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From: Borislav Petkov <bp@alien8.de>
To: Nikunj A Dadhania <nikunj@amd.com>
Cc: linux-kernel@vger.kernel.org, thomas.lendacky@amd.com,
	x86@kernel.org, kvm@vger.kernel.org, mingo@redhat.com,
	tglx@linutronix.de, dave.hansen@linux.intel.com,
	dionnaglaze@google.com, pgonda@google.com, seanjc@google.com,
	pbonzini@redhat.com
Subject: Re: [PATCH v7 01/16] virt: sev-guest: Use AES GCM crypto library
Date: Thu, 25 Jan 2024 11:36:43 +0100	[thread overview]
Message-ID: <20240125103643.GWZbI5u88U341ORBq1@fat_crate.local> (raw)
In-Reply-To: <20231220151358.2147066-2-nikunj@amd.com>

On Wed, Dec 20, 2023 at 08:43:43PM +0530, Nikunj A Dadhania wrote:
> @@ -307,11 +197,16 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
>  	 * If the message size is greater than our buffer length then return
>  	 * an error.
>  	 */
> -	if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
> +	if (unlikely((resp_hdr->msg_sz + ctx->authsize) > sz))
>  		return -EBADMSG;
>  
>  	/* Decrypt the payload */
> -	return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
> +	memcpy(iv, &resp_hdr->msg_seqno, sizeof(resp_hdr->msg_seqno));

sizeof(iv) != sizeof(resp_hdr->msg_seqno) and it fits now.

However, for protection against future bugs, this should be:

	memcpy(iv, &resp_hdr->msg_seqno, min(sizeof(iv), sizeof(resp_hdr->msg_seqno)));

> +	if (!aesgcm_decrypt(ctx, payload, resp->payload, resp_hdr->msg_sz,
> +			    &resp_hdr->algo, AAD_LEN, iv, resp_hdr->authtag))
> +		return -EBADMSG;
> +
> +	return 0;
>  }
>  
>  static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
> @@ -319,6 +214,8 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
>  {
>  	struct snp_guest_msg *req = &snp_dev->secret_request;
>  	struct snp_guest_msg_hdr *hdr = &req->hdr;
> +	struct aesgcm_ctx *ctx = snp_dev->ctx;
> +	u8 iv[GCM_AES_IV_SIZE] = {};
>  
>  	memset(req, 0, sizeof(*req));
>  
> @@ -338,7 +235,14 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
>  	dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
>  		hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
>  
> -	return __enc_payload(snp_dev, req, payload, sz);
> +	if (WARN_ON((sz + ctx->authsize) > sizeof(req->payload)))
> +		return -EBADMSG;
> +
> +	memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));

Ditto.

> +	aesgcm_encrypt(ctx, req->payload, payload, sz, &hdr->algo, AAD_LEN,
> +		       iv, hdr->authtag);
> +
> +	return 0;

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2024-01-25 10:37 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-20 15:13 [PATCH v7 00/16] Add Secure TSC support for SNP guests Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 01/16] virt: sev-guest: Use AES GCM crypto library Nikunj A Dadhania
2024-01-25 10:36   ` Borislav Petkov [this message]
2024-01-27  3:54     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 02/16] virt: sev-guest: Replace dev_dbg with pr_debug Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 03/16] virt: sev-guest: Add SNP guest request structure Nikunj A Dadhania
2024-01-25 11:59   ` Borislav Petkov
2024-01-27  4:01     ` Nikunj A. Dadhania
2024-01-31 13:58     ` Nikunj A. Dadhania
2024-02-01 10:29       ` Borislav Petkov
2024-02-01 11:10         ` Nikunj A. Dadhania
2024-02-01 14:07           ` Borislav Petkov
2024-02-02  3:50             ` Nikunj A. Dadhania
2024-02-02 16:14               ` Borislav Petkov
2024-02-05  9:23                 ` Nikunj A. Dadhania
2024-02-06 10:04                   ` Borislav Petkov
2024-01-26 21:16   ` Tom Lendacky
2024-01-27  4:05     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 04/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 05/16] x86/sev: Cache the secrets page address Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 06/16] virt: sev-guest: Move SNP Guest command mutex Nikunj A Dadhania
2024-01-26 22:11   ` Tom Lendacky
2024-01-27  4:06     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 07/16] x86/sev: Move and reorganize sev guest request api Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 08/16] x86/mm: Add generic guest initialization hook Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 09/16] x86/cpufeatures: Add synthetic Secure TSC bit Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 10/16] x86/sev: Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-02-01 15:46   ` Paolo Bonzini
2024-02-01 15:48     ` Paolo Bonzini
2023-12-20 15:13 ` [PATCH v7 11/16] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 12/16] x86/sev: Prevent RDTSC/RDTSCP interception " Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 14/16] x86/sev: Mark Secure TSC as reliable Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 15/16] x86/cpu/amd: Do not print FW_BUG for Secure TSC Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 16/16] x86/sev: Enable Secure TSC for SNP guests Nikunj A Dadhania
2024-01-25  6:08 ` [PATCH v7 00/16] Add Secure TSC support " Nikunj A. Dadhania
2024-01-26  1:00   ` Dionna Amalie Glaze
2024-01-27  4:10     ` Nikunj A. Dadhania

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