[2/2,V2] Add encrypted file support
diff mbox

Message ID 1880260679.6420.1470192775404.JavaMail.zimbra@raptorengineeringinc.com
State Superseded
Headers show

Commit Message

Timothy Pearson Aug. 3, 2016, 2:52 a.m. UTC
In certain cases, such as network booting over an untrusted connection,
it may be useful to fully encrypt and sign the kernel files.

Enable fully encrypted boot using builtin keyring via the addition of
the string "ENCRYPTED" to the first line of the /etc/pb-lockdown file.
This disables detached (plaintext) signature verification.

Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>
---
 discover/boot.c             | 349 +++++++++++++++++++++++++++++++++++++++-----
 ui/ncurses/nc-boot-editor.c |   9 +-
 2 files changed, 323 insertions(+), 35 deletions(-)

Patch
diff mbox

diff --git a/discover/boot.c b/discover/boot.c
index 0ae803f..864d580 100644
--- a/discover/boot.c
+++ b/discover/boot.c
@@ -39,6 +39,7 @@  enum {
 };
 
 enum {
+	KEXEC_LOAD_DECRYPTION_FALURE = 252,
 	KEXEC_LOAD_SIG_SETUP_INVALID = 253,
 	KEXEC_LOAD_SIGNATURE_FAILURE = 254,
 };
@@ -56,6 +57,7 @@  struct boot_task {
 	bool dry_run;
 	bool cancelled;
 	bool verify_signature;
+	bool decrypt_files;
 	struct load_url_result *image_signature;
 	struct load_url_result *initrd_signature;
 	struct load_url_result *dtb_signature;
@@ -127,6 +129,173 @@  static int copy_file_to_destination(const char * source_file,
 }
 
