From 397f536c853dd5e6145e26c0720a736f18c2e4f2 Mon Sep 17 00:00:00 2001
From: Peter Rabbitson <peter@protocol.ai>
Date: Tue, 21 Jan 2020 16:57:58 +0100
Subject: [PATCH] Add various sanity checks for size specifications

---
 parse.go     | 30 +++++++++++++++++++++++++++++-
 splitting.go |  3 ---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/parse.go b/parse.go
index 5d472b7..59656bf 100644
--- a/parse.go
+++ b/parse.go
@@ -8,9 +8,25 @@ import (
 	"strings"
 )
 
+const (
+	// DefaultBlockSize is the chunk size that splitters produce (or aim to).
+	DefaultBlockSize int64 = 1024 * 256
+
+	// 1 MB, on-wire block size for "datablocks ( unixfs, etc )"
+	// copy of https://github.com/ipfs/go-unixfs/blob/v0.2.3/importer/helpers/helpers.go#L8
+	BlockSizeLimit int = 1048576
+
+	// in case we are using raw-leaves: this would match BlockSizeLimit, but we can't assume that
+	// be conservative and substract the PB wraping size of a full DAG-PB+UnixFS node describing 1M
+	// (2b(type2/file)+4b(data-field:3-byte-len-delimited)+4b(size-field:3-byte-varint))+(4b(DAG-type-1:3-byte-len-delimited))
+	// FIXME - this calculation will need an update for CBOR
+	BlockPayloadLimit int = (BlockSizeLimit - (2 + 4 + 4 + 4))
+)
+
 var (
 	ErrRabinMin = errors.New("rabin min must be greater than 16")
-	ErrSize     = errors.New("chunker size muster greater than 0")
+	ErrSize     = errors.New("chunker size must be greater than 0")
+	ErrSizeMax  = fmt.Errorf("chunker parameters may not exceed the maximum block payload size of %d", BlockPayloadLimit)
 )
 
 // FromString returns a Splitter depending on the given string:
@@ -28,6 +44,8 @@ func FromString(r io.Reader, chunker string) (Splitter, error) {
 			return nil, err
 		} else if size <= 0 {
 			return nil, ErrSize
+		} else if size > BlockPayloadLimit {
+			return nil, ErrSizeMax
 		}
 		return NewSizeSplitter(r, int64(size)), nil
 
@@ -51,6 +69,8 @@ func parseRabinString(r io.Reader, chunker string) (Splitter, error) {
 		size, err := strconv.Atoi(parts[1])
 		if err != nil {
 			return nil, err
+		} else if int(float32(size)*1.5) > BlockPayloadLimit { // FIXME - there is probably a better way to bubble up this calculation from NewRabin()
+			return nil, ErrSizeMax
 		}
 		return NewRabin(r, uint64(size)), nil
 	case 4:
@@ -84,6 +104,14 @@ func parseRabinString(r io.Reader, chunker string) (Splitter, error) {
 			return nil, err
 		}
 
+		if min >= avg {
+			return nil, errors.New("incorrect format: rabin-min must be smaller than rabin-avg")
+		} else if avg >= max {
+			return nil, errors.New("incorrect format: rabin-avg must be smaller than rabin-max")
+		} else if max > BlockPayloadLimit {
+			return nil, ErrSizeMax
+		}
+
 		return NewRabinMinMax(r, uint64(min), uint64(avg), uint64(max)), nil
 	default:
 		return nil, errors.New("incorrect format (expected 'rabin' 'rabin-[avg]' or 'rabin-[min]-[avg]-[max]'")
diff --git a/splitting.go b/splitting.go
index 2b23739..a137820 100644
--- a/splitting.go
+++ b/splitting.go
@@ -13,9 +13,6 @@ import (
 
 var log = logging.Logger("chunk")
 
-// DefaultBlockSize is the chunk size that splitters produce (or aim to).
-var DefaultBlockSize int64 = 1024 * 256
-
 // A Splitter reads bytes from a Reader and creates "chunks" (byte slices)
 // that can be used to build DAG nodes.
 type Splitter interface {
-- 
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