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-rw-r--r--src/core/exec-credential.c1023
1 files changed, 1023 insertions, 0 deletions
diff --git a/src/core/exec-credential.c b/src/core/exec-credential.c
new file mode 100644
index 0000000..6bcfb68
--- /dev/null
+++ b/src/core/exec-credential.c
@@ -0,0 +1,1023 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/mount.h>
+
+#include "acl-util.h"
+#include "creds-util.h"
+#include "exec-credential.h"
+#include "execute.h"
+#include "fileio.h"
+#include "glob-util.h"
+#include "io-util.h"
+#include "label-util.h"
+#include "mkdir-label.h"
+#include "mount-util.h"
+#include "mount.h"
+#include "mountpoint-util.h"
+#include "process-util.h"
+#include "random-util.h"
+#include "recurse-dir.h"
+#include "rm-rf.h"
+#include "tmpfile-util.h"
+
+ExecSetCredential *exec_set_credential_free(ExecSetCredential *sc) {
+ if (!sc)
+ return NULL;
+
+ free(sc->id);
+ free(sc->data);
+ return mfree(sc);
+}
+
+ExecLoadCredential *exec_load_credential_free(ExecLoadCredential *lc) {
+ if (!lc)
+ return NULL;
+
+ free(lc->id);
+ free(lc->path);
+ return mfree(lc);
+}
+
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+ exec_set_credential_hash_ops,
+ char, string_hash_func, string_compare_func,
+ ExecSetCredential, exec_set_credential_free);
+
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+ exec_load_credential_hash_ops,
+ char, string_hash_func, string_compare_func,
+ ExecLoadCredential, exec_load_credential_free);
+
+bool exec_context_has_credentials(const ExecContext *c) {
+ assert(c);
+
+ return !hashmap_isempty(c->set_credentials) ||
+ !hashmap_isempty(c->load_credentials) ||
+ !set_isempty(c->import_credentials);
+}
+
+bool exec_context_has_encrypted_credentials(ExecContext *c) {
+ ExecLoadCredential *load_cred;
+ ExecSetCredential *set_cred;
+
+ assert(c);
+
+ HASHMAP_FOREACH(load_cred, c->load_credentials)
+ if (load_cred->encrypted)
+ return true;
+
+ HASHMAP_FOREACH(set_cred, c->set_credentials)
+ if (set_cred->encrypted)
+ return true;
+
+ return false;
+}
+
+static int get_credential_directory(
+ const char *runtime_prefix,
+ const char *unit,
+ char **ret) {
+
+ char *p;
+
+ assert(ret);
+
+ if (!runtime_prefix || !unit) {
+ *ret = NULL;
+ return 0;
+ }
+
+ p = path_join(runtime_prefix, "credentials", unit);
+ if (!p)
+ return -ENOMEM;
+
+ *ret = p;
+ return 1;
+}
+
+int exec_context_get_credential_directory(
+ const ExecContext *context,
+ const ExecParameters *params,
+ const char *unit,
+ char **ret) {
+
+ assert(context);
+ assert(params);
+ assert(unit);
+ assert(ret);
+
+ if (!exec_context_has_credentials(context)) {
+ *ret = NULL;
+ return 0;
+ }
+
+ return get_credential_directory(params->prefix[EXEC_DIRECTORY_RUNTIME], unit, ret);
+}
+
+int unit_add_default_credential_dependencies(Unit *u, const ExecContext *c) {
+ _cleanup_free_ char *p = NULL, *m = NULL;
+ int r;
+
+ assert(u);
+ assert(c);
+
+ if (!exec_context_has_credentials(c))
+ return 0;
+
+ /* Let's make sure the credentials directory of this service is unmounted *after* the service itself
+ * shuts down. This only matters if mount namespacing is not used for the service, and hence the
+ * credentials mount appears on the host. */
+
+ r = get_credential_directory(u->manager->prefix[EXEC_DIRECTORY_RUNTIME], u->id, &p);
+ if (r <= 0)
+ return r;
+
+ r = unit_name_from_path(p, ".mount", &m);
+ if (r < 0)
+ return r;
+
+ return unit_add_dependency_by_name(u, UNIT_AFTER, m, /* add_reference= */ true, UNIT_DEPENDENCY_FILE);
+}
+
+int exec_context_destroy_credentials(Unit *u) {
+ _cleanup_free_ char *p = NULL;
+ int r;
+
+ assert(u);
+
