src/import/pull-common.c

/***
  This file is part of systemd.

  Copyright 2015 Lennart Poettering

  systemd 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.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/prctl.h>

#include "alloc-util.h"
#include "btrfs-util.h"
#include "capability-util.h"
#include "copy.h"
#include "dirent-util.h"
#include "escape.h"
#include "fd-util.h"
#include "io-util.h"
#include "path-util.h"
#include "process-util.h"
#include "pull-common.h"
#include "pull-job.h"
#include "rm-rf.h"
#include "signal-util.h"
#include "siphash24.h"
#include "string-util.h"
#include "strv.h"
#include "util.h"
#include "web-util.h"

#define FILENAME_ESCAPE "/.#\"\'"
#define HASH_URL_THRESHOLD_LENGTH (_POSIX_PATH_MAX - 16)

int pull_find_old_etags(
                const char *url,
                const char *image_root,
                int dt,
                const char *prefix,
                const char *suffix,
                char ***etags) {

        _cleanup_free_ char *escaped_url = NULL;
        _cleanup_closedir_ DIR *d = NULL;
        _cleanup_strv_free_ char **l = NULL;
        struct dirent *de;
        int r;

        assert(url);
        assert(etags);

        if (!image_root)
                image_root = "/var/lib/machines";

        escaped_url = xescape(url, FILENAME_ESCAPE);
        if (!escaped_url)
                return -ENOMEM;

        d = opendir(image_root);
        if (!d) {
                if (errno == ENOENT) {
                        *etags = NULL;
                        return 0;
                }

                return -errno;
        }

        FOREACH_DIRENT_ALL(de, d, return -errno) {
                const char *a, *b;
                char *u;

                if (de->d_type != DT_UNKNOWN &&
                    de->d_type != dt)
                        continue;

                if (prefix) {
                        a = startswith(de->d_name, prefix);
                        if (!a)
                                continue;
                } else
                        a = de->d_name;

                a = startswith(a, escaped_url);
                if (!a)
                        continue;

                a = startswith(a, ".");
                if (!a)
                        continue;

                if (suffix) {
                        b = endswith(de->d_name, suffix);
                        if (!b)
                                continue;
                } else
                        b = strchr(de->d_name, 0);

                if (a >= b)
                        continue;

                r = cunescape_length(a, b - a, 0, &u);
                if (r < 0)
                        return r;

                if (!http_etag_is_valid(u)) {
                        free(u);
                        continue;
                }

                r = strv_consume(&l, u);
                if (r < 0)
                        return r;
        }

        *etags = l;
        l = NULL;

        return 0;
}

int pull_make_local_copy(const char *final, const char *image_root, const char *local, bool force_local) {
        const char *p;
        int r;

        assert(final);
        assert(local);

        if (!image_root)
                image_root = "/var/lib/machines";

        p = strjoina(image_root, "/", local);

        if (force_local)
                (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME);

        r = btrfs_subvol_snapshot(final, p, BTRFS_SNAPSHOT_QUOTA);
        if (r == -ENOTTY) {
                r = copy_tree(final, p, false);
                if (r < 0)
                        return log_error_errno(r, "Failed to copy image: %m");
        } else if (r < 0)
                return log_error_errno(r, "Failed to create local image: %m");

        log_info("Created new local image '%s'.", local);

        return 0;
}

static int hash_url(const char *url, char **ret) {
        uint64_t h;
        static const sd_id128_t k = SD_ID128_ARRAY(df,89,16,87,01,cc,42,30,98,ab,4a,19,a6,a5,63,4f);

        assert(url);

        h = siphash24(url, strlen(url), k.bytes);
        if (asprintf(ret, "%"PRIx64, h) < 0)
                return -ENOMEM;

        return 0;
}

int pull_make_path(const char *url, const char *etag, const char *image_root, const char *prefix, const char *suffix, char **ret) {
        _cleanup_free_ char *escaped_url = NULL, *escaped_etag = NULL;
        char *path;

