diff options
Diffstat (limited to 'libmount/src/context_veritydev.c')
| -rw-r--r-- | libmount/src/context_veritydev.c | 520 |
1 files changed, 520 insertions, 0 deletions
diff --git a/libmount/src/context_veritydev.c b/libmount/src/context_veritydev.c new file mode 100644 index 0000000..d663456 --- /dev/null +++ b/libmount/src/context_veritydev.c @@ -0,0 +1,520 @@ +/* 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 + +/* 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; + 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 + 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_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; + + 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; + struct crypt_device *crypt_dev = NULL; + /* 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 + int (*sym_crypt_init_by_name)(struct crypt_device **, const char *) = NULL; + int (*sym_crypt_deactivate_by_name)(struct crypt_device *, const char *, uint32_t) = NULL; + void (*sym_crypt_free)(struct crypt_device *) = NULL; +#else + int (*sym_crypt_init_by_name)(struct crypt_device **, const char *) = &crypt_init_by_name; + int (*sym_crypt_deactivate_by_name)(struct crypt_device *, const char *, uint32_t) = &crypt_deactivate_by_name; + void (*sym_crypt_free)(struct crypt_device *) = &crypt_free; +#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_init_by_name) = get_symbol(cxt, dl, "crypt_init_by_name", &rc); + if (!rc) + *(void **)(&sym_crypt_deactivate_by_name) = get_symbol(cxt, dl, "crypt_deactivate_by_name", &rc); + if (!rc) + *(void **)(&sym_crypt_free) = get_symbol(cxt, dl, "crypt_free", &rc); +#endif + if (!rc) { + rc = (*sym_crypt_init_by_name)(&crypt_dev, src); + if (!rc) { + rc = (*sym_crypt_deactivate_by_name)(crypt_dev, src, flags); + if (!rc) + cxt->flags &= ~MNT_FL_VERITYDEV_READY; + } + + (*sym_crypt_free)(crypt_dev); + } + +#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; +} |