 #if defined(HAVE_LIBGPGME)
+static int decrypt_file(const char * filename,
+	FILE * authorized_signatures_handle, const char * keyring_path)
+{
+	int result = 0;
+	int valid = 0;
+	size_t bytes_read = 0;
+	unsigned char buffer[8192];
+
+	if (filename == NULL)
+		return -1;
+
+	gpgme_signature_t verification_signatures;
+	gpgme_verify_result_t verification_result;
+	gpgme_data_t ciphertext_data;
+	gpgme_data_t plaintext_data;
+	gpgme_engine_info_t enginfo;
+	gpgme_ctx_t gpg_context;
+	gpgme_error_t err;
+
+	/* Initialize gpgme */
+	setlocale (LC_ALL, "");
+	gpgme_check_version(NULL);
+	gpgme_set_locale(NULL, LC_CTYPE, setlocale (LC_CTYPE, NULL));
+	err = gpgme_engine_check_version(GPGME_PROTOCOL_OpenPGP);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: OpenPGP support not available\n", __func__);
+		return -1;
+	}
+	err = gpgme_get_engine_info(&enginfo);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: GPG engine failed to initialize\n", __func__);
+		return -1;
+	}
+	err = gpgme_new(&gpg_context);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: GPG context could not be created\n", __func__);
+		return -1;
+	}
+	err = gpgme_set_protocol(gpg_context, GPGME_PROTOCOL_OpenPGP);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: GPG protocol could not be set\n", __func__);
+		return -1;
+	}
+	if (keyring_path)
+		err = gpgme_ctx_set_engine_info (gpg_context,
+			GPGME_PROTOCOL_OpenPGP,
+			enginfo->file_name, keyring_path);
+	else
+		err = gpgme_ctx_set_engine_info (gpg_context,
+			GPGME_PROTOCOL_OpenPGP,
+			enginfo->file_name, enginfo->home_dir);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: Could not set GPG engine information\n", __func__);
+		return -1;
+	}
+	err = gpgme_data_new(&plaintext_data);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: Could not create GPG plaintext data buffer\n",
+			__func__);
+		return -1;
+	}
+	err = gpgme_data_new_from_file(&ciphertext_data, filename, 1);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: Could not create GPG ciphertext data buffer"
+			" from file '%s'\n", __func__, filename);
+		return -1;
+	}
+
+	/* Decrypt and verify file */
+	err = gpgme_op_decrypt_verify(gpg_context, ciphertext_data,
+		plaintext_data);
+	if (err != GPG_ERR_NO_ERROR) {
+		pb_log("%s: Could not decrypt file\n", __func__);
+		return -1;
+	}
+	verification_result = gpgme_op_verify_result(gpg_context);
+	verification_signatures = verification_result->signatures;
+	while (verification_signatures) {
+		if (verification_signatures->status == GPG_ERR_NO_ERROR) {
+			pb_log("%s: Good signature for key ID '%s' ('%s')\n",
+				__func__,
+				verification_signatures->fpr, filename);
+			/* Verify fingerprint is present in authorized
+			 * signatures file
+			 */
+			char *auth_sig_line = NULL;
+			size_t auth_sig_len = 0;
+			ssize_t auth_sig_read;
+			rewind(authorized_signatures_handle);
+			while ((auth_sig_read = getline(&auth_sig_line,
+				&auth_sig_len,
+				authorized_signatures_handle)) != -1) {
+				auth_sig_len = strlen(auth_sig_line);
+				while ((auth_sig_line[auth_sig_len-1] == '\n')
+					|| (auth_sig_line[auth_sig_len-1] == '\r'))
+					auth_sig_len--;
+				auth_sig_line[auth_sig_len] = 0;
+				if (strcmp(auth_sig_line,
+					verification_signatures->fpr) == 0)
+					valid = 1;
+			}
+			free(auth_sig_line);
+		}
+		else {
+			pb_log("%s: Signature for key ID '%s' ('%s') invalid."
+				"  Status: %08x\n", __func__,
+				verification_signatures->fpr, filename,
+				verification_signatures->status);
+		}
+		verification_signatures = verification_signatures->next;
+	}
+
+	gpgme_data_release(ciphertext_data);
+
+	if (valid) {
+		/* Write decrypted file over ciphertext */
+		FILE *plaintext_file_handle = NULL;
+		plaintext_file_handle = fopen(filename, "wb");
+		if (!plaintext_file_handle) {
+			pb_log("%s: Could not create GPG plaintext file '%s'\n",
+				__func__, filename);
+			return -1;
+		}
+		gpgme_data_seek(plaintext_data, 0, SEEK_SET);
+		if (err != GPG_ERR_NO_ERROR) {
+			pb_log("%s: Could not seek in GPG plaintext buffer\n",
+				__func__);
+			return -1;
+		}
+		while ((bytes_read = gpgme_data_read(plaintext_data, buffer,
+			8192)) > 0) {
+			size_t l2 = fwrite(buffer, 1, bytes_read,
+				plaintext_file_handle);
+			if (l2 < bytes_read) {
+				if (ferror(plaintext_file_handle)) {
+					/* General error */
+					result = -1;
+					pb_log("%s: failed: unknown fault\n",
+						__func__);
+				}
+				else {
+					/* No space on destination device */
+					result = -1;
+					pb_log("%s: failed: temporary storage"
+						" full\n", __func__);
+				}
+			}
+		}
+		fclose(plaintext_file_handle);
+	}
+
+	/* Clean up */
+	gpgme_data_release(plaintext_data);
+	gpgme_release(gpg_context);
+
+	if (!valid) {
+		pb_log("%s: Incorrect GPG signature\n", __func__);
+		return -1;
+	}
+	else {
+		pb_log("%s: GPG signature for decrypted file '%s' verified\n",
+			__func__, filename);
+	}
+
+	return result;
+}
+
 static int verify_file_signature(const char * plaintext_filename,
 	const char * signature_filename, FILE * authorized_signatures_handle,
 	const char * keyring_path)
@@ -280,10 +449,11 @@  static int kexec_load(struct boot_task *boot_task)
 		boot_task->local_dtb_signature : NULL;
 	const char* local_image_signature = (boot_task->verify_signature) ?
 		boot_task->local_image_signature : NULL;
-	const char* local_cmdline_signature = (boot_task->verify_signature) ?
+	const char* local_cmdline_signature =
+		(boot_task->verify_signature || boot_task->decrypt_files) ?
 		boot_task->local_cmdline_signature : NULL;
 
