[PATCH 2/2] [V3] Add encrypted file support
Timothy Pearson
tpearson at raptorengineering.com
Fri Aug 5 07:25:30 AEST 2016
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 at raptorengineering.com>
---
discover/boot.c | 140 +++++++++++++++++++++++-------
discover/gpg.c | 206 +++++++++++++++++++++++++++++++++++++++++++-
discover/gpg.h | 8 ++
ui/ncurses/nc-boot-editor.c | 9 +-
4 files changed, 326 insertions(+), 37 deletions(-)
diff --git a/discover/boot.c b/discover/boot.c
index 174573b..02634b5 100644
--- a/discover/boot.c
+++ b/discover/boot.c
@@ -34,6 +34,7 @@ enum {
};
enum {
+ KEXEC_LOAD_DECRYPTION_FALURE = 252,
KEXEC_LOAD_SIG_SETUP_INVALID = 253,
KEXEC_LOAD_SIGNATURE_FAILURE = 254,
};
@@ -51,6 +52,7 @@ 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;
@@ -83,10 +85,11 @@ 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];
@@ -172,37 +175,83 @@ 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;
+ }
}
}
@@ -240,7 +289,7 @@ static int kexec_load(struct boot_task *boot_task)
pb_log("%s: failed: (%d)\n", __func__, result);
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);
@@ -543,7 +592,13 @@ 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",
@@ -554,6 +609,14 @@ 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;
+ }
/* we make a copy of the local paths, as the boot hooks might update
* and/or create these */
@@ -568,6 +631,8 @@ 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;
}
@@ -578,7 +643,11 @@ 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"));
@@ -598,6 +667,8 @@ 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:
@@ -645,6 +716,7 @@ struct boot_task *boot(void *ctx, struct discover_boot_option *opt,
struct boot_task *boot_task;
const char *boot_desc;
int rc;
+ int lockdown_type;
if (opt && opt->option->name)
boot_desc = opt->option->name;
@@ -684,7 +756,9 @@ struct boot_task *boot(void *ctx, struct discover_boot_option *opt,
boot_task->status_fn = status_fn;
boot_task->status_arg = status_arg;
- boot_task->verify_signature = (lockdown_status() == PB_LOCKDOWN_SIGN);
+ lockdown_type = lockdown_status();
+ boot_task->verify_signature = (lockdown_type == PB_LOCKDOWN_SIGN);
+ boot_task->decrypt_files = (lockdown_type == PB_LOCKDOWN_DECRYPT);
if (cmd && cmd->boot_args) {
boot_task->args = talloc_strdup(boot_task, cmd->boot_args);
@@ -695,7 +769,7 @@ 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) {
@@ -751,7 +825,9 @@ 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/discover/gpg.c b/discover/gpg.c
index e0f4e4b..fa744d5 100644
--- a/discover/gpg.c
+++ b/discover/gpg.c
@@ -95,6 +95,173 @@ int copy_file_to_destination(const char * source_file,
return result;
}
+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;
+}
+
int verify_file_signature(const char * plaintext_filename,
const char * signature_filename, FILE * authorized_signatures_handle,
const char * keyring_path)
@@ -225,8 +392,39 @@ int verify_file_signature(const char * plaintext_filename,
}
int lockdown_status() {
- if (access(LOCKDOWN_FILE, F_OK) == -1)
- return PB_LOCKDOWN_NONE;
- else
- return PB_LOCKDOWN_SIGN;
+ /* assume most restrictive lockdown type */
+ int ret = PB_LOCKDOWN_SIGN;
+
+ if (access(LOCKDOWN_FILE, F_OK) == -1) {
+ ret = PB_LOCKDOWN_NONE;
+ }
+ 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.
+ */
+ ret = PB_LOCKDOWN_DECRYPT;
+ }
+ }
+ free(auth_sig_line);
+ }
+ }
+
+ return ret;
}
\ No newline at end of file
diff --git a/discover/gpg.h b/discover/gpg.h
index ac39c2e..f64f6af 100644
--- a/discover/gpg.h
+++ b/discover/gpg.h
@@ -24,6 +24,7 @@
enum {
PB_LOCKDOWN_NONE = 0,
PB_LOCKDOWN_SIGN = 1,
+ PB_LOCKDOWN_DECRYPT = 2,
};
#if defined(HAVE_LIBGPGME)
@@ -39,6 +40,9 @@ int verify_file_signature(const char * plaintext_filename,
const char * signature_filename, FILE * authorized_signatures_handle,
const char * keyring_path);
+int decrypt_file(const char * filename,
+ FILE * authorized_signatures_handle, const char * keyring_path);
+
#if !defined(HAVE_LIBGPGME)
int lockdown_status(void) { return PB_LOCKDOWN_NONE; }
@@ -50,6 +54,10 @@ int verify_file_signature(const char * plaintext_filename,
const char * signature_filename, FILE * authorized_signatures_handle,
const char * keyring_path) { return -1; }
+int decrypt_file(const char * filename,
+ FILE * authorized_signatures_handle, const char * keyring_path)
+ { return -1; }
+
#endif /* HAVE_LIBGPGME */
#endif /* _PB_GPG_H */
\ No newline at end of file
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 =
--
2.8.1
More information about the Petitboot
mailing list