fleet#30825
File: ee/server/service/hostidentity/httpsig/httpsig.go:86-88
Timestamp: 2025-07-15T07:26:38.930Z
Learning: In ee/server/service/hostidentity/httpsig/httpsig.go, the Fetch method stub returning "not implemented" is safe because the verification profile requires MetaKeyID in RequiredMetadata, ensuring the httpsig library always calls FetchByKeyID instead of Fetch for valid signatures.

server/datastore/mysql/mysql.go (3)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:108-111
Timestamp: 2025-07-08T16:12:48.797Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the SCEP depot interface methods like Put() do not accept context parameters, and the common_mysql.WithRetryTxx callback function type TxFn only receives a transaction parameter, not a context. Therefore, using context.Background() in tx.ExecContext calls within the transaction callback is the correct approach.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:115-115
Timestamp: 2025-07-08T16:11:49.555Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the error from result.RowsAffected() is intentionally ignored because the information is only used for logging purposes, not for critical program logic.

ee/server/service/hostidentity/scep.go (3)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:108-111
Timestamp: 2025-07-08T16:12:48.797Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the SCEP depot interface methods like Put() do not accept context parameters, and the common_mysql.WithRetryTxx callback function type TxFn only receives a transaction parameter, not a context. Therefore, using context.Background() in tx.ExecContext calls within the transaction callback is the correct approach.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:115-115
Timestamp: 2025-07-08T16:11:49.555Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the error from result.RowsAffected() is intentionally ignored because the information is only used for logging purposes, not for critical program logic.

ee/server/integrationtest/hostidentity/suite.go (2)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:108-111
Timestamp: 2025-07-08T16:12:48.797Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the SCEP depot interface methods like Put() do not accept context parameters, and the common_mysql.WithRetryTxx callback function type TxFn only receives a transaction parameter, not a context. Therefore, using context.Background() in tx.ExecContext calls within the transaction callback is the correct approach.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: server/fleet/datastore.go:13-14
Timestamp: 2025-07-08T16:12:48.182Z
Learning: The Fleet team is not currently testing or enforcing OSS build compatibility, so imports of enterprise-only packages (like ee/server/service/hostidentity/types) into OSS code are acceptable for now.

ee/server/service/hostidentity/depot/depot.go (3)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:108-111
Timestamp: 2025-07-08T16:12:48.797Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the SCEP depot interface methods like Put() do not accept context parameters, and the common_mysql.WithRetryTxx callback function type TxFn only receives a transaction parameter, not a context. Therefore, using context.Background() in tx.ExecContext calls within the transaction callback is the correct approach.

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:115-115
Timestamp: 2025-07-08T16:11:49.555Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the error from result.RowsAffected() is intentionally ignored because the information is only used for logging purposes, not for critical program logic.

ee/server/integrationtest/hostidentity/scep_rate_limit_test.go (1)

Learnt from: getvictor
PR: fleetdm/fleet#30589
File: ee/server/service/hostidentity/depot/depot.go:104-119
Timestamp: 2025-07-08T16:06:54.576Z
Learning: In ee/server/service/hostidentity/depot/depot.go, the security concern where shared challenges allow certificate revocation (lines 104-119) is a known issue that will be addressed in a later feature, not an immediate concern to fix.

🧬 Code Graph Analysis (1)

cmd/fleet/serve.go (1)

ee/server/service/hostidentity/depot/depot.go (1)

• NewHostIdentitySCEPDepot (39-49)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (23)

• GitHub Check: Analyze (go)
• GitHub Check: Analyze (javascript)
• GitHub Check: test-go (mysql, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (vuln, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (vuln, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (service, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (fleetctl, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (fleetctl, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (service, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (main, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (main, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (integration-mdm, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (integration-core, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (integration-core, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (mysql, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (integration-enterprise, ubuntu-latest, mysql:9.3.0, false)
• GitHub Check: test-go (integration-enterprise, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: test-go (integration-mdm, ubuntu-latest, mysql:8.0.36, false)
• GitHub Check: lint (macos-latest)
• GitHub Check: lint (ubuntu-latest)
• GitHub Check: lint (windows-latest)
• GitHub Check: build-binaries
• GitHub Check: publish

🔇 Additional comments (16)

ee/server/service/hostidentity/types/host_identity_certificates.go (1)

18-18: Clean addition to support rate limiting

The new CreatedAt field is properly structured with the correct database tag and will work well with the rate limiting feature. This is a simple, focused change that adds exactly what's needed.

