journal: implement message catalog

The message catalog can be used to attach short help texts to log lines,
keyed by their MESSAGE_ID= fields. This is useful to help the
administrator understand the context and cause of a message, find
possible solutions and find further related documentation.

Since this is keyed off MESSAGE_ID= this will only work for native
journal messages.

The message catalog supports i18n, and is useful to augment english
language system messages with explanations in the local language.

This commit only includes short explanatory messages for a few example
message IDs, we'll add more complete documentation for the relevant
systemd messages later on.

6 files changed, 759 insertions, 3 deletions

diff --git a/src/journal/catalog.c b/src/journal/catalog.c
new file mode 100644
index 0000000000..7be0d20f42
--- /dev/null
+++ b/src/journal/catalog.c
@@ -0,0 +1,584 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 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 <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <locale.h>
+
+#include "util.h"
+#include "log.h"
+#include "sparse-endian.h"
+#include "sd-id128.h"
+#include "hashmap.h"
+#include "strv.h"
+#include "strbuf.h"
+#include "conf-files.h"
+#include "mkdir.h"
+#include "catalog.h"
+
+static const char * const conf_file_dirs[] = {
+        "/usr/local/lib/systemd/catalog/",
+        "/usr/lib/systemd/catalog/",
+        NULL
+};
+
+#define CATALOG_SIGNATURE (uint8_t[]) { 'R', 'H', 'H', 'H', 'K', 'S', 'L', 'P' }
+
+typedef struct CatalogHeader {
+        uint8_t signature[8];  /* "RHHHKSLP" */
+        le32_t compatible_flags;
+        le32_t incompatible_flags;
+        le32_t header_size;
+        le32_t n_items;
+} CatalogHeader;
+
+typedef struct CatalogItem {
+        sd_id128_t id;
+        char language[32];
+        le32_t offset;
+} CatalogItem;
+
+static unsigned catalog_hash_func(const void *p) {
+        const CatalogItem *i = p;
+
+        assert_cc(sizeof(unsigned) == sizeof(uint8_t)*4);
+
+        return (((unsigned) i->id.bytes[0] << 24) |
+                ((unsigned) i->id.bytes[1] << 16) |
+                ((unsigned) i->id.bytes[2] << 8) |
+                ((unsigned) i->id.bytes[3])) ^
+               (((unsigned) i->id.bytes[4] << 24) |
+                ((unsigned) i->id.bytes[5] << 16) |
+                ((unsigned) i->id.bytes[6] << 8) |
+                ((unsigned) i->id.bytes[7])) ^
+               (((unsigned) i->id.bytes[8] << 24) |
+                ((unsigned) i->id.bytes[9] << 16) |
+                ((unsigned) i->id.bytes[10] << 8) |
+                ((unsigned) i->id.bytes[11])) ^
+               (((unsigned) i->id.bytes[12] << 24) |
+                ((unsigned) i->id.bytes[13] << 16) |
+                ((unsigned) i->id.bytes[14] << 8) |
+                ((unsigned) i->id.bytes[15])) ^
+                string_hash_func(i->language);
+}
+
+static int catalog_compare_func(const void *a, const void *b) {
+        const CatalogItem *i = a, *j = b;
+        unsigned k;
+
+        for (k = 0; k < ELEMENTSOF(j->id.bytes); k++) {
+                 if (i->id.bytes[k] < j->id.bytes[k])
+                        return -1;
+                 if (i->id.bytes[k] > j->id.bytes[k])
+                        return 1;
+        }
+
+        return strncmp(i->language, j->language, sizeof(i->language));
+}
+
+static int finish_item(
+                Hashmap *h,
+                struct strbuf *sb,
+                sd_id128_t id,
+                const char *language,
+                const char *payload) {
+
+        ssize_t offset;
+        CatalogItem *i;
+        int r;
+
+        assert(h);
+        assert(sb);
+        assert(payload);
+
+        offset = strbuf_add_string(sb, payload, strlen(payload));
+        if (offset < 0)
+                return log_oom();
+
+        if (offset > 0xFFFFFFFF) {
+                log_error("Too many catalog entries.");
+                return -E2BIG;
+        }
+
+        i = new0(CatalogItem, 1);
+        if (!i)
+                return log_oom();
+
+        i->id = id;
+        strncpy(i->language, language, sizeof(i->language));
+        i->offset = htole32((uint32_t) offset);
+
+        r = hashmap_put(h, i, i);
+        if (r == EEXIST) {
+                log_warning("Duplicate entry for " SD_ID128_FORMAT_STR ".%s, ignoring.", SD_ID128_FORMAT_VAL(id), language ? language : "C");
+                free(i);
+                return 0;
+        }
+
+        return 0;
+}
+
+static int import_file(Hashmap *h, struct strbuf *sb, const char *path) {