        assert(url);
        assert(ret);

        if (!image_root)
                image_root = "/var/lib/machines";

        escaped_url = xescape(url, FILENAME_ESCAPE);
        if (!escaped_url)
                return -ENOMEM;

        if (etag) {
                escaped_etag = xescape(etag, FILENAME_ESCAPE);
                if (!escaped_etag)
                        return -ENOMEM;
        }

        path = strjoin(image_root, "/", strempty(prefix), escaped_url, escaped_etag ? "." : "",
                       strempty(escaped_etag), strempty(suffix), NULL);
        if (!path)
                return -ENOMEM;

        /* URLs might make the path longer than the maximum allowed length for a file name.
         * When that happens, a URL hash is used instead. Paths returned by this function
         * can be later used with tempfn_random() which adds 16 bytes to the resulting name. */
        if (strlen(path) >= HASH_URL_THRESHOLD_LENGTH) {
                _cleanup_free_ char *hash = NULL;
                int r;

                free(path);

                r = hash_url(url, &hash);
                if (r < 0)
                        return r;

                path = strjoin(image_root, "/", strempty(prefix), hash, escaped_etag ? "." : "",
                               strempty(escaped_etag), strempty(suffix), NULL);
                if (!path)
                        return -ENOMEM;
        }

        *ret = path;
        return 0;
}

int pull_make_settings_job(
                PullJob **ret,
                const char *url,
                CurlGlue *glue,
                PullJobFinished on_finished,
                void *userdata) {

        _cleanup_free_ char *last_component = NULL, *ll = NULL, *settings_url = NULL;
        _cleanup_(pull_job_unrefp) PullJob *job = NULL;
        const char *q;
        int r;

        assert(ret);
        assert(url);
        assert(glue);

        r = import_url_last_component(url, &last_component);
        if (r < 0)
                return r;

        r = tar_strip_suffixes(last_component, &ll);
        if (r < 0)
                return r;

        q = strjoina(ll, ".nspawn");

        r = import_url_change_last_component(url, q, &settings_url);
        if (r < 0)
                return r;

        r = pull_job_new(&job, settings_url, glue, userdata);
        if (r < 0)
                return r;

        job->on_finished = on_finished;
        job->compressed_max = job->uncompressed_max = 1ULL * 1024ULL * 1024ULL;

        *ret = job;
        job = NULL;

        return 0;
}

int pull_make_verification_jobs(
                PullJob **ret_checksum_job,
                PullJob **ret_signature_job,
                ImportVerify verify,
                const char *url,
                CurlGlue *glue,
                PullJobFinished on_finished,
                void *userdata) {

        _cleanup_(pull_job_unrefp) PullJob *checksum_job = NULL, *signature_job = NULL;
        int r;

        assert(ret_checksum_job);
        assert(ret_signature_job);
        assert(verify >= 0);
        assert(verify < _IMPORT_VERIFY_MAX);
        assert(url);
        assert(glue);

        if (verify != IMPORT_VERIFY_NO) {
                _cleanup_free_ char *checksum_url = NULL;

                /* Queue job for the SHA256SUMS file for the image */
                r = import_url_change_last_component(url, "SHA256SUMS", &checksum_url);
                if (r < 0)
                        return r;

                r = pull_job_new(&checksum_job, checksum_url, glue, userdata);
                if (r < 0)
                        return r;

                checksum_job->on_finished = on_finished;
                checksum_job->uncompressed_max = checksum_job->compressed_max = 1ULL * 1024ULL * 1024ULL;
        }

        if (verify == IMPORT_VERIFY_SIGNATURE) {
                _cleanup_free_ char *signature_url = NULL;

                /* Queue job for the SHA256SUMS.gpg file for the image. */
                r = import_url_change_last_component(url, "SHA256SUMS.gpg", &signature_url);
                if (r < 0)
                        return r;

                r = pull_job_new(&signature_job, signature_url, glue, userdata);
                if (r < 0)
                        return r;

                signature_job->on_finished = on_finished;
                signature_job->uncompressed_max = signature_job->compressed_max = 1ULL * 1024ULL * 1024ULL;
        }

