From a06c236183511b5de86f35b4df8686cc15a4243a Mon Sep 17 00:00:00 2001
From: nilusyi <nilusyi@tencent.com>
Date: Thu, 26 Dec 2024 17:44:40 +0800
Subject: [PATCH 1/4] disk/cryptodisk: Allow user to retry failed passphrase

Give the user a chance to re-enter their cryptodisk passphrase after a typo,
rather than immediately failing (and likely dumping them into a GRUB shell).

By default, we allow 3 tries before giving up. A value in the
cryptodisk_passphrase_tries environment variable will override this default.

The user can give up early by entering an empty passphrase, just as they
could before this patch.

Signed-off-by: Forest <forestix@nom.one>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 docs/grub.texi              |  8 +++++
 grub-core/disk/cryptodisk.c | 71 +++++++++++++++++++++++++++----------
 2 files changed, 61 insertions(+), 18 deletions(-)

diff --git a/docs/grub.texi b/docs/grub.texi
index 0addf2b90..de03d5a97 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -3285,6 +3285,7 @@ These variables have special meaning to GRUB.
 * color_normal::
 * config_directory::
 * config_file::
+* cryptodisk_passphrase_tries::
 * debug::
 * default::
 * fallback::
@@ -3457,6 +3458,13 @@ processed by commands @command{configfile} (@pxref{configfile}) or @command{norm
 (@pxref{normal}).  It is restored to the previous value when command completes.
 
 
+@node cryptodisk_passphrase_tries
+@subsection cryptodisk_passphrase_tries
+When prompting the user for a cryptodisk passphrase, allow this many attempts
+before giving up. Defaults to @samp{3} if unset or set to an invalid value.
+(The user can give up early by entering an empty passphrase.)
+
+
 @node debug
 @subsection debug
 
diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index b62fc02b7..1fcd001b1 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -17,6 +17,7 @@
  */
 
 #include <grub/cryptodisk.h>
+#include <grub/env.h>
 #include <grub/mm.h>
 #include <grub/misc.h>
 #include <grub/dl.h>
@@ -1202,7 +1203,12 @@ grub_cryptodisk_scan_device_real (const char *name,
       grub_free (part);
     }
 
-  if (!cargs->key_len)
+  if (cargs->key_len) {
+	ret = cr->recover_key (source, dev, cargs);
+	if (ret != GRUB_ERR_NONE)
+	  goto error;
+  }
+  else
     {
       if (grub_errno)
 	{
@@ -1211,28 +1217,57 @@ grub_cryptodisk_scan_device_real (const char *name,
 	}
 
       /* Get the passphrase from the user, if no key data. */
-      askpass = 1;
-      part = grub_partition_get_name (source->partition);
-      grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
-		    source->partition != NULL ? "," : "",
-		    part != NULL ? part : N_("UNKNOWN"), dev->uuid);
-      grub_free (part);
+      unsigned long tries = 3;
+	    const char *tries_env;
 
+      askpass = 1;
       cargs->key_data = grub_malloc (GRUB_CRYPTODISK_MAX_PASSPHRASE);
       if (cargs->key_data == NULL)
-	goto error;
+	goto error_no_close;
 
-      if (!grub_password_get ((char *) cargs->key_data, GRUB_CRYPTODISK_MAX_PASSPHRASE))
-	{
-	  grub_error (GRUB_ERR_BAD_ARGUMENT, "passphrase not supplied");
-	  goto error;
-	}
-      cargs->key_len = grub_strlen ((char *) cargs->key_data);
-    }
+  tries_env = grub_env_get ("cryptodisk_passphrase_tries");
+	if (tries_env != NULL && tries_env[0] != '\0')
+	  {
+	    unsigned long tries_env_val;
+	    const char *p;
+	    tries_env_val = grub_strtoul (tries_env, &p, 0);
+	    if (*p == '\0' && tries_env_val != ~0UL)
+	      tries = tries_env_val;
+	    else
+	      grub_printf_ (N_("Invalid cryptodisk_passphrase_tries value `%s'. Defaulting to %lu.\n"),
+			    tries_env,
+			    tries);
+	  }
 
-  ret = cr->recover_key (source, dev, cargs);
-  if (ret != GRUB_ERR_NONE)
-    goto error;
+	for (; tries > 0; tries--)
+	  {
+	    part = grub_partition_get_name (source->partition);
+	    grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
+			 source->partition != NULL ? "," : "",
+			 part != NULL ? part : N_("UNKNOWN"),
+			 dev->uuid);
+	    grub_free (part);
+	    if (!grub_password_get ((char *) cargs->key_data, GRUB_CRYPTODISK_MAX_PASSPHRASE))
+	      {
+          grub_error (GRUB_ERR_BAD_ARGUMENT, "passphrase not supplied");
+          goto error;
+	      }
+	    cargs->key_len = grub_strlen ((char *) cargs->key_data);
+	    ret = cr->recover_key (source, dev, cargs);
+	    if (ret == GRUB_ERR_NONE)
+	      break;
+	    if (ret != GRUB_ERR_ACCESS_DENIED || tries == 1)
+	      goto error;
+	    grub_puts_ (N_("Invalid passphrase."));
+	    /*
+	     * Since recover_key() calls a function that returns grub_errno,
+	     * a leftover error value from a previously rejected passphrase
+	     * will trigger a phantom failure. We therefore clear it before
+	     * trying a new passphrase.
+	     */
+	    grub_errno = GRUB_ERR_NONE;
+	  }
+      }
 
   ret = grub_cryptodisk_insert (dev, name, source);
   if (ret != GRUB_ERR_NONE)
-- 
2.41.1