bug: S3 CopyObject fails with an HTTP 412 error when a valid x-amz-copy-source-if-modified-since header value is provided #13331
Description
Is there an existing issue for this?
- I have searched the existing issues
Current Behavior
Calling the S3 CopyObject operation for an existing source object with a valid x-amz-copy-source-if-modified-since header value causes the request to fail with an HTTP 412 status. The request however, doesn't fail if called against a real AWS S3 bucket.
Expected Behavior
No response
How are you starting LocalStack?
With a docker run command
Steps To Reproduce
How are you starting localstack (e.g., bin/localstack command, arguments, or docker-compose.yml)
docker run --rm -it -p 4566:4566 localstack/localstack:s3-latest
Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)
Bucket setup snippet:
import boto3
import botocore.config
bucket = "testbucket"
client = boto3.client(
"s3",
endpoint_url="http://localhost:4566",
aws_access_key_id="112233445566",
aws_secret_access_key="test",
config=botocore.config.Config(signature_version="s3v4"),
verify=False,
)
client.create_bucket(Bucket=bucket)
client.put_bucket_versioning(
Bucket=bucket,
VersioningConfiguration={
"Status": "Enabled",
},
)Bug reproduction script:
import boto3
import botocore.config
bucket = "testbucket"
source_key = "sourcekey"
target_key = "target"
client = boto3.client(
"s3",
endpoint_url="http://localhost:4566",
aws_access_key_id="112233445566",
aws_secret_access_key="test",
config=botocore.config.Config(signature_version="s3v4"),
verify=False,
)
client.put_object(Bucket=bucket, Key=source_key, Body=b"stuff")
source_properties = client.head_object(Bucket=bucket, Key=source_key)
client.copy_object(
Bucket=bucket,
Key=target_key,
CopySource={
"Bucket": bucket,
"Key": source_key,
},
CopySourceIfUnmodifiedSince=source_properties["LastModified"],
)Environment
- OS: Linux NV-F4SHWL3 6.6.87.2-microsoft-standard-WSL2 #1 SMP PREEMPT_DYNAMIC Thu Jun 5 18:30:46 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
- LocalStack: localstack/localstack:s3-latest
LocalStack version: 4.10.1.dev1
LocalStack Docker image sha: cea0c7dc0edc
LocalStack build date: 2025-10-30
LocalStack build git hash: 6f9927619Anything else?
No response