linux-kernel - Re: [PATCH] efi: Do not import certificates from UEFI Secure Boot for T2 Macs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 10 Feb 2022 04:43:04 +0000
From:   Aditya Garg <gargaditya08@...e.com>
To:     Matthew Garrett <mjg59@...f.ucam.org>
CC:     Ard Biesheuvel <ardb@...nel.org>, Jeremy Kerr <jk@...abs.org>,
        "joeyli.kernel@...il.com" <joeyli.kernel@...il.com>,
        "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "eric.snowberg@...cle.com" <eric.snowberg@...cle.com>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "jlee@...e.com" <jlee@...e.com>,
        "James.Bottomley@...senpartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "mic@...ikod.net" <mic@...ikod.net>,
        "dmitry.kasatkin@...il.com" <dmitry.kasatkin@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        Orlando Chamberlain <redecorating@...tonmail.com>,
        Aun-Ali Zaidi <admin@...eit.net>
Subject: Re: [PATCH] efi: Do not import certificates from UEFI Secure Boot for
 T2 Macs


> ie, can you try something like this?
> 
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index f3e54f6616f0..01cbd4811d1e 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -32,6 +32,8 @@
> #include <linux/stringify.h>
> #include <linux/workqueue.h>
> #include <linux/completion.h>
> +#include <linux/ucs2_string.h>
> +#include <linux/slab.h>
> 
> #include <asm/efi.h>
> 
> @@ -203,6 +205,21 @@ static void efi_call_rts(struct work_struct *work)
> 				       (efi_time_t *)arg2);
> 		break;
> 	case EFI_GET_VARIABLE:
> +		unsigned long utf8_name_size;
> +		char *utf8_name;
> +		char guid_str[sizeof(efi_guid_t)+1];
> +
> +		utf8_name_size = ucs2_utf8size((efi_char16_t *)arg1);
> +		utf8_name = kmalloc(utf8_name_size+1, GFP_KERNEL);
> +		if (!utf8_name) {
> +			printk(KERN_INFO "failed to allocate UTF8 buffer\n");
> +			break;
> +		}
> +
> +		ucs2_as_utf8(utf8_name, (efi_char16_t *)arg1, utf8_name_size + 1);
> +		efi_guid_to_str((efi_guid_t *)arg2, guid_str);
> +
> +		printk(KERN_INFO "Reading EFI variable %s-%s\n", utf8_name, guid_str);
> 		status = efi_call_virt(get_variable, (efi_char16_t *)arg1,
> 				       (efi_guid_t *)arg2, (u32 *)arg3,
> 				       (unsigned long *)arg4, (void *)arg5);
> 
Hi Matthew

I haven't tested this yet (Kernel is compiling) but I have found out that this part of the code is causing a crash


static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
				  unsigned long *size, efi_status_t *status)
{
	unsigned long lsize = 4;
	unsigned long tmpdb[4];
	void *db;

	*status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
	if (*status == EFI_NOT_FOUND)
		return NULL;

	if (*status != EFI_BUFFER_TOO_SMALL) {
		pr_err("Couldn't get size: 0x%lx\n", *status);
		return NULL;
	}

	db = kmalloc(lsize, GFP_KERNEL);
	if (!db)
		return NULL;

	*status = efi.get_variable(name, guid, NULL, &lsize, db);
	if (*status != EFI_SUCCESS) {
		kfree(db);
		pr_err("Error reading db var: 0x%lx\n", *status);
		return NULL;
	}

	*size = lsize;
	return db;
}

If I remove the return 0 I had added from other 3 left functions, crash doesn't occur.

When the kernel compiles with your patch, I’ll send whatever I get.

Regards
Aditya