server/datastore/mysql/host_identity_scep.go (1)

50-50: Good addition to retrieve the created_at timestamp

The SQL query now includes the created_at column which will properly populate the new field in the HostIdentityCertificate struct. This matches the database schema and supports the rate limiting functionality.

cmd/fleet/serve.go (1)

1209-1209: Configuration parameter properly passed for rate limiting

The call to NewHostIdentitySCEPDepot now includes the configuration parameter, which enables the depot to access rate limiting settings. This change aligns with the updated function signature and is necessary for the rate limiting feature to work.

server/datastore/mysql/mysql.go (1)

195-196: Function signature updated to support configuration

The method now accepts a *config.FleetConfig parameter and properly forwards it to the underlying depot constructor. This change enables the rate limiting feature by providing access to configuration settings.

ee/server/service/hostidentity/scep.go (3)

27-38: Well-implemented rate limit error type

The RateLimitError struct properly implements both the error interface and the StatusCoder interface needed for HTTP status code handling. The HTTP 429 status code is the correct choice for rate limiting scenarios.

---

12-12: Good addition of backoff library

The backoff library import is appropriate for handling retry logic and permanent errors in the rate limiting implementation.

---

175-181: Correct error handling for rate limiting

The logic properly detects permanent errors from the backoff library and converts them to HTTP 429 responses. This provides clear feedback to clients when they're being rate limited.

ee/server/integrationtest/hostidentity/suite.go (3)

36-38: Good backward compatibility approach

The original SetUpSuite function now calls the new SetUpSuiteWithConfig with nil as the modifier, maintaining backward compatibility while extending functionality.

---

40-52: Clean configuration modifier pattern

The configuration modifier pattern allows tests to customize the Fleet configuration before the depot is created. The conditional application ensures the modifier is only called when provided.

---

55-55: Proper configuration passing to depot

The updated depot creation correctly passes the address of the modified configuration, aligning with the new constructor signature.

ee/server/service/hostidentity/depot/depot.go (3)

33-33: Good configuration integration

The depot now properly stores and uses the Fleet configuration for rate limiting. The constructor signature change cleanly integrates the configuration parameter.

Also applies to: 39-39, 47-47

---

112-126: Solid rate limiting implementation

The rate limiting logic is well-implemented:

• Checks if cooldown is configured before applying limits
• Properly handles both "not found" and other database errors
• Correctly compares elapsed time against cooldown period
• Returns appropriate permanent backoff error for rate limiting
• Continues processing when rate limit doesn't apply

The error message clearly identifies the problematic host for debugging purposes.

---

13-13: Appropriate library imports

The addition of the backoff library and ctxerr import supports the new rate limiting functionality and proper error handling.

Also applies to: 17-17

ee/server/integrationtest/hostidentity/scep_rate_limit_test.go (3)

25-34: Well-structured test setup

The test setup properly configures the cooldown period and ensures database cleanup. The 5-minute cooldown is appropriate for testing rate limiting behavior.

---

36-71: Comprehensive rate limiting test coverage

The test thoroughly validates the rate limiting functionality:

• Initial request succeeds as expected
• Immediate subsequent request is properly rate limited (HTTP 429)
• Rate limiting persists over time within the cooldown period
• Different hosts are not affected by rate limits for other hosts

This provides excellent coverage of the rate limiting behavior.

---

75-163: Robust SCEP certificate request helper

The helper function implements a realistic SCEP certificate request workflow:

• Proper ECC key generation and CSR creation
• Correct SCEP client setup and CA certificate retrieval
• Appropriate HTTP request handling with status code checking
• Proper handling of HTTP 429 responses
• Complete SCEP message parsing and certificate extraction

The implementation follows SCEP protocol standards and provides good error handling.

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🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch victor/30989-scep-rate-limit

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[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 64.33%. Comparing base (8f2f805) to head (9fae641).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
ee/server/service/hostidentity/depot/depot.go	85.71%	2 Missing ⚠️
cmd/fleet/serve.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #31038    +/-   ##
========================================
  Coverage   64.32%   64.33%            
========================================
  Files        1892     1893     +1     
  Lines      185748   186082   +334     
  Branches     5354     5354            
========================================
+ Hits       119483   119714   +231     
- Misses      56892    56977    +85     
- Partials     9373     9391    +18     

Flag	Coverage Δ
backend	65.24% <91.66%> (+<0.01%)	⬆️

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[getvictor]

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