+ r = get_credential_directory(u->manager->prefix[EXEC_DIRECTORY_RUNTIME], u->id, &p);
+ if (r <= 0)
+ return r;
+
+ /* This is either a tmpfs/ramfs of its own, or a plain directory. Either way, let's first try to
+ * unmount it, and afterwards remove the mount point */
+ if (umount2(p, MNT_DETACH|UMOUNT_NOFOLLOW) >= 0)
+ (void) mount_invalidate_state_by_path(u->manager, p);
+
+ (void) rm_rf(p, REMOVE_ROOT|REMOVE_CHMOD);
+
+ return 0;
+}
+
+static int write_credential(
+ int dfd,
+ const char *id,
+ const void *data,
+ size_t size,
+ uid_t uid,
+ gid_t gid,
+ bool ownership_ok) {
+
+ _cleanup_(unlink_and_freep) char *tmp = NULL;
+ _cleanup_close_ int fd = -EBADF;
+ int r;
+
+ r = tempfn_random_child("", "cred", &tmp);
+ if (r < 0)
+ return r;
+
+ fd = openat(dfd, tmp, O_CREAT|O_RDWR|O_CLOEXEC|O_EXCL|O_NOFOLLOW|O_NOCTTY, 0600);
+ if (fd < 0) {
+ tmp = mfree(tmp);
+ return -errno;
+ }
+
+ r = loop_write(fd, data, size);
+ if (r < 0)
+ return r;
+
+ if (fchmod(fd, 0400) < 0) /* Take away "w" bit */
+ return -errno;
+
+ if (uid_is_valid(uid) && uid != getuid()) {
+ r = fd_add_uid_acl_permission(fd, uid, ACL_READ);
+ if (r < 0) {
+ if (!ERRNO_IS_NOT_SUPPORTED(r) && !ERRNO_IS_PRIVILEGE(r))
+ return r;
+
+ if (!ownership_ok) /* Ideally we use ACLs, since we can neatly express what we want
+ * to express: that the user gets read access and nothing
+ * else. But if the backing fs can't support that (e.g. ramfs)
+ * then we can use file ownership instead. But that's only safe if
+ * we can then re-mount the whole thing read-only, so that the
+ * user can no longer chmod() the file to gain write access. */
+ return r;
+
+ if (fchown(fd, uid, gid) < 0)
+ return -errno;
+ }
+ }
+
+ if (renameat(dfd, tmp, dfd, id) < 0)
+ return -errno;
+
+ tmp = mfree(tmp);
+ return 0;
+}
+
+typedef enum CredentialSearchPath {
+ CREDENTIAL_SEARCH_PATH_TRUSTED,
+ CREDENTIAL_SEARCH_PATH_ENCRYPTED,
+ CREDENTIAL_SEARCH_PATH_ALL,
+ _CREDENTIAL_SEARCH_PATH_MAX,
+ _CREDENTIAL_SEARCH_PATH_INVALID = -EINVAL,
+} CredentialSearchPath;
+
+static char **credential_search_path(const ExecParameters *params, CredentialSearchPath path) {
+
+ _cleanup_strv_free_ char **l = NULL;
+
+ assert(params);
+ assert(path >= 0 && path < _CREDENTIAL_SEARCH_PATH_MAX);
+
+ /* Assemble a search path to find credentials in. For non-encrypted credentials, We'll look in
+ * /etc/credstore/ (and similar directories in /usr/lib/ + /run/). If we're looking for encrypted
+ * credentials, we'll look in /etc/credstore.encrypted/ (and similar dirs). */
+
+ if (IN_SET(path, CREDENTIAL_SEARCH_PATH_ENCRYPTED, CREDENTIAL_SEARCH_PATH_ALL)) {
+ if (strv_extend(&l, params->received_encrypted_credentials_directory) < 0)
+ return NULL;
+
+ if (strv_extend_strv(&l, CONF_PATHS_STRV("credstore.encrypted"), /* filter_duplicates= */ true) < 0)
+ return NULL;
+ }
+
+ if (IN_SET(path, CREDENTIAL_SEARCH_PATH_TRUSTED, CREDENTIAL_SEARCH_PATH_ALL)) {
+ if (params->received_credentials_directory)
+ if (strv_extend(&l, params->received_credentials_directory) < 0)
+ return NULL;
+
+ if (strv_extend_strv(&l, CONF_PATHS_STRV("credstore"), /* filter_duplicates= */ true) < 0)
+ return NULL;
+ }
+
+ if (DEBUG_LOGGING) {
+ _cleanup_free_ char *t = strv_join(l, ":");
+
+ log_debug("Credential search path is: %s", strempty(t));
+ }
+
+ return TAKE_PTR(l);
+}
+
+static int maybe_decrypt_and_write_credential(
+ int dir_fd,
+ const char *id,
+ bool encrypted,
+ uid_t uid,
+ gid_t gid,
+ bool ownership_ok,
+ const char *data,
+ size_t size,
+ uint64_t *left) {
+
+ _cleanup_free_ void *plaintext = NULL;
+ size_t add;
+ int r;
+
+ if (encrypted) {
+ size_t plaintext_size = 0;
+
