From c7c578cdf31e66f635ff625d8c60781050fd7c66 Mon Sep 17 00:00:00 2001
From: Niklas Ott <ceriath12@gmail.com>
Date: Wed, 24 Apr 2024 15:22:52 +0200
Subject: [PATCH] encoding/base32: use correct length for unpadded buffer in
 Read

If unpadded content was passed, in some occassions content was omitted,
because the division result was floored. Ceiling it makes sure all
content is always read.

Fixes #65166

Change-Id: I1d8ee7ef436080483ed8f0e615b70a1013455f92
Reviewed-on: https://go-review.googlesource.com/c/go/+/581415
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 src/encoding/base32/base32.go      |  2 +-
 src/encoding/base32/base32_test.go | 37 ++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/encoding/base32/base32.go b/src/encoding/base32/base32.go
index 4a61199a59..9e988ef39b 100644
--- a/src/encoding/base32/base32.go
+++ b/src/encoding/base32/base32.go
@@ -467,7 +467,7 @@ func (d *decoder) Read(p []byte) (n int, err error) {
 	}
 
 	// Read a chunk.
-	nn := len(p) / 5 * 8
+	nn := (len(p) + 4) / 5 * 8
 	if nn < 8 {
 		nn = 8
 	}
diff --git a/src/encoding/base32/base32_test.go b/src/encoding/base32/base32_test.go
index 33638adeac..f5d3c49e38 100644
--- a/src/encoding/base32/base32_test.go
+++ b/src/encoding/base32/base32_test.go
@@ -92,6 +92,43 @@ func TestEncoderBuffering(t *testing.T) {
 	}
 }
 
+func TestDecoderBufferingWithPadding(t *testing.T) {
+	for bs := 0; bs <= 12; bs++ {
+		for _, s := range pairs {
+			decoder := NewDecoder(StdEncoding, strings.NewReader(s.encoded))
+			buf := make([]byte, len(s.decoded)+bs)
+
+			var n int
+			var err error
+			n, err = decoder.Read(buf)
+
+			if err != nil && err != io.EOF {
+				t.Errorf("Read from %q at pos %d = %d, unexpected error %v", s.encoded, len(s.decoded), n, err)
+			}
+			testEqual(t, "Decoding/%d of %q = %q, want %q\n", bs, s.encoded, string(buf[:n]), s.decoded)
+		}
+	}
+}
+
+func TestDecoderBufferingWithoutPadding(t *testing.T) {
+	for bs := 0; bs <= 12; bs++ {
+		for _, s := range pairs {
+			encoded := strings.TrimRight(s.encoded, "=")
+			decoder := NewDecoder(StdEncoding.WithPadding(NoPadding), strings.NewReader(encoded))
+			buf := make([]byte, len(s.decoded)+bs)
+
+			var n int
+			var err error
+			n, err = decoder.Read(buf)
+
+			if err != nil && err != io.EOF {
+				t.Errorf("Read from %q at pos %d = %d, unexpected error %v", encoded, len(s.decoded), n, err)
+			}
+			testEqual(t, "Decoding/%d of %q = %q, want %q\n", bs, encoded, string(buf[:n]), s.decoded)
+		}
+	}
+}
+
 func TestDecode(t *testing.T) {
 	for _, p := range pairs {
 		dbuf := make([]byte, StdEncoding.DecodedLen(len(p.encoded)))
-- 
2.48.1