journalctl: be smarter about journal error checks

There are many ways in which we can get those checks wrong, so it is
better to warn and then error out on a real access failure.

The error messages are wrapped to <80 lines, because their primary
use is to be displayed in the terminal, and it is easier to read them
this way. Reading them in the journal can be a bit trickier, but
this is a bug in logs-show.c.

3 files changed, 136 insertions, 57 deletions

diff --git a/src/journal/journal-internal.h b/src/journal/journal-internal.h
index 97de0e75ff..bc9e44d42d 100644
--- a/src/journal/journal-internal.h
+++ b/src/journal/journal-internal.h
@@ -30,6 +30,7 @@
 #include "journal-def.h"
 #include "list.h"
 #include "hashmap.h"
+#include "set.h"
 #include "journal-file.h"
 
 typedef struct Match Match;
@@ -123,6 +124,8 @@ struct sd_journal {
         bool on_network;
 
         size_t data_threshold;
+
+        Set *errors;
 };
 
 char *journal_make_match_string(sd_journal *j);
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 8543adfb8a..91dbde3ba1 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -883,63 +883,111 @@ static int verify(sd_journal *j) {
         return r;
 }
 
-static int access_check(void) {
-
 #ifdef HAVE_ACL
-        /* If /var/log/journal doesn't even exist, unprivileged users have no access at all */
-        if (access("/var/log/journal", F_OK) < 0 && geteuid() != 0 && in_group("systemd-journal") <= 0) {
-                log_error("Unprivileged users can't see messages unless persistent log storage is enabled. Users in the group 'systemd-journal' can always see messages.");
-                return -EACCES;
+static int access_check_var_log_journal(sd_journal *j) {
+        _cleanup_strv_free_ char **g = NULL;
+        bool have_access;
+        int r;
+
+        assert(j);
+
+        have_access = in_group("systemd-journal") > 0;
+
+        if (!have_access) {
+                /* Let's enumerate all groups from the default ACL of
+                 * the directory, which generally should allow access
+                 * to most journal files too */
+                r = search_acl_groups(&g, "/var/log/journal/", &have_access);
+                if (r < 0)
+                        return r;
         }
 
-        /* If /var/log/journal exists, try to pring a nice notice if the user lacks access to it */
-        if (!arg_quiet && geteuid() != 0) {
-                _cleanup_strv_free_ char **g = NULL;
-                bool have_access;
-                int r;
+        if (!have_access) {
 
-                have_access = in_group("systemd-journal") > 0;
+                if (strv_isempty(g))
+                        log_notice("Hint: You are currently not seeing messages from other users and\n"
+                                   "the system. Users in the group 'systemd-journal' can see all messages.\n"
+                                   "Pass -q to turn this notice off.");
+                else {
+                        _cleanup_free_ char *s = NULL;
 
-                if (!have_access) {
-                        /* Let's enumerate all groups from the default
-                         * ACL of the directory, which generally
-                         * should allow access to most journal
-                         * files too */
-                        r = search_acl_groups(&g, "/var/log/journal/", &have_access);
+                        r = strv_extend(&g, "systemd-journal");
                         if (r < 0)
-                                return r;
+                                return log_oom();
+
+                        strv_sort(g);
+                        strv_uniq(g);
+
+                        s = strv_join(g, "', '");
+                        if (!s)
+                                return log_oom();
+
+                        log_notice("Hint: You are currently not seeing messages from other users and the system.\n"
+                                   "Users in the groups '%s' can see all messages.\n"
+                                   "Pass -q to turn this notice off.", s);
                 }
+        }
 
-                if (!have_access) {
+        return 0;
+}
+#endif
 
-                        if (strv_isempty(g))
-                                log_notice("Hint: You are currently not seeing messages from other users and the system. Users in the group 'systemd-journal' can see all messages. Pass -q to turn this notice off.");
-                        else {
-                                _cleanup_free_ char *s = NULL;
+static int access_check(sd_journal *j) {
+        uint64_t eacces = EACCES, *code;
+        Iterator it;
+        int r = 0;
 