+ r = decrypt_credential_and_warn(id, now(CLOCK_REALTIME), NULL, NULL, data, size,
+ &plaintext, &plaintext_size);
+ if (r < 0)
+ return r;
+
+ data = plaintext;
+ size = plaintext_size;
+ }
+
+ add = strlen(id) + size;
+ if (add > *left)
+ return -E2BIG;
+
+ r = write_credential(dir_fd, id, data, size, uid, gid, ownership_ok);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to write credential '%s': %m", id);
+
+ *left -= add;
+ return 0;
+}
+
+static int load_credential_glob(
+ const char *path,
+ bool encrypted,
+ char **search_path,
+ ReadFullFileFlags flags,
+ int write_dfd,
+ uid_t uid,
+ gid_t gid,
+ bool ownership_ok,
+ uint64_t *left) {
+
+ int r;
+
+ STRV_FOREACH(d, search_path) {
+ _cleanup_globfree_ glob_t pglob = {};
+ _cleanup_free_ char *j = NULL;
+
+ j = path_join(*d, path);
+ if (!j)
+ return -ENOMEM;
+
+ r = safe_glob(j, 0, &pglob);
+ if (r == -ENOENT)
+ continue;
+ if (r < 0)
+ return r;
+
+ for (size_t n = 0; n < pglob.gl_pathc; n++) {
+ _cleanup_free_ char *fn = NULL;
+ _cleanup_(erase_and_freep) char *data = NULL;
+ size_t size;
+
+ /* path is absolute, hence pass AT_FDCWD as nop dir fd here */
+ r = read_full_file_full(
+ AT_FDCWD,
+ pglob.gl_pathv[n],
+ UINT64_MAX,
+ encrypted ? CREDENTIAL_ENCRYPTED_SIZE_MAX : CREDENTIAL_SIZE_MAX,
+ flags,
+ NULL,
+ &data, &size);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to read credential '%s': %m",
+ pglob.gl_pathv[n]);
+
+ r = path_extract_filename(pglob.gl_pathv[n], &fn);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to extract filename from '%s': %m",
+ pglob.gl_pathv[n]);
+
+ r = maybe_decrypt_and_write_credential(
+ write_dfd,
+ fn,
+ encrypted,
+ uid,
+ gid,
+ ownership_ok,
+ data, size,
+ left);
+ if (r == -EEXIST)
+ continue;
+ if (r < 0)
+ return r;
+ }
+ }
+
+ return 0;
+}
+
+static int load_credential(
+ const ExecContext *context,
+ const ExecParameters *params,
+ const char *id,
+ const char *path,
+ bool encrypted,
+ const char *unit,
+ int read_dfd,
+ int write_dfd,
+ uid_t uid,
+ gid_t gid,
+ bool ownership_ok,
+ uint64_t *left) {
+
+ ReadFullFileFlags flags = READ_FULL_FILE_SECURE|READ_FULL_FILE_FAIL_WHEN_LARGER;
+ _cleanup_strv_free_ char **search_path = NULL;
+ _cleanup_(erase_and_freep) char *data = NULL;
+ _cleanup_free_ char *bindname = NULL;
+ const char *source = NULL;
+ bool missing_ok = true;
+ size_t size, maxsz;
+ int r;
+
+ assert(context);
+ assert(params);
+ assert(id);
+ assert(path);
+ assert(unit);
+ assert(read_dfd >= 0 || read_dfd == AT_FDCWD);
+ assert(write_dfd >= 0);
+ assert(left);
+
+ if (read_dfd >= 0) {
+ /* If a directory fd is specified, then read the file directly from that dir. In this case we
+ * won't do AF_UNIX stuff (we simply don't want to recursively iterate down a tree of AF_UNIX
+ * IPC sockets). It's OK if a file vanishes here in the time we enumerate it and intend to
+ * open it. */
+
+ if (!filename_is_valid(path)) /* safety check */
+ return -EINVAL;
+
+ missing_ok = true;
+ source = path;
+
+ } else if (path_is_absolute(path)) {
+ /* If this is an absolute path, read the data directly from it, and support AF_UNIX
+ * sockets */
+
+ if (!path_is_valid(path)) /* safety check */
+ return -EINVAL;
+
+ flags |= READ_FULL_FILE_CONNECT_SOCKET;
+
+ /* Pass some minimal info about the unit and the credential name we are looking to acquire
+ * via the source socket address in case we read off an AF_UNIX socket. */
+ if (asprintf(&bindname, "@%" PRIx64"/unit/%s/%s", random_u64(), unit, id) < 0)
+ return -ENOMEM;
+
+ missing_ok = false;
+ source = path;
+
+ } else if (credential_name_valid(path)) {
