Add base64url encoding/decoding per RFC 4648

This adds functionality needed for parsing and generating JSON Web Key
data structures in DPP.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/utils/base64.c

@@ -13,21 +13,14 @@
 
 static const unsigned char base64_table[65] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static const unsigned char base64_url_table[65] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
 
-/**
- * base64_encode - Base64 encode
- * @src: Data to be encoded
- * @len: Length of the data to be encoded
- * @out_len: Pointer to output length variable, or %NULL if not used
- * Returns: Allocated buffer of out_len bytes of encoded data,
- * or %NULL on failure
- *
- * Caller is responsible for freeing the returned buffer. Returned buffer is
- * nul terminated to make it easier to use as a C string. The nul terminator is
- * not included in out_len.
- */
-unsigned char * base64_encode(const unsigned char *src, size_t len,
-			      size_t *out_len)
+
+static unsigned char * base64_gen_encode(const unsigned char *src, size_t len,
+					 size_t *out_len,
+					 const unsigned char *table,
+					 int add_pad)
 {
 	unsigned char *out, *pos;
 	const unsigned char *end, *in;
@@ -35,7 +28,8 @@ unsigned char * base64_encode(const unsigned char *src, size_t len,
 	int line_len;
 
 	olen = len * 4 / 3 + 4; /* 3-byte blocks to 4-byte */
-	olen += olen / 72; /* line feeds */
+	if (add_pad)
+		olen += olen / 72; /* line feeds */
 	olen++; /* nul termination */
 	if (olen < len)
 		return NULL; /* integer overflow */
@@ -48,35 +42,35 @@ unsigned char * base64_encode(const unsigned char *src, size_t len,
 	pos = out;
 	line_len = 0;
 	while (end - in >= 3) {
-		*pos++ = base64_table[(in[0] >> 2) & 0x3f];
-		*pos++ = base64_table[(((in[0] & 0x03) << 4) |
-				       (in[1] >> 4)) & 0x3f];
-		*pos++ = base64_table[(((in[1] & 0x0f) << 2) |
-				       (in[2] >> 6)) & 0x3f];
-		*pos++ = base64_table[in[2] & 0x3f];
+		*pos++ = table[(in[0] >> 2) & 0x3f];
+		*pos++ = table[(((in[0] & 0x03) << 4) | (in[1] >> 4)) & 0x3f];
+		*pos++ = table[(((in[1] & 0x0f) << 2) | (in[2] >> 6)) & 0x3f];
+		*pos++ = table[in[2] & 0x3f];
 		in += 3;
 		line_len += 4;
-		if (line_len >= 72) {
+		if (add_pad && line_len >= 72) {
 			*pos++ = '\n';
 			line_len = 0;
 		}
 	}
 
 	if (end - in) {
-		*pos++ = base64_table[(in[0] >> 2) & 0x3f];
+		*pos++ = table[(in[0] >> 2) & 0x3f];
 		if (end - in == 1) {
-			*pos++ = base64_table[((in[0] & 0x03) << 4) & 0x3f];
-			*pos++ = '=';
+			*pos++ = table[((in[0] & 0x03) << 4) & 0x3f];
+			if (add_pad)
+				*pos++ = '=';
 		} else {
-			*pos++ = base64_table[(((in[0] & 0x03) << 4) |
-					       (in[1] >> 4)) & 0x3f];
-			*pos++ = base64_table[((in[1] & 0x0f) << 2) & 0x3f];
+			*pos++ = table[(((in[0] & 0x03) << 4) |
+					(in[1] >> 4)) & 0x3f];
+			*pos++ = table[((in[1] & 0x0f) << 2) & 0x3f];
 		}
-		*pos++ = '=';
+		if (add_pad)
+			*pos++ = '=';
 		line_len += 4;
 	}
 
-	if (line_len)
+	if (add_pad && line_len)
 		*pos++ = '\n';
 
 	*pos = '\0';
@@ -86,26 +80,18 @@ unsigned char * base64_encode(const unsigned char *src, size_t len,
 }
 
