X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BoarSSL;a=blobdiff_plain;f=SSLTLS%2FRecordDecryptCCM.cs;fp=SSLTLS%2FRecordDecryptCCM.cs;h=4a60e8d8dd79e2140565a8844716c591dc2b40a4;hp=0000000000000000000000000000000000000000;hb=2a0a5eed19628889318549def8dc7a6158ee7676;hpb=c16004e3afb8aa2524aeec88aa7c9c67400e93c1

diff --git a/SSLTLS/RecordDecryptCCM.cs b/SSLTLS/RecordDecryptCCM.cs
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+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+using System;
+using System.Text;
+
+using Crypto;
+
+namespace SSLTLS {
+
+internal class RecordDecryptCCM : RecordDecrypt {
+
+	IBlockCipher bc;
+	byte[] iv;
+	ulong seq;
+	byte[] tmp, tag, ctr, cbcmac;
+	bool ccm8;
+
+	internal RecordDecryptCCM(IBlockCipher bc, byte[] iv, bool ccm8)
+	{
+		this.bc = bc;
+		this.iv = new byte[12];
+		Array.Copy(iv, 0, this.iv, 0, 4);
+		seq = 0;
+		tag = new byte[16];
+		tmp = new byte[32];
+		ctr = new byte[16];
+		cbcmac = new byte[16];
+		this.ccm8 = ccm8;
+	}
+
+	internal override bool CheckLength(int len)
+	{
+		int tagLen = ccm8 ? 8 : 16;
+		return len >= (8 + tagLen) && len <= (16384 + 8 + tagLen);
+	}
+
+	internal override bool Decrypt(int recordType, int version,
+		byte[] data, ref int off, ref int len)
+	{
+		Array.Copy(data, off, iv, 4, 8);
+		off += 8;
+		len -= ccm8 ? 16 : 24;
+
+		/*
+		 * Assemble block B0 and AAD.
+		 */
+		tmp[0] = (byte)(0x40 | ((ccm8 ? 6 : 14) << 2) | 2);
+		Array.Copy(iv, 0, tmp, 1, 12);
+		tmp[13] = 0;
+		IO.Enc16be(len, tmp, 14);
+
+		tmp[16] = 0;
+		tmp[17] = 13;
+		IO.Enc64be(seq, tmp, 18);
+		IO.WriteHeader(recordType, version, len, tmp, 26);
+		tmp[31] = 0;
+		seq ++;
+
+		for (int i = 0; i < cbcmac.Length; i ++) {
+			cbcmac[i] = 0;
+		}
+		bc.CBCMac(cbcmac, tmp, 0, 32);
+
+		/*
+		 * Make initial counter value, and compute tag mask.
+		 * Since the counter least significant byte has value 0,
+		 * getting it to the next value is simple and requires
+		 * no carry propagation.
+		 */
+		ctr[0] = 2;
+		Array.Copy(iv, 0, ctr, 1, 12);
+		for (int i = 13; i < 16; i ++) {
+			ctr[i] = 0;
+		}
+		Array.Copy(ctr, 0, tag, 0, 16);
+		bc.BlockEncrypt(tag);
+		ctr[15] = 1;
+
+		/*
+		 * Perform CTR decryption, and compute CBC-MAC. Since
+		 * CBC-MAC requires full blocks, we have to do the
+		 * processing of the last partial block in a temporary
+		 * buffer. The CBC-MAC is computed on the plaintext,
+		 * padded with zeros in the last block.
+		 */
+		int len1 = len & ~15;
+		int len2 = len - len1;
+		bc.CTRCBCRun(ctr, cbcmac, true, data, off, len1);
+		if (len2 > 0) {
+			bc.BlockEncrypt(ctr);
+			for (int i = 0; i < len2; i ++) {
+				data[off + len1 + i] ^= ctr[i];
+			}
+			Array.Copy(data, off + len1, tmp, 0, len2);
+			for (int i = len2; i < 16; i ++) {
+				tmp[i] = 0;
+			}
+			bc.CBCMac(cbcmac, tmp, 0, 16);
+		}
+
+		/*
+		 * Check that the record MAC matches the expected value
+		 * (taking into account the tag mask).
+		 */
+		int z = 0;
+		for (int i = 0; i < (ccm8 ? 8 : 16); i ++) {
+			z |= cbcmac[i] ^ tag[i] ^ data[off + len + i];
+		}
+		return z == 0;
+	}
+}
+
+}