-	if (boot_task->verify_signature) {
+	if ((boot_task->verify_signature) || (boot_task->decrypt_files)) {
 		char kernel_filename[MAX_FILENAME_SIZE];
 		char initrd_filename[MAX_FILENAME_SIZE];
 		char dtb_filename[MAX_FILENAME_SIZE];
@@ -369,37 +539,83 @@  static int kexec_load(struct boot_task *boot_task)
 			fflush(cmdline_handle);
 		}
 
-		/* Check signatures */
-		if (verify_file_signature(kernel_filename,
-			local_image_signature,
-			authorized_signatures_handle, "/etc/gpg"))
-			result = KEXEC_LOAD_SIGNATURE_FAILURE;
-		if (verify_file_signature(cmdline_template,
-			local_cmdline_signature,
-			authorized_signatures_handle, "/etc/gpg"))
-			result = KEXEC_LOAD_SIGNATURE_FAILURE;
-		if (boot_task->local_initrd_signature)
-			if (verify_file_signature(initrd_filename,
-				local_initrd_signature,
-				authorized_signatures_handle, "/etc/gpg"))
+		if (boot_task->verify_signature) {
+			/* Check signatures */
+			if (verify_file_signature(kernel_filename,
+				local_image_signature,
+				authorized_signatures_handle,
+				"/etc/gpg"))
 				result = KEXEC_LOAD_SIGNATURE_FAILURE;
-		if (boot_task->local_dtb_signature)
-			if (verify_file_signature(dtb_filename,
-				local_dtb_signature,
-				authorized_signatures_handle, "/etc/gpg"))
+			if (verify_file_signature(cmdline_template,
+				local_cmdline_signature,
+				authorized_signatures_handle,
+				"/etc/gpg"))
 				result = KEXEC_LOAD_SIGNATURE_FAILURE;
+			if (boot_task->local_initrd_signature)
+				if (verify_file_signature(initrd_filename,
+					local_initrd_signature,
+					authorized_signatures_handle,
+					"/etc/gpg"))
+					result = KEXEC_LOAD_SIGNATURE_FAILURE;
+			if (boot_task->local_dtb_signature)
+				if (verify_file_signature(dtb_filename,
+					local_dtb_signature,
+					authorized_signatures_handle,
+					"/etc/gpg"))
+					result = KEXEC_LOAD_SIGNATURE_FAILURE;
+
+			/* Clean up */
+			if (cmdline_handle) {
+				fclose(cmdline_handle);
+				unlink(cmdline_template);
+			}
+			fclose(authorized_signatures_handle);
 
-		/* Clean up */
-		if (cmdline_handle) {
-			fclose(cmdline_handle);
-			unlink(cmdline_template);
+			if (result == KEXEC_LOAD_SIGNATURE_FAILURE) {
+				pb_log("%s: Aborting kexec due to signature"
+					" verification failure\n", __func__);
+				goto abort_kexec;
+			}
 		}
-		fclose(authorized_signatures_handle);
+		else if (boot_task->decrypt_files) {
+			/* Decrypt files */
+			if (decrypt_file(kernel_filename,
+				authorized_signatures_handle,
+				"/etc/gpg"))
+				result = KEXEC_LOAD_DECRYPTION_FALURE;
+			if (verify_file_signature(cmdline_template,
+				local_cmdline_signature,
+				authorized_signatures_handle,
+				"/etc/gpg"))
+				result = KEXEC_LOAD_SIGNATURE_FAILURE;
+			if (boot_task->local_initrd)
+				if (decrypt_file(initrd_filename,
+					authorized_signatures_handle,
+					"/etc/gpg"))
+					result = KEXEC_LOAD_DECRYPTION_FALURE;
+			if (boot_task->local_dtb)
+				if (decrypt_file(dtb_filename,
+					authorized_signatures_handle,
+					"/etc/gpg"))
+					result = KEXEC_LOAD_DECRYPTION_FALURE;
+
+			/* Clean up */
+			if (cmdline_handle) {
+				fclose(cmdline_handle);
+				unlink(cmdline_template);
+			}
+			fclose(authorized_signatures_handle);
 