-                                r = strv_extend(&g, "systemd-journal");
-                                if (r < 0)
-                                        return log_oom();
+        assert(j);
+        assert(j->errors);
+        assert(j->files);
 
-                                strv_sort(g);
-                                strv_uniq(g);
+        if (set_isempty(j->errors)) {
+                if (hashmap_isempty(j->files))
+                        log_info("No journal files were found.");
+                return 0;
+        }
 
-                                s = strv_join(g, "', '");
-                                if (!s)
-                                        return log_oom();
+        if (!set_contains(j->errors, &eacces)) {
+#ifdef HAVE_ACL
+                /* If /var/log/journal doesn't even exist,
+                   unprivileged users have no access at all */
+                if (access("/var/log/journal", F_OK) < 0 &&
+                    geteuid() != 0 &&
+                    in_group("systemd-journal") <= 0) {
+                        log_error("Unprivileged users can't see messages unless persistent log storage\n"
+                                  "is enabled. Users in the group 'systemd-journal' can always see messages.");
+                        return -EACCES;
+                }
 
-                                log_notice("Hint: You are currently not seeing messages from other users and the system. Users in the groups '%s' can see all messages. Pass -q to turn this notice off.", s);
-                        }
+                /* If /var/log/journal exists, try to pring a nice
+                   notice if the user lacks access to it */
+                if (!arg_quiet && geteuid() != 0) {
+                        r = access_check_var_log_journal(j);
+                        if (r < 0)
+                                return r;
                 }
-        }
 #else
-        if (geteuid() != 0 && in_group("systemd-journal") <= 0) {
-                log_error("No access to messages. Only users in the group 'systemd-journal' can see messages.");
-                return -EACCES;
-        }
+                if (geteuid() != 0 && in_group("systemd-journal") <= 0)
+                        log_error("No access to messages.\n"
+                                  "Users in the group 'systemd-journal' can see messages.");
 #endif
+                if (hashmap_isempty(j->files)) {
+                        log_error("No journal files were opened, due to insufficient permissions.");
+                        r = -EACCES;
+                }
+        }
 
-        return 0;
+        SET_FOREACH(code, j->errors, it) {
+                int err = -PTR_TO_INT(code);
+                assert(err > 0);
+                if (err != EACCES)
+                        log_warning("Error was encountered while opening journal files: %s",
+                                    strerror(err));
+        }
+
+        log_notice("Hint: run journalctl in debug mode: SYSTEMD_LOG_LEVEL=debug journalct ...");
+
+        return r;
 }
 
 int main(int argc, char *argv[]) {
@@ -987,10 +1035,6 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
-        r = access_check();
-        if (r < 0)
-                return EXIT_FAILURE;
-
         if (arg_directory)
                 r = sd_journal_open_directory(&j, arg_directory, 0);
         else
@@ -1000,6 +1044,10 @@ int main(int argc, char *argv[]) {
                 return EXIT_FAILURE;
         }
 
+        r = access_check(j);
+        if (r < 0)
+                return EXIT_FAILURE;
+
         if (arg_action == ACTION_VERIFY) {
                 r = verify(j);
                 goto finish;
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index ef4b9b2242..c62ad811dc 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -49,6 +49,15 @@
 
 #define DEFAULT_DATA_THRESHOLD (64*1024)
 
+/* We return an error here only if we didn't manage to
+   memorize the real error. */
+static int set_put_error(Set* errors, int r) {
+        if (r >= 0)
+                return r;
+
+        return set_put(errors, INT_TO_PTR(r));
+}
+
 static void detach_location(sd_journal *j) {
         Iterator i;
         JournalFile *f;
@@ -1239,7 +1248,7 @@ static int add_file(sd_journal *j, const char *prefix, const char *filename) {
 
         if (hashmap_size(j->files) >= JOURNAL_FILES_MAX) {
                 log_debug("Too many open journal files, not adding %s, ignoring.", path);
-                return 0;
+                return set_put_error(j->errors, -ETOOMANYREFS);
         }
 
         r = journal_file_open(path, O_RDONLY, 0, false, false, NULL, j->mmap, NULL, &f);
@@ -1380,8 +1389,13 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
                 if (dirent_is_file_with_suffix(de, ".journal") ||
                     dirent_is_file_with_suffix(de, ".journal~")) {
                         r = add_file(j, m->path, de->d_name);
-                        if (r < 0)
-                                log_debug("Failed to add file %s/%s: %s", m->path, de->d_name, strerror(-r));
+                        if (r < 0) {
+                                log_debug("Failed to add file %s/%s: %s",
+                                          m->path, de->d_name, strerror(-r));
+                                r = set_put_error(j->errors, r);
+                                if (r < 0)
+                                        return r;
+                        }
                 }
         }
 
