blob: e795c071c9a999e6428e9d07dec7221b6b414941 [file] [log] [blame]
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* This file is part of libmount from util-linux project.
*
* Copyright (C) 2019 Microsoft Corporation
*
* libmount is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*/
#include "mountP.h"
#if defined(HAVE_CRYPTSETUP)
#ifdef CRYPTSETUP_VIA_DLOPEN
#include <dlfcn.h>
#endif
#include <libcryptsetup.h>
#include "path.h"
#ifdef CRYPTSETUP_VIA_DLOPEN
static void *get_symbol(struct libmnt_context *cxt, void *dl, const char *name, int *rc)
{
char *dl_error = NULL;
void *sym = dlsym(dl, name);
*rc = 0;
if ((dl_error = dlerror()) == NULL)
return sym;
DBG(VERITY, ul_debugobj(cxt, "veritydev specific options detected but cannot dlopen symbol %s: %s", name, dl_error));
*rc = -ENOTSUP;
return NULL;
}
#endif
static void libcryptsetup_log(int level __attribute__((__unused__)), const char *msg, void *data)
{
struct libmnt_context *cxt = (struct libmnt_context *)data;
DBG(VERITY, ul_debugobj(cxt, "cryptsetup: %s", msg));
}
/* Taken from https://gitlab.com/cryptsetup/cryptsetup/blob/master/lib/utils_crypt.c#L225 */
static size_t crypt_hex_to_bytes(const char *hex, char **result)
{
char buf[3] = "xx\0", *endp, *bytes;
size_t i, len;
len = strlen(hex);
if (len % 2)
return -EINVAL;
len /= 2;
bytes = malloc(len);
if (!bytes)
return -ENOMEM;
for (i = 0; i < len; i++) {
memcpy(buf, &hex[i * 2], 2);
bytes[i] = strtoul(buf, &endp, 16);
if (endp != &buf[2]) {
free(bytes);
return -EINVAL;
}
}
*result = bytes;
return i;
}
int mnt_context_setup_veritydev(struct libmnt_context *cxt)
{
const char *backing_file, *optstr;
char *val = NULL, *key = NULL, *root_hash_binary = NULL, *mapper_device = NULL,
*mapper_device_full = NULL, *backing_file_basename = NULL, *root_hash = NULL,
*hash_device = NULL, *root_hash_file = NULL, *fec_device = NULL, *hash_sig = NULL;
size_t len, hash_size, hash_sig_size = 0, keysize = 0;
struct crypt_params_verity crypt_params = {};
struct crypt_device *crypt_dev = NULL;
int rc = 0;
/* Use the same default for FEC parity bytes as cryptsetup uses */
uint64_t offset = 0, fec_offset = 0, fec_roots = 2;
struct stat hash_sig_st;
#ifdef CRYPTSETUP_VIA_DLOPEN
/* To avoid linking libmount to libcryptsetup, and keep the default dependencies list down, use dlopen */
void *dl = NULL;
void (*sym_crypt_set_debug_level)(int) = NULL;
void (*sym_crypt_set_log_callback)(struct crypt_device *, void (*log)(int, const char *, void *), void *) = NULL;
int (*sym_crypt_init_data_device)(struct crypt_device **, const char *, const char *) = NULL;
int (*sym_crypt_load)(struct crypt_device *, const char *, void *) = NULL;
int (*sym_crypt_get_volume_key_size)(struct crypt_device *) = NULL;
#ifdef HAVE_CRYPT_ACTIVATE_BY_SIGNED_KEY
int (*sym_crypt_activate_by_signed_key)(struct crypt_device *, const char *, const char *, size_t, const char *, size_t, uint32_t) = NULL;
#endif
int (*sym_crypt_activate_by_volume_key)(struct crypt_device *, const char *, const char *, size_t, uint32_t) = NULL;
void (*sym_crypt_free)(struct crypt_device *) = NULL;
int (*sym_crypt_init_by_name)(struct crypt_device **, const char *) = NULL;
int (*sym_crypt_get_verity_info)(struct crypt_device *, struct crypt_params_verity *) = NULL;
int (*sym_crypt_volume_key_get)(struct crypt_device *, int, char *, size_t *, const char *, size_t) = NULL;
#else
void (*sym_crypt_set_debug_level)(int) = &crypt_set_debug_level;
void (*sym_crypt_set_log_callback)(struct crypt_device *, void (*log)(int, const char *, void *), void *) = &crypt_set_log_callback;
int (*sym_crypt_init_data_device)(struct crypt_device **, const char *, const char *) = &crypt_init_data_device;
int (*sym_crypt_load)(struct crypt_device *, const char *, void *) = &crypt_load;
int (*sym_crypt_get_volume_key_size)(struct crypt_device *) = &crypt_get_volume_key_size;
#ifdef HAVE_CRYPT_ACTIVATE_BY_SIGNED_KEY
