rfc2047: skip whitespace everywhere during base64 decoding

> The encoded output stream must be represented in lines of no more
> than 76 characters each.  All line breaks or other characters not
> found in Table 1 must be ignored by decoding software.  In base64
> data, characters other than those in Table 1, line breaks, and other
> white space probably indicate a transmission error, about which a
> warning message or even a message rejection might be appropriate
> under some circumstances.

1 files changed, 16 insertions, 7 deletions

diff --git a/rfc2047.c b/rfc2047.c
index b581976..3074b4d 100644
--- a/rfc2047.c
+++ b/rfc2047.c
@@ -82,16 +82,25 @@ blaze822_decode_b64(char *s, char *e, char **deco, size_t *decleno)
 	*deco = buf;
 
 	while (s + 4 <= e) {
-		while (s < e && isfws((unsigned char)*s))
-			s++;
-		if (s >= e)
-			break;
-
 		uint32_t v = 0;
 		unsigned char t = 0;
 
-		unsigned char c0 = s[0], c1 = s[1], c2 = s[2], c3 = s[3];
-		s += 4;
+#define SKIP_WS \
+		while (s < e && isfws((unsigned char)*s)) \
+			s++; \
+		if (s >= e) \
+			break;
+
+		SKIP_WS;
+		unsigned char c0 = *s++;
+		SKIP_WS;
+		unsigned char c1 = *s++;
+		SKIP_WS;
+		unsigned char c2 = *s++;
+		SKIP_WS;
+		unsigned char c3 = *s++;
+
+#undef SKIP_WS
 
 		if ((c0 | c1 | c2 | c3) > 127)
 			goto error;