-		if (result == KEXEC_LOAD_SIGNATURE_FAILURE) {
-			pb_log("%s: Aborting kexec due to"
-				" signature verification failure\n", __func__);
-			goto abort_kexec;
+			if (result == KEXEC_LOAD_DECRYPTION_FALURE) {
+				pb_log("%s: Aborting kexec due to"
+					" decryption failure\n", __func__);
+				goto abort_kexec;
+			}
+			if (result == KEXEC_LOAD_SIGNATURE_FAILURE) {
+				pb_log("%s: Aborting kexec due to signature"
+					" verification failure\n", __func__);
+				goto abort_kexec;
+			}
 		}
 	}
 #endif
@@ -439,7 +655,7 @@  static int kexec_load(struct boot_task *boot_task)
 
 #if defined(HAVE_LIBGPGME)
 abort_kexec:
-	if (boot_task->verify_signature) {
+	if ((boot_task->verify_signature) || (boot_task->decrypt_files)) {
 		unlink(local_image);
 		if (local_initrd)
 			unlink(local_initrd);
@@ -744,7 +960,13 @@  static void boot_process(struct load_url_result *result, void *data)
 				load_pending(task->dtb_signature) ||
 				load_pending(task->cmdline_signature))
 			return;
+	}
+	if (task->decrypt_files) {
+		if (load_pending(task->cmdline_signature))
+			return;
+	}
 
+	if (task->verify_signature) {
 		if (check_load(task, "kernel image signature",
 					task->image_signature) ||
 				check_load(task, "initrd signature",
@@ -755,6 +977,14 @@  static void boot_process(struct load_url_result *result, void *data)
 					task->cmdline_signature))
 			goto no_sig_load;
 	}
+	if (task->decrypt_files) {
+		if (load_pending(task->cmdline_signature))
+			return;
+
+		if (check_load(task, "command line signature",
+					task->cmdline_signature))
+			goto no_decrypt_sig_load;
+	}
 #endif
 
 	/* we make a copy of the local paths, as the boot hooks might update
@@ -771,6 +1001,8 @@  static void boot_process(struct load_url_result *result, void *data)
 			task->initrd_signature->local : NULL;
 		task->local_dtb_signature = task->dtb_signature ?
 			task->dtb_signature->local : NULL;
+	}
+	if (task->verify_signature || task->decrypt_files) {
 		task->local_cmdline_signature = task->cmdline_signature ?
 			task->cmdline_signature->local : NULL;
 	}
@@ -782,7 +1014,11 @@  static void boot_process(struct load_url_result *result, void *data)
 			_("performing kexec_load"));
 
 	rc = kexec_load(task);
-	if (rc == KEXEC_LOAD_SIGNATURE_FAILURE) {
+	if (rc == KEXEC_LOAD_DECRYPTION_FALURE) {
+		update_status(task->status_fn, task->status_arg,
+				BOOT_STATUS_ERROR, _("decryption failed"));
+	}
+	else if (rc == KEXEC_LOAD_SIGNATURE_FAILURE) {
 		update_status(task->status_fn, task->status_arg,
 				BOOT_STATUS_ERROR,
 				_("signature verification failed"));
@@ -802,6 +1038,8 @@  no_sig_load:
 	cleanup_load(task->image_signature);
 	cleanup_load(task->initrd_signature);
 	cleanup_load(task->dtb_signature);
+
+no_decrypt_sig_load:
 	cleanup_load(task->cmdline_signature);
 