int (*sym_crypt_activate_by_signed_key)(struct crypt_device *, const char *, const char *, size_t, const char *, size_t, uint32_t) = &crypt_activate_by_signed_key;
#endif
int (*sym_crypt_activate_by_volume_key)(struct crypt_device *, const char *, const char *, size_t, uint32_t) = &crypt_activate_by_volume_key;
void (*sym_crypt_free)(struct crypt_device *) = &crypt_free;
int (*sym_crypt_init_by_name)(struct crypt_device **, const char *) = &crypt_init_by_name;
int (*sym_crypt_get_verity_info)(struct crypt_device *, struct crypt_params_verity *) = &crypt_get_verity_info;
int (*sym_crypt_volume_key_get)(struct crypt_device *, int, char *, size_t *, const char *, size_t) = &crypt_volume_key_get;
#endif
assert(cxt);
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
/* dm-verity volumes are read-only, and mount will fail if not set */
mnt_context_set_mflags(cxt, (cxt->mountflags | MS_RDONLY));
backing_file = mnt_fs_get_srcpath(cxt->fs);
if (!backing_file)
return -EINVAL;
/* To avoid clashes, prefix libmnt_ to all mapper devices */
backing_file_basename = basename(backing_file);
mapper_device = calloc(strlen(backing_file_basename) + strlen("libmnt_") + 1, sizeof(char));
if (!mapper_device)
return -ENOMEM;
strcat(mapper_device, "libmnt_");
strcat(mapper_device, backing_file_basename);
DBG(VERITY, ul_debugobj(cxt, "trying to setup verity device for %s", backing_file));
optstr = mnt_fs_get_user_options(cxt->fs);
/*
* verity.hashdevice=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_HASH_DEVICE) &&
mnt_optstr_get_option(optstr, "verity.hashdevice", &val, &len) == 0 && val) {
hash_device = strndup(val, len);
rc = hash_device ? 0 : -ENOMEM;
}
/*
* verity.roothash=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_ROOT_HASH) &&
mnt_optstr_get_option(optstr, "verity.roothash", &val, &len) == 0 && val) {
root_hash = strndup(val, len);
rc = root_hash ? 0 : -ENOMEM;
}
/*
* verity.hashoffset=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_HASH_OFFSET) &&
mnt_optstr_get_option(optstr, "verity.hashoffset", &val, &len) == 0) {
rc = mnt_parse_offset(val, len, &offset);
if (rc) {
DBG(VERITY, ul_debugobj(cxt, "failed to parse verity.hashoffset="));
rc = -MNT_ERR_MOUNTOPT;
}
}
/*
* verity.roothashfile=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_ROOT_HASH_FILE) &&
mnt_optstr_get_option(optstr, "verity.roothashfile", &val, &len) == 0 && val) {
root_hash_file = strndup(val, len);
rc = root_hash_file ? 0 : -ENOMEM;
}
/*
* verity.fecdevice=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_FEC_DEVICE) &&
mnt_optstr_get_option(optstr, "verity.fecdevice", &val, &len) == 0 && val) {
fec_device = strndup(val, len);
rc = fec_device ? 0 : -ENOMEM;
}
/*
* verity.fecoffset=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_FEC_OFFSET) &&
mnt_optstr_get_option(optstr, "verity.fecoffset", &val, &len) == 0) {
rc = mnt_parse_offset(val, len, &fec_offset);
if (rc) {
DBG(VERITY, ul_debugobj(cxt, "failed to parse verity.fecoffset="));
rc = -MNT_ERR_MOUNTOPT;
}
}
/*
* verity.fecroots=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_FEC_ROOTS) &&
mnt_optstr_get_option(optstr, "verity.fecroots", &val, &len) == 0) {
rc = mnt_parse_offset(val, len, &fec_roots);
if (rc) {
DBG(VERITY, ul_debugobj(cxt, "failed to parse verity.fecroots="));
rc = -MNT_ERR_MOUNTOPT;
}
}
/*
* verity.roothashsig=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_ROOT_HASH_SIG) &&
mnt_optstr_get_option(optstr, "verity.roothashsig", &val, &len) == 0 && val) {
rc = ul_path_stat(NULL, &hash_sig_st, val);
if (rc == 0)
rc = !S_ISREG(hash_sig_st.st_mode) || !hash_sig_st.st_size ? -EINVAL : 0;
if (rc == 0) {
hash_sig_size = hash_sig_st.st_size;
hash_sig = malloc(hash_sig_size);
rc = hash_sig ? 0 : -ENOMEM;
}
if (rc == 0) {
rc = ul_path_read(NULL, hash_sig, hash_sig_size, val);
rc = rc < (int)hash_sig_size ? -1 : 0;
}
}
if (!rc && root_hash && root_hash_file) {
