Hi Steffen,
On Mon, 26 Apr 2021 at 05:19, Steffen Jaeckel
<jaeckel-fl...@eyet-services.de> wrote:
>
> Hook into the autoboot flow as an alternative to the existing
> mechanisms.
>
> Signed-off-by: Steffen Jaeckel <jaeckel-fl...@eyet-services.de>
> ---
>
> common/Kconfig.boot | 23 +++++++++---
> common/autoboot.c | 85 ++++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 95 insertions(+), 13 deletions(-)
>
> diff --git a/common/Kconfig.boot b/common/Kconfig.boot
> index 5a18d62d78..d8012ead3e 100644
> --- a/common/Kconfig.boot
> +++ b/common/Kconfig.boot
> @@ -812,10 +812,16 @@ config AUTOBOOT_ENCRYPTION
> depends on AUTOBOOT_KEYED
> help
> This option allows a string to be entered into U-Boot to stop the
> - autoboot. The string itself is hashed and compared against the hash
> - in the environment variable 'bootstopkeysha256'. If it matches then
> - boot stops and a command-line prompt is presented.
> -
> + autoboot.
> + The behavior depends whether CONFIG_CRYPT_PW is enabled or not.
> + In case CONFIG_CRYPT_PW is enabled, the string will be forwarded
> + to the crypt-based functionality and be compared against the
> + string in the environment variable 'bootstopkeycrypt'.
> + In case CONFIG_CRYPT_PW is disabled the string itself is hashed
> + and compared against the hash in the environment variable
> + 'bootstopkeysha256'.
> + If it matches in either case then boot stops and
> + a command-line prompt is presented.
> This provides a way to ship a secure production device which can
> also
> be accessed at the U-Boot command line.
>
> @@ -853,6 +859,15 @@ config AUTOBOOT_KEYED_CTRLC
> Setting this variable provides an escape sequence from the
> limited "password" strings.
>
> +config AUTOBOOT_STOP_STR_CRYPT
> + string "Stop autobooting via crypt-hashed password"
> + depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION
> + help
> + This option adds the feature to only stop the autobooting,
> + and therefore boot into the U-Boot prompt, when the input
> + string / password matches a values that is hashed via
> + one of support crypt options and saved in the environment.
> +
> config AUTOBOOT_STOP_STR_SHA256
> string "Stop autobooting via SHA256 encrypted password"
> depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION
> diff --git a/common/autoboot.c b/common/autoboot.c
> index 0bb08e7a4c..de60635d2a 100644
> --- a/common/autoboot.c
> +++ b/common/autoboot.c
> @@ -23,6 +23,7 @@
> #include <linux/delay.h>
> #include <u-boot/sha256.h>
> #include <bootcount.h>
> +#include <crypt.h>
>
> DECLARE_GLOBAL_DATA_PTR;
>
> @@ -38,18 +39,80 @@ DECLARE_GLOBAL_DATA_PTR;
> static int stored_bootdelay;
> static int menukey;
>
> -#ifdef CONFIG_AUTOBOOT_ENCRYPTION
> -#define AUTOBOOT_STOP_STR_SHA256 CONFIG_AUTOBOOT_STOP_STR_SHA256
> -#else
> -#define AUTOBOOT_STOP_STR_SHA256 ""
> +#if defined(CONFIG_AUTOBOOT_ENCRYPTION)
> +#if defined(CONFIG_CRYPT_PW) && defined(CONFIG_AUTOBOOT_STOP_STR_CRYPT)
> +#define AUTOBOOT_STOP_STR_ENC CONFIG_AUTOBOOT_STOP_STR_CRYPT
> +#define HAS_STOP_STR_CRYPT 1
See other patch about splitting Kconfig
> +#elif defined(CONFIG_AUTOBOOT_STOP_STR_SHA256)
> +#define AUTOBOOT_STOP_STR_ENC CONFIG_AUTOBOOT_STOP_STR_SHA256
> +#endif
> +#endif
> +#if !defined(AUTOBOOT_STOP_STR_ENC)
> +#define AUTOBOOT_STOP_STR_ENC ""
> #endif
> -
> #ifdef CONFIG_USE_AUTOBOOT_MENUKEY
> #define AUTOBOOT_MENUKEY CONFIG_USE_AUTOBOOT_MENUKEY
> #else
> #define AUTOBOOT_MENUKEY 0
> #endif
>
> +/**
> + * passwd_abort_crypt() - check for a crypt-style hashed key sequence to
> abort booting
> + *
> + * This checks for the user entering a password within a given time.
