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# STR policy evaluations =======================================================
# Controls: STR-001 through STR-007
package controls.aws.str
import data.common.exemptions as exemptions
import data.common.outputs as outputs
import data.common.policydoc as policydoc
# Helpers ----------------------------------------------------------------------
s3_buckets := {r.name: r |
some r in input.resource_changes
r.type == "aws_s3_bucket"
r.change.actions[_] in ["create", "update"]
}
companion_exists(companion_type, bucket_name) if {
some r in input.configuration.root_module.resources
r.type == companion_type
some ref in r.expressions.bucket.references
ref == concat(".", ["aws_s3_bucket", bucket_name])
}
# STR-001 — Require S3 Block Public Access ------------------------------------
deny contains msg if {
some policy_id in {"ICP-TF-AWS-STR-001", "ICP-TF-AWS-GAC-001"}
some name, bucket in s3_buckets
not companion_exists("aws_s3_bucket_public_access_block", name)
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("S3 bucket '%s' is missing a public access block", [name]),
)
}
deny contains msg if {
some policy_id in {"ICP-TF-AWS-STR-001", "ICP-TF-AWS-GAC-001"}
some r in input.resource_changes
r.type == "aws_s3_bucket_public_access_block"
r.change.actions[_] in ["create", "update"]
flags := [
r.change.after.block_public_acls,
r.change.after.block_public_policy,
r.change.after.ignore_public_acls,
r.change.after.restrict_public_buckets,
]
false in flags
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("S3 public access block '%s' has one or more flags disabled", [r.name]),
)
}
# STR-002 — Prohibit Public Read Access on S3 Buckets -------------------------
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-002"
some r in input.resource_changes
r.type == "aws_s3_bucket_policy"
r.change.actions[_] in ["create", "update"]
some stmt in policydoc.statements(r.change.after.policy)
stmt.Effect == "Allow"
policydoc.public_principal(stmt)
some action in policydoc.actions(stmt)
_read_action(action)
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("S3 bucket policy '%s' grants public read access", [r.name]),
)
}
_read_action(a) if a == "*"
_read_action(a) if a == "s3:*"
_read_action(a) if a == "s3:GetObject"
_read_action(a) if a == "s3:ListBucket"
_read_action(a) if a == "s3:GetBucketAcl"
# STR-003 — Prohibit Public Write Access on S3 Buckets ------------------------
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-003"
some r in input.resource_changes
r.type == "aws_s3_bucket_policy"
r.change.actions[_] in ["create", "update"]
some stmt in policydoc.statements(r.change.after.policy)
stmt.Effect == "Allow"
policydoc.public_principal(stmt)
some action in policydoc.actions(stmt)
_write_action(action)
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("S3 bucket policy '%s' grants public write access", [r.name]),
)
}
_write_action(a) if a == "*"
_write_action(a) if a == "s3:*"
_write_action(a) if a == "s3:PutObject"
_write_action(a) if a == "s3:DeleteObject"
_write_action(a) if a == "s3:PutBucketAcl"
# STR-004 — Require Default S3 Server-Side Encryption -------------------------
deny contains msg if {
some policy_id in {"ICP-TF-AWS-STR-004", "ICP-TF-AWS-GAC-002"}
some name, bucket in s3_buckets
not companion_exists("aws_s3_bucket_server_side_encryption_configuration", name)
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("S3 bucket '%s' is missing server-side encryption configuration", [name]),
)
}
# STR-005 — Require TLS-Only Access to S3 Buckets ----------------------------
deny contains msg if {
some policy_id in {"ICP-TF-AWS-STR-005", "ICP-TF-AWS-GAC-004"}
some name, _ in s3_buckets
not companion_exists("aws_s3_bucket_policy", name)
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("S3 bucket '%s' has no bucket policy — TLS-only deny statement required", [name]),
)
}
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-005"
some r in input.resource_changes
r.type == "aws_s3_bucket_policy"
r.change.actions[_] in ["create", "update"]
not _has_secure_transport_deny(r.change.after.policy)
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("S3 bucket policy '%s' is missing a SecureTransport deny statement", [r.name]),
)
}
_has_secure_transport_deny(raw) if {
some stmt in policydoc.statements(raw)
stmt.Effect == "Deny"
stmt.Condition.Bool["aws:SecureTransport"] == "false"
}
# STR-006 — Restrict Cross-Account Grants in S3 Bucket Policies ---------------
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-006"
some r in input.resource_changes
r.type == "aws_s3_bucket_policy"
r.change.actions[_] in ["create", "update"]
some stmt in policydoc.statements(r.change.after.policy)
stmt.Effect == "Allow"
_broad_principal(stmt)
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("S3 bucket policy '%s' grants access to a broad or wildcard principal", [r.name]),
)
}
_broad_principal(stmt) if stmt.Principal == "*"
_broad_principal(stmt) if stmt.Principal.AWS == "*"
_broad_principal(stmt) if endswith(stmt.Principal.AWS, ":root")
# STR-007 — Enforce S3 Bucket Owner Object Ownership --------------------------
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-007"
some name, _ in s3_buckets
not companion_exists("aws_s3_bucket_ownership_controls", name)
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("S3 bucket '%s' is missing ownership controls", [name]),
)
}
deny contains msg if {
policy_id := "ICP-TF-AWS-STR-007"
some r in input.resource_changes
r.type == "aws_s3_bucket_ownership_controls"
r.change.actions[_] in ["create", "update"]
some rule in r.change.after.rule
rule.object_ownership != "BucketOwnerEnforced"
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("S3 ownership controls '%s' object_ownership is not BucketOwnerEnforced", [r.name]),
)
}
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