ossl: Keep mutable AES-GCM state on the stack

ossl(4)'s AES-GCM implementation keeps mutable state in the session
structure, together with the key schedule.  This was done for
convenience, as both are initialized together.  However, some OCF
consumers, particularly ZFS, assume that requests may be dispatched to
the same session in parallel.  Without serialization, this results in
incorrect output.

Fix the problem by explicitly copying per-session state onto the stack
at the beginning of each operation.

PR:		275306
Reviewed by:	jhb
Fixes:		9a3444d91c70 ("ossl: Add a VAES-based AES-GCM implementation for amd64")
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D42783

1 files changed, 15 insertions, 14 deletions

diff --git a/sys/crypto/openssl/ossl_aes.c b/sys/crypto/openssl/ossl_aes.c
index c0cb8ba08d35..65b6f126736e 100644
--- a/sys/crypto/openssl/ossl_aes.c
+++ b/sys/crypto/openssl/ossl_aes.c
@@ -167,10 +167,9 @@ static int
 ossl_aes_gcm(struct ossl_session_cipher *s, struct cryptop *crp,
     const struct crypto_session_params *csp)
 {
-	struct ossl_cipher_context key;
+	struct ossl_gcm_context ctx;
 	struct crypto_buffer_cursor cc_in, cc_out;
 	unsigned char iv[AES_BLOCK_LEN], tag[AES_BLOCK_LEN];
-	struct ossl_gcm_context *ctx;
 	const unsigned char *inseg;
 	unsigned char *outseg;
 	size_t inlen, outlen, seglen;
@@ -182,24 +181,25 @@ ossl_aes_gcm(struct ossl_session_cipher *s, struct cryptop *crp,
 	if (crp->crp_cipher_key != NULL) {
 		if (encrypt)
 			error = s->cipher->set_encrypt_key(crp->crp_cipher_key,
-			    8 * csp->csp_cipher_klen, &key);
+			    8 * csp->csp_cipher_klen,
+			    (struct ossl_cipher_context *)&ctx);
 		else
 			error = s->cipher->set_decrypt_key(crp->crp_cipher_key,
-			    8 * csp->csp_cipher_klen, &key);
+			    8 * csp->csp_cipher_klen,
+			    (struct ossl_cipher_context *)&ctx);
 		if (error)
 			return (error);
-		ctx = (struct ossl_gcm_context *)&key;
 	} else if (encrypt) {
-		ctx = (struct ossl_gcm_context *)&s->enc_ctx;
+		memcpy(&ctx, &s->enc_ctx, sizeof(struct ossl_gcm_context));
 	} else {
-		ctx = (struct ossl_gcm_context *)&s->dec_ctx;
+		memcpy(&ctx, &s->dec_ctx, sizeof(struct ossl_gcm_context));
 	}
 
 	crypto_read_iv(crp, iv);
-	ctx->ops->setiv(ctx, iv, csp->csp_ivlen);
+	ctx.ops->setiv(&ctx, iv, csp->csp_ivlen);
 
 	if (crp->crp_aad != NULL) {
-		if (ctx->ops->aad(ctx, crp->crp_aad, crp->crp_aad_length) != 0)
+		if (ctx.ops->aad(&ctx, crp->crp_aad, crp->crp_aad_length) != 0)
 			return (EINVAL);
 	} else {
 		crypto_cursor_init(&cc_in, &crp->crp_buf);
@@ -208,7 +208,7 @@ ossl_aes_gcm(struct ossl_session_cipher *s, struct cryptop *crp,
 		    alen -= seglen) {
 			inseg = crypto_cursor_segment(&cc_in, &inlen);
 			seglen = MIN(alen, inlen);
-			if (ctx->ops->aad(ctx, inseg, seglen) != 0)
+			if (ctx.ops->aad(&ctx, inseg, seglen) != 0)
 				return (EINVAL);
 			crypto_cursor_advance(&cc_in, seglen);
 		}
@@ -229,10 +229,10 @@ ossl_aes_gcm(struct ossl_session_cipher *s, struct cryptop *crp,
 		seglen = MIN(plen, MIN(inlen, outlen));
 
 		if (encrypt) {
-			if (ctx->ops->encrypt(ctx, inseg, outseg, seglen) != 0)
+			if (ctx.ops->encrypt(&ctx, inseg, outseg, seglen) != 0)
 				return (EINVAL);
 		} else {
-			if (ctx->ops->decrypt(ctx, inseg, outseg, seglen) != 0)
+			if (ctx.ops->decrypt(&ctx, inseg, outseg, seglen) != 0)
 				return (EINVAL);
 		}
 
@@ -242,18 +242,19 @@ ossl_aes_gcm(struct ossl_session_cipher *s, struct cryptop *crp,
 
 	error = 0;
 	if (encrypt) {
-		ctx->ops->tag(ctx, tag, GMAC_DIGEST_LEN);
+		ctx.ops->tag(&ctx, tag, GMAC_DIGEST_LEN);
 		crypto_copyback(crp, crp->crp_digest_start, GMAC_DIGEST_LEN,
 		    tag);
 	} else {
 		crypto_copydata(crp, crp->crp_digest_start, GMAC_DIGEST_LEN,
 		    tag);
-		if (ctx->ops->finish(ctx, tag, GMAC_DIGEST_LEN) != 0)
+		if (ctx.ops->finish(&ctx, tag, GMAC_DIGEST_LEN) != 0)
 			error = EBADMSG;
 	}
 
 	explicit_bzero(iv, sizeof(iv));
 	explicit_bzero(tag, sizeof(tag));
+	explicit_bzero(&ctx, sizeof(ctx));
 
 	return (error);
 }