From 0003b01876cb929ab10ac4fe409db20d6e4c1f0e Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Fri, 10 May 2019 16:08:38 +0200
Subject: [PATCH] base64: Avoid false positive warning from Coverity.

Reported by Kamil Dudka <kdudka@redhat.com>.

Idea by Paul Eggert.

* lib/base64.c (base64_encode_fast, base64_encode): Add a no-op
'& 0x3f' to the array index expressions. This convinces Coverity that
there is no out-of-bounds array reference, regardless of the input.
---
 ChangeLog    | 9 +++++++++
 lib/base64.c | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index afaf50787e..c9cb893065 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2019-05-10  Bruno Haible  <bruno@clisp.org>
+
+	base64: Avoid false positive warning from Coverity.
+	Reported by Kamil Dudka <kdudka@redhat.com>.
+	Idea by Paul Eggert.
+	* lib/base64.c (base64_encode_fast, base64_encode): Add a no-op
+	'& 0x3f' to the array index expressions. This convinces Coverity that
+	there is no out-of-bounds array reference, regardless of the input.
+
 2019-05-09  Bruno Haible  <bruno@clisp.org>
 
 	gettext: Update to gettext 0.20.
diff --git a/lib/base64.c b/lib/base64.c
index f3f7298aa8..a00e0f46ed 100644
--- a/lib/base64.c
+++ b/lib/base64.c
@@ -70,7 +70,7 @@ base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out)
 {
   while (inlen)
     {
-      *out++ = b64c[to_uchar (in[0]) >> 2];
+      *out++ = b64c[(to_uchar (in[0]) >> 2) & 0x3f];
       *out++ = b64c[((to_uchar (in[0]) << 4) + (to_uchar (in[1]) >> 4)) & 0x3f];
       *out++ = b64c[((to_uchar (in[1]) << 2) + (to_uchar (in[2]) >> 6)) & 0x3f];
       *out++ = b64c[to_uchar (in[2]) & 0x3f];
@@ -103,7 +103,7 @@ base64_encode (const char *restrict in, size_t inlen,
 
   while (inlen && outlen)
     {
-      *out++ = b64c[to_uchar (in[0]) >> 2];
+      *out++ = b64c[(to_uchar (in[0]) >> 2) & 0x3f];
       if (!--outlen)
         break;
       *out++ = b64c[((to_uchar (in[0]) << 4)
-- 
2.39.5