[image] Add the "imgdecrypt" command

Add the "imgdecrypt" command that can be used to decrypt a detached
encrypted data image using a cipher key obtained from a separate CMS
envelope image.  For example:

  # Create non-detached encrypted CMS messages
  #
  openssl cms -encrypt -binary -aes-256-gcm -recip client.crt \
              -in vmlinuz -outform DER -out vmlinuz.cms
  openssl cms -encrypt -binary -aes-256-gcm -recip client.crt \
              -in initrd.img -outform DER -out initrd.img.cms

  # Detach data from envelopes (using iPXE's contrib/crypto/cmsdetach)
  #
  cmsdetach vmlinuz.cms -d vmlinuz.dat -e vmlinuz.env
  cmsdetach initrd.img.cms -d initrd.img.dat -e initrd.img.env

and then within iPXE:

  #!ipxe
  imgfetch http://192.168.0.1/vmlinuz.dat
  imgfetch http://192.168.0.1/initrd.img.dat
  imgdecrypt vmlinuz.dat    http://192.168.0.1/vmlinuz.env
  imgdecrypt initrd.img.dat http://192.168.0.1/initrd.img.env
  boot vmlinuz

Signed-off-by: Michael Brown <mcb30@ipxe.org>

5 files changed, 220 insertions, 0 deletions

diff --git a/src/config/config.c b/src/config/config.c
index 6bcd3c1..f532c1d 100644
--- a/src/config/config.c
+++ b/src/config/config.c
@@ -299,6 +299,9 @@ REQUIRE_OBJECT ( image_mem_cmd );
 #ifdef SHIM_CMD
 REQUIRE_OBJECT ( shim_cmd );
 #endif
+#ifdef IMAGE_CRYPT_CMD
+REQUIRE_OBJECT ( image_crypt_cmd );
+#endif
 