+        _cleanup_fclose_ FILE *f = NULL;
+        _cleanup_free_ char *payload = NULL;
+        unsigned n = 0;
+        sd_id128_t id;
+        char language[32];
+        bool got_id = false, empty_line = true;
+        int r;
+
+        assert(h);
+        assert(sb);
+        assert(path);
+
+        f = fopen(path, "re");
+        if (!f) {
+                log_error("Failed to open file %s: %m", path);
+                return -errno;
+        }
+
+        for (;;) {
+                char line[LINE_MAX];
+                size_t a, b, c;
+                char *t;
+
+                if (!fgets(line, sizeof(line), f)) {
+                        if (feof(f))
+                                break;
+
+                        log_error("Failed to read file %s: %m", path);
+                        return -errno;
+                }
+
+                n++;
+
+                truncate_nl(line);
+
+                if (line[0] == 0) {
+                        empty_line = true;
+                        continue;
+                }
+
+                if (strchr(COMMENTS, line[0]))
+                        continue;
+
+                if (empty_line &&
+                    strlen(line) >= 2+1+32 &&
+                    line[0] == '-' &&
+                    line[1] == '-' &&
+                    line[2] == ' ' &&
+                    (line[2+1+32] == ' ' || line[2+1+32] == 0)) {
+
+                        bool with_language;
+                        sd_id128_t jd;
+
+                        /* New entry */
+
+                        with_language = line[2+1+32] != 0;
+                        line[2+1+32] = 0;
+
+                        if (sd_id128_from_string(line + 2 + 1, &jd) >= 0) {
+
+                                if (got_id) {
+                                        r = finish_item(h, sb, id, language, payload);
+                                        if (r < 0)
+                                                return r;
+                                }
+
+                                if (with_language) {
+                                        t = strstrip(line + 2 + 1 + 32 + 1);
+
+                                        c = strlen(t);
+                                        if (c <= 0) {
+                                                log_error("[%s:%u] Language too short.", path, n);
+                                                return -EINVAL;
+                                        }
+                                        if (c > sizeof(language)) {
+                                                log_error("[%s:%u] language too long.", path, n);
+                                                return -EINVAL;
+                                        }
+
+                                        strncpy(language, t, sizeof(language));
+                                } else
+                                        zero(language);
+
+                                got_id = true;
+                                empty_line = false;
+                                id = jd;
+
+                                if (payload)
+                                        payload[0] = 0;
+
+                                continue;
+                        }
+                }
+
+                /* Payload */
+                if (!got_id) {
+                        log_error("[%s:%u] Got payload before ID.", path, n);
+                        return -EINVAL;
+                }
+
+                a = payload ? strlen(payload) : 0;
+                b = strlen(line);
+
+                c = a + (empty_line ? 1 : 0) + b + 1 + 1;
+                t = realloc(payload, c);
+                if (!t)
+                        return log_oom();
+
+                if (empty_line) {
+                        t[a] = '\n';
+                        memcpy(t + a + 1, line, b);
+                        t[a+b+1] = '\n';
+                        t[a+b+2] = 0;
+                } else {
+                        memcpy(t + a, line, b);
+                        t[a+b] = '\n';
+                        t[a+b+1] = 0;
+                }
+
+                payload = t;
+                empty_line = false;
+        }
+
+        if (got_id) {
+                r = finish_item(h, sb, id, language, payload);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int catalog_update(void) {
+        _cleanup_strv_free_ char **files = NULL;
+        _cleanup_fclose_ FILE *w = NULL;
+        _cleanup_free_ char *p = NULL;
+        char **f;
+        Hashmap *h;
+        struct strbuf *sb = NULL;
