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fdt: Allow device tree to specify secure booting

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When secure booting is chosen:
* The u-boot shell is never invoked during boot--we just do a simple
  table lookup to find the command.  This means we could even remove
  the shell parsing from u-boot and still be able to boot.
* The boot command can't be interruped.
* Failure doesn't cause us to fall back to the shell.

Signed-off-by: Gabe Black <gabeblack@google.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Doug Anderson 2012-10-25 16:31:09 +00:00 committed by Gerald Van Baren
parent 3b73459ea3
commit 67e1ea26e8
1 changed files with 62 additions and 0 deletions
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62
common/main.c
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@ -283,6 +283,59 @@ int abortboot(int bootdelay)
# endif /* CONFIG_AUTOBOOT_KEYED */
#endif /* CONFIG_BOOTDELAY >= 0 */
/*
* Runs the given boot command securely. Specifically:
* - Doesn't run the command with the shell (run_command or parse_string_outer),
* since that's a lot of code surface that an attacker might exploit.
* Because of this, we don't do any argument parsing--the secure boot command
* has to be a full-fledged u-boot command.
* - Doesn't check for keypresses before booting, since that could be a
* security hole; also disables Ctrl-C.
* - Doesn't allow the command to return.
*
* Upon any failures, this function will drop into an infinite loop after
* printing the error message to console.
*/
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0) && \
defined(CONFIG_OF_CONTROL)
static void secure_boot_cmd(char *cmd)
{
cmd_tbl_t *cmdtp;
int rc;
if (!cmd) {
printf("## Error: Secure boot command not specified\n");
goto err;
}
/* Disable Ctrl-C just in case some command is used that checks it. */
disable_ctrlc(1);
/* Find the command directly. */
cmdtp = find_cmd(cmd);
if (!cmdtp) {
printf("## Error: \"%s\" not defined\n", cmd);
goto err;
}
/* Run the command, forcing no flags and faking argc and argv. */
rc = (cmdtp->cmd)(cmdtp, 0, 1, &cmd);
/* Shouldn't ever return from boot command. */
printf("## Error: \"%s\" returned (code %d)\n", cmd, rc);
err:
/*
* Not a whole lot to do here. Rebooting won't help much, since we'll
* just end up right back here. Just loop.
*/
hang();
}
#endif /* CONFIG_OF_CONTROL */
/****************************************************************************/
void main_loop (void)
@ -397,6 +450,15 @@ void main_loop (void)
env = fdtdec_get_config_string(gd->fdt_blob, "bootcmd");
if (env)
s = env;
/*
* If the bootsecure option was chosen, use secure_boot_cmd().
* Always use 'env' in this case, since bootsecure requres that the
* bootcmd was specified in the FDT too.
*/
if (fdtdec_get_config_int(gd->fdt_blob, "bootsecure", 0))
secure_boot_cmd(env);
#endif /* CONFIG_OF_CONTROL */
debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");