DBG(VERITY, ul_debugobj(cxt, "verity.roothash and verity.roothashfile are mutually exclusive"));
rc = -EINVAL;
} else if (!rc && root_hash_file) {
rc = ul_path_read_string(NULL, &root_hash, root_hash_file);
rc = rc < 1 ? rc : 0;
}
if (!rc && (!hash_device || !root_hash)) {
DBG(VERITY, ul_debugobj(cxt, "verity.hashdevice and one of verity.roothash or verity.roothashfile are mandatory"));
rc = -EINVAL;
}
#ifdef CRYPTSETUP_VIA_DLOPEN
if (rc == 0) {
int dl_flags = RTLD_LAZY | RTLD_LOCAL;
/* glibc extension: mnt_context_deferred_delete_veritydev is called immediately after, don't unload on dl_close */
#ifdef RTLD_NODELETE
dl_flags |= RTLD_NODELETE;
#endif
/* glibc extension: might help to avoid further symbols clashes */
#ifdef RTLD_DEEPBIND
dl_flags |= RTLD_DEEPBIND;
#endif
dl = dlopen("libcryptsetup.so.12", dl_flags);
if (!dl) {
DBG(VERITY, ul_debugobj(cxt, "veritydev specific options detected but cannot dlopen libcryptsetup"));
rc = -ENOTSUP;
}
}
/* clear errors first, then load all the libcryptsetup symbols */
dlerror();
if (rc == 0)
*(void **)(&sym_crypt_set_debug_level) = get_symbol(cxt, dl, "crypt_set_debug_level", &rc);
if (rc == 0)
*(void **)(&sym_crypt_set_log_callback) = get_symbol(cxt, dl, "crypt_set_log_callback", &rc);
if (rc == 0)
*(void **)(&sym_crypt_init_data_device) = get_symbol(cxt, dl, "crypt_init_data_device", &rc);
if (rc == 0)
*(void **)(&sym_crypt_load) = get_symbol(cxt, dl, "crypt_load", &rc);
if (rc == 0)
*(void **)(&sym_crypt_get_volume_key_size) = get_symbol(cxt, dl, "crypt_get_volume_key_size", &rc);
#ifdef HAVE_CRYPT_ACTIVATE_BY_SIGNED_KEY
if (rc == 0)
*(void **)(&sym_crypt_activate_by_signed_key) = get_symbol(cxt, dl, "crypt_activate_by_signed_key", &rc);
#endif
if (rc == 0)
*(void **)(&sym_crypt_activate_by_volume_key) = get_symbol(cxt, dl, "crypt_activate_by_volume_key", &rc);
if (rc == 0)
*(void **)(&sym_crypt_free) = get_symbol(cxt, dl, "crypt_free", &rc);
if (rc == 0)
*(void **)(&sym_crypt_init_by_name) = get_symbol(cxt, dl, "crypt_init_by_name", &rc);
if (rc == 0)
*(void **)(&sym_crypt_get_verity_info) = get_symbol(cxt, dl, "crypt_get_verity_info", &rc);
if (rc == 0)
*(void **)(&sym_crypt_volume_key_get) = get_symbol(cxt, dl, "crypt_volume_key_get", &rc);
#endif
if (rc)
goto done;
if (mnt_context_is_verbose(cxt))
(*sym_crypt_set_debug_level)(CRYPT_DEBUG_ALL);
(*sym_crypt_set_log_callback)(NULL, libcryptsetup_log, cxt);
rc = (*sym_crypt_init_data_device)(&crypt_dev, hash_device, backing_file);
if (rc)
goto done;
memset(&crypt_params, 0, sizeof(struct crypt_params_verity));
crypt_params.hash_area_offset = offset;
crypt_params.fec_area_offset = fec_offset;
crypt_params.fec_roots = fec_roots;
crypt_params.fec_device = fec_device;
crypt_params.flags = 0;
rc = (*sym_crypt_load)(crypt_dev, CRYPT_VERITY, &crypt_params);
if (rc < 0)
goto done;
hash_size = (*sym_crypt_get_volume_key_size)(crypt_dev);
if (crypt_hex_to_bytes(root_hash, &root_hash_binary) != hash_size) {
DBG(VERITY, ul_debugobj(cxt, "root hash %s is not of length %zu", root_hash, hash_size));
rc = -EINVAL;
goto done;
}
if (hash_sig) {
#ifdef HAVE_CRYPT_ACTIVATE_BY_SIGNED_KEY
rc = (*sym_crypt_activate_by_signed_key)(crypt_dev, mapper_device, root_hash_binary, hash_size,
hash_sig, hash_sig_size, CRYPT_ACTIVATE_READONLY);
#else
rc = -EINVAL;
DBG(VERITY, ul_debugobj(cxt, "verity.roothashsig=%s passed but libcryptsetup does not provide crypt_activate_by_signed_key()", hash_sig));
#endif
} else
rc = (*sym_crypt_activate_by_volume_key)(crypt_dev, mapper_device, root_hash_binary, hash_size,
CRYPT_ACTIVATE_READONLY);
/*
* If the mapper device already exists, and if libcryptsetup supports it, get the root
* hash associated with the existing one and compare it with the parameter passed by
* the user. If they match, then we can be sure the user intended to mount the exact
* same device, and simply reuse it and return success.
