From b6a0a070f2e14808e835c2fcfa3820a55041902f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Petr=20=C5=A0tetiar?= Date: Mon, 9 Dec 2019 14:11:45 +0100 Subject: blob: introduce blob_parse_untrusted MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit blob_parse can be only used on trusted input as it has no possibility to check the length of the provided input buffer, which might lead to undefined behaviour and/or crashes when supplied with malformed, corrupted or otherwise specially crafted input. So this introduces blob_parse_untrusted variant which expects additional input buffer length argument and thus should be able to process also inputs from untrusted sources. Signed-off-by: Petr Štetiar --- blob.c | 24 ++++++++++++++++++++++++ blob.h | 7 +++++++ 2 files changed, 31 insertions(+) --- a/blob.c +++ b/blob.c @@ -253,6 +253,30 @@ blob_parse_attr(struct blob_attr *attr, } int +blob_parse_untrusted(struct blob_attr *attr, size_t attr_len, struct blob_attr **data, const struct blob_attr_info *info, int max) +{ + struct blob_attr *pos; + size_t len = 0; + int found = 0; + size_t rem; + + if (!attr || attr_len < sizeof(struct blob_attr)) + return 0; + + len = blob_raw_len(attr); + if (len != attr_len) + return 0; + + memset(data, 0, sizeof(struct blob_attr *) * max); + blob_for_each_attr_len(pos, attr, len, rem) { + found += blob_parse_attr(pos, rem, data, info, max); + } + + return found; +} + +/* use only on trusted input, otherwise consider blob_parse_untrusted */ +int blob_parse(struct blob_attr *attr, struct blob_attr **data, const struct blob_attr_info *info, int max) { struct blob_attr *pos; --- a/blob.h +++ b/blob.h @@ -199,6 +199,7 @@ extern void blob_nest_end(struct blob_bu extern struct blob_attr *blob_put(struct blob_buf *buf, int id, const void *ptr, unsigned int len); extern bool blob_check_type(const void *ptr, unsigned int len, int type); extern int blob_parse(struct blob_attr *attr, struct blob_attr **data, const struct blob_attr_info *info, int max); +extern int blob_parse_untrusted(struct blob_attr *attr, size_t attr_len, struct blob_attr **data, const struct blob_attr_info *info, int max); extern struct blob_attr *blob_memdup(struct blob_attr *attr); extern struct blob_attr *blob_put_raw(struct blob_buf *buf, const void *ptr, unsigned int len); @@ -254,5 +255,11 @@ blob_put_u64(struct blob_buf *buf, int i (blob_pad_len(pos) >= sizeof(struct blob_attr)); \ rem -= blob_pad_len(pos), pos = blob_next(pos)) +#define blob_for_each_attr_len(pos, attr, attr_len, rem) \ + for (rem = attr ? blob_len(attr) : 0, \ + pos = (struct blob_attr *) (attr ? blob_data(attr) : NULL); \ + rem >= sizeof(struct blob_attr) && rem < attr_len && (blob_pad_len(pos) <= rem) && \ + (blob_pad_len(pos) >= sizeof(struct blob_attr)); \ + rem -= blob_pad_len(pos), pos = blob_next(pos)) #endif