 no_load:
@@ -888,12 +1126,53 @@  struct boot_task *boot(void *ctx, struct discover_boot_option *opt,
 	boot_task->status_fn = status_fn;
 	boot_task->status_arg = status_arg;
 #if defined(HAVE_LIBGPGME)
-	if (access(LOCKDOWN_FILE, F_OK) == -1)
+	if (access(LOCKDOWN_FILE, F_OK) == -1) {
 		boot_task->verify_signature = false;
-	else
-		boot_task->verify_signature = true;
+		boot_task->decrypt_files = false;
+	}
+	else {
+		/* determine lockdown type */
+		FILE *authorized_signatures_handle = NULL;
+		authorized_signatures_handle = fopen(LOCKDOWN_FILE, "r");
+		if (authorized_signatures_handle) {
+			char *auth_sig_line = NULL;
+			size_t auth_sig_len = 0;
+			ssize_t auth_sig_read;
+			rewind(authorized_signatures_handle);
+			if ((auth_sig_read = getline(&auth_sig_line,
+				&auth_sig_len,
+				authorized_signatures_handle)) != -1) {
+				auth_sig_len = strlen(auth_sig_line);
+				while ((auth_sig_line[auth_sig_len-1] == '\n')
+					|| (auth_sig_line[auth_sig_len-1] == '\r'))
+					auth_sig_len--;
+				auth_sig_line[auth_sig_len] = 0;
+				if (strcmp(auth_sig_line, "ENCRYPTED") == 0) {
+					/* first line indicates encrypted files
+					 * expected.  enable decryption.
+					 */
+					boot_task->verify_signature = false;
+					boot_task->decrypt_files = true;
+				}
+			}
+			else {
+				/* file present but empty.  assume most
+				 * restrictive lockdown type
+				 */
+				boot_task->verify_signature = true;
+				boot_task->decrypt_files = false;
+			}
+			free(auth_sig_line);
+		}
+		else {
+			/* assume most restrictive lockdown type */
+			boot_task->verify_signature = true;
+			boot_task->decrypt_files = false;
+		}
+	}
 #else
 	boot_task->verify_signature = false;
+	boot_task->decrypt_files = false;
 #endif
 
 	if (cmd && cmd->boot_args) {
@@ -905,7 +1184,7 @@  struct boot_task *boot(void *ctx, struct discover_boot_option *opt,
 		boot_task->args = NULL;
 	}
 
-	if (boot_task->verify_signature) {
+	if (boot_task->verify_signature || boot_task->decrypt_files) {
 		if (cmd && cmd->args_sig_file) {
 			cmdline_sig = pb_url_parse(opt, cmd->args_sig_file);
 		} else if (opt && opt->args_sig_file) {
@@ -961,7 +1240,9 @@  struct boot_task *boot(void *ctx, struct discover_boot_option *opt,
 			rc |= start_url_load(boot_task, "dtb signature",
 				dtb_sig, &boot_task->dtb_signature);
 		}
+	}
 
+	if (boot_task->verify_signature || boot_task->decrypt_files) {
 		rc |= start_url_load(boot_task,
 			"kernel command line signature", cmdline_sig,
 			&boot_task->cmdline_signature);
diff --git a/ui/ncurses/nc-boot-editor.c b/ui/ncurses/nc-boot-editor.c
index 7dcecf6..b92294f 100644
--- a/ui/ncurses/nc-boot-editor.c
+++ b/ui/ncurses/nc-boot-editor.c
@@ -193,6 +193,9 @@  static struct pb_boot_data *boot_editor_prepare_data(
 			boot_editor->widgets.args_sig_file_f);
 		bd->args_sig_file = conditional_prefix(bd, prefix, s);
 	}
+	else {
+		bd->args_sig_file = NULL;
+	}
 
 	return bd;
 }
@@ -508,6 +511,10 @@  static void boot_editor_setup_widgets(struct boot_editor *boot_editor,
 		boot_editor->widgets.args_sig_file_f = widget_new_textbox(set,
 				0, 0, field_size, boot_editor->args_sig_file);
 	}
+	else {
+		boot_editor->widgets.args_sig_file_l = NULL;
+		boot_editor->widgets.args_sig_file_f = NULL;
+	}
 
 	boot_editor->widgets.ok_b = widget_new_button(set, 0, 0, 6,
 					_("OK"), ok_click, boot_editor);
@@ -628,7 +635,7 @@  struct boot_editor *boot_editor_init(struct cui *cui,
 		if (boot_editor->use_signature_files)
 			boot_editor->args_sig_file = bd->args_sig_file;
 		else
-			boot_editor->args_sig_file = "";
+			boot_editor->args_sig_file = talloc_strdup(bd, "");
 		boot_editor_find_device(boot_editor, bd, sysinfo);
 	} else {
 		boot_editor->image = boot_editor->initrd =