        *ret_checksum_job = checksum_job;
        *ret_signature_job = signature_job;

        checksum_job = signature_job = NULL;

        return 0;
}

int pull_verify(PullJob *main_job,
                PullJob *settings_job,
                PullJob *checksum_job,
                PullJob *signature_job) {

        _cleanup_close_pair_ int gpg_pipe[2] = { -1, -1 };
        _cleanup_free_ char *fn = NULL;
        _cleanup_close_ int sig_file = -1;
        const char *p, *line;
        char sig_file_path[] = "/tmp/sigXXXXXX", gpg_home[] = "/tmp/gpghomeXXXXXX";
        _cleanup_(sigkill_waitp) pid_t pid = 0;
        bool gpg_home_created = false;
        int r;

        assert(main_job);
        assert(main_job->state == PULL_JOB_DONE);

        if (!checksum_job)
                return 0;

        assert(main_job->calc_checksum);
        assert(main_job->checksum);
        assert(checksum_job->state == PULL_JOB_DONE);

        if (!checksum_job->payload || checksum_job->payload_size <= 0) {
                log_error("Checksum is empty, cannot verify.");
                return -EBADMSG;
        }

        r = import_url_last_component(main_job->url, &fn);
        if (r < 0)
                return log_oom();

        if (!filename_is_valid(fn)) {
                log_error("Cannot verify checksum, could not determine valid server-side file name.");
                return -EBADMSG;
        }

        line = strjoina(main_job->checksum, " *", fn, "\n");

        p = memmem(checksum_job->payload,
                   checksum_job->payload_size,
                   line,
                   strlen(line));

        if (!p || (p != (char*) checksum_job->payload && p[-1] != '\n')) {
                log_error("DOWNLOAD INVALID: Checksum did not check out, payload has been tampered with.");
                return -EBADMSG;
        }

        log_info("SHA256 checksum of %s is valid.", main_job->url);

        assert(!settings_job || IN_SET(settings_job->state, PULL_JOB_DONE, PULL_JOB_FAILED));

        if (settings_job &&
            settings_job->state == PULL_JOB_DONE &&
            settings_job->error == 0 &&
            !settings_job->etag_exists) {

                _cleanup_free_ char *settings_fn = NULL;

                assert(settings_job->calc_checksum);
                assert(settings_job->checksum);

                r = import_url_last_component(settings_job->url, &settings_fn);
                if (r < 0)
                        return log_oom();

                if (!filename_is_valid(settings_fn)) {
                        log_error("Cannot verify checksum, could not determine server-side settings file name.");
                        return -EBADMSG;
                }

                line = strjoina(settings_job->checksum, " *", settings_fn, "\n");

                p = memmem(checksum_job->payload,
                           checksum_job->payload_size,
                           line,
                           strlen(line));

                if (!p || (p != (char*) checksum_job->payload && p[-1] != '\n')) {
                        log_error("DOWNLOAD INVALID: Checksum of settings file did not checkout, settings file has been tampered with.");
                        return -EBADMSG;
                }

                log_info("SHA256 checksum of %s is valid.", settings_job->url);
        }

        if (!signature_job)
                return 0;

        assert(signature_job->state == PULL_JOB_DONE);

        if (!signature_job->payload || signature_job->payload_size <= 0) {
                log_error("Signature is empty, cannot verify.");
                return -EBADMSG;
        }

        r = pipe2(gpg_pipe, O_CLOEXEC);
        if (r < 0)
                return log_error_errno(errno, "Failed to create pipe for gpg: %m");

        sig_file = mkostemp(sig_file_path, O_RDWR);
        if (sig_file < 0)
                return log_error_errno(errno, "Failed to create temporary file: %m");

