fileio: add READ_FULL_FILE_UNBASE64 flag for read_full_file_full()

src/basic/fileio.c

@@ -17,6 +17,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
+#include "hexdecoct.h"
 #include "log.h"
 #include "macro.h"
 #include "missing.h"
@@ -278,6 +279,7 @@ int read_full_stream_full(
 
         assert(f);
         assert(ret_contents);
+        assert(!(flags & READ_FULL_FILE_UNBASE64) || ret_size);
 
         n_next = LINE_MAX; /* Start size */
 
@@ -354,6 +356,12 @@ int read_full_stream_full(
                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
         }
 
+        if (flags & READ_FULL_FILE_UNBASE64) {
+                buf[l++] = 0;
+                r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, (void **) ret_contents, ret_size);
+                goto finalize;
+        }
+
         if (!ret_size) {
                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise

src/basic/fileio.h

@@ -29,7 +29,8 @@ typedef enum {
 } WriteStringFileFlags;
 
 typedef enum {
-        READ_FULL_FILE_SECURE = 1 << 0,
+        READ_FULL_FILE_SECURE   = 1 << 0,
+        READ_FULL_FILE_UNBASE64 = 1 << 1,
 } ReadFullFileFlags;
 
 int write_string_stream_ts(FILE *f, const char *line, WriteStringFileFlags flags, struct timespec *ts);