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Limit the IAM EC2 policy for the master nodes #3186

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Aug 28, 2017
Merged

Limit the IAM EC2 policy for the master nodes #3186

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72 changes: 55 additions & 17 deletions pkg/model/iam/iam_builder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -52,10 +52,13 @@ type IAMStatementEffect string
const IAMStatementEffectAllow IAMStatementEffect = "Allow"
const IAMStatementEffectDeny IAMStatementEffect = "Deny"

type Condition map[string]interface{}

type IAMStatement struct {
Effect IAMStatementEffect
Action stringorslice.StringOrSlice
Resource stringorslice.StringOrSlice
Effect IAMStatementEffect
Action stringorslice.StringOrSlice
Resource stringorslice.StringOrSlice
Condition Condition `json:",omitempty"`
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Why, this makes writing IAM statements almost pleasurable ;-)

}

func (l *IAMStatement) Equal(r *IAMStatement) bool {
Expand Down Expand Up @@ -106,14 +109,7 @@ func (b *IAMPolicyBuilder) BuildAWSIAMPolicy() (*IAMPolicy, error) {
return p, nil
}

if b.Role == api.InstanceGroupRoleNode {
p.Statement = append(p.Statement, &IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:Describe*"}),
Resource: wildcard,
})

}
addEC2Permissions(p, iamPrefix, b, wildcard, legacyIAM)

{
// We provide ECR access on the nodes (naturally), but we also provide access on the master.
Expand All @@ -135,12 +131,6 @@ func (b *IAMPolicyBuilder) BuildAWSIAMPolicy() (*IAMPolicy, error) {
}

if b.Role == api.InstanceGroupRoleMaster {
p.Statement = append(p.Statement, &IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:*"}),
Resource: wildcard,
})

p.Statement = append(p.Statement, &IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"elasticloadbalancing:*"}),
Expand Down Expand Up @@ -251,6 +241,54 @@ func (b *IAMPolicyBuilder) BuildAWSIAMPolicy() (*IAMPolicy, error) {
return p, nil
}

// addEC2Permissions updates the IAM Policy with statements granting tailored
// access to EC2 resources, depending on the instance role
func addEC2Permissions(p *IAMPolicy, iamPrefix string, b *IAMPolicyBuilder, wildcard stringorslice.StringOrSlice, legacyIAM bool) {
if (b.Role == api.InstanceGroupRoleNode) || (b.Role == api.InstanceGroupRoleMaster) {
p.Statement = append(p.Statement, &IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:Describe*"}),
Resource: wildcard,
})
}

if b.Role == api.InstanceGroupRoleMaster {
if legacyIAM {
p.Statement = append(p.Statement,
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:*"}),
Resource: wildcard,
},
)
} else {
p.Statement = append(p.Statement,
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{
"ec2:CreateRoute",
"ec2:CreateTags",
"ec2:CreateVolume",
"ec2:DeleteVolume",
"ec2:ModifyInstanceAttribute",
}),
Resource: wildcard,
},
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:*"}),
Resource: wildcard,
Condition: Condition{
"StringEquals": map[string]string{
"ec2:ResourceTag/KubernetesCluster": b.Cluster.GetName(),
},
},
},
)
}
}
}

func addRoute53Permissions(p *IAMPolicy, hostedZoneID string) {
// Remove /hostedzone/ prefix (if present)
hostedZoneID = strings.TrimPrefix(hostedZoneID, "/")
Expand Down
120 changes: 120 additions & 0 deletions pkg/model/iam/iam_builder_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -219,3 +219,123 @@ func TestS3PolicyGeneration(t *testing.T) {
}
}
}

func TestEC2PolicyGeneration(t *testing.T) {
wildcard := stringorslice.Slice([]string{"*"})
clusterName := "my-cluster.k8s.local"
defaultEC2Statements := []*IAMStatement{
{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:Describe*"}),
Resource: wildcard,
},
}

grid := []struct {
Role kops.InstanceGroupRole
LegacyIAM bool
IAMPolicy IAMPolicy
}{
{
Role: "Node",
LegacyIAM: false,
IAMPolicy: IAMPolicy{
Statement: defaultEC2Statements,
},
},
{
Role: "Node",
LegacyIAM: true,
IAMPolicy: IAMPolicy{
Statement: defaultEC2Statements,
},
},
{
Role: "Master",
LegacyIAM: false,
IAMPolicy: IAMPolicy{
Statement: append(
defaultEC2Statements,
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{
"ec2:CreateRoute",
"ec2:CreateTags",
"ec2:CreateVolume",
"ec2:DeleteVolume",
"ec2:ModifyInstanceAttribute",
}),
Resource: wildcard,
},
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:*"}),
Resource: wildcard,
Condition: Condition{
"StringEquals": map[string]string{
"ec2:ResourceTag/KubernetesCluster": clusterName,
},
},
},
),
},
},
{
Role: "Master",
LegacyIAM: true,
IAMPolicy: IAMPolicy{
Statement: append(
defaultEC2Statements,
&IAMStatement{
Effect: IAMStatementEffectAllow,
Action: stringorslice.Slice([]string{"ec2:*"}),
Resource: wildcard,
},
),
},
},
{
Role: "Bastion",
LegacyIAM: false,
IAMPolicy: IAMPolicy{
Statement: nil,
},
},
{
Role: "Bastion",
LegacyIAM: true,
IAMPolicy: IAMPolicy{
Statement: nil,
},
},
}

for i, x := range grid {
ip := &IAMPolicy{}
b := IAMPolicyBuilder{
Role: x.Role,
Cluster: &kops.Cluster{},
}
b.Cluster.SetName(clusterName)

addEC2Permissions(ip, "arn:aws", &b, wildcard, x.LegacyIAM)

expectedPolicy, err := x.IAMPolicy.AsJSON()
if err != nil {
t.Errorf("case %d failed to convert expected IAM Policy to JSON. Error: %q", i, err)
continue
}
actualPolicy, err := ip.AsJSON()
if err != nil {
t.Errorf("case %d failed to convert generated IAM Policy to JSON. Error: %q", i, err)
continue
}

if expectedPolicy != actualPolicy {
diffString := diff.FormatDiff(expectedPolicy, actualPolicy)
t.Logf("diff:\n%s\n", diffString)
t.Errorf("case %d failed, policy output differed from expected.", i)
continue
}
}
}
23 changes: 16 additions & 7 deletions tests/integration/minimal/cloudformation.json
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Original file line number Diff line number Diff line change
Expand Up @@ -536,13 +536,7 @@
"Statement": [
{
"Action": [
"ecr:GetAuthorizationToken",
"ecr:BatchCheckLayerAvailability",
"ecr:GetDownloadUrlForLayer",
"ecr:GetRepositoryPolicy",
"ecr:DescribeRepositories",
"ecr:ListImages",
"ecr:BatchGetImage"
"ec2:Describe*"
],
"Effect": "Allow",
"Resource": [
Expand All @@ -558,6 +552,21 @@
"*"
]
},
{
"Action": [
"ecr:GetAuthorizationToken",
"ecr:BatchCheckLayerAvailability",
"ecr:GetDownloadUrlForLayer",
"ecr:GetRepositoryPolicy",
"ecr:DescribeRepositories",
"ecr:ListImages",
"ecr:BatchGetImage"
],
"Effect": "Allow",
"Resource": [
"*"
]
},
{
"Action": [
"elasticloadbalancing:*"
Expand Down