* The kernel does the refcounting for us.
* If libcryptsetup does not support getting the root hash out of an existing device,
* then return an error and tell the user that the device is already in use.
* Pass through only OOM errors or mismatching root hash errors.
*/
if (rc == -EEXIST) {
DBG(VERITY, ul_debugobj(cxt, "%s already in use as /dev/mapper/%s", backing_file, mapper_device));
(*sym_crypt_free)(crypt_dev);
rc = (*sym_crypt_init_by_name)(&crypt_dev, mapper_device);
if (!rc) {
rc = (*sym_crypt_get_verity_info)(crypt_dev, &crypt_params);
if (!rc) {
key = calloc(hash_size, 1);
if (!key) {
rc = -ENOMEM;
goto done;
}
}
if (!rc) {
keysize = hash_size;
rc = (*sym_crypt_volume_key_get)(crypt_dev, CRYPT_ANY_SLOT, key, &keysize, NULL, 0);
}
if (!rc) {
DBG(VERITY, ul_debugobj(cxt, "comparing root hash of existing device with %s", root_hash));
if (memcmp(key, root_hash_binary, hash_size)) {
DBG(VERITY, ul_debugobj(cxt, "existing device's hash does not match with %s", root_hash));
rc = -EINVAL;
goto done;
}
} else {
DBG(VERITY, ul_debugobj(cxt, "libcryptsetup does not support extracting root hash of existing device"));
}
}
if (rc) {
rc = -EEXIST;
} else {
/*
* Ensure that, if signatures are supported, we only reuse the device if the previous mount
* used the same settings, so that a previous unsigned mount will not be reused if the user
* asks to use signing for the new one, and viceversa.
*/
#ifdef HAVE_CRYPT_ACTIVATE_BY_SIGNED_KEY
if (!!hash_sig != !!(crypt_params.flags & CRYPT_VERITY_ROOT_HASH_SIGNATURE)) {
rc = -EINVAL;
DBG(VERITY, ul_debugobj(cxt, "existing device and new mount have to either be both opened with signature or both without"));
goto done;
}
#endif
DBG(VERITY, ul_debugobj(cxt, "root hash of %s matches %s, reusing device", mapper_device, root_hash));
}
}
if (!rc) {
cxt->flags |= MNT_FL_VERITYDEV_READY;
mapper_device_full = calloc(strlen(mapper_device) + strlen("/dev/mapper/") + 1, sizeof(char));
if (!mapper_device_full)
rc = -ENOMEM;
else {
strcat(mapper_device_full, "/dev/mapper/");
strcat(mapper_device_full, mapper_device);
rc = mnt_fs_set_source(cxt->fs, mapper_device_full);
}
}
done:
if (sym_crypt_free)
(*sym_crypt_free)(crypt_dev);
#ifdef CRYPTSETUP_VIA_DLOPEN
if (dl)
dlclose(dl);
#endif
free(root_hash_binary);
free(mapper_device_full);
free(mapper_device);
free(hash_device);
free(root_hash);
free(root_hash_file);
free(fec_device);
free(hash_sig);
free(key);
return rc;
}
int mnt_context_deferred_delete_veritydev(struct libmnt_context *cxt)
{
const char *src;
/* If mounting failed delete immediately, otherwise setup auto cleanup for user umount */
uint32_t flags = mnt_context_get_status(cxt) ? CRYPT_DEACTIVATE_DEFERRED : 0;
#ifdef CRYPTSETUP_VIA_DLOPEN
void *dl = NULL;
int dl_flags = RTLD_LAZY | RTLD_LOCAL;
/* glibc extension: might help to avoid further symbols clashes */
#ifdef RTLD_DEEPBIND
dl_flags |= RTLD_DEEPBIND;
#endif
void (*sym_crypt_set_debug_level)(int) = NULL;