+        _cleanup_free_ CatalogItem *items = NULL;
+        CatalogItem *i;
+        CatalogHeader header;
+        size_t k;
+        Iterator j;
+        unsigned n;
+        int r;
+
+        h = hashmap_new(catalog_hash_func, catalog_compare_func);
+        if (!h)
+                return -ENOMEM;
+
+        sb = strbuf_new();
+        if (!sb) {
+                r = log_oom();
+                goto finish;
+        }
+
+        r = conf_files_list_strv(&files, ".catalog", (const char **) conf_file_dirs);
+        if (r < 0) {
+                log_error("Failed to get catalog files: %s", strerror(-r));
+                goto finish;
+        }
+
+        STRV_FOREACH(f, files) {
+                log_debug("reading file '%s'", *f);
+                import_file(h, sb, *f);
+        }
+
+        if (hashmap_size(h) <= 0) {
+                log_info("No items in catalog.");
+                r = 0;
+                goto finish;
+        }
+
+        strbuf_complete(sb);
+
+        items = new(CatalogItem, hashmap_size(h));
+        if (!items) {
+                r = log_oom();
+                goto finish;
+        }
+
+        n = 0;
+        HASHMAP_FOREACH(i, h, j) {
+                log_debug("Found " SD_ID128_FORMAT_STR ", language %s", SD_ID128_FORMAT_VAL(i->id), isempty(i->language) ? "C" : i->language);
+                items[n++] = *i;
+        }
+
+        assert(n == hashmap_size(h));
+        qsort(items, n, sizeof(CatalogItem), catalog_compare_func);
+
+        mkdir_p("/var/lib/systemd/catalog", 0775);
+
+        r = fopen_temporary("/var/lib/systemd/catalog/database", &w, &p);
+        if (r < 0) {
+                log_error("Failed to open database for writing: %s", strerror(-r));
+                goto finish;
+        }
+
+        zero(header);
+        memcpy(header.signature, CATALOG_SIGNATURE, sizeof(header.signature));
+        header.header_size = htole32(ALIGN_TO(sizeof(CatalogHeader), 8));
+        header.n_items = htole32(hashmap_size(h));
+
+        k = fwrite(&header, 1, sizeof(header), w);
+        if (k != sizeof(header)) {
+                log_error("Failed to write header.");
+                goto finish;
+        }
+
+        k = fwrite(items, 1, n * sizeof(CatalogItem), w);
+        if (k != n * sizeof(CatalogItem)) {
+                log_error("Failed to write database.");
+                goto finish;
+        }
+
+        k = fwrite(sb->buf, 1, sb->len, w);
+        if (k != sb->len) {
+                log_error("Failed to write strings.");
+                goto finish;
+        }
+
+        fflush(w);
+
+        if (ferror(w)) {
+                log_error("Failed to write database.");
+                goto finish;
+        }
+
+        fchmod(fileno(w), 0644);
+
+        if (rename(p, "/var/lib/systemd/catalog/database") < 0) {
+                log_error("rename() failed: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        free(p);
+        p = NULL;
+
+        r = 0;
+
+finish:
+        hashmap_free_free(h);
+
+        if (sb)
+                strbuf_cleanup(sb);
+
+        if (p)
+                unlink(p);
+
+        return r;
+}
+
+static int open_mmap(int *_fd, struct stat *_st, void **_p) {
+        const CatalogHeader *h;
+        int fd;
+        void *p;
+        struct stat st;
+
+        assert(_fd);
+        assert(_st);
+        assert(_p);
+
+        fd = open("/var/lib/systemd/catalog/database", O_RDONLY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        if (fstat(fd, &st) < 0) {
+                close_nointr_nofail(fd);
+                return -errno;
+        }
+
+        if (st.st_size < (off_t) sizeof(CatalogHeader)) {
+                close_nointr_nofail(fd);
+                return -EINVAL;
+        }
+
+        p = mmap(NULL, PAGE_ALIGN(st.st_size), PROT_READ, MAP_SHARED, fd, 0);
+        if (p == MAP_FAILED) {
+                close_nointr_nofail(fd);
+                return -errno;
+        }
+
+        h = p;
+        if (memcmp(h->signature, CATALOG_SIGNATURE, sizeof(h->signature)) != 0 ||
+            le32toh(h->header_size) < sizeof(CatalogHeader) ||
+            h->incompatible_flags != 0 ||
+            le32toh(h->n_items) <= 0 ||
+            st.st_size < (off_t) (le32toh(h->header_size) + sizeof(CatalogItem) * le32toh(h->n_items))) {
+                close_nointr_nofail(fd);
+                munmap(p, st.st_size);
+                return -EBADMSG;
+        }
+
+        *_fd = fd;
+        *_st = st;
+        *_p = p;
+
+        return 0;
+}
+
+static const char *find_id(void *p, sd_id128_t id) {
