MalformedPolicy cloud config_error ai_generated true

AccessDenied: The bucket policy is too large. The maximum size for a bucket policy is 20 KB.

ID: cloud/aws-s3-bucket-policy-too-large

Also available as: JSON · Markdown · 中文
90%Fix Rate
85%Confidence
1Evidence
2023-04-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
AWS S3 API 2006-03-01 active — — —
AWS CLI 2.15 active — — —

Root Cause

The combined size of the bucket policy JSON document exceeds AWS's 20 KB limit, often due to many statements or long ARNs.

generic

中文

存储桶策略 JSON 文档的总大小超过 AWS 的 20 KB 限制，通常由过多语句或长 ARN 导致。

Official Documentation

https://docs.aws.amazon.com/AmazonS3/latest/userguide/bucket-policies.html

Workarounds

  1. 95% success Use IAM policies instead of bucket policies for user/role-based access. Move per-user statements to IAM and keep only cross-account or service-wide rules in the bucket policy. 
    Use IAM policies instead of bucket policies for user/role-based access. Move per-user statements to IAM and keep only cross-account or service-wide rules in the bucket policy.
  2. 85% success Consolidate multiple statements using wildcards and condition keys. Example: change separate statements for each prefix to a single statement with 's3:prefix' condition and multiple values in Resource. 
    Consolidate multiple statements using wildcards and condition keys. Example: change separate statements for each prefix to a single statement with 's3:prefix' condition and multiple values in Resource.
  3. 90% success Use S3 Access Points with their own policies to offload permissions from the bucket policy. Create an access point and attach a policy there. 
    Use S3 Access Points with their own policies to offload permissions from the bucket policy. Create an access point and attach a policy there.

中文步骤

  1. 使用 IAM 策略代替存储桶策略来管理用户/角色权限。将用户级别的语句移到 IAM，存储桶策略仅保留跨账户或服务范围的规则。
  2. 使用通配符和条件键合并多个语句。例如：将每个前缀的单独语句改为一个带 's3:prefix' 条件和多个 Resource 值的语句。
  3. 使用 S3 接入点及其策略来分担存储桶策略的权限。创建接入点并在其上附加策略。

Dead Ends

Common approaches that don't work:

  1. 99% fail

    Compressing the JSON or removing whitespace saves negligible space while breaking readability.

  2. 70% fail

    Splitting policy across multiple buckets requires restructuring app logic and often isn't feasible.

  3. 85% fail

    Using a different IAM role per statement on the same policy doesn't reduce size; it may increase it.