Security Headers Manager¶

The Security Headers Manager provides comprehensive HTTP security header management following OWASP best practices.

Overview¶

The SecurityHeadersManager is a singleton class that manages security headers for HTTP responses, including Content Security Policy (CSP), HTTP Strict Transport Security (HSTS), and other essential security headers.

Class Reference¶

SecurityHeadersManager¶

from guard import SecurityHeadersManager

security_headers_manager = SecurityHeadersManager()

Methods¶

configure¶

Configure security headers settings.

security_headers_manager.configure(
    enabled=True,
    csp={
        "default-src": ["'self'"],
        "script-src": ["'self'", "https://trusted.cdn.com"],
        "style-src": ["'self'", "'unsafe-inline'"],
        "img-src": ["'self'", "data:", "https:"],
        "font-src": ["'self'", "https://fonts.gstatic.com"],
        "connect-src": ["'self'"],
        "frame-ancestors": ["'none'"],
        "base-uri": ["'self'"],
        "form-action": ["'self'"]
    },
    hsts_max_age=31536000,  # 1 year
    hsts_include_subdomains=True,
    hsts_preload=False,
    frame_options="SAMEORIGIN",
    content_type_options="nosniff",
    xss_protection="1; mode=block",
    referrer_policy="strict-origin-when-cross-origin",
    permissions_policy="geolocation=(), microphone=(), camera=()",
    custom_headers={
        "X-Custom-Header": "CustomValue"
    },
    cors_origins=["https://app.example.com"],
    cors_allow_credentials=True,
    cors_allow_methods=["GET", "POST"],
    cors_allow_headers=["*"]
)

Parameters:

enabled (bool): Enable/disable security headers. Default: True
csp (dict[str, list[str]] | None): Content Security Policy directives
hsts_max_age (int | None): HSTS max-age in seconds (e.g., 31536000 for 1 year)
hsts_include_subdomains (bool): Include subdomains in HSTS. Default: True
hsts_preload (bool): Enable HSTS preload. Default: False
frame_options (str | None): X-Frame-Options value (DENY, SAMEORIGIN)
content_type_options (str | None): X-Content-Type-Options value
xss_protection (str | None): X-XSS-Protection value
referrer_policy (str | None): Referrer-Policy value
permissions_policy (str | None): Permissions-Policy value
custom_headers (dict[str, str] | None): Additional custom security headers
cors_origins (list[str] | None): Allowed CORS origins
cors_allow_credentials (bool): Allow credentials in CORS. Default: False
cors_allow_methods (list[str] | None): Allowed CORS methods
cors_allow_headers (list[str] | None): Allowed CORS headers

get_headers¶

Get security headers for a response.

headers = await security_headers_manager.get_headers(
    request_path="/api/endpoint"
)

Parameters:

request_path (str | None): Optional request path for path-specific headers

Returns:

dict[str, str]: Dictionary of security headers

get_cors_headers¶

Get CORS headers if origin is allowed.

cors_headers = await security_headers_manager.get_cors_headers(
    origin="https://app.example.com"
)

Parameters:

origin (str): Request origin

Returns:

dict[str, str]: Dictionary of CORS headers

validate_csp_report¶

Validate and process CSP violation reports.

is_valid = await security_headers_manager.validate_csp_report(
    report={
        "csp-report": {
            "document-uri": "https://example.com/page",
            "violated-directive": "script-src",
            "blocked-uri": "https://evil.com/script.js",
            "source-file": "https://example.com/app.js",
            "line-number": 10
        }
    }
)

Parameters:

report (dict[str, Any]): CSP violation report

Returns:

bool: True if report is valid

initialize_redis¶

Initialize Redis connection for caching header configurations.

await security_headers_manager.initialize_redis(redis_handler)

Parameters:

redis_handler (Any): Redis handler instance

initialize_agent¶

Initialize agent integration for security event tracking.

await security_headers_manager.initialize_agent(agent_handler)

Parameters:

agent_handler (Any): Agent handler instance

reset¶

Reset all security headers configuration.

await security_headers_manager.reset()

Default Headers¶

The following headers are configured by default:

Header	Default Value	Description
`X-Content-Type-Options`	`nosniff`	Prevents MIME type sniffing
`X-Frame-Options`	`SAMEORIGIN`	Prevents clickjacking attacks
`X-XSS-Protection`	`1; mode=block`	Enables XSS filtering
`Referrer-Policy`	`strict-origin-when-cross-origin`	Controls referrer information
`Permissions-Policy`	`geolocation=(), microphone=(), camera=()`	Restricts browser features
`X-Permitted-Cross-Domain-Policies`	`none`	Restricts Adobe Flash cross-domain access
`X-Download-Options`	`noopen`	Prevents file download execution in IE
`Cross-Origin-Embedder-Policy`	`require-corp`	Controls cross-origin resource embedding
`Cross-Origin-Opener-Policy`	`same-origin`	Controls cross-origin window interactions
`Cross-Origin-Resource-Policy`	`same-origin`	Controls cross-origin resource access

Content Security Policy (CSP)¶

CSP helps prevent XSS attacks by specifying which sources are allowed for various content types.

Common CSP Directives¶

default-src: Default policy for all resource types
script-src: Valid sources for JavaScript
style-src: Valid sources for stylesheets
img-src: Valid sources for images
font-src: Valid sources for fonts
connect-src: Valid sources for fetch, XMLHttpRequest, WebSocket
frame-src: Valid sources for frames
frame-ancestors: Valid parents that may embed a page
base-uri: Restricts URLs for <base> element
form-action: Valid endpoints for form submissions
report-uri: URL to send CSP violation reports

CSP Source Values¶

'self': Same origin
'none': No sources allowed
'unsafe-inline': Allow inline scripts/styles (use with caution)
'unsafe-eval': Allow eval() (use with caution)
https:: Any HTTPS source
data:: Data URIs
Specific domains: https://trusted.cdn.com

HTTP Strict Transport Security (HSTS)¶

HSTS forces browsers to use HTTPS connections.

