diff options
Diffstat (limited to 'src/home/homework-blob.c')
| -rw-r--r-- | src/home/homework-blob.c | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/src/home/homework-blob.c b/src/home/homework-blob.c new file mode 100644 index 0000000..6b22ab6 --- /dev/null +++ b/src/home/homework-blob.c @@ -0,0 +1,301 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "copy.h" +#include "fileio.h" +#include "fd-util.h" +#include "format-util.h" +#include "fs-util.h" +#include "home-util.h" +#include "homework-blob.h" +#include "homework.h" +#include "install-file.h" +#include "macro.h" +#include "path-util.h" +#include "recurse-dir.h" +#include "rm-rf.h" +#include "sha256.h" +#include "string-util.h" +#include "tmpfile-util.h" +#include "umask-util.h" +#include "utf8.h" + +static int copy_one_blob( + int src_fd, + int dest_dfd, + const char *name, + uint64_t *total_size, + uid_t uid, + Hashmap *manifest) { + _cleanup_(unlink_and_freep) char *dest_tmpname = NULL; + _cleanup_close_ int dest = -EBADF; + uint8_t hash[SHA256_DIGEST_SIZE], *known_hash; + off_t initial, size; + int r; + + assert(src_fd >= 0); + assert(dest_dfd >= 0); + assert(name); + assert(total_size); + assert(uid_is_valid(uid)); + assert(manifest); + + if (!suitable_blob_filename(name)) { + log_warning("Blob %s has invalid filename. Skipping.", name); + return 0; + } + + known_hash = hashmap_get(manifest, name); + if (!known_hash) { + log_warning("Blob %s is missing from manifest. Skipping.", name); + return 0; + } + + r = fd_verify_regular(src_fd); + if (r < 0) { + log_warning_errno(r, "Blob %s is not a regular file. Skipping.", name); + return 0; + } + + initial = lseek(src_fd, 0, SEEK_CUR); + if (initial < 0) + return log_debug_errno(errno, "Failed to get initial pos on fd for blob %s: %m", name); + if (initial > 0) + log_debug("Blob %s started offset %s into file", name, FORMAT_BYTES(initial)); + + /* Hashing is relatively cheaper compared to copying, especially since we're possibly copying across + * filesystems or even devices here. So first we check the hash and bail early if the file's contents + * don't match what's in the manifest. */ + + r = sha256_fd(src_fd, BLOB_DIR_MAX_SIZE, hash); + if (r == -EFBIG) + return log_warning_errno(r, "Blob %s is larger than blob directory size limit. Not copying any further.", name); + if (r < 0) + return log_debug_errno(r, "Failed to compute sha256 for blob %s: %m", name); + if (memcmp(hash, known_hash, SHA256_DIGEST_SIZE) != 0) { + log_warning("Blob %s has incorrect hash. Skipping.", name); + return 0; + } + + size = lseek(src_fd, 0, SEEK_CUR); + if (size < 0) + return log_debug_errno(errno, "Failed to get final pos on fd for blob %s: %m", name); + if (!DEC_SAFE(&size, initial)) + return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid seek position on fd for %s. Couldn't get size.", name); + + if (!INC_SAFE(total_size, size)) + *total_size = UINT64_MAX; + log_debug("Blob %s size is %s, making the new total dir size %s", name, FORMAT_BYTES(size), + *total_size != UINT64_MAX ? FORMAT_BYTES(*total_size) : "overflow!"); + if (*total_size > BLOB_DIR_MAX_SIZE) + return log_warning_errno(SYNTHETIC_ERRNO(EFBIG), + "Blob %s will cause blob directory to exceed its size limit. Not copying any further.", name); + + /* Next we copy but don't yet link the file into the blob directory */ + + if (lseek(src_fd, initial, SEEK_SET) < 0) + return log_debug_errno(errno, "Failed to rewind fd for blob %s: %m", name); + + dest = open_tmpfile_linkable_at(dest_dfd, name, O_RDWR|O_CLOEXEC, &dest_tmpname); + if (dest < 0) + return log_debug_errno(dest, "Failed to create dest tmpfile for blob %s: %m", name); + + if (fchmod(dest, 0644) < 0) + return log_debug_errno(errno, "Failed to chmod blob %s: %m", name); + if (fchown(dest, uid, uid) < 0) + return log_debug_errno(errno, "Failed to chown blob %s: %m", name); + + r = copy_bytes(src_fd, dest, BLOB_DIR_MAX_SIZE, 0); + if (r < 0) + return log_debug_errno(r, "Failed to copy blob %s: %m", name); + + /* The source FD might have changed while we were busy copying, thus invalidating the hash. + * So, we re-hash the data we just copied to make sure that this didn't happen. */ + + if (lseek(dest, 0, SEEK_SET) < 0) + return log_debug_errno(errno, "Failed to rewind blob %s for rehash: %m", name); + + r = sha256_fd(dest, BLOB_DIR_MAX_SIZE, hash); + if (r < 0) + return log_debug_errno(r, "Failed to rehash blob %s: %m", name); + if (memcmp(hash, known_hash, SHA256_DIGEST_SIZE) != 0) { + log_warning("Blob %s has changed while we were copying it. Skipping.", name); + return 0; + } + + /* The file's contents still match the blob manifest, so it's safe to expose it in the directory */ + + r = link_tmpfile_at(dest, dest_dfd, dest_tmpname, name, 0); + if (r < 0) + return log_debug_errno(r, "Failed to link blob %s: %m", name); + dest_tmpname = mfree(dest_tmpname); + + return 0; +} + +static