calipso: Add validation of CALIPSO option.

Lengths, checksum and the DOI are checked.  Checking of the
level and categories are left for the socket layer.

CRC validation is performed in the calipso module to avoid
unconditionally linking crc_ccitt() into ipv6.

Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c
index fa371a8827cf..ea80450efe56 100644
--- a/net/ipv6/calipso.c
+++ b/net/ipv6/calipso.c
@@ -321,6 +321,47 @@ doi_walk_return:
 }
 
 /**
+ * calipso_validate - Validate a CALIPSO option
+ * @skb: the packet
+ * @option: the start of the option
+ *
+ * Description:
+ * This routine is called to validate a CALIPSO option.
+ * If the option is valid then %true is returned, otherwise
+ * %false is returned.
+ *
+ * The caller should have already checked that the length of the
+ * option (including the TLV header) is >= 10 and that the catmap
+ * length is consistent with the option length.
+ *
+ * We leave checks on the level and categories to the socket layer.
+ */
+bool calipso_validate(const struct sk_buff *skb, const unsigned char *option)
+{
+	struct calipso_doi *doi_def;
+	bool ret_val;
+	u16 crc, len = option[1] + 2;
+	static const u8 zero[2];
+
+	/* The original CRC runs over the option including the TLV header
+	 * with the CRC-16 field (at offset 8) zeroed out. */
+	crc = crc_ccitt(0xffff, option, 8);
+	crc = crc_ccitt(crc, zero, sizeof(zero));
+	if (len > 10)
+		crc = crc_ccitt(crc, option + 10, len - 10);
+	crc = ~crc;
+	if (option[8] != (crc & 0xff) || option[9] != ((crc >> 8) & 0xff))
+		return false;
+
+	rcu_read_lock();
+	doi_def = calipso_doi_search(get_unaligned_be32(option + 2));
+	ret_val = !!doi_def;
+	rcu_read_unlock();
+
+	return ret_val;
+}
+
+/**
  * calipso_map_cat_hton - Perform a category mapping from host to network
  * @doi_def: the DOI definition
  * @secattr: the security attributes