[#393] util/signature: Remove bytes pool and provide buffer explicitly

Chained verification is done in a single thread there is no need to use
pool to do this. Also because newly allocated items are 5 MiB in size
we can run out of memory given that typical header it much less in size.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

signature/sign.go

@@ -242,22 +242,32 @@ func VerifyServiceMessage(msg interface{}) error {
 		panic(fmt.Sprintf("unsupported session message %T", v))
 	}
 
-	return verifyMatryoshkaLevel(serviceMessageBody(msg), meta, verify)
+	body := serviceMessageBody(msg)
+	size := body.StableSize()
+	if sz := meta.StableSize(); sz > size {
+		size = sz
+	}
+	if sz := verify.StableSize(); sz > size {
+		size = sz
+	}
+
+	buf := make([]byte, 0, size)
+	return verifyMatryoshkaLevel(body, meta, verify, buf)
 }
 
-func verifyMatryoshkaLevel(body stableMarshaler, meta metaHeader, verify verificationHeader) error {
-	if err := verifyServiceMessagePart(meta, verify.GetMetaSignature); err != nil {
+func verifyMatryoshkaLevel(body stableMarshaler, meta metaHeader, verify verificationHeader, buf []byte) error {
+	if err := verifyServiceMessagePart(meta, verify.GetMetaSignature, buf); err != nil {
 		return fmt.Errorf("could not verify meta header: %w", err)
 	}
 
 	origin := verify.getOrigin()
 
-	if err := verifyServiceMessagePart(origin, verify.GetOriginSignature); err != nil {
+	if err := verifyServiceMessagePart(origin, verify.GetOriginSignature, buf); err != nil {
 		return fmt.Errorf("could not verify origin of verification header: %w", err)
 	}
 
 	if origin == nil {
-		if err := verifyServiceMessagePart(body, verify.GetBodySignature); err != nil {
+		if err := verifyServiceMessagePart(body, verify.GetBodySignature, buf); err != nil {
 			return fmt.Errorf("could not verify body: %w", err)
 		}
 
@@ -268,13 +278,14 @@ func verifyMatryoshkaLevel(body stableMarshaler, meta metaHeader, verify verific
 		return errors.New("body signature at the matryoshka upper level")
 	}
 
-	return verifyMatryoshkaLevel(body, meta.getOrigin(), origin)
+	return verifyMatryoshkaLevel(body, meta.getOrigin(), origin, buf)
 }
 
-func verifyServiceMessagePart(part stableMarshaler, sigRdr func() *refs.Signature) error {
+func verifyServiceMessagePart(part stableMarshaler, sigRdr func() *refs.Signature, buf []byte) error {
 	return signature.VerifyDataWithSource(
 		&StableMarshalerWrapper{part},
 		sigRdr,
+		signature.WithBuffer(buf),
 	)
 }
 

util/signature/data.go

@@ -29,18 +29,17 @@ func SignDataWithHandler(key *ecdsa.PrivateKey, src DataSource, handler KeySigna
 		return crypto.ErrEmptyPrivateKey
 	}
 
-	data, err := dataForSignature(src)
-	if err != nil {
-		return err
-	}
-	defer bytesPool.Put(data)
-
 	cfg := defaultCfg()
 
 	for i := range opts {
 		opts[i](cfg)
 	}
 
+	data, err := readSignedData(cfg, src)
+	if err != nil {
+		return err
+	}
+
 	sigData, err := sign(cfg, key, data)
 	if err != nil {
 		return err
@@ -56,18 +55,17 @@ func SignDataWithHandler(key *ecdsa.PrivateKey, src DataSource, handler KeySigna
 }
 
 func VerifyDataWithSource(dataSrc DataSource, sigSrc KeySignatureSource, opts ...SignOption) error {
-	data, err := dataForSignature(dataSrc)
-	if err != nil {
-		return err
-	}
-	defer bytesPool.Put(data)
-
 	cfg := defaultCfg()
 
 	for i := range opts {
 		opts[i](cfg)
 	}
 
+	data, err := readSignedData(cfg, dataSrc)
+	if err != nil {
+		return err
+	}
+
 	return verify(cfg, data, sigSrc())
 }
 
@@ -78,3 +76,13 @@ func SignData(key *ecdsa.PrivateKey, v DataWithSignature, opts ...SignOption) er
 func VerifyData(src DataWithSignature, opts ...SignOption) error {
 	return VerifyDataWithSource(src, src.GetSignature, opts...)
 }
+
+func readSignedData(cfg *cfg, src DataSource) ([]byte, error) {
+	size := src.SignedDataSize()
+	if cfg.buffer == nil || cap(cfg.buffer) < size {
+		cfg.buffer = make([]byte, size)
+	} else {
+		cfg.buffer = cfg.buffer[:size]
+	}
+	return src.ReadSignedData(cfg.buffer)
+}

util/signature/options.go

@@ -11,6 +11,7 @@ import (
 type cfg struct {
 	schemeFixed bool
 	scheme      refs.SignatureScheme
+	buffer      []byte
 }
 
 func defaultCfg() *cfg {
@@ -51,3 +52,10 @@ func SignWithRFC6979() SignOption {
 		c.scheme = refs.ECDSA_RFC6979_SHA256
 	}
 }
+
+// WithBuffer allows providing pre-allocated buffer for signature verification.
+func WithBuffer(buf []byte) SignOption {
+	return func(c *cfg) {
+		c.buffer = buf
+	}
+}

util/signature/util.go

@@ -1,30 +0,0 @@
-package signature
-
-import (
-	"errors"
-	"sync"
-)
-
-var bytesPool = sync.Pool{
-	New: func() interface{} {
-		return make([]byte, 5<<20)
-	},
-}
-
-func dataForSignature(src DataSource) ([]byte, error) {
-	if src == nil {
-		return nil, errors.New("nil source")
-	}
-
-	buf := bytesPool.Get().([]byte)
-
-	if size := src.SignedDataSize(); size < 0 {
-		return nil, errors.New("negative length")
-	} else if size <= cap(buf) {
-		buf = buf[:size]
-	} else {
-		buf = make([]byte, size)
-	}
-
-	return src.ReadSignedData(buf)
-}