+        CatalogItem key, *f = NULL;
+        const CatalogHeader *h = p;
+        const char *loc;
+
+        zero(key);
+        key.id = id;
+
+        loc = setlocale(LC_MESSAGES, NULL);
+        if (loc && loc[0] && !streq(loc, "C") && !streq(loc, "POSIX")) {
+                strncpy(key.language, loc, sizeof(key.language));
+                key.language[strcspn(key.language, ".@")] = 0;
+
+                f = bsearch(&key, (const uint8_t*) p + le32toh(h->header_size), le32toh(h->n_items), sizeof(CatalogItem), catalog_compare_func);
+                if (!f) {
+                        char *e;
+
+                        e = strchr(key.language, '_');
+                        if (e) {
+                                *e = 0;
+                                f = bsearch(&key, (const uint8_t*) p + le32toh(h->header_size), le32toh(h->n_items), sizeof(CatalogItem), catalog_compare_func);
+                        }
+                }
+        }
+
+        if (!f) {
+                zero(key.language);
+                f = bsearch(&key, (const uint8_t*) p + le32toh(h->header_size), le32toh(h->n_items), sizeof(CatalogItem), catalog_compare_func);
+        }
+
+        if (!f)
+                return NULL;
+
+        return (const char*) p +
+                le32toh(h->header_size) +
+                le32toh(h->n_items) * sizeof(CatalogItem) +
+                le32toh(f->offset);
+}
+
+int catalog_get(sd_id128_t id, char **_text) {
+        _cleanup_close_ int fd = -1;
+        void *p = NULL;
+        struct stat st;
+        char *text = NULL;
+        int r;
+        const char *s;
+
+        assert(_text);
+
+        r = open_mmap(&fd, &st, &p);
+        if (r < 0)
+                return r;
+
+        s = find_id(p, id);
+        if (!s) {
+                r = -ENOENT;
+                goto finish;
+        }
+
+        text = strdup(s);
+        if (!text) {
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        *_text = text;
+        r = 0;
+
+finish:
+        if (p)
+                munmap(p, st.st_size);
+
+        return r;
+}
+
+static char *find_header(const char *s, const char *header) {
+
+        for (;;) {
+                const char *v, *e;
+
+                v = startswith(s, header);
+                if (v) {
+                        v += strspn(v, WHITESPACE);
+                        return strndup(v, strcspn(v, NEWLINE));
+                }
+
+                /* End of text */
+                e = strchr(s, '\n');
+                if (!e)
+                        return NULL;
+
+                /* End of header */
+                if (e == s)
+                        return NULL;
+
+                s = e + 1;
+        }
+}
+
+int catalog_list(FILE *f) {
+        _cleanup_close_ int fd = -1;
+        void *p = NULL;
+        struct stat st;
+        const CatalogHeader *h;
+        const CatalogItem *items;
+        int r;
+        unsigned n;
+        sd_id128_t last_id;
+        bool last_id_set = false;
+
+        r = open_mmap(&fd, &st, &p);
+        if (r < 0)
+                return r;
+
+        h = p;
+        items = (const CatalogItem*) ((const uint8_t*) p + le32toh(h->header_size));
+
+        for (n = 0; n < le32toh(h->n_items); n++) {
+                const char *s;
+                _cleanup_free_ char *subject = NULL, *defined_by = NULL;
+
+                if (last_id_set && sd_id128_equal(last_id, items[n].id))
+                        continue;
+
+                assert_se(s = find_id(p, items[n].id));
+
+                subject = find_header(s, "Subject:");
+                defined_by = find_header(s, "Defined-By:");
+
+                fprintf(f, SD_ID128_FORMAT_STR " %s: %s\n", SD_ID128_FORMAT_VAL(items[n].id), strna(defined_by), strna(subject));
+
+                last_id_set = true;
+                last_id = items[n].id;
+        }
+
+        munmap(p, st.st_size);
+
+        return 0;
+}
diff --git a/src/journal/catalog.h b/src/journal/catalog.h
new file mode 100644
index 0000000000..9add773c95
--- /dev/null
+++ b/src/journal/catalog.h
@@ -0,0 +1,28 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 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 "sd-id128.h"
+
+int catalog_update(void);
+int catalog_get(sd_id128_t id, char **data);
+int catalog_list(FILE *f);
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 011a11b70b..46a7be20ce 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -51,6 +51,7 @@
 #include "journal-qrcode.h"
 #include "fsprg.h"
 #include "unit-name.h"
+#include "catalog.h"
 