 
-/**
- * base64_decode - Base64 decode
- * @src: Data to be decoded
- * @len: Length of the data to be decoded
- * @out_len: Pointer to output length variable
- * Returns: Allocated buffer of out_len bytes of decoded data,
- * or %NULL on failure
- *
- * Caller is responsible for freeing the returned buffer.
- */
-unsigned char * base64_decode(const unsigned char *src, size_t len,
-			      size_t *out_len)
+static unsigned char * base64_gen_decode(const unsigned char *src, size_t len,
+					 size_t *out_len,
+					 const unsigned char *table)
 {
 	unsigned char dtable[256], *out, *pos, block[4], tmp;
 	size_t i, count, olen;
 	int pad = 0;
+	size_t extra_pad;
 
 	os_memset(dtable, 0x80, 256);
 	for (i = 0; i < sizeof(base64_table) - 1; i++)
-		dtable[base64_table[i]] = (unsigned char) i;
+		dtable[table[i]] = (unsigned char) i;
 	dtable['='] = 0;
 
 	count = 0;
@@ -114,21 +100,28 @@ unsigned char * base64_decode(const unsigned char *src, size_t len,
 			count++;
 	}
 
-	if (count == 0 || count % 4)
+	if (count == 0)
 		return NULL;
+	extra_pad = (4 - count % 4) % 4;
 
-	olen = count / 4 * 3;
+	olen = (count + extra_pad) / 4 * 3;
 	pos = out = os_malloc(olen);
 	if (out == NULL)
 		return NULL;
 
 	count = 0;
-	for (i = 0; i < len; i++) {
-		tmp = dtable[src[i]];
+	for (i = 0; i < len + extra_pad; i++) {
+		unsigned char val;
+
+		if (i >= len)
+			val = '=';
+		else
+			val = src[i];
+		tmp = dtable[val];
 		if (tmp == 0x80)
 			continue;
 
-		if (src[i] == '=')
+		if (val == '=')
 			pad++;
 		block[count] = tmp;
 		count++;
@@ -155,3 +148,53 @@ unsigned char * base64_decode(const unsigned char *src, size_t len,
 	*out_len = pos - out;
 	return out;
 }
+
+
+/**
+ * base64_encode - Base64 encode
+ * @src: Data to be encoded
+ * @len: Length of the data to be encoded
+ * @out_len: Pointer to output length variable, or %NULL if not used
+ * Returns: Allocated buffer of out_len bytes of encoded data,
+ * or %NULL on failure
+ *
+ * Caller is responsible for freeing the returned buffer. Returned buffer is
+ * nul terminated to make it easier to use as a C string. The nul terminator is
+ * not included in out_len.
+ */
+unsigned char * base64_encode(const unsigned char *src, size_t len,
+			      size_t *out_len)
+{
+	return base64_gen_encode(src, len, out_len, base64_table, 0);
+}
+
+
+unsigned char * base64_url_encode(const unsigned char *src, size_t len,
+				  size_t *out_len, int add_pad)
+{
+	return base64_gen_encode(src, len, out_len, base64_url_table, add_pad);
+}
+
+
+/**
+ * base64_decode - Base64 decode
+ * @src: Data to be decoded
+ * @len: Length of the data to be decoded
+ * @out_len: Pointer to output length variable
+ * Returns: Allocated buffer of out_len bytes of decoded data,
+ * or %NULL on failure
+ *
+ * Caller is responsible for freeing the returned buffer.
+ */
+unsigned char * base64_decode(const unsigned char *src, size_t len,
+			      size_t *out_len)
+{
+	return base64_gen_decode(src, len, out_len, base64_table);
+}
+
+
+unsigned char * base64_url_decode(const unsigned char *src, size_t len,
+				  size_t *out_len)
+{
+	return base64_gen_decode(src, len, out_len, base64_url_table);
+}

src/utils/base64.h

@@ -13,5 +13,9 @@ unsigned char * base64_encode(const unsigned char *src, size_t len,
 			      size_t *out_len);
 unsigned char * base64_decode(const unsigned char *src, size_t len,
 			      size_t *out_len);
+unsigned char * base64_url_encode(const unsigned char *src, size_t len,
+				  size_t *out_len, int add_pad);
+unsigned char * base64_url_decode(const unsigned char *src, size_t len,
+				  size_t *out_len);
 
 #endif /* BASE64_H */