+ /* If this is a relative path, take it as credential name relative to the credentials
+ * directory we received ourselves. We don't support the AF_UNIX stuff in this mode, since we
+ * are operating on a credential store, i.e. this is guaranteed to be regular files. */
+
+ search_path = credential_search_path(params, CREDENTIAL_SEARCH_PATH_ALL);
+ if (!search_path)
+ return -ENOMEM;
+
+ missing_ok = true;
+ } else
+ source = NULL;
+
+ if (encrypted)
+ flags |= READ_FULL_FILE_UNBASE64;
+
+ maxsz = encrypted ? CREDENTIAL_ENCRYPTED_SIZE_MAX : CREDENTIAL_SIZE_MAX;
+
+ if (search_path) {
+ STRV_FOREACH(d, search_path) {
+ _cleanup_free_ char *j = NULL;
+
+ j = path_join(*d, path);
+ if (!j)
+ return -ENOMEM;
+
+ r = read_full_file_full(
+ AT_FDCWD, j, /* path is absolute, hence pass AT_FDCWD as nop dir fd here */
+ UINT64_MAX,
+ maxsz,
+ flags,
+ NULL,
+ &data, &size);
+ if (r != -ENOENT)
+ break;
+ }
+ } else if (source)
+ r = read_full_file_full(
+ read_dfd, source,
+ UINT64_MAX,
+ maxsz,
+ flags,
+ bindname,
+ &data, &size);
+ else
+ r = -ENOENT;
+
+ if (r == -ENOENT && (missing_ok || hashmap_contains(context->set_credentials, id))) {
+ /* Make a missing inherited credential non-fatal, let's just continue. After all apps
+ * will get clear errors if we don't pass such a missing credential on as they
+ * themselves will get ENOENT when trying to read them, which should not be much
+ * worse than when we handle the error here and make it fatal.
+ *
+ * Also, if the source file doesn't exist, but a fallback is set via SetCredentials=
+ * we are fine, too. */
+ log_debug_errno(r, "Couldn't read inherited credential '%s', skipping: %m", path);
+ return 0;
+ }
+ if (r < 0)
+ return log_debug_errno(r, "Failed to read credential '%s': %m", path);
+
+ return maybe_decrypt_and_write_credential(write_dfd, id, encrypted, uid, gid, ownership_ok, data, size, left);
+}
+
+struct load_cred_args {
+ const ExecContext *context;
+ const ExecParameters *params;
+ bool encrypted;
+ const char *unit;
+ int dfd;
+ uid_t uid;
+ gid_t gid;
+ bool ownership_ok;
+ uint64_t *left;
+};
+
+static int load_cred_recurse_dir_cb(
+ RecurseDirEvent event,
+ const char *path,
+ int dir_fd,
+ int inode_fd,
+ const struct dirent *de,
+ const struct statx *sx,
+ void *userdata) {
+
+ struct load_cred_args *args = ASSERT_PTR(userdata);
+ _cleanup_free_ char *sub_id = NULL;
+ int r;
+
+ if (event != RECURSE_DIR_ENTRY)
+ return RECURSE_DIR_CONTINUE;
+
+ if (!IN_SET(de->d_type, DT_REG, DT_SOCK))
+ return RECURSE_DIR_CONTINUE;
+
+ sub_id = strreplace(path, "/", "_");
+ if (!sub_id)
+ return -ENOMEM;
+
+ if (!credential_name_valid(sub_id))
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Credential would get ID %s, which is not valid, refusing", sub_id);
+
+ if (faccessat(args->dfd, sub_id, F_OK, AT_SYMLINK_NOFOLLOW) >= 0) {
+ log_debug("Skipping credential with duplicated ID %s at %s", sub_id, path);
+ return RECURSE_DIR_CONTINUE;
+ }
+ if (errno != ENOENT)
+ return log_debug_errno(errno, "Failed to test if credential %s exists: %m", sub_id);
+
+ r = load_credential(
+ args->context,
+ args->params,
+ sub_id,
+ de->d_name,
+ args->encrypted,
+ args->unit,
+ dir_fd,
+ args->dfd,
+ args->uid,
+ args->gid,
+ args->ownership_ok,
+ args->left);
+ if (r < 0)
+ return r;
+
+ return RECURSE_DIR_CONTINUE;
+}
+
+static int acquire_credentials(
+ const ExecContext *context,
+ const ExecParameters *params,
+ const char *unit,
+ const char *p,
+ uid_t uid,
+ gid_t gid,
+ bool ownership_ok) {
+
+ uint64_t left = CREDENTIALS_TOTAL_SIZE_MAX;
+ _cleanup_close_ int dfd = -EBADF;
+ const char *ic;
+ ExecLoadCredential *lc;
+ ExecSetCredential *sc;
+ int r;
