From 070249043e4f6927f478a75f9179762ee4c723aa Mon Sep 17 00:00:00 2001
From: Conrad Meyer <cem@FreeBSD.org>
Date: Fri, 26 Oct 2018 20:53:01 +0000
Subject: [PATCH] rijndael (AES): Avoid leaking sensitive data on kernel stack

Noticed this investigating Fortuna.  Remove useless duplicate stack copies
of sensitive contents when possible, or if not possible, be sure to zero
them out when we're finished.

Approved by:	secteam (gordon)
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D16935
---
 sys/crypto/rijndael/rijndael-api-fst.c | 31 +++++++++++++++++---------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/sys/crypto/rijndael/rijndael-api-fst.c b/sys/crypto/rijndael/rijndael-api-fst.c
index bf7b4d14e6a3..f4565f0dd75e 100644
--- a/sys/crypto/rijndael/rijndael-api-fst.c
+++ b/sys/crypto/rijndael/rijndael-api-fst.c
@@ -36,7 +36,6 @@ typedef u_int8_t	BYTE;
 
 int rijndael_makeKey(keyInstance *key, BYTE direction, int keyLen,
 	const char *keyMaterial) {
-	u_int8_t cipherKey[RIJNDAEL_MAXKB];
 
 	if (key == NULL) {
 		return BAD_KEY_INSTANCE;
@@ -59,13 +58,12 @@ int rijndael_makeKey(keyInstance *key, BYTE direction, int keyLen,
 	}
 
 	/* initialize key schedule: */
-	memcpy(cipherKey, key->keyMaterial, keyLen/8);
 	if (direction == DIR_ENCRYPT) {
-		key->Nr = rijndaelKeySetupEnc(key->rk, cipherKey, keyLen);
+		key->Nr = rijndaelKeySetupEnc(key->rk, key->keyMaterial, keyLen);
 	} else {
-		key->Nr = rijndaelKeySetupDec(key->rk, cipherKey, keyLen);
+		key->Nr = rijndaelKeySetupDec(key->rk, key->keyMaterial, keyLen);
 	}
-	rijndaelKeySetupEnc(key->ek, cipherKey, keyLen);
+	rijndaelKeySetupEnc(key->ek, key->keyMaterial, keyLen);
 	return TRUE;
 }
 
@@ -186,6 +184,7 @@ int rijndael_blockEncrypt(cipherInstance *cipher, keyInstance *key,
 		return BAD_CIPHER_STATE;
 	}
 
+	explicit_bzero(block, sizeof(block));
 	return 128*numBlocks;
 }
 
@@ -258,6 +257,7 @@ int rijndael_padEncrypt(cipherInstance *cipher, keyInstance *key,
 		return BAD_CIPHER_STATE;
 	}
 
+	explicit_bzero(block, sizeof(block));
 	return 16*(numBlocks + 1);
 }
 
@@ -357,12 +357,13 @@ int rijndael_blockDecrypt(cipherInstance *cipher, keyInstance *key,
 		return BAD_CIPHER_STATE;
 	}
 
+	explicit_bzero(block, sizeof(block));
 	return 128*numBlocks;
 }
 
 int rijndael_padDecrypt(cipherInstance *cipher, keyInstance *key,
 		const BYTE *input, int inputOctets, BYTE *outBuffer) {
-	int i, numBlocks, padLen;
+	int i, numBlocks, padLen, rval;
 	u_int8_t block[16];
 	u_int32_t iv[4];
 
@@ -392,11 +393,13 @@ int rijndael_padDecrypt(cipherInstance *cipher, keyInstance *key,
 		rijndaelDecrypt(key->rk, key->Nr, input, block);
 		padLen = block[15];
 		if (padLen >= 16) {
-			return BAD_DATA;
+			rval = BAD_DATA;
+			goto out;
 		}
 		for (i = 16 - padLen; i < 16; i++) {
 			if (block[i] != padLen) {
-				return BAD_DATA;
+				rval = BAD_DATA;
+				goto out;
 			}
 		}
 		memcpy(outBuffer, block, 16 - padLen);
@@ -424,11 +427,13 @@ int rijndael_padDecrypt(cipherInstance *cipher, keyInstance *key,
 		((u_int32_t*)block)[3] ^= iv[3];
 		padLen = block[15];
 		if (padLen <= 0 || padLen > 16) {
-			return BAD_DATA;
+			rval = BAD_DATA;
+			goto out;
 		}
 		for (i = 16 - padLen; i < 16; i++) {
 			if (block[i] != padLen) {
-				return BAD_DATA;
+				rval = BAD_DATA;
+				goto out;
 			}
 		}
 		memcpy(outBuffer, block, 16 - padLen);
@@ -438,5 +443,9 @@ int rijndael_padDecrypt(cipherInstance *cipher, keyInstance *key,
 		return BAD_CIPHER_STATE;
 	}
 
-	return 16*numBlocks - padLen;
+	rval = 16*numBlocks - padLen;
+
+out:
+	explicit_bzero(block, sizeof(block));
+	return rval;
 }