int replace_blob_at( + int src_base_dfd, + const char *src_name, + int dest_base_dfd, + const char *dest_name, + Hashmap *manifest, + mode_t mode, + uid_t uid) { + _cleanup_free_ char *fn = NULL; + _cleanup_close_ int src_dfd = -EBADF, dest_dfd = -EBADF; + _cleanup_free_ DirectoryEntries *de = NULL; + uint64_t total_size = 0; + int r; + + assert(src_base_dfd >= 0); + assert(src_name); + assert(dest_base_dfd >= 0); + assert(dest_name); + assert(uid_is_valid(uid)); + + src_dfd = openat(src_base_dfd, src_name, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW); + if (src_dfd < 0) { + if (errno == ENOENT) + return 0; + return log_debug_errno(errno, "Failed to open src blob dir: %m"); + } + + r = tempfn_random(dest_name, NULL, &fn); + if (r < 0) + return r; + + dest_dfd = open_mkdir_at(dest_base_dfd, fn, O_EXCL|O_CLOEXEC, mode); + if (dest_dfd < 0) + return log_debug_errno(dest_dfd, "Failed to create/open dest blob dir: %m"); + + r = readdir_all(src_dfd, RECURSE_DIR_SORT, &de); + if (r < 0) { + log_debug_errno(r, "Failed to read src blob dir: %m"); + goto fail; + } + for (size_t i = 0; i < de->n_entries; i++) { + const char *name = de->entries[i]->d_name; + _cleanup_close_ int src_fd = -EBADF; + + src_fd = openat(src_dfd, name, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW); + if (src_fd < 0) { + r = log_debug_errno(errno, "Failed to open %s in src blob dir: %m", name); + goto fail; + } + + r = copy_one_blob(src_fd, dest_dfd, name, &total_size, uid, manifest); + if (r == -EFBIG) + break; + if (r < 0) + goto fail; + } + + if (fchown(dest_dfd, uid, uid) < 0) { + r = log_debug_errno(errno, "Failed to chown dest blob dir: %m"); + goto fail; + } + + r = install_file(dest_base_dfd, fn, dest_base_dfd, dest_name, INSTALL_REPLACE); + if (r < 0) { + log_debug_errno(r, "Failed to move dest blob dir into place: %m"); + goto fail; + } + + return 0; + +fail: + (void) rm_rf_at(dest_base_dfd, fn, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_MISSING_OK); + return r; +} + +int home_reconcile_blob_dirs(UserRecord *h, int root_fd, int reconciled) { + _cleanup_close_ int sys_base_dfd = -EBADF; + int r; + + assert(h); + assert(root_fd >= 0); + assert(reconciled >= 0); + + if (reconciled == USER_RECONCILE_IDENTICAL) + return 0; + + sys_base_dfd = open(home_system_blob_dir(), O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW); + if (sys_base_dfd < 0) + return log_error_errno(errno, "Failed to open system blob dir: %m"); + + if (reconciled == USER_RECONCILE_HOST_WON) { + r = replace_blob_at(sys_base_dfd, h->user_name, root_fd, ".identity-blob", + h->blob_manifest, 0700, h->uid); + if (r < 0) + return log_error_errno(r, "Failed to replace embedded blobs with system blobs: %m"); + + log_info("Replaced embedded blob dir with contents of system blob dir."); + } else { + assert(reconciled == USER_RECONCILE_EMBEDDED_WON); + + r = replace_blob_at(root_fd, ".identity-blob", sys_base_dfd, h->user_name, + h->blob_manifest, 0755, 0); + if (r < 0) + return log_error_errno(r, "Failed to replace system blobs with embedded blobs: %m"); + + log_info("Replaced system blob dir with contents of embedded blob dir."); + } + return 0; +} + +int home_apply_new_blob_dir(UserRecord *h, Hashmap *blobs) { + _cleanup_free_ char *fn = NULL; + _cleanup_close_ int base_dfd = -EBADF, dfd = -EBADF; + uint64_t total_size = 0; + const char *filename; + const void *v; + int r; + + assert(h); + + if (!blobs) /* Shortcut: If no blobs are passed from dbus, we have nothing to do. */ + return 0; + + base_dfd = open(home_system_blob_dir(), O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW); + if (base_dfd < 0) + return log_error_errno(errno, "Failed to open system blob base dir: %m"); + + if (hashmap_isempty(blobs)) { + /* Shortcut: If blobs was passed but empty, we can simply delete the contents + * of the directory. */ + r = rm_rf_at(base_dfd, h->user_name, REMOVE_PHYSICAL|REMOVE_MISSING_OK); + if (r < 0) + return log_error_errno(r, "Failed to empty out system blob dir: %m"); + return 0; + } + + r = tempfn_random(h->user_name, NULL, &fn); + if (r < 0) + return r; + + dfd = open_mkdir_at(base_dfd, fn, O_EXCL|O_CLOEXEC, 0755); + if (dfd < 0) + return log_error_errno(errno, "Failed to create system blob dir: %m"); + + HASHMAP_FOREACH_KEY(v, filename, blobs) { + r = copy_one_blob(PTR_TO_FD(v), dfd, filename, &total_size, 0, h->blob_manifest); + if (r == -EFBIG) + break; + if (r < 0) { + log_error_errno(r, "Failed to copy %s into system blob dir: %m", filename); + goto fail; + } + } + + r = install_file(base_dfd, fn, base_dfd, h->user_name, INSTALL_REPLACE); + if (r < 0) { + log_error_errno(r, "Failed to move system blob dir into place: %m"); + goto fail; + } + + log_info("Replaced system blob directory."); + return 0; + +fail: + (void) rm_rf_at(base_dfd, fn, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_MISSING_OK); + return r; +} |