 #define DEFAULT_FSS_INTERVAL_USEC (15*USEC_PER_MINUTE)
 
@@ -74,6 +75,7 @@ static usec_t arg_since, arg_until;
 static bool arg_since_set = false, arg_until_set = false;
 static const char *arg_unit = NULL;
 static const char *arg_field = NULL;
+static bool arg_catalog = false;
 
 static enum {
         ACTION_SHOW,
@@ -82,6 +84,8 @@ static enum {
         ACTION_SETUP_KEYS,
         ACTION_VERIFY,
         ACTION_DISK_USAGE,
+        ACTION_LIST_CATALOG,
+        ACTION_UPDATE_CATALOG
 } arg_action = ACTION_SHOW;
 
 static int help(void) {
@@ -100,6 +104,7 @@ static int help(void) {
                "     --no-tail           Show all lines, even in follow mode\n"
                "  -o --output=STRING     Change journal output mode (short, short-monotonic,\n"
                "                         verbose, export, json, json-pretty, json-sse, cat)\n"
+               "  -x --catalog           Add message explanations where available\n"
                "  -a --all               Show all fields, including long and unprintable\n"
                "  -q --quiet             Don't show privilege warning\n"
                "     --no-pager          Do not pipe output into a pager\n"
@@ -116,6 +121,8 @@ static int help(void) {
                "     --header            Show journal header information\n"
                "     --disk-usage        Show total disk usage\n"
                "  -F --field=FIELD       List all values a certain field takes\n"
+               "     --list-catalog      Show message IDs of all entries in the message catalog\n"
+               "     --update-catalog    Update the message catalog database\n"
 #ifdef HAVE_GCRYPT
                "     --setup-keys        Generate new FSS key pair\n"
                "     --verify            Verify journal file consistency\n"
@@ -139,7 +146,9 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_VERIFY_KEY,
                 ARG_DISK_USAGE,
                 ARG_SINCE,
-                ARG_UNTIL
+                ARG_UNTIL,
+                ARG_LIST_CATALOG,
+                ARG_UPDATE_CATALOG
         };
 
         static const struct option options[] = {
@@ -168,6 +177,9 @@ static int parse_argv(int argc, char *argv[]) {
                 { "until",        required_argument, NULL, ARG_UNTIL        },
                 { "unit",         required_argument, NULL, 'u'              },
                 { "field",        required_argument, NULL, 'F'              },
+                { "catalog",      no_argument,       NULL, 'x'              },
+                { "list-catalog", no_argument,       NULL, ARG_LIST_CATALOG },
+                { "update-catalog",no_argument,      NULL, ARG_UPDATE_CATALOG },
                 { NULL,           0,                 NULL, 0                }
         };
 
@@ -176,7 +188,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "hfo:an::qmbD:p:c:u:F:", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "hfo:an::qmbD:p:c:u:F:x", options, NULL)) >= 0) {
 
                 switch (c) {
 
@@ -376,6 +388,18 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_field = optarg;
                         break;
 
+                case 'x':
+                        arg_catalog = true;
+                        break;
+
+                case ARG_LIST_CATALOG:
+                        arg_action = ACTION_LIST_CATALOG;
+                        break;
+
+                case ARG_UPDATE_CATALOG:
+                        arg_action = ACTION_UPDATE_CATALOG;
+                        break;
+
                 default:
                         log_error("Unknown option code %c", c);
                         return -EINVAL;
@@ -841,6 +865,16 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
+        if (arg_action == ACTION_LIST_CATALOG)  {
+                r = catalog_list(stdout);
+                goto finish;
+        }
+
+        if (arg_action == ACTION_UPDATE_CATALOG)  {
+                r = catalog_update();
+                goto finish;
+        }
+
         r = access_check();
         if (r < 0)
                 goto finish;
@@ -1030,7 +1064,8 @@ int main(int argc, char *argv[]) {
                         flags =
                                 arg_all * OUTPUT_SHOW_ALL |
                                 (!on_tty() || pager_have()) * OUTPUT_FULL_WIDTH |
-                                on_tty() * OUTPUT_COLOR;
+                                on_tty() * OUTPUT_COLOR |
+                                arg_catalog * OUTPUT_CATALOG;
 