+
+ assert(context);
+ assert(p);
+
+ dfd = open(p, O_DIRECTORY|O_CLOEXEC);
+ if (dfd < 0)
+ return -errno;
+
+ r = fd_acl_make_writable(dfd); /* Add the "w" bit, if we are reusing an already set up credentials dir where it was unset */
+ if (r < 0)
+ return r;
+
+ /* First, load credentials off disk (or acquire via AF_UNIX socket) */
+ HASHMAP_FOREACH(lc, context->load_credentials) {
+ _cleanup_close_ int sub_fd = -EBADF;
+
+ /* If this is an absolute path, then try to open it as a directory. If that works, then we'll
+ * recurse into it. If it is an absolute path but it isn't a directory, then we'll open it as
+ * a regular file. Finally, if it's a relative path we will use it as a credential name to
+ * propagate a credential passed to us from further up. */
+
+ if (path_is_absolute(lc->path)) {
+ sub_fd = open(lc->path, O_DIRECTORY|O_CLOEXEC|O_RDONLY);
+ if (sub_fd < 0 && !IN_SET(errno,
+ ENOTDIR, /* Not a directory */
+ ENOENT)) /* Doesn't exist? */
+ return log_debug_errno(errno, "Failed to open '%s': %m", lc->path);
+ }
+
+ if (sub_fd < 0)
+ /* Regular file (incl. a credential passed in from higher up) */
+ r = load_credential(
+ context,
+ params,
+ lc->id,
+ lc->path,
+ lc->encrypted,
+ unit,
+ AT_FDCWD,
+ dfd,
+ uid,
+ gid,
+ ownership_ok,
+ &left);
+ else
+ /* Directory */
+ r = recurse_dir(
+ sub_fd,
+ /* path= */ lc->id, /* recurse_dir() will suffix the subdir paths from here to the top-level id */
+ /* statx_mask= */ 0,
+ /* n_depth_max= */ UINT_MAX,
+ RECURSE_DIR_SORT|RECURSE_DIR_IGNORE_DOT|RECURSE_DIR_ENSURE_TYPE,
+ load_cred_recurse_dir_cb,
+ &(struct load_cred_args) {
+ .context = context,
+ .params = params,
+ .encrypted = lc->encrypted,
+ .unit = unit,
+ .dfd = dfd,
+ .uid = uid,
+ .gid = gid,
+ .ownership_ok = ownership_ok,
+ .left = &left,
+ });
+ if (r < 0)
+ return r;
+ }
+
+ /* Next, look for system credentials and credentials in the credentials store. Note that these do not
+ * override any credentials found earlier. */
+ SET_FOREACH(ic, context->import_credentials) {
+ _cleanup_free_ char **search_path = NULL;
+
+ search_path = credential_search_path(params, CREDENTIAL_SEARCH_PATH_TRUSTED);
+ if (!search_path)
+ return -ENOMEM;
+
+ r = load_credential_glob(
+ ic,
+ /* encrypted = */ false,
+ search_path,
+ READ_FULL_FILE_SECURE|READ_FULL_FILE_FAIL_WHEN_LARGER,
+ dfd,
+ uid,
+ gid,
+ ownership_ok,
+ &left);
+ if (r < 0)
+ return r;
+
+ search_path = strv_free(search_path);
+ search_path = credential_search_path(params, CREDENTIAL_SEARCH_PATH_ENCRYPTED);
+ if (!search_path)
+ return -ENOMEM;
+
+ r = load_credential_glob(
+ ic,
+ /* encrypted = */ true,
+ search_path,
+ READ_FULL_FILE_SECURE|READ_FULL_FILE_FAIL_WHEN_LARGER|READ_FULL_FILE_UNBASE64,
+ dfd,
+ uid,
+ gid,
+ ownership_ok,
+ &left);
+ if (r < 0)
+ return r;
+ }
+
+ /* Finally, we add in literally specified credentials. If the credentials already exist, we'll not
+ * add them, so that they can act as a "default" if the same credential is specified multiple times. */
+ HASHMAP_FOREACH(sc, context->set_credentials) {
+ _cleanup_(erase_and_freep) void *plaintext = NULL;
+ const char *data;
+ size_t size, add;
+
+ /* Note that we check ahead of time here instead of relying on O_EXCL|O_CREAT later to return
+ * EEXIST if the credential already exists. That's because the TPM2-based decryption is kinda
+ * slow and involved, hence it's nice to be able to skip that if the credential already
+ * exists anyway. */
+ if (faccessat(dfd, sc->id, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
+ continue;
+ if (errno != ENOENT)
+ return log_debug_errno(errno, "Failed to test if credential %s exists: %m", sc->id);
