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package iolimits
import (
"fmt"
"io"
)
// All constants below are intended to be used as limits for `ReadAtMost`. The
// immediate use-case for limiting the size of in-memory copied data is to
// protect against OOM DOS attacks as described inCVE-2020-1702. Instead of
// copying data until running out of memory, we error out after hitting the
// specified limit.
const (
// megaByte denotes one megabyte and is intended to be used as a limit in
// `ReadAtMost`.
megaByte = 1 << 20
// MaxManifestBodySize is the maximum allowed size of a manifest. The limit
// of 4 MB aligns with the one of a Docker registry:
// https://github.com/docker/distribution/blob/a8371794149d1d95f1e846744b05c87f2f825e5a/registry/handlers/manifests.go#L30
MaxManifestBodySize = 4 * megaByte
// MaxAuthTokenBodySize is the maximum allowed size of an auth token.
// The limit of 1 MB is considered to be greatly sufficient.
MaxAuthTokenBodySize = megaByte
// MaxSignatureListBodySize is the maximum allowed size of a signature list.
// The limit of 4 MB is considered to be greatly sufficient.
MaxSignatureListBodySize = 4 * megaByte
// MaxSignatureBodySize is the maximum allowed size of a signature.
// The limit of 4 MB is considered to be greatly sufficient.
MaxSignatureBodySize = 4 * megaByte
// MaxErrorBodySize is the maximum allowed size of an error-response body.
// The limit of 1 MB is considered to be greatly sufficient.
MaxErrorBodySize = megaByte
// MaxConfigBodySize is the maximum allowed size of a config blob.
// The limit of 4 MB is considered to be greatly sufficient.
MaxConfigBodySize = 4 * megaByte
// MaxOpenShiftStatusBody is the maximum allowed size of an OpenShift status body.
// The limit of 4 MB is considered to be greatly sufficient.
MaxOpenShiftStatusBody = 4 * megaByte
// MaxTarFileManifestSize is the maximum allowed size of a (docker save)-like manifest (which may contain multiple images)
// The limit of 1 MB is considered to be greatly sufficient.
MaxTarFileManifestSize = megaByte
)
// ReadAtMost reads from reader and errors out if the specified limit (in bytes) is exceeded.
func ReadAtMost(reader io.Reader, limit int) ([]byte, error) {
limitedReader := io.LimitReader(reader, int64(limit+1))
res, err := io.ReadAll(limitedReader)
if err != nil {
return nil, err
}
if len(res) > limit {
return nil, fmt.Errorf("exceeded maximum allowed size of %d bytes", limit)
}
return res, nil
}
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