@@ -1454,9 +1468,13 @@ static int add_root_directory(sd_journal *j, const char *p) {
                 if (dirent_is_file_with_suffix(de, ".journal") ||
                     dirent_is_file_with_suffix(de, ".journal~")) {
                         r = add_file(j, m->path, de->d_name);
-                        if (r < 0)
-                                log_debug("Failed to add file %s/%s: %s", m->path, de->d_name, strerror(-r));
-
+                        if (r < 0) {
+                                log_debug("Failed to add file %s/%s: %s",
+                                          m->path, de->d_name, strerror(-r));
+                                r = set_put_error(j->errors, r);
+                                if (r < 0)
+                                        return r;
+                        }
                 } else if ((de->d_type == DT_DIR || de->d_type == DT_LNK || de->d_type == DT_UNKNOWN) &&
                            sd_id128_from_string(de->d_name, &id) >= 0) {
 
@@ -1495,7 +1513,7 @@ static int remove_directory(sd_journal *j, Directory *d) {
 }
 
 static int add_search_paths(sd_journal *j) {
-
+        int r;
         const char search_paths[] =
                 "/run/log/journal\0"
                 "/var/log/journal\0";
@@ -1506,8 +1524,11 @@ static int add_search_paths(sd_journal *j) {
         /* We ignore most errors here, since the idea is to only open
          * what's actually accessible, and ignore the rest. */
 
-        NULSTR_FOREACH(p, search_paths)
-                add_root_directory(j, p);
+        NULSTR_FOREACH(p, search_paths) {
+                r = add_root_directory(j, p);
+                if (r < 0)
+                        return set_put_error(j->errors, r);
+        }
 
         return 0;
 }
@@ -1550,7 +1571,8 @@ static sd_journal *journal_new(int flags, const char *path) {
         j->files = hashmap_new(string_hash_func, string_compare_func);
         j->directories_by_path = hashmap_new(string_hash_func, string_compare_func);
         j->mmap = mmap_cache_new();
-        if (!j->files || !j->directories_by_path || !j->mmap)
+        j->errors = set_new(trivial_hash_func, trivial_compare_func);
+        if (!j->files || !j->directories_by_path || !j->mmap || !j->errors)
                 goto fail;
 
         return j;
@@ -1607,8 +1629,10 @@ _public_ int sd_journal_open_directory(sd_journal **ret, const char *path, int f
                 return -ENOMEM;
 
         r = add_root_directory(j, path);
-        if (r < 0)
+        if (r < 0) {
+                set_put_error(j->errors, r);
                 goto fail;
+        }
 
         *ret = j;
         return 0;
@@ -1650,6 +1674,7 @@ _public_ void sd_journal_close(sd_journal *j) {
 
         free(j->path);
         free(j->unique_field);
+        set_free(j->errors);
         free(j);
 }
 
@@ -1968,8 +1993,11 @@ static void process_inotify_event(sd_journal *j, struct inotify_event *e) {
 
                         if (e->mask & (IN_CREATE|IN_MOVED_TO|IN_MODIFY|IN_ATTRIB)) {
                                 r = add_file(j, d->path, e->name);
-                                if (r < 0)
-                                        log_debug("Failed to add file %s/%s: %s", d->path, e->name, strerror(-r));
+                                if (r < 0) {
+                                        log_debug("Failed to add file %s/%s: %s",
+                                                  d->path, e->name, strerror(-r));
+                                        set_put_error(j->errors, r);
+                                }
 
                         } else if (e->mask & (IN_DELETE|IN_MOVED_FROM|IN_UNMOUNT)) {