+
+ if (sc->encrypted) {
+ r = decrypt_credential_and_warn(sc->id, now(CLOCK_REALTIME), NULL, NULL, sc->data, sc->size, &plaintext, &size);
+ if (r < 0)
+ return r;
+
+ data = plaintext;
+ } else {
+ data = sc->data;
+ size = sc->size;
+ }
+
+ add = strlen(sc->id) + size;
+ if (add > left)
+ return -E2BIG;
+
+ r = write_credential(dfd, sc->id, data, size, uid, gid, ownership_ok);
+ if (r < 0)
+ return r;
+
+ left -= add;
+ }
+
+ r = fd_acl_make_read_only(dfd); /* Now take away the "w" bit */
+ if (r < 0)
+ return r;
+
+ /* After we created all keys with the right perms, also make sure the credential store as a whole is
+ * accessible */
+
+ if (uid_is_valid(uid) && uid != getuid()) {
+ r = fd_add_uid_acl_permission(dfd, uid, ACL_READ | ACL_EXECUTE);
+ if (r < 0) {
+ if (!ERRNO_IS_NOT_SUPPORTED(r) && !ERRNO_IS_PRIVILEGE(r))
+ return r;
+
+ if (!ownership_ok)
+ return r;
+
+ if (fchown(dfd, uid, gid) < 0)
+ return -errno;
+ }
+ }
+
+ return 0;
+}
+
+static int setup_credentials_internal(
+ const ExecContext *context,
+ const ExecParameters *params,
+ const char *unit,
+ const char *final, /* This is where the credential store shall eventually end up at */
+ const char *workspace, /* This is where we can prepare it before moving it to the final place */
+ bool reuse_workspace, /* Whether to reuse any existing workspace mount if it already is a mount */
+ bool must_mount, /* Whether to require that we mount something, it's not OK to use the plain directory fall back */
+ uid_t uid,
+ gid_t gid) {
+
+ int r, workspace_mounted; /* negative if we don't know yet whether we have/can mount something; true
+ * if we mounted something; false if we definitely can't mount anything */
+ bool final_mounted;
+ const char *where;
+
+ assert(context);
+ assert(final);
+ assert(workspace);
+
+ if (reuse_workspace) {
+ r = path_is_mount_point(workspace, NULL, 0);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ workspace_mounted = true; /* If this is already a mount, and we are supposed to reuse
+ * it, let's keep this in mind */
+ else
+ workspace_mounted = -1; /* We need to figure out if we can mount something to the workspace */
+ } else
+ workspace_mounted = -1; /* ditto */
+
+ r = path_is_mount_point(final, NULL, 0);
+ if (r < 0)
+ return r;
+ if (r > 0) {
+ /* If the final place already has something mounted, we use that. If the workspace also has
+ * something mounted we assume it's actually the same mount (but with MS_RDONLY
+ * different). */
+ final_mounted = true;
+
+ if (workspace_mounted < 0) {
+ /* If the final place is mounted, but the workspace isn't, then let's bind mount
+ * the final version to the workspace, and make it writable, so that we can make
+ * changes */
+
+ r = mount_nofollow_verbose(LOG_DEBUG, final, workspace, NULL, MS_BIND|MS_REC, NULL);
+ if (r < 0)
+ return r;
+
+ r = mount_nofollow_verbose(LOG_DEBUG, NULL, workspace, NULL, MS_BIND|MS_REMOUNT|credentials_fs_mount_flags(/* ro= */ false), NULL);
+ if (r < 0)
+ return r;
+
+ workspace_mounted = true;
+ }
+ } else
+ final_mounted = false;
+
+ if (workspace_mounted < 0) {
+ /* Nothing is mounted on the workspace yet, let's try to mount something now */
+
+ r = mount_credentials_fs(workspace, CREDENTIALS_TOTAL_SIZE_MAX, /* ro= */ false);
+ if (r < 0) {
+ /* If that didn't work, try to make a bind mount from the final to the workspace, so
+ * that we can make it writable there. */
+ r = mount_nofollow_verbose(LOG_DEBUG, final, workspace, NULL, MS_BIND|MS_REC, NULL);
+ if (r < 0) {
+ if (!ERRNO_IS_PRIVILEGE(r))
+ /* Propagate anything that isn't a permission problem. */