        r = loop_write(sig_file, signature_job->payload, signature_job->payload_size, false);
        if (r < 0) {
                log_error_errno(r, "Failed to write to temporary file: %m");
                goto finish;
        }

        if (!mkdtemp(gpg_home)) {
                r = log_error_errno(errno, "Failed to create tempory home for gpg: %m");
                goto finish;
        }

        gpg_home_created = true;

        pid = fork();
        if (pid < 0)
                return log_error_errno(errno, "Failed to fork off gpg: %m");
        if (pid == 0) {
                const char *cmd[] = {
                        "gpg",
                        "--no-options",
                        "--no-default-keyring",
                        "--no-auto-key-locate",
                        "--no-auto-check-trustdb",
                        "--batch",
                        "--trust-model=always",
                        NULL, /* --homedir=  */
                        NULL, /* --keyring= */
                        NULL, /* --verify */
                        NULL, /* signature file */
                        NULL, /* dash */
                        NULL  /* trailing NULL */
                };
                unsigned k = ELEMENTSOF(cmd) - 6;
                int null_fd;

                /* Child */

                (void) reset_all_signal_handlers();
                (void) reset_signal_mask();
                assert_se(prctl(PR_SET_PDEATHSIG, SIGTERM) == 0);

                gpg_pipe[1] = safe_close(gpg_pipe[1]);

                if (dup2(gpg_pipe[0], STDIN_FILENO) != STDIN_FILENO) {
                        log_error_errno(errno, "Failed to dup2() fd: %m");
                        _exit(EXIT_FAILURE);
                }

                if (gpg_pipe[0] != STDIN_FILENO)
                        gpg_pipe[0] = safe_close(gpg_pipe[0]);

                null_fd = open("/dev/null", O_WRONLY|O_NOCTTY);
                if (null_fd < 0) {
                        log_error_errno(errno, "Failed to open /dev/null: %m");
                        _exit(EXIT_FAILURE);
                }

                if (dup2(null_fd, STDOUT_FILENO) != STDOUT_FILENO) {
                        log_error_errno(errno, "Failed to dup2() fd: %m");
                        _exit(EXIT_FAILURE);
                }

                if (null_fd != STDOUT_FILENO)
                        null_fd = safe_close(null_fd);

                cmd[k++] = strjoina("--homedir=", gpg_home);

                /* We add the user keyring only to the command line
                 * arguments, if it's around since gpg fails
                 * otherwise. */
                if (access(USER_KEYRING_PATH, F_OK) >= 0)
                        cmd[k++] = "--keyring=" USER_KEYRING_PATH;
                else
                        cmd[k++] = "--keyring=" VENDOR_KEYRING_PATH;

                cmd[k++] = "--verify";
                cmd[k++] = sig_file_path;
                cmd[k++] = "-";
                cmd[k++] = NULL;

                stdio_unset_cloexec();

                execvp("gpg2", (char * const *) cmd);
                execvp("gpg", (char * const *) cmd);
                log_error_errno(errno, "Failed to execute gpg: %m");
                _exit(EXIT_FAILURE);
        }

        gpg_pipe[0] = safe_close(gpg_pipe[0]);

        r = loop_write(gpg_pipe[1], checksum_job->payload, checksum_job->payload_size, false);
        if (r < 0) {
                log_error_errno(r, "Failed to write to pipe: %m");
                goto finish;
        }

        gpg_pipe[1] = safe_close(gpg_pipe[1]);

        r = wait_for_terminate_and_warn("gpg", pid, true);
        pid = 0;
        if (r < 0)
                goto finish;
        if (r > 0) {
                log_error("DOWNLOAD INVALID: Signature verification failed.");
                r = -EBADMSG;
        } else {
                log_info("Signature verification succeeded.");
                r = 0;
        }

finish:
        if (sig_file >= 0)
                (void) unlink(sig_file_path);

        if (gpg_home_created)
                (void) rm_rf(gpg_home, REMOVE_ROOT|REMOVE_PHYSICAL);

        return r;
}