                         r = output_journal(stdout, j, arg_output, 0, flags);
                         if (r < 0)
diff --git a/src/journal/libsystemd-journal.sym b/src/journal/libsystemd-journal.sym
index ad78fcc74d..d4b0c32612 100644
--- a/src/journal/libsystemd-journal.sym
+++ b/src/journal/libsystemd-journal.sym
@@ -84,4 +84,5 @@ global:
 LIBSYSTEMD_JOURNAL_196 {
 global:
         sd_journal_fd_reliable;
+        sd_journal_get_catalog;
 } LIBSYSTEMD_JOURNAL_195;
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index a346691e21..c86f1eaab1 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -38,11 +38,15 @@
 #include "compress.h"
 #include "journal-internal.h"
 #include "missing.h"
+#include "catalog.h"
+#include "replace-var.h"
 
 #define JOURNAL_FILES_MAX 1024
 
 #define JOURNAL_FILES_RECHECK_USEC (2 * USEC_PER_SEC)
 
+#define REPLACE_VAR_MAX 256
+
 static void detach_location(sd_journal *j) {
         Iterator i;
         JournalFile *f;
@@ -2389,3 +2393,59 @@ _public_ int sd_journal_reliable_fd(sd_journal *j) {
 
         return !j->on_network;
 }
+
+static char *lookup_field(const char *field, void *userdata) {
+        sd_journal *j = userdata;
+        const void *data;
+        size_t size, d;
+        int r;
+
+        assert(field);
+        assert(j);
+
+        r = sd_journal_get_data(j, field, &data, &size);
+        if (r < 0 ||
+            size > REPLACE_VAR_MAX)
+                return strdup(field);
+
+        d = strlen(field) + 1;
+
+        return strndup((const char*) data + d, size - d);
+}
+
+_public_ int sd_journal_get_catalog(sd_journal *j, char **ret) {
+        const void *data;
+        size_t size;
+        sd_id128_t id;
+        _cleanup_free_ char *text = NULL, *cid = NULL;
+        char *t;
+        int r;
+
+        if (!j)
+                return -EINVAL;
+        if (!ret)
+                return -EINVAL;
+
+        r = sd_journal_get_data(j, "MESSAGE_ID", &data, &size);
+        if (r < 0)
+                return r;
+
+        cid = strndup((const char*) data + 11, size - 11);
+        if (!cid)
+                return -ENOMEM;
+
+        r = sd_id128_from_string(cid, &id);
+        if (r < 0)
+                return r;
+
+        r = catalog_get(id, &text);
+        if (r < 0)
+                return r;
+
+        t = replace_var(text, lookup_field, j);
+        if (!t)
+                return -ENOMEM;
+
+        *ret = t;
+        return 0;
+}
diff --git a/src/journal/test-catalog.c b/src/journal/test-catalog.c
new file mode 100644
index 0000000000..cec8a11c43
--- /dev/null
+++ b/src/journal/test-catalog.c
@@ -0,0 +1,48 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 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 <locale.h>
+
+#include "util.h"
+#include "log.h"
+#include "catalog.h"
+#include "sd-messages.h"
+
+int main(int argc, char *argv[]) {
+
+        _cleanup_free_ char *text = NULL;
+
+        setlocale(LC_ALL, "de_DE.UTF-8");
+
+        log_set_max_level(LOG_DEBUG);
+
+        assert_se(catalog_update() >= 0);
+
+        assert_se(catalog_list(stdout) >= 0);
+
+        assert_se(catalog_get(SD_MESSAGE_COREDUMP, &text) >= 0);
+
+        printf(">>>%s<<<\n", text);
+
+        fflush(stdout);
+
+        return 0;
+}