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# IAM policy evaluations =======================================================
# Controls: IAM-001 through IAM-006

package controls.aws.iam

import data.common.definitions as defs
import data.common.exemptions as exemptions
import data.common.outputs as outputs
import data.common.policydoc as policydoc

# IAM-001 — Require Policy Attachment to Groups or Roles ----------------------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-001"

	some _, rc in input.resource_changes
	rc.type in {"aws_iam_user_policy", "aws_iam_user_policy_attachment"}
	rc.change.actions != ["delete"]

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("IAM policy attached directly to user via '%s.%s'", [rc.type, rc.name]),
	)
}

# IAM-002 — Prohibit Long-Term IAM User Access Keys ---------------------------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-002"

	some _, rc in input.resource_changes
	rc.type == "aws_iam_access_key"
	rc.change.actions != ["delete"]

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("Long-term IAM access key created: '%s'", [rc.name]),
	)
}

# IAM-003 — Restrict Broad KMS Key Permissions --------------------------------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-003"

	some _, rc in input.resource_changes
	rc.type in {"aws_iam_role_policy", "aws_iam_user_policy", "aws_iam_group_policy"}
	rc.change.actions != ["delete"]

	doc := json.unmarshal(rc.change.after.policy)
	some stmt in doc.Statement
	stmt.Effect == "Allow"

	some action in policydoc.as_list(stmt.Action)
	_broad_kms_action(action)

	some resource in policydoc.as_list(stmt.Resource)
	resource == "*"

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("Broad KMS action '%s' on Resource * in '%s.%s'", [action, rc.type, rc.name]),
	)
}

_broad_kms_action(action) if action == "kms:*"
_broad_kms_action(action) if action == "kms:Decrypt"
_broad_kms_action(action) if action == "kms:ReEncryptFrom"

# IAM-004 — Require Permissions Boundary on Delegated Roles -------------------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-004"

	some _, rc in input.resource_changes
	rc.type == "aws_iam_role"
	rc.change.actions != ["delete"]

	not _has_permissions_boundary(rc.change.after)

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("IAM role '%s' has no permissions boundary set", [rc.name]),
	)
}

_has_permissions_boundary(after) if {
	after.permissions_boundary != null
	after.permissions_boundary != ""
}

# IAM-005 — Prevent Confused-Deputy in Cross-Account Trust Policies -----------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-005"

	some _, rc in input.resource_changes
	rc.type == "aws_iam_role"
	rc.change.actions != ["delete"]

	doc := json.unmarshal(rc.change.after.assume_role_policy)
	some stmt in doc.Statement
	stmt.Effect == "Allow"

	_public_principal(stmt)
	not stmt.Condition

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("IAM role '%s' trust policy allows Principal * without a scoping Condition", [rc.name]),
	)
}

_public_principal(stmt) if stmt.Principal == "*"
_public_principal(stmt) if stmt.Principal.AWS == "*"

_public_principal(stmt) if {
	some p in policydoc.as_list(stmt.Principal.AWS)
	p == "*"
}

# IAM-006 — Detect Hardcoded Credentials and Secrets in Terraform -------------

deny contains msg if {
	policy_id := "ICP-TF-AWS-IAM-006"

	some name, provider in input.configuration.provider_config
	startswith(name, "aws")

	some field in defs.aws_cred_fields
	provider.expressions[field].constant_value

	meta := data.policies[policy_id]
	meta.status == "active"

	not exemptions.policy_exemption(policy_id)
	not exemptions.severity_exemption(meta.severity)

	msg := outputs.violation(
		policy_id,
		meta,
		sprintf("Hardcoded AWS %s detected in provider block '%s'", [field, name]),
	)
}