 /*
  * Drag in miscellaneous objects
diff --git a/src/config/general.h b/src/config/general.h
index f936e87..b82e560 100644
--- a/src/config/general.h
+++ b/src/config/general.h
@@ -158,6 +158,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 //#define REBOOT_CMD		/* Reboot command */
 //#define POWEROFF_CMD		/* Power off command */
 //#define IMAGE_TRUST_CMD	/* Image trust management commands */
+//#define IMAGE_CRYPT_CMD	/* Image encryption management commands */
 //#define PCI_CMD		/* PCI commands */
 //#define PARAM_CMD		/* Request parameter commands */
 //#define NEIGHBOUR_CMD		/* Neighbour management commands */
diff --git a/src/hci/commands/image_crypt_cmd.c b/src/hci/commands/image_crypt_cmd.c
new file mode 100644
index 0000000..26e9d79
--- /dev/null
+++ b/src/hci/commands/image_crypt_cmd.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <stdio.h>
+#include <getopt.h>
+#include <ipxe/image.h>
+#include <ipxe/command.h>
+#include <ipxe/parseopt.h>
+#include <usr/imgmgmt.h>
+#include <usr/imgcrypt.h>
+
+/** @file
+ *
+ * Image encryption management commands
+ *
+ */
+
+/** "imgdecrypt" options */
+struct imgdecrypt_options {
+	/** Decrypted image name */
+	char *name;
+	/** Keep envelope after decryption */
+	int keep;
+	/** Download timeout */
+	unsigned long timeout;
+};
+
+/** "imgdecrypt" option list */
+static struct option_descriptor imgdecrypt_opts[] = {
+	OPTION_DESC ( "name", 'n', required_argument,
+		      struct imgdecrypt_options, name, parse_string ),
+	OPTION_DESC ( "keep", 'k', no_argument,
+		      struct imgdecrypt_options, keep, parse_flag ),
+	OPTION_DESC ( "timeout", 't', required_argument,
+		      struct imgdecrypt_options, timeout, parse_timeout),
+};
+
+/** "imgdecrypt" command descriptor */
+static struct command_descriptor imgdecrypt_cmd =
+	COMMAND_DESC ( struct imgdecrypt_options, imgdecrypt_opts, 2, 2,
+		       "<uri|image> <envelope uri|image>" );
+
+/**
+ * The "imgdecrypt" command
+ *
+ * @v argc		Argument count
+ * @v argv		Argument list
+ * @ret rc		Return status code
+ */
+static int imgdecrypt_exec ( int argc, char **argv ) {
+	struct imgdecrypt_options opts;
+	const char *image_name_uri;
+	const char *envelope_name_uri;
+	struct image *image;
+	struct image *envelope;
+	int rc;
+
+	/* Parse options */
+	if ( ( rc = parse_options ( argc, argv, &imgdecrypt_cmd, &opts ) ) != 0)
+		return rc;
+
+	/* Parse image name/URI string */
+	image_name_uri = argv[optind];
+
+	/* Parse envelope name/URI string */
+	envelope_name_uri = argv[ optind + 1 ];
+
+	/* Acquire the image */
+	if ( ( rc = imgacquire ( image_name_uri, opts.timeout, &image ) ) != 0 )
+		goto err_acquire_image;
+
+	/* Acquire the envelope image */
+	if ( ( rc = imgacquire ( envelope_name_uri, opts.timeout,
+				 &envelope ) ) != 0 )
+		goto err_acquire_envelope;
+
+	/* Decrypt image */
+	if ( ( rc = imgdecrypt ( image, envelope, opts.name ) ) != 0 ) {
+		printf ( "Could not decrypt: %s\n", strerror ( rc ) );
+		goto err_decrypt;
+	}
+
+	/* Success */
+	rc = 0;
+
+ err_decrypt:
+	/* Discard envelope unless --keep was specified */
+	if ( ! opts.keep )
+		unregister_image ( envelope );
+ err_acquire_envelope:
+ err_acquire_image:
+	return rc;
+}
+
+/** Image encryption management commands */
+struct command image_crypt_commands[] __command = {
+	{
+		.name = "imgdecrypt",
+		.exec = imgdecrypt_exec,
+	},
+};
diff --git a/src/include/usr/imgcrypt.h b/src/include/usr/imgcrypt.h
new file mode 100644
index 0000000..c9408c7
--- /dev/null
+++ b/src/include/usr/imgcrypt.h
@@ -0,0 +1,17 @@
+#ifndef _USR_IMGCRYPT_H
+#define _USR_IMGCRYPT_H
+
+/** @file
+ *
+ * Image encryption management
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <ipxe/image.h>
+
+extern int imgdecrypt ( struct image *image, struct image *envelope,
+			const char *name );
+
+#endif /* _USR_IMGCRYPT_H */
diff --git a/src/usr/imgcrypt.c b/src/usr/imgcrypt.c
new file mode 100644
index 0000000..1b649f1
--- /dev/null
+++ b/src/usr/imgcrypt.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <string.h>
+#include <syslog.h>
+#include <ipxe/image.h>
+#include <ipxe/cms.h>
+#include <ipxe/privkey.h>
+#include <usr/imgcrypt.h>
+
+/** @file
+ *
+ * Image encryption management
+ *
+ */
+
+/**
+ * Decrypt image using downloaded envelope
+ *
+ * @v image		Image to decrypt
+ * @v envelope		Image containing decryption key
+ * @v name		Decrypted image name (or NULL to use default)
+ * @ret rc		Return status code
+ */
+int imgdecrypt ( struct image *image, struct image *envelope,
+		 const char *name ) {
+	struct cms_message *cms;
+	int rc;
+
+	/* Parse envelope */
+	if ( ( rc = cms_message ( envelope, &cms ) ) != 0 )
+		goto err_parse;
+
+	/* Decrypt image */
+	if ( ( rc = cms_decrypt ( cms, image, name, &private_key ) ) != 0 )
+		goto err_decrypt;
+
+	/* Drop reference to message */
+	cms_put ( cms );
+	cms = NULL;
+
+	/* Record decryption */
+	syslog ( LOG_NOTICE, "Image \"%s\" decrypted OK\n", image->name );
+
+	return 0;
+
+ err_decrypt:
+	cms_put ( cms );
+ err_parse:
+	syslog ( LOG_ERR, "Image \"%s\" decryption failed: %s\n",
+		 image->name, strerror ( rc ) );
+	return rc;
+}