base64: Encoding/Decoding with URL and Filename Safe Alphabet (#471)

include/re_base64.h

@@ -6,5 +6,6 @@
 
 
 int base64_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen);
+int base64url_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen);
 int base64_print(struct re_printf *pf, const uint8_t *ptr, size_t len);
 int base64_decode(const char *in, size_t ilen, uint8_t *out, size_t *olen);

src/base64/b64.c

@@ -13,6 +13,12 @@ static const char b64_table[65] =
 	"abcdefghijklmnopqrstuvwxyz"
 	"0123456789+/";
 
+/* Base 64 Encoding with URL and Filename Safe Alphabet, RFC 4648 section 5 */
+static const char b64url_table[65] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	"abcdefghijklmnopqrstuvwxyz"
+	"0123456789-_";
+
 
 /**
  * Base-64 encode a buffer
@@ -53,10 +59,63 @@ int base64_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen)
 			++pad;
 		}
 
-		*out++ = b64_table[v>>18 & 0x3f];
-		*out++ = b64_table[v>>12 & 0x3f];
-		*out++ = (pad >= 2) ? '=' : b64_table[v>>6  & 0x3f];
-		*out++ = (pad >= 1) ? '=' : b64_table[v>>0  & 0x3f];
+		*out++ = b64_table[v >> 18 & 0x3f];
+		*out++ = b64_table[v >> 12 & 0x3f];
+		*out++ = (pad >= 2) ? '=' : b64_table[v >> 6 & 0x3f];
+		*out++ = (pad >= 1) ? '=' : b64_table[v >> 0 & 0x3f];
+	}
+
+	*olen = out - o;
+
+	return 0;
+}
+
+
+/**
+ * Base-64 url encode a buffer (without padding)
+ *
+ * @param in   Input buffer
+ * @param ilen Length of input buffer
+ * @param out  Output buffer
+ * @param olen Size of output buffer, actual written on return
+ *
+ * @return 0 if success, otherwise errorcode
+ */
+int base64url_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen)
+{
+	const uint8_t *in_end = in + ilen;
+	const char *o = out;
+
+	if (!in || !out || !olen)
+		return EINVAL;
+
+	if (*olen < 4 * ((ilen+2)/3))
+		return EOVERFLOW;
+
+	for (; in < in_end; ) {
+		uint32_t v;
+		int pad = 0;
+
+		v  = *in++ << 16;
+		if (in < in_end) {
+			v |= *in++ << 8;
+		}
+		else {
+			++pad;
+		}
+		if (in < in_end) {
+			v |= *in++ << 0;
+		}
+		else {
+			++pad;
+		}
+
+		*out++ = b64url_table[v >> 18 & 0x3f];
+		*out++ = b64url_table[v >> 12 & 0x3f];
+		if (pad < 2)
+			*out++ = b64url_table[v >> 6 & 0x3f];
+		if (pad < 1)
+			*out++ = b64url_table[v >> 0 & 0x3f];
 	}
 
 	*olen = out - o;
@@ -103,9 +162,9 @@ static inline uint32_t b64val(char c)
 		return c - 'a' + 26;
 	else if ('0' <= c && c <= '9')
 		return c - '0' + 52;
-	else if ('+' == c)
+	else if ('+' == c || '-' == c)
 		return 62;
-	else if ('/' == c)
+	else if ('/' == c || '_' == c)
 		return 63;
 	else if ('=' == c)
 		return 1<<24; /* special trick */
@@ -135,13 +194,21 @@ int base64_decode(const char *in, size_t ilen, uint8_t *out, size_t *olen)
 	if (*olen < 3 * (ilen/4))
 		return EOVERFLOW;
 
-	for (;in+3 < in_end; ) {
+	for (;in+1 < in_end; ) {
 		uint32_t v;
 
 		v  = b64val(*in++) << 18;
 		v |= b64val(*in++) << 12;
-		v |= b64val(*in++) << 6;
-		v |= b64val(*in++) << 0;
+
+		if (in < in_end)
+			v |= b64val(*in++) << 6;
+		else
+			v |= (1<<24) << 6; /* padding fallback */
+
+		if (in < in_end)
+			v |= b64val(*in++) << 0;
+		else
+			v |= (1<<24) << 0; /* padding fallback */
 
 		*out++ = v>>16;
 		if (!(v & (1<<30)))