+ return r;
+
+ if (must_mount)
+ /* If it's not OK to use the plain directory fallback, propagate all
+ * errors too. */
+ return r;
+
+ /* If we lack privileges to bind mount stuff, then let's gracefully proceed
+ * for compat with container envs, and just use the final dir as is. */
+
+ workspace_mounted = false;
+ } else {
+ /* Make the new bind mount writable (i.e. drop MS_RDONLY) */
+ r = mount_nofollow_verbose(LOG_DEBUG, NULL, workspace, NULL, MS_BIND|MS_REMOUNT|credentials_fs_mount_flags(/* ro= */ false), NULL);
+ if (r < 0)
+ return r;
+
+ workspace_mounted = true;
+ }
+ } else
+ workspace_mounted = true;
+ }
+
+ assert(!must_mount || workspace_mounted > 0);
+ where = workspace_mounted ? workspace : final;
+
+ (void) label_fix_full(AT_FDCWD, where, final, 0);
+
+ r = acquire_credentials(context, params, unit, where, uid, gid, workspace_mounted);
+ if (r < 0)
+ return r;
+
+ if (workspace_mounted) {
+ bool install;
+
+ /* Determine if we should actually install the prepared mount in the final location by bind
+ * mounting it there. We do so only if the mount is not established there already, and if the
+ * mount is actually non-empty (i.e. carries at least one credential). Not that in the best
+ * case we are doing all this in a mount namespace, thus no one else will see that we
+ * allocated a file system we are getting rid of again here. */
+ if (final_mounted)
+ install = false; /* already installed */
+ else {
+ r = dir_is_empty(where, /* ignore_hidden_or_backup= */ false);
+ if (r < 0)
+ return r;
+
+ install = r == 0; /* install only if non-empty */
+ }
+
+ if (install) {
+ /* Make workspace read-only now, so that any bind mount we make from it defaults to
+ * read-only too */
+ r = mount_nofollow_verbose(LOG_DEBUG, NULL, workspace, NULL, MS_BIND|MS_REMOUNT|credentials_fs_mount_flags(/* ro= */ true), NULL);
+ if (r < 0)
+ return r;
+
+ /* And mount it to the final place, read-only */
+ r = mount_nofollow_verbose(LOG_DEBUG, workspace, final, NULL, MS_MOVE, NULL);
+ } else
+ /* Otherwise get rid of it */
+ r = umount_verbose(LOG_DEBUG, workspace, MNT_DETACH|UMOUNT_NOFOLLOW);
+ if (r < 0)
+ return r;
+ } else {
+ _cleanup_free_ char *parent = NULL;
+
+ /* If we do not have our own mount put used the plain directory fallback, then we need to
+ * open access to the top-level credential directory and the per-service directory now */
+
+ r = path_extract_directory(final, &parent);
+ if (r < 0)
+ return r;
+ if (chmod(parent, 0755) < 0)
+ return -errno;
+ }
+
+ return 0;
+}
+
+int exec_setup_credentials(
+ const ExecContext *context,
+ const ExecParameters *params,
+ const char *unit,
+ uid_t uid,
+ gid_t gid) {
+
+ _cleanup_free_ char *p = NULL, *q = NULL;
+ int r;
+
+ assert(context);
+ assert(params);
+
+ if (!exec_context_has_credentials(context))
+ return 0;
+
+ if (!params->prefix[EXEC_DIRECTORY_RUNTIME])
+ return -EINVAL;
+
+ /* This where we'll place stuff when we are done; this main credentials directory is world-readable,
+ * and the subdir we mount over with a read-only file system readable by the service's user */
+ q = path_join(params->prefix[EXEC_DIRECTORY_RUNTIME], "credentials");
+ if (!q)
+ return -ENOMEM;
+
+ r = mkdir_label(q, 0755); /* top-level dir: world readable/searchable */
+ if (r < 0 && r != -EEXIST)
+ return r;
+
+ p = path_join(q, unit);
+ if (!p)
+ return -ENOMEM;
+
+ r = mkdir_label(p, 0700); /* per-unit dir: private to user */
+ if (r < 0 && r != -EEXIST)
+ return r;
+
+ r = safe_fork("(sd-mkdcreds)", FORK_DEATHSIG_SIGTERM|FORK_WAIT|FORK_NEW_MOUNTNS, NULL);
+ if (r < 0) {
+ _cleanup_(rmdir_and_freep) char *u = NULL; /* remove the temporary workspace if we can */