> + *
> + * The entered password is hashed via one of the crypt-style hash methods
> + * and compared to the pre-defined value from either
> + * the environment variable "bootstopkeycrypt"
> + * or
> + * the config value CONFIG_AUTOBOOT_STOP_STR_CRYPT
> + *
> + * @etime: Timeout value ticks (stop when get_ticks() reachs this)
> + * @return 0 if autoboot should continue, 1 if it should stop
> + */
> +static int passwd_abort_crypt(uint64_t etime)
> +{
> + const char *crypt_env_str = env_get("bootstopkeycrypt");
> + char presskey[MAX_DELAY_STOP_STR];
> + u_int presskey_len = 0;
uint
> + int abort = 0;
> + int err;
> +
> + if (IS_ENABLED(HAS_STOP_STR_CRYPT) && !crypt_env_str)
> + crypt_env_str = AUTOBOOT_STOP_STR_ENC;
> +
> + if (!crypt_env_str)
> + return 0;
> +
> + /* We expect the stop-string to be newline terminated. */
newline-terminated
No need for the period
> + do {
> + if (tstc()) {
> + /* Check for input string overflow */
> + if (presskey_len >= MAX_DELAY_STOP_STR)
> + return 0;
> +
> + presskey[presskey_len] = getchar();
> +
> + if ((presskey[presskey_len] == '\r') ||
> + (presskey[presskey_len] == '\n')) {
> + presskey[presskey_len] = '\0';
> + err = crypt_compare(crypt_env_str, presskey,
> + &abort);
> + if (err)
> + debug_bootkeys(
> + "crypt_compare() failed with:
> %s\n",
> + errno_str(err));
> + /* you had one chance */
> + break;
> + } else {
> + presskey_len++;
> + }
> + }
> + } while (get_ticks() <= etime);
> +
> + return abort;
> +}
> +
> /*
> * Use a "constant-length" time compare function for this
> * hash compare:
> @@ -89,7 +152,7 @@ static int passwd_abort_sha256(uint64_t etime)
> int ret;
>
> if (sha_env_str == NULL)
> - sha_env_str = AUTOBOOT_STOP_STR_SHA256;
> + sha_env_str = AUTOBOOT_STOP_STR_ENC;
I think you might need to rename that variable since it is not always a sha now.
>
> presskey = malloc_cache_aligned(MAX_DELAY_STOP_STR);
> c = strstr(sha_env_str, ":");
> @@ -245,10 +308,14 @@ static int abortboot_key_sequence(int bootdelay)
> printf(CONFIG_AUTOBOOT_PROMPT, bootdelay);
> # endif
>
> - if (IS_ENABLED(CONFIG_AUTOBOOT_ENCRYPTION))
> - abort = passwd_abort_sha256(etime);
> - else
> + if (IS_ENABLED(CONFIG_AUTOBOOT_ENCRYPTION)) {
> + if (IS_ENABLED(CONFIG_CRYPT_PW))
> + abort = passwd_abort_crypt(etime);
> + else
> + abort = passwd_abort_sha256(etime);
> + } else {
> abort = passwd_abort_key(etime);
> + }
> if (!abort)
> debug_bootkeys("key timeout\n");
>
> --
> 2.31.1
>
Regards,
Simon
