diff options
Diffstat (limited to 'resolv/ns_rr_cursor_init.c')
-rw-r--r-- | resolv/ns_rr_cursor_init.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/resolv/ns_rr_cursor_init.c b/resolv/ns_rr_cursor_init.c new file mode 100644 index 0000000..6ee80b3 --- /dev/null +++ b/resolv/ns_rr_cursor_init.c @@ -0,0 +1,62 @@ +/* Initialize a simple DNS packet parser. + Copyright (C) 2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <arpa/nameser.h> +#include <errno.h> +#include <stdbool.h> +#include <string.h> + +bool +__ns_rr_cursor_init (struct ns_rr_cursor *c, + const unsigned char *buf, size_t len) +{ + c->begin = buf; + c->end = buf + len; + + /* Check for header size and 16-bit question count value (it must be 1). */ + if (len < 12 || buf[4] != 0 || buf[5] != 1) + { + __set_errno (EMSGSIZE); + c->current = c->end; + return false; + } + c->current = buf + 12; + + int consumed = __ns_name_length_uncompressed (c->current, c->end); + if (consumed < 0) + { + __set_errno (EMSGSIZE); + c->current = c->end; + c->first_rr = NULL; + return false; + } + c->current += consumed; + + /* Ensure there is room for question type and class. */ + if (c->end - c->current < 4) + { + __set_errno (EMSGSIZE); + c->current = c->end; + c->first_rr = NULL; + return false; + } + c->current += 4; + c->first_rr = c->current; + + return true; +} |