From aba4df9dbb436343f7d29a47801d82a33dcaaad3 Mon Sep 17 00:00:00 2001
From: Stephan Bosch <stephan.bosch@dovecot.fi>
Date: Sat, 30 Mar 2019 18:57:34 +0100
Subject: [PATCH] lib: base64 - Add decode flag for prohibiting whitespace.

---
 src/lib/base64.c      | 25 +++++++++++++++++++++----
 src/lib/base64.h      |  6 ++++--
 src/lib/test-base64.c | 28 ++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/src/lib/base64.c b/src/lib/base64.c
index 42bf5322f6..980aa12005 100644
--- a/src/lib/base64.c
+++ b/src/lib/base64.c
@@ -324,10 +324,12 @@ bool base64_encode_finish(struct base64_encoder *enc, buffer_t *dest)
 	((c) == '\n' || (c) == '\r' || (c) == ' ' || (c) == '\t')
 
 static inline void
-base64_skip_whitespace(struct base64_decoder *dec ATTR_UNUSED,
-		       const unsigned char *src_c,
+base64_skip_whitespace(struct base64_decoder *dec, const unsigned char *src_c,
 		       size_t src_size, size_t *src_pos)
 {
+	if (HAS_ALL_BITS(dec->flags, BASE64_DECODE_FLAG_NO_WHITESPACE))
+		return;
+
 	/* skip any whitespace in the padding */
 	while ((*src_pos) < src_size && IS_EMPTY(src_c[(*src_pos)]))
 		(*src_pos)++;
@@ -341,6 +343,8 @@ int base64_decode_more(struct base64_decoder *dec,
 	const unsigned char *src_c = src;
 	bool expect_boundary = HAS_ALL_BITS(dec->flags,
 					    BASE64_DECODE_FLAG_EXPECT_BOUNDARY);
+	bool no_whitespace = HAS_ALL_BITS(dec->flags,
+					  BASE64_DECODE_FLAG_NO_WHITESPACE);
 	size_t src_pos, dst_avail;
 	int ret = 1;
 
@@ -369,6 +373,10 @@ int base64_decode_more(struct base64_decoder *dec,
 			dec->seen_boundary = TRUE;
 			return 0;
 		}
+		if (no_whitespace) {
+			dec->seen_boundary = TRUE;
+			return 0;
+		}
 		/* more whitespace may follow */
 		return 1;
 	}
@@ -391,6 +399,10 @@ int base64_decode_more(struct base64_decoder *dec,
 		unsigned char dm = b64->decmap[in];
 
 		if (dm == 0xff) {
+			if (no_whitespace) {
+				ret = -1;
+				break;
+			}
 			if (unlikely(!IS_EMPTY(in))) {
 				ret = -1;
 				break;
@@ -492,8 +504,13 @@ int base64_decode_more(struct base64_decoder *dec,
 				ret = -1;
 				break;
 			}
-			/* more whitespace may follow */
-			ret = 1;
+			if (no_whitespace) {
+				dec->seen_boundary = TRUE;
+				ret = 0;
+			} else {
+				/* more whitespace may follow */
+				ret = 1;
+			}
 			break;
 		}
 	}
diff --git a/src/lib/base64.h b/src/lib/base64.h
index 7121a38824..cfb7807095 100644
--- a/src/lib/base64.h
+++ b/src/lib/base64.h
@@ -94,6 +94,8 @@ enum base64_decode_flags {
 	   to decode such a Base64 prefix. The base64_decode_finish() function
 	   will still check that the Base64 data ends properly (padding). */
 	BASE64_DECODE_FLAG_EXPECT_BOUNDARY = BIT(0),
+	/* Prohibit whitespace in the input. */
+	BASE64_DECODE_FLAG_NO_WHITESPACE   = BIT(1),
 };
 
 struct base64_decoder {
@@ -145,8 +147,8 @@ base64_decode_reset(struct base64_decoder *dec)
    buffer. dest may point to same buffer as src. Returns 1 if all ok, 0 if end
    of base64 data found, -1 if data is invalid.
 
-   Any CR, LF characters are ignored, as well as whitespace at beginning or end
-   of line.
+   By default, any CR, LF characters are ignored, as well as any whitespace.
+   This can be overridden using the BASE64_DECODE_FLAG_NO_WHITESPACE flag.
 
    If src_pos is non-NULL, it's updated to first non-translated character in
    src.
diff --git a/src/lib/test-base64.c b/src/lib/test-base64.c
index 79702de5d0..2926649283 100644
--- a/src/lib/test-base64.c
+++ b/src/lib/test-base64.c
@@ -365,6 +365,13 @@ tests_base64_decode_lowlevel[] = {
 		.ret = 0,
 		.src_pos = UINT_MAX,
 	},
+	{
+		.scheme = &base64_scheme,
+		.input = "aGVsbG8gd29ybGQ=\t",
+		.output = "hello world",
+		.ret = 0,
+		.src_pos = UINT_MAX,
+	},
 	{
 		.scheme = &base64_scheme,
 		.input = "\taGVsbG8gd29ybGQ=\t",
@@ -388,6 +395,22 @@ tests_base64_decode_lowlevel[] = {
 		.src_pos = 18,
 		.flags = BASE64_DECODE_FLAG_EXPECT_BOUNDARY,
 	},
+	{
+		.scheme = &base64_scheme,
+		.input = "aGVsbG8gd29ybGQ=\t",
+		.output = "hello world",
+		.ret = -1,
+		.src_pos = 16,
+		.flags = BASE64_DECODE_FLAG_NO_WHITESPACE,
+	},
+	{
+		.scheme = &base64_scheme,
+		.input = "\taGVsbG8gd29ybGQ=\t",
+		.output = "",
+		.ret = -1,
+		.src_pos = 0,
+		.flags = BASE64_DECODE_FLAG_NO_WHITESPACE,
+	},
 	{
 		.scheme = &base64_scheme,
 		.input = "\nZm9v\n \tIGJh  \t\ncml0cw==",
@@ -741,8 +764,13 @@ test_base64_random_lowlevel(void)
 					 BASE64_DECODE_FLAG_EXPECT_BOUNDARY);
 	test_base64_random_lowlevel_case(&base64url_scheme,
 					 BASE64_DECODE_FLAG_EXPECT_BOUNDARY);
+	test_base64_random_lowlevel_case(&base64_scheme,
+					 BASE64_DECODE_FLAG_NO_WHITESPACE);
+	test_base64_random_lowlevel_case(&base64url_scheme, 
+					 BASE64_DECODE_FLAG_NO_WHITESPACE);
 	test_end();
 }
+
 void test_base64(void)
 {
 	test_base64_encode();
-- 
2.47.3