HSTS Configuration¶

hsts_config = {
    "max_age": 31536000,        # 1 year in seconds
    "include_subdomains": True,  # Apply to all subdomains
    "preload": False            # Submit to HSTS preload list
}

HSTS Preload Requirements¶

To enable HSTS preload:

Serve a valid certificate
Redirect all HTTP to HTTPS
Serve all subdomains over HTTPS
Set max_age to at least 31536000 (1 year)
Include includeSubDomains
Include preload

CORS Integration¶

The Security Headers Manager integrates with CORS configuration:

# CORS headers are automatically added when:
# 1. An origin header is present in the request
# 2. The origin is in the allowed list
cors_config = {
    "origins": ["https://app.example.com", "https://admin.example.com"],
    "allow_credentials": True,
    "allow_methods": ["GET", "POST", "PUT", "DELETE"],
    "allow_headers": ["*"]
}

Redis Caching¶

Header configurations are cached in Redis for performance:

CSP configuration: Cached with key security_headers:csp_config
HSTS configuration: Cached with key security_headers:hsts_config
Custom headers: Cached with key security_headers:custom_headers
TTL: 86400 seconds (24 hours)

Agent Integration¶

When agent is configured, the following events are sent:

security_headers_applied: When headers are added to a response
csp_violation: When a CSP violation report is received

Example Usage¶

Basic Configuration¶

from fastapi import FastAPI
from guard.middleware import SecurityMiddleware
from guard import SecurityConfig

app = FastAPI()

config = SecurityConfig(
    security_headers={
        "enabled": True,
        "hsts": {
            "max_age": 31536000,
            "include_subdomains": True,
            "preload": False
        },
        "frame_options": "DENY",
        "content_type_options": "nosniff",
        "xss_protection": "1; mode=block",
        "referrer_policy": "no-referrer",
        "permissions_policy": "geolocation=(), microphone=(), camera=()"
    }
)

app.add_middleware(SecurityMiddleware, config=config)

Advanced CSP Configuration¶

config = SecurityConfig(
    security_headers={
        "enabled": True,
        "csp": {
            "default-src": ["'self'"],
            "script-src": ["'self'", "'unsafe-inline'", "https://cdn.jsdelivr.net"],
            "style-src": ["'self'", "'unsafe-inline'", "https://fonts.googleapis.com"],
            "img-src": ["'self'", "data:", "https:"],
            "font-src": ["'self'", "https://fonts.gstatic.com"],
            "connect-src": ["'self'", "https://api.example.com"],
            "frame-ancestors": ["'none'"],
            "base-uri": ["'self'"],
            "form-action": ["'self'"],
            "report-uri": ["/api/csp-report"]
        }
    }
)

CSP Report Endpoint¶

from fastapi import Request

@app.post("/api/csp-report")
async def handle_csp_report(request: Request):
    report = await request.json()
    is_valid = await security_headers_manager.validate_csp_report(report)

    if is_valid:
        # Report is logged automatically by the manager
        return {"status": "received"}

    return {"status": "invalid"}

Disabling Specific Headers¶

config = SecurityConfig(
    security_headers={
        "enabled": True,
        "frame_options": None,  # Disable X-Frame-Options
        "permissions_policy": None,  # Disable Permissions-Policy
        # Other headers remain at defaults
    }
)

Best Practices¶

Gradual HSTS Rollout: Start with a small max_age and gradually increase
Test Thoroughly: Security headers can break functionality if too restrictive
Monitor CSP Reports: Set up monitoring for CSP violations
Use HTTPS: Many security headers require HTTPS to be effective
Browser Compatibility: Check browser support for specific headers

Security Considerations¶

Header Injection Prevention: All header values are validated against injection attacks, newlines, and excessive length
CORS Security: Wildcard origins (*) cannot be used with credentials to prevent security vulnerabilities
Thread Safety: SecurityHeadersManager uses thread-safe singleton pattern with double-checked locking
Cache Security: Cache keys are generated using SHA256 hashing to prevent cache poisoning attacks
CSP Validation: Unsafe directives like 'unsafe-inline' and 'unsafe-eval' trigger security warnings
HSTS Preload: Strict validation ensures preload requirements (max_age ≥ 1 year, includeSubDomains)
CSP Bypasses: Be aware of potential CSP bypasses with 'unsafe-inline' and 'unsafe-eval'
HSTS Commitment: Once HSTS is enabled with a long max_age, it cannot be easily undone
Frame Options: Consider using CSP's frame-ancestors instead of X-Frame-Options
Legacy Headers: Some headers like X-XSS-Protection are being phased out in modern browsers
Performance: Complex CSP policies can impact page load performance

Security Headers Manager¶

Overview¶

Class Reference¶

SecurityHeadersManager¶

Methods¶

configure¶

get_headers¶

get_cors_headers¶

validate_csp_report¶

initialize_redis¶

initialize_agent¶

reset¶

Default Headers¶

Content Security Policy (CSP)¶

Common CSP Directives¶

CSP Source Values¶

HTTP Strict Transport Security (HSTS)¶

HSTS Configuration¶

HSTS Preload Requirements¶

CORS Integration¶

Redis Caching¶

Agent Integration¶

Example Usage¶

Basic Configuration¶

Advanced CSP Configuration¶

CSP Report Endpoint¶

Disabling Specific Headers¶

Best Practices¶

Security Considerations¶

See Also¶