From 3fd8276c37bae159d404f14d57f8e52d68c1cd43 Mon Sep 17 00:00:00 2001
From: Wentao Shang <wentaoshang@gmail.com>
Date: Mon, 6 Mar 2017 20:35:43 -0800
Subject: [PATCH] crypto/ccm: fix auth_data_len upperbound value
RFC3610 states that len_encoding is only valid for "0x0001 ... 0xFEFF"
If 0 < l(a) < (2^16 - 2^8), then the length field is encoded as two
octets which contain the value l(a) in most-significant-byte first
order.
---
sys/crypto/modes/ccm.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/sys/crypto/modes/ccm.c b/sys/crypto/modes/ccm.c
index 7f118ed6ac..6c7d1e7ba4 100644
--- a/sys/crypto/modes/ccm.c
+++ b/sys/crypto/modes/ccm.c
@@ -108,13 +108,17 @@ int ccm_compute_adata_mac(cipher_t* cipher, uint8_t* auth_data,
/* 16 octet block size + max. 10 len encoding */
uint8_t auth_data_encoded[26], len_encoding = 0;
- if ( auth_data_len < (((uint32_t) 2) << 16)) { /* length (0x0001 ... 0xFEFF) */
+ /* If 0 < l(a) < (2^16 - 2^8), then the length field is encoded as two
+ * octets. (RFC3610 page 2)
+ */
+ if (auth_data_len <= 0xFEFF) {
+ /* length (0x0001 ... 0xFEFF) */
len_encoding = 2;
auth_data_encoded[1] = auth_data_len & 0xFF;
auth_data_encoded[0] = (auth_data_len >> 8) & 0xFF;
} else {
- DEBUG("UNSUPPORTED Adata length\n");
+ DEBUG("UNSUPPORTED Adata length: %" PRIu32 "\n", auth_data_len);
return -1;
}
--
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