From 184b6a054e04bb4c7fb4885a30d62314229dc551 Mon Sep 17 00:00:00 2001
Message-Id: <184b6a054e04bb4c7fb4885a30d62314229dc551.1652945863.git.stefan@agner.ch>
From: Stefan Agner <stefan@agner.ch>
Date: Thu, 24 Feb 2022 12:38:48 +0100
Subject: [PATCH] loadenv: add file_env to load var from file

Introduce file_env which allows to load the value of a variable from a
file. The variable value is terminated at the first non-printable
character.
---
 grub-core/commands/loadenv.c | 73 +++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/grub-core/commands/loadenv.c b/grub-core/commands/loadenv.c
index 3fd664aac..7e7b18139 100644
--- a/grub-core/commands/loadenv.c
+++ b/grub-core/commands/loadenv.c
@@ -40,6 +40,14 @@ static const struct grub_arg_option options[] =
     {0, 0, 0, 0, 0, 0}
   };
 
+static const struct grub_arg_option options_file_env[] =
+  {
+    /* TRANSLATORS: This option is used to override default filename
+       for loading and storing environment.  */
+    {"file", 'f', 0, N_("Specify filename."), 0, ARG_TYPE_PATHNAME},
+    {0, 0, 0, 0, 0, 0}
+  };
+
 /* Opens 'filename' with compression filters disabled. Optionally disables the
    PUBKEY filter (that insists upon properly signed files) as well.  PUBKEY
    filter is restored before the function returns. */
@@ -442,7 +450,64 @@ grub_cmd_save_env (grub_extcmd_context_t ctxt, int argc, char **args)
   return grub_errno;
 }
 
-static grub_extcmd_t cmd_load, cmd_list, cmd_save;
+static grub_err_t
+grub_cmd_file_env (grub_extcmd_context_t ctxt, int argc, char **args)
+{
+  grub_off_t offset = 0;
+  struct grub_arg_list *state = ctxt->state;
+  grub_file_t file;
+  grub_size_t size;
+  char *buf;
+
+  if (argc != 1)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("variable name expected"));
+
+  /* state[0] is the -f flag; state[1] is the --skip-sig flag */
+  file = open_envblk_file ((state[0].set) ? state[0].arg : 0,
+		           GRUB_FILE_TYPE_CAT);
+  if (! file)
+    return grub_errno;
+
+  size = grub_file_size (file);
+  buf = grub_malloc (size + 1);
+  if (! buf)
+    goto fail;
+
+  /* make sure buffer is terminated in any case */
+  buf[size] = '\0';
+  while (size > 0)
+    {
+      grub_ssize_t ret;
+
+      ret = grub_file_read (file, buf + offset, size);
+      if (ret <= 0)
+	goto fail;
+
+      /* terminate at the first non-printable character */
+      while (ret)
+        {
+	  if (!grub_isprint(buf[offset]))
+	    {
+	      buf[offset] = '\0';
+	      size = 0;
+	      break;
+	    }
+
+	  ret--;
+	  size--;
+	  offset++;
+        }
+    }
+
+  grub_env_set (args[0], buf);
+
+ fail:
+  grub_free (buf);
+  grub_file_close (file);
+  return grub_errno;
+}
+
+static grub_extcmd_t cmd_load, cmd_list, cmd_save, cmd_file;
 
 GRUB_MOD_INIT(loadenv)
 {
@@ -460,6 +525,11 @@ GRUB_MOD_INIT(loadenv)
 			  N_("[-f FILE] variable_name [...]"),
 			  N_("Save variables to environment block file."),
 			  options);
+  cmd_file =
+    grub_register_extcmd ("file_env", grub_cmd_file_env, 0,
+			  N_("[-f FILE] variable_name"),
+			  N_("Set variable to content of a file."),
+			  options_file_env);
 }
 
 GRUB_MOD_FINI(loadenv)
@@ -467,4 +537,5 @@ GRUB_MOD_FINI(loadenv)
   grub_unregister_extcmd (cmd_load);
   grub_unregister_extcmd (cmd_list);
   grub_unregister_extcmd (cmd_save);
+  grub_unregister_extcmd (cmd_file);
 }
-- 
2.36.1