vfs_snapper: add DBus string encoding and decoding helpers

Snapper uses the following mechanism for encoding and decoding strings
used in DBus traffic:
Characters above 127 (0x7F - ASCII DEL) must be encoded hexadecimal as
"\x??". As a consequence "\" must be encoded as "\\".

This change adds string encoding and decoding helpers to vfs_snapper.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11055

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

diff --git a/source3/modules/vfs_snapper.c b/source3/modules/vfs_snapper.c
index ed6e0737647b5ecf58e18d232a7045fe58e88282..35f2a82c53b29c11ca8d68a48a6ad47d8f6e85e6 100644 (file)
--- a/source3/modules/vfs_snapper.c
+++ b/source3/modules/vfs_snapper.c
@@ -91,6 +91,130 @@ static NTSTATUS snapper_err_ntstatus_map(const char *snapper_err_str)
        return NT_STATUS_UNSUCCESSFUL;
 }
 
+/*
+ * Strings are UTF-8. Other characters must be encoded hexadecimal as "\x??".
+ * As a consequence "\" must be encoded as "\\".
+ */
+static NTSTATUS snapper_dbus_str_encode(TALLOC_CTX *mem_ctx, const char *in_str,
+                                       char **_out_str)
+{
+       size_t in_len;
+       char *out_str;
+       int i;
+       int out_off;
+       int out_len;
+
+       if (in_str == NULL) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       in_len = strlen(in_str);
+
+       /* output can be max 4 times the length of @in_str, +1 for terminator */
+       out_len = (in_len * 4) + 1;
+
+       out_str = talloc_array(mem_ctx, char, out_len);
+       if (out_str == NULL) {
+               return NT_STATUS_NO_MEMORY;
+       }
+
+       out_off = 0;
+       for (i = 0; i < in_len; i++) {
+               size_t pushed;
+
+               if (in_str[i] == '\\') {
+                       pushed = snprintf(out_str + out_off, out_len - out_off,
+                                         "\\\\");
+               } else if ((unsigned char)in_str[i] > 127) {
+                       pushed = snprintf(out_str + out_off, out_len - out_off,
+                                         "\\x%02x", (unsigned char)in_str[i]);
+               } else {
+                       /* regular character */
+                       *(out_str + out_off) = in_str[i];
+                       pushed = sizeof(char);
+               }
+               if (pushed >= out_len - out_off) {
+                       /* truncated, should never happen */
+                       talloc_free(out_str);
+                       return NT_STATUS_INTERNAL_ERROR;
+               }
+               out_off += pushed;
+       }
+
+       *(out_str + out_off) = '\0';
+       *_out_str = out_str;
+
+       return NT_STATUS_OK;
+}
+
+static NTSTATUS snapper_dbus_str_decode(TALLOC_CTX *mem_ctx, const char *in_str,
+                                       char **_out_str)
+{
+       size_t in_len;
+       char *out_str;
+       int i;
+       int out_off;
+       int out_len;
+
+       if (in_str == NULL) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       in_len = strlen(in_str);
+
+       /* output cannot be larger than input, +1 for terminator */
+       out_len = in_len + 1;
+
+       out_str = talloc_array(mem_ctx, char, out_len);
+       if (out_str == NULL) {
+               return NT_STATUS_NO_MEMORY;
+       }
+
+       out_off = 0;
+       for (i = 0; i < in_len; i++) {
+               int j;
+               char hex_buf[3];
+               unsigned int non_ascii_byte;
+
+               if (in_str[i] != '\\') {
+                       out_str[out_off] = in_str[i];
+                       out_off++;
+                       continue;
+               }
+
+               i++;
+               if (in_str[i] == '\\') {
+                       out_str[out_off] = '\\';
+                       out_off++;
+                       continue;
+               } else if (in_str[i] != 'x') {
+                       goto err_invalid_src_encoding;
+               }
+
+               /* non-ASCII, encoded as two hex chars */
+               for (j = 0; j < 2; j++) {
+                       i++;
+                       if ((in_str[i] == '\0') || !isxdigit(in_str[i])) {
+                               goto err_invalid_src_encoding;
+                       }
+                       hex_buf[j] = in_str[i];
+               }
+               hex_buf[2] = '\0';
+
+               sscanf(hex_buf, "%x", &non_ascii_byte);
+               out_str[out_off] = (unsigned char)non_ascii_byte;
+               out_off++;
+       }
+
+       out_str[out_off] = '\0';
+       *_out_str = out_str;
+
+       return NT_STATUS_OK;
+err_invalid_src_encoding:
+       DEBUG(0, ("invalid encoding %s\n", in_str));
+       return NT_STATUS_INVALID_PARAMETER;
+}
+
 static DBusConnection *snapper_dbus_conn_create(void)
 {
        DBusError err;