repository: Better error message if blob is larger than 4GB

internal/index/index.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"math"
 	"sync"
 	"time"
 
@@ -69,11 +70,9 @@ func (idx *Index) addToPacks(id restic.ID) int {
 	return len(idx.packs) - 1
 }
 
-const maxuint32 = 1<<32 - 1
-
 func (idx *Index) store(packIndex int, blob restic.Blob) {
 	// assert that offset and length fit into uint32!
-	if blob.Offset > maxuint32 || blob.Length > maxuint32 || blob.UncompressedLength > maxuint32 {
+	if blob.Offset > math.MaxUint32 || blob.Length > math.MaxUint32 || blob.UncompressedLength > math.MaxUint32 {
 		panic("offset or length does not fit in uint32. You have packs > 4GB!")
 	}
 

internal/repository/repository.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"math"
 	"os"
 	"runtime"
 	"sort"
@@ -917,6 +918,10 @@ func (r *Repository) Close() error {
 // occupies in the repo (compressed or not, including encryption overhead).
 func (r *Repository) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (newID restic.ID, known bool, size int, err error) {
 
+	if int64(len(buf)) > math.MaxUint32 {
+		return restic.ID{}, false, 0, fmt.Errorf("blob is larger than 4GB")
+	}
+
 	// compute plaintext hash if not already set
 	if id.IsNull() {
 		// Special case the hash calculation for all zero chunks. This is especially