Add a single, central base64 decoder

Similar to the hex blob decoder, we need this once for tar and
once for the filemap xattr parser.

Simply add a single, central implementation to libutil, with a
simple unit test, and then use it in both libtar and gensquashfs.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 9 insertions, 53 deletions

diff --git a/lib/tar/pax_header.c b/lib/tar/pax_header.c
index cc2f2b0..b61aab6 100644
--- a/lib/tar/pax_header.c
+++ b/lib/tar/pax_header.c
@@ -11,56 +11,6 @@
 #include <string.h>
 #include <stdlib.h>
 
-static sqfs_u8 base64_convert(char in)
-{
-	if (isupper(in))
-		return in - 'A';
-	if (islower(in))
-		return in - 'a' + 26;
-	if (isdigit(in))
-		return in - '0' + 52;
-	if (in == '+')
-		return 62;
-	if (in == '/' || in == '-')
-		return 63;
-	return 0;
-}
-
-static size_t base64_decode(sqfs_u8 *out, const char *in, size_t len)
-{
-	sqfs_u8 *start = out;
-
-	while (len > 0) {
-		unsigned int diff = 0, value = 0;
-
-		while (diff < 4 && len > 0) {
-			if (*in == '=' || *in == '_' || *in == '\0') {
-				len = 0;
-			} else {
-				value = (value << 6) | base64_convert(*(in++));
-				--len;
-				++diff;
-			}
-		}
-
-		if (diff < 2)
-			break;
-
-		value <<= 6 * (4 - diff);
-
-		switch (diff) {
-		case 4:  out[2] = value & 0xff; /* fall-through */
-		case 3:  out[1] = (value >> 8) & 0xff; /* fall-through */
-		default: out[0] = (value >> 16) & 0xff;
-		}
-
-		out += (diff * 3) / 4;
-	}
-
-	*out = '\0';
-	return out - start;
-}
-
 static int pax_read_decimal(const char *str, sqfs_u64 *out)
 {
 	sqfs_u64 result = 0;
@@ -201,10 +151,16 @@ static int pax_xattr_schily(tar_header_decoded_t *out,
 static int pax_xattr_libarchive(tar_header_decoded_t *out,
 				tar_xattr_t *xattr)
 {
+	int ret;
+
+	ret = base64_decode((const char *)xattr->value, xattr->value_len,
+			    xattr->value, &xattr->value_len);
+	if (ret)
+		return -1;
+
 	urldecode(xattr->key);
-	xattr->value_len = base64_decode(xattr->value,
-					 (const char *)xattr->value,
-					 xattr->value_len);
+
+	xattr->value[xattr->value_len] = '\0';
 	xattr->next = out->xattr;
 	out->xattr = xattr;
 	return 0;