void (*sym_crypt_set_log_callback)(struct crypt_device *, void (*log)(int, const char *, void *), void *) = NULL;
int (*sym_crypt_deactivate_by_name)(struct crypt_device *, const char *, uint32_t) = NULL;
#else
void (*sym_crypt_set_debug_level)(int) = &crypt_set_debug_level;
void (*sym_crypt_set_log_callback)(struct crypt_device *, void (*log)(int, const char *, void *), void *) = &crypt_set_log_callback;
int (*sym_crypt_deactivate_by_name)(struct crypt_device *, const char *, uint32_t) = &crypt_deactivate_by_name;
#endif
int rc = 0;
assert(cxt);
assert(cxt->fs);
if (!(cxt->flags & MNT_FL_VERITYDEV_READY))
return 0;
src = mnt_fs_get_srcpath(cxt->fs);
if (!src)
return -EINVAL;
#ifdef CRYPTSETUP_VIA_DLOPEN
dl = dlopen("libcryptsetup.so.12", dl_flags);
if (!dl) {
DBG(VERITY, ul_debugobj(cxt, "veritydev specific options detected but cannot dlopen libcryptsetup"));
return -ENOTSUP;
}
/* clear errors first */
dlerror();
if (!rc)
*(void **)(&sym_crypt_set_debug_level) = get_symbol(cxt, dl, "crypt_set_debug_level", &rc);
if (!rc)
*(void **)(&sym_crypt_set_log_callback) = get_symbol(cxt, dl, "crypt_set_log_callback", &rc);
if (!rc)
*(void **)(&sym_crypt_deactivate_by_name) = get_symbol(cxt, dl, "crypt_deactivate_by_name", &rc);
#endif
if (!rc) {
if (mnt_context_is_verbose(cxt))
(*sym_crypt_set_debug_level)(CRYPT_DEBUG_ALL);
(*sym_crypt_set_log_callback)(NULL, libcryptsetup_log, cxt);
rc = (*sym_crypt_deactivate_by_name)(NULL, src, flags);
if (!rc)
cxt->flags &= ~MNT_FL_VERITYDEV_READY;
}
#ifdef CRYPTSETUP_VIA_DLOPEN
dlclose(dl);
#endif
DBG(VERITY, ul_debugobj(cxt, "deleted [rc=%d]", rc));
return rc;
}
#else
int mnt_context_setup_veritydev(struct libmnt_context *cxt __attribute__ ((__unused__)))
{
return 0;
}
int mnt_context_deferred_delete_veritydev(struct libmnt_context *cxt __attribute__ ((__unused__)))
{
return 0;
}
#endif
int mnt_context_is_veritydev(struct libmnt_context *cxt)
{
const char *src;
assert(cxt);
/* The mount flags have to be merged, otherwise we have to use
* expensive mnt_context_get_user_mflags() instead of cxt->user_mountflags. */
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!cxt->fs)
return 0;
src = mnt_fs_get_srcpath(cxt->fs);
if (!src)
return 0; /* backing file not set */
if (cxt->user_mountflags & (MNT_MS_HASH_DEVICE |
MNT_MS_ROOT_HASH |
MNT_MS_HASH_OFFSET)) {
#ifndef HAVE_CRYPTSETUP
DBG(VERITY, ul_debugobj(cxt, "veritydev specific options detected but libmount built without libcryptsetup"));
return -ENOTSUP;
#else
DBG(VERITY, ul_debugobj(cxt, "veritydev specific options detected"));
return 1;
#endif
}
if (!strncmp(src, "/dev/mapper/libmnt_", strlen("/dev/mapper/libmnt_"))) {
#ifndef HAVE_CRYPTSETUP
DBG(VERITY, ul_debugobj(cxt, "veritydev prefix detected in source device but libmount built without libcryptsetup"));
return -ENOTSUP;
#else
DBG(VERITY, ul_debugobj(cxt, "veritydev prefix detected in source device"));
return 1;
#endif
}
return 0;
}