Guide

Control egress

Choose how outbound traffic is allowed or denied, configure inspection, and audit policy decisions from the sandbox.

Deny outbound traffic by default

A default deny policy blocks outbound calls unless a rule allows them. Start with deny, then add the smallest host list your workload needs.

1. Open the sandbox from Sandbox groups > your group > Sandboxes.
2. From the sandbox details, select Egress policy.
3. Set Default action to Deny.
4. Set Traffic inspection to Full.
5. Add *.github.com with action Allow.
6. Select Save. Wait a few seconds before you test the policy.

Bash

aca sandbox create --disk ubuntu --label name=demo-egress
aca sandbox egress set -l name=demo-egress --default Deny \
  --rule "*.github.com:Allow" \
  --traffic-inspection Full
aca sandbox egress show -l name=demo-egress

PowerShell

aca sandbox create --disk ubuntu --label name=demo-egress
aca sandbox egress set -l name=demo-egress --default Deny `
  --rule "*.github.com:Allow" `
  --traffic-inspection Full
aca sandbox egress show -l name=demo-egress

SDK

import os

from azure.identity import DefaultAzureCredential
from azure.containerapps.sandbox import (
    EgressHostRule,
    EgressPolicy,
    SandboxGroupClient,
    endpoint_for_region,
)

credential = DefaultAzureCredential()
client = SandboxGroupClient(
    endpoint_for_region(os.environ["ACA_SANDBOXGROUP_REGION"]),
    credential,
    subscription_id=os.environ["AZURE_SUBSCRIPTION_ID"],
    resource_group=os.environ["ACA_RESOURCE_GROUP"],
    sandbox_group=os.environ["ACA_SANDBOX_GROUP"],
)

sandbox = client.get_sandbox_client(os.environ["SANDBOX_ID"])
sandbox.set_egress_policy(EgressPolicy(
    default_action="Deny",
    traffic_inspection="Full",
    host_rules=[EgressHostRule(pattern="*.github.com", action="Allow")],
))
policy = sandbox.get_egress_policy()
print(policy.default_action, len(policy.host_rules))

Use --rule "<pattern>:<Action>" for simple host rules. The action is Allow or Deny.

Bash

aca sandbox egress set -l name=demo-egress --default Deny \
  --rule "*.github.com:Allow" \
  --rule "example.com:Deny" \
  --traffic-inspection Full

PowerShell

aca sandbox egress set -l name=demo-egress --default Deny `
  --rule "*.github.com:Allow" `
  --rule "example.com:Deny" `
  --traffic-inspection Full

You can also set the policy when you create a sandbox:

Bash

aca sandbox create --disk ubuntu \
  --label name=demo-egress \
  --egress-default Deny \
  --egress-rule "*.github.com:Allow" \
  --traffic-inspection Full

PowerShell

aca sandbox create --disk ubuntu `
  --label name=demo-egress `
  --egress-default Deny `
  --egress-rule "*.github.com:Allow" `
  --traffic-inspection Full

Allow outbound traffic by default

Alternatively, use an allow-by-default policy for sandboxes that need normal outbound access, with deny rules for specific destinations.

Bash

aca sandbox create --disk ubuntu \
  --label name=demo-egress-allow \
  --egress-default Allow \
  --egress-rule "example.com:Deny" \
  --traffic-inspection Full

PowerShell

aca sandbox create --disk ubuntu `
  --label name=demo-egress-allow `
  --egress-default Allow `
  --egress-rule "example.com:Deny" `
  --traffic-inspection Full

For an existing sandbox:

Bash

aca sandbox egress set -l name=demo-egress --default Allow \
  --rule "example.com:Deny" \
  --traffic-inspection Full

PowerShell

aca sandbox egress set -l name=demo-egress --default Allow `
  --rule "example.com:Deny" `
  --traffic-inspection Full

Control traffic inspection

Traffic inspection controls how the egress proxy evaluates outbound TLS traffic. Choose the lowest inspection level that supports the policy rules you need.

Mode	Use when
Full	You need egress enforcement, including default deny, deny rules, path or method matches, rewrites, or header transforms. This mode also blocks non-HTTP TCP and UDP traffic, except Azure DNS.
Partial	You only need rewrites or transforms for selected HTTPS hosts. Other HTTPS traffic passes through without request inspection. Deny rules are not supported in this mode.
None	You do not need the egress proxy for this sandbox. Traffic bypasses proxy inspection and egress policy enforcement.

