[Tarantool-patches] [PATCH v2] base64: Properly ignore invalid characters

[Sergey Nikiforov <void@tarantool.org>]

Not all invalid characters were ignored by base64 decoder
causing data corruption and reads beyond decode table
(faults under ASAN).

Added corresponding check into base64 unit test.

Fixes: #5627
---

Branch: https://github.com/tarantool/tarantool/tree/void234/gh-5627-fix-base64-invalid-chars-processing
Issue: https://github.com/tarantool/tarantool/issues/5627

 test/unit/base64.c      | 23 ++++++++++++++++++++++-
 test/unit/base64.result |  5 ++++-
 third_party/base64.c    |  3 ++-
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/test/unit/base64.c b/test/unit/base64.c
index ada497adf..c0f53a5e1 100644
--- a/test/unit/base64.c
+++ b/test/unit/base64.c
@@ -58,9 +58,28 @@ base64_nowrap_test(const char *str)
 	base64_test(str, BASE64_NOWRAP, symbols, lengthof(symbols));
 }
 
+static void
+base64_invalid_chars_test(void)
+{
+	/* Upper bit must be cleared */
+	const char invalid_data[] = { '\x7b', '\x7c', '\x7d', '\x7e' };
+	char outbuf[8];
+
+	plan(1);
+
+	/* Invalid chars should be ignored, not decoded into garbage */
+	is(base64_decode(invalid_data, sizeof(invalid_data),
+	                 outbuf, sizeof(outbuf)),
+	   0, "ignoring invalid chars");
+
+	check_plan();
+}
+
 int main(int argc, char *argv[])
 {
-	plan(28);
+	plan(28
+	     + 1 /* invalid chars test */
+	     );
 	header();
 
 	const char *option_tests[] = {
@@ -78,6 +97,8 @@ int main(int argc, char *argv[])
 		base64_nowrap_test(option_tests[i]);
 	}
 
+	base64_invalid_chars_test();
+
 	footer();
 	return check_plan();
 }
diff --git a/test/unit/base64.result b/test/unit/base64.result
index cd1f2b3f6..3bc2c2275 100644
--- a/test/unit/base64.result
+++ b/test/unit/base64.result
@@ -1,4 +1,4 @@
-1..28
+1..29
 	*** main ***
     1..3
     ok 1 - length
@@ -175,4 +175,7 @@ ok 27 - subtests
     ok 3 - decode length ok
     ok 4 - encode/decode
 ok 28 - subtests
+    1..1
+    ok 1 - ignoring invalid chars
+ok 29 - subtests
 	*** main: done ***
diff --git a/third_party/base64.c b/third_party/base64.c
index 8ecab23eb..7c69315ea 100644
--- a/third_party/base64.c
+++ b/third_party/base64.c
@@ -222,7 +222,8 @@ base64_decode_value(int value)
 		32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
 		44, 45, 46, 47, 48, 49, 50, 51
 	};
-	static const int decoding_size = sizeof(decoding);
+	static const int decoding_size =
+		sizeof(decoding) / sizeof(decoding[0]);
 	int codepos = value;
 	codepos -= 43;
 	if (codepos < 0 || codepos >= decoding_size)
-- 
2.25.1