+ _cleanup_free_ char *t = NULL;
+
+ /* If this is not a privilege or support issue then propagate the error */
+ if (!ERRNO_IS_NOT_SUPPORTED(r) && !ERRNO_IS_PRIVILEGE(r))
+ return r;
+
+ /* Temporary workspace, that remains inaccessible all the time. We prepare stuff there before moving
+ * it into place, so that users can't access half-initialized credential stores. */
+ t = path_join(params->prefix[EXEC_DIRECTORY_RUNTIME], "systemd/temporary-credentials");
+ if (!t)
+ return -ENOMEM;
+
+ /* We can't set up a mount namespace. In that case operate on a fixed, inaccessible per-unit
+ * directory outside of /run/credentials/ first, and then move it over to /run/credentials/
+ * after it is fully set up */
+ u = path_join(t, unit);
+ if (!u)
+ return -ENOMEM;
+
+ FOREACH_STRING(i, t, u) {
+ r = mkdir_label(i, 0700);
+ if (r < 0 && r != -EEXIST)
+ return r;
+ }
+
+ r = setup_credentials_internal(
+ context,
+ params,
+ unit,
+ p, /* final mount point */
+ u, /* temporary workspace to overmount */
+ true, /* reuse the workspace if it is already a mount */
+ false, /* it's OK to fall back to a plain directory if we can't mount anything */
+ uid,
+ gid);
+ if (r < 0)
+ return r;
+
+ } else if (r == 0) {
+
+ /* We managed to set up a mount namespace, and are now in a child. That's great. In this case
+ * we can use the same directory for all cases, after turning off propagation. Question
+ * though is: where do we turn off propagation exactly, and where do we place the workspace
+ * directory? We need some place that is guaranteed to be a mount point in the host, and
+ * which is guaranteed to have a subdir we can mount over. /run/ is not suitable for this,
+ * since we ultimately want to move the resulting file system there, i.e. we need propagation
+ * for /run/ eventually. We could use our own /run/systemd/bind mount on itself, but that
+ * would be visible in the host mount table all the time, which we want to avoid. Hence, what
+ * we do here instead we use /dev/ and /dev/shm/ for our purposes. We know for sure that
+ * /dev/ is a mount point and we now for sure that /dev/shm/ exists. Hence we can turn off
+ * propagation on the former, and then overmount the latter.
+ *
+ * Yes it's nasty playing games with /dev/ and /dev/shm/ like this, since it does not exist
+ * for this purpose, but there are few other candidates that work equally well for us, and
+ * given that we do this in a privately namespaced short-lived single-threaded process that
+ * no one else sees this should be OK to do. */
+
+ /* Turn off propagation from our namespace to host */
+ r = mount_nofollow_verbose(LOG_DEBUG, NULL, "/dev", NULL, MS_SLAVE|MS_REC, NULL);
+ if (r < 0)
+ goto child_fail;
+
+ r = setup_credentials_internal(
+ context,
+ params,
+ unit,
+ p, /* final mount point */
+ "/dev/shm", /* temporary workspace to overmount */
+ false, /* do not reuse /dev/shm if it is already a mount, under no circumstances */
+ true, /* insist that something is mounted, do not allow fallback to plain directory */
+ uid,
+ gid);
+ if (r < 0)
+ goto child_fail;
+
+ _exit(EXIT_SUCCESS);
+
+ child_fail:
+ _exit(EXIT_FAILURE);
+ }
+
+ /* If the credentials dir is empty and not a mount point, then there's no point in having it. Let's
+ * try to remove it. This matters in particular if we created the dir as mount point but then didn't
+ * actually end up mounting anything on it. In that case we'd rather have ENOENT than EACCESS being
+ * seen by users when trying access this inode. */
+ (void) rmdir(p);
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-19 23:05:22 +0000