Bash

aca sandbox egress set -l name=demo-egress \
  --default Deny \
  --rule "*.github.com:Allow" \
  --traffic-inspection Full

PowerShell

aca sandbox egress set -l name=demo-egress `
  --default Deny `
  --rule "*.github.com:Allow" `
  --traffic-inspection Full

Create-time policy flags support the same inspection setting:

Bash

aca sandbox create --disk ubuntu \
  --label name=demo-egress \
  --egress-default Deny \
  --egress-rule "*.github.com:Allow" \
  --traffic-inspection Full

PowerShell

aca sandbox create --disk ubuntu `
  --label name=demo-egress `
  --egress-default Deny `
  --egress-rule "*.github.com:Allow" `
  --traffic-inspection Full

Use a policy file for advanced rules

Use policy files for path or method matches, rewrites, transforms, and header operations.

Supported rule fields:

Field	Supported values
match.host	Required host name or wildcard pattern.
match.path	Optional path match, such as /headers.
match.methods	Optional HTTP methods, such as [GET, POST].
action.type	Allow, Deny, Rewrite, or Transform.
action.host	Rewrite target host. Only valid when action.type is Rewrite.
action.path	Rewrite target path. Only valid when action.type is Rewrite.
action.scheme	Rewrite target scheme, such as https. Only valid when action.type is Rewrite.
action.headers	Header mutations. Valid when action.type is Transform or Rewrite.
headers[].operation	Set, Insert, or Remove. Only valid inside action.headers.

Bash

aca sandbox egress init > egress.yaml
aca sandbox egress schema > egress.schema.json
aca sandbox egress apply -l name=demo-egress --file egress.yaml
aca sandbox egress export -l name=demo-egress > current-egress.yaml

PowerShell

aca sandbox egress init > egress.yaml
aca sandbox egress schema > egress.schema.json
aca sandbox egress apply -l name=demo-egress --file egress.yaml
aca sandbox egress export -l name=demo-egress > current-egress.yaml

Example advanced policy:

defaultAction: Deny
trafficInspection: Full
rules:
  - name: inject-test-header
    match:
      host: "httpbin.org"
      path: "/headers"
      methods: [GET]
    action:
      type: Transform
      headers:
        - operation: Insert
          name: X-Test-Header
          value: egress-test

Rules are evaluated in order. The first matching rule wins.

Verify allowed and blocked hosts

Test from inside the sandbox after the policy has propagated. An allowed host should return a normal HTTP status. A blocked host should fail or return a non-200 status.

1. Open the sandbox, then select Connect > Interactive shell.
2. Run curl https://example.com to test a blocked host.
3. Run curl https://api.github.com to test an allowed host.
4. Select Network audit to review the recorded decisions.

Bash

aca sandbox exec -l name=demo-egress -c \
  "curl -fsS -o /dev/null -w 'HTTP %{http_code}\n' --max-time 8 https://example.com" || echo "blocked"

aca sandbox exec -l name=demo-egress -c \
  "curl -sS -o /dev/null -w 'HTTP %{http_code}\n' --max-time 8 https://api.github.com"

PowerShell

aca sandbox exec -l name=demo-egress -c `
  "curl -fsS -o /dev/null -w 'HTTP %{http_code}\n' --max-time 8 https://example.com"
if ($LASTEXITCODE -ne 0) { Write-Host "blocked" }

aca sandbox exec -l name=demo-egress -c `
  "curl -sS -o /dev/null -w 'HTTP %{http_code}\n' --max-time 8 https://api.github.com"

SDK

import time

time.sleep(10)

result = sandbox.exec(
    "curl -fsS -o /dev/null -w '%{http_code}' --max-time 8 "
    "https://example.com || echo CURL_FAIL"
)
print(result.stdout.strip())

result = sandbox.exec(
    "curl -sS -o /dev/null -w '%{http_code}' --max-time 8 "
    "https://api.github.com"
)
print(result.stdout.strip())

Audit decisions

The audit view shows outbound connection attempts and the policy decision for each host.

1. Open the sandbox, then select Network audit.
2. Use the host filter to find a domain.
3. Review the decision, timestamp, and target host for each entry.
4. Update Egress policy if the sandbox needs another allowed host.

Bash

aca sandbox egress decisions -l name=demo-egress

PowerShell

aca sandbox egress decisions -l name=demo-egress

SDK

decisions = sandbox.get_egress_decisions()
if decisions.network_egress:
    for entry in decisions.network_egress.denied:
        print("Denied:", entry.host, entry.method, entry.path)
    for entry in decisions.network_egress.allowed:
        print("Allowed:", entry.host, entry.method, entry.path)

Use -o json for scripts. The JSON output separates allowed and denied decisions.

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