Re: [PATCH 4/5] boot: if we are in secure boot mode

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Mar 09, 2017 at 03:34:09PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> request confirmation before booting an unsigned image
> 
> with a default timeout
> 
> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> ---
>  commands/go.c         |  7 +++++++
>  common/Kconfig        |  8 ++++++++
>  common/Makefile       |  1 +
>  common/bootm.c        |  7 +++++++
>  common/secure_boot.c  | 43 +++++++++++++++++++++++++++++++++++++++++++
>  include/bootm.h       |  1 +
>  include/secure_boot.h | 25 +++++++++++++++++++++++++
>  7 files changed, 92 insertions(+)
>  create mode 100644 common/secure_boot.c
>  create mode 100644 include/secure_boot.h
> 
> diff --git a/commands/go.c b/commands/go.c
> index fb319b320..61c9ce43f 100644
> --- a/commands/go.c
> +++ b/commands/go.c
> @@ -26,6 +26,7 @@
>  #include <fcntl.h>
>  #include <linux/ctype.h>
>  #include <errno.h>
> +#include <secure_boot.h>
>  
>  static int do_go(int argc, char *argv[])
>  {
> @@ -37,6 +38,12 @@ static int do_go(int argc, char *argv[])
>  	if (argc < 2)
>  		return COMMAND_ERROR_USAGE;
>  
> +	rcode = secure_boot_start_unsigned();
> +	if (rcode)
> +		return rcode ? 1 : 0;

When rcode is true, then if rcode is true, return 1, otherwise return 0?

> +
> +	rcode = 1;
> +
>  	if (!isdigit(*argv[1])) {
>  		fd = open(argv[1], O_RDONLY);
>  		if (fd < 0) {
> diff --git a/common/Kconfig b/common/Kconfig
> index f7ff04664..9e7d027a2 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -21,6 +21,9 @@ config HAS_KALLSYMS
>  config HAS_MODULES
>  	bool
>  
> +config HAS_SECURE_BOOT
> +	bool
> +
>  config HAS_CACHE
>  	bool
>  	help
> @@ -184,6 +187,11 @@ config NVVAR
>  	  while global variables can be changed during runtime without changing the
>  	  default.
>  
> +config SECURE_BOOT_TIMEOUT
> +	prompt "Secure Boot unsigned boot timeout"
> +	int
> +	default 3
> +
>  menu "memory layout"
>  
>  source "pbl/Kconfig"
> diff --git a/common/Makefile b/common/Makefile
> index 5f58c81d2..e57cc2c15 100644
> --- a/common/Makefile
> +++ b/common/Makefile
> @@ -61,6 +61,7 @@ obj-$(CONFIG_UBIFORMAT)		+= ubiformat.o
>  obj-$(CONFIG_BAREBOX_UPDATE_IMX_NAND_FCB) += imx-bbu-nand-fcb.o
>  obj-$(CONFIG_CONSOLE_RATP)	+= ratp.o
>  obj-$(CONFIG_BOOT)		+= boot.o
> +obj-$(CONFIG_HAS_SECURE_BOOT)	+= secure_boot.o
>  
>  quiet_cmd_pwd_h = PWDH    $@
>  ifdef CONFIG_PASSWORD
> diff --git a/common/bootm.c b/common/bootm.c
> index 81625d915..0ebf65681 100644
> --- a/common/bootm.c
> +++ b/common/bootm.c
> @@ -23,6 +23,7 @@
>  #include <environment.h>
>  #include <linux/stat.h>
>  #include <magicvar.h>
> +#include <secure_boot.h>
>  
>  static LIST_HEAD(handler_list);
>  
> @@ -625,6 +626,12 @@ int bootm_boot(struct bootm_data *bootm_data)
>  		printf("Passing control to %s handler\n", handler->name);
>  	}
>  
> +	if (!handler->is_secure_supported && is_secure_mode()) {
> +		ret = secure_boot_start_unsigned();
> +		if (ret)
> +			goto err_out;
> +	}
> +
>  	ret = handler->bootm(data);
>  	if (data->dryrun)
>  		printf("Dryrun. Aborted\n");
> diff --git a/common/secure_boot.c b/common/secure_boot.c
> new file mode 100644
> index 000000000..e625ef4e1
> --- /dev/null
> +++ b/common/secure_boot.c
> @@ -0,0 +1,43 @@
> +/*
> + * Copyright (c) 2017 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> + *
> + * Under GPLv2 Only
> + */
> +#include <common.h>
> +#include <secure_boot.h>
> +#include <console_countdown.h>
> +#include <globalvar.h>
> +#include <magicvar.h>
> +#include <init.h>
> +
> +static unsigned int sb_confirm_timeout = CONFIG_SECURE_BOOT_TIMEOUT;

Use globalvar_add_simple_int instead of putting this into the config.

> +
> +int secure_boot_start_unsigned(void)

This function name is very misleading. It sounds like it starts an
unsigned image, but this function doesn't start anything. Second guess
is that it returns a boolean whether it's allowed to start an unsigned
image, but actually it returns the opposite.

> +{
> +	int ret;
> +	char str[2] = { };
> +	int timeout = sb_confirm_timeout;
> +
> +	if (!is_secure_mode())
> +		return 0;
> +
> +	printf("Are you sure you wish to run an unsigned binary\n");
> +	printf("in a secure environment?\n");
> +	printf("press y to confirm\n");
> +
> +	ret = console_countdown(timeout, CONSOLE_COUNTDOWN_ANYKEY, str);

console_countdown puts exactly one character in *str, no need to pass an
array.

> +	if (ret != -EINTR)
> +		return -EINVAL;
> +
> +	return str[0] == 'y' ? 0 : -EINVAL;
> +}
> +
> +static int init_sb_confirm_timeout(void)
> +{
> +	return globalvar_add_simple_int("sb.confirm_timeout",
> +			&sb_confirm_timeout, "%u");
> +}

Ok, you already made it a globalvar. No need to put the default into
kconfig then.

Sascha

-- 
Pengutronix e.K.                           |                             |
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