SOPS 3.11 unable to encrypt a file with encryption context on AWS KMS

[shearn89]

I have a KMS key set up with an alias, and a policy that requires an encryption context. Using 3.11.0, I'm unable to encrypt a fresh file:

❯ sops --verbose -i -e --encryption-context AppName:vantage values.encrypted.yaml
[AWSKMS]         INFO[0000] Encryption failed                             arn="arn:aws:kms:eu-west-2:123412341234:alias/shearn89-sandbox-myapp-sops"
Could not generate data key: [failed to encrypt new data key with master key "arn:aws:kms:eu-west-2:123412341234:alias/shearn89-sandbox-myapp-sops": failed to encrypt sops data key with AWS KMS: operation error KMS: Encrypt, https response error StatusCode: 400, RequestID: guid, api error AccessDeniedException: User: arn:aws:iam::123412341234:user/alex.shearn is not authorized to perform: kms:Encrypt on resource: arn:aws:kms:eu-west-2:123412341234:key/key-guid with an explicit deny in a resource-based policy]

If I remove the context statement, it works. If I downgrade to 3.10.2, it also works...

Policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Delegate access to IAM",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::123412341234:root"
      },
      "Action": "kms:*",
      "Resource": "*"
    },
    {
      "Sid": "Explicitly require encryption context for enc/decrypt operations, overriding IAM",
      "Effect": "Deny",
      "Principal": {
        "AWS": "*"
      },
      "Action": [
        "kms:ReEncrypt*",
        "kms:GenerateDataKey*",
        "kms:Encrypt",
        "kms:Decrypt"
      ],
      "Resource": "*",
      "Condition": {
        "StringNotEquals": {
          "kms:EncryptionContext:AppName": "myapp"
        }
      }
    }
  ]
}

[matheuscscp]

This works for me:

export AWS_PROFILE=sso-demo
sops encrypt \
  --encrypted-regex '^(data|stringData)$' \
  --in-place \
  --kms arn:aws:kms:eu-west-2:<redacted>:key/<redacted> \
  --encryption-context foo:bar \
  secret.yaml

Result:

apiVersion: v1
kind: Secret
metadata:
    name: flux-github-app-demo-app
    namespace: flux-system
    labels:
        reconcile.fluxcd.io/watch: Enabled
type: Opaque
stringData:
    githubAppID: <redacted>
    githubAppInstallationID: <redacted>
    githubAppPrivateKey: <redacted>
sops:
    kms:
        - arn: arn:aws:kms:eu-west-2:<redacted>:key/<redacted>
          context:
            foo: bar
          created_at: "2025-10-21T13:07:05Z"
          enc: <redacted>
          aws_profile: ""
    lastmodified: "2025-10-21T13:07:06Z"
    mac: <redacted>
    encrypted_regex: ^(data|stringData)$
    version: 3.11.0

Decryption also works:

sops decrypt --in-place secret.yaml

Result:

apiVersion: v1
kind: Secret
metadata:
    name: flux-github-app-demo-app
    namespace: flux-system
    labels:
        reconcile.fluxcd.io/watch: Enabled
type: Opaque
stringData:
    githubAppID: <redacted>
    githubAppInstallationID: <redacted>
    githubAppPrivateKey: |
        <redacted>

[shearn89]

Would you mind sharing a redacted snippet of the KMS key policy applied to the key, I wonder if that's my problem?

[matheuscscp]

Here you go:

{
	"Version": "2012-10-17",
	"Statement": [
		{
			"Sid": "Enable IAM User Permissions",
			"Effect": "Allow",
			"Principal": {
				"AWS": "arn:aws:iam::<redacted>:root"
			},
			"Action": "kms:*",
			"Resource": "*"
		},
		{
			"Sid": "Allow kustomize-controller to decrypt using the key",
			"Effect": "Allow",
			"Principal": {
				"AWS": "arn:aws:iam::<redacted>:role/flux-d2-kustomize-controller"
			},
			"Action": [
				"kms:Decrypt",
				"kms:DescribeKey"
			],
			"Resource": "*"
		}
	]
}

[felixfontein]

This is more likely caused by a dependency upgrade (i.e. some behavior change in Amazon's SDK).

[shearn89]

Okay - work is busy this week but if I get time I’ll try and build from source so I can do a git bisect to find the issue…

[shearn89]

Okay - ran a git bisect, and 84c7673 is the first bad commit.

[shearn89]

Introduced in #1939, @felixfontein.

[shearn89]

Happy to help with testing any branch fixes, or setting up example keys/policies. The policy in the first post is what we use, and then we set --encryption-context AppName:myapp on first encryption.