src/lib/module-dir.c

/* Copyright (c) 2003-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "str.h"
#include "sort.h"
#include "module-dir.h"

#ifdef HAVE_MODULES

#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>
#include <dlfcn.h>

#ifndef RTLD_GLOBAL
#  define RTLD_GLOBAL 0
#endif

#ifndef RTLD_NOW
#  define RTLD_NOW 0
#endif

static const char *module_name_drop_suffix(const char *name);

void *module_get_symbol_quiet(struct module *module, const char *symbol)
{
    /* clear out old errors */
    (void)dlerror();

    return dlsym(module->handle, symbol);
}

void *module_get_symbol(struct module *module, const char *symbol)
{
    const char *error;
    void *ret;

    ret = module_get_symbol_quiet(module, symbol);
    if (ret == NULL) {
        error = dlerror();
        if (error != NULL) {
            i_error("module %s: dlsym(%s) failed: %s",
                module->path, symbol, error);
            ret = NULL;
        }
    }
    return ret;
}

static void *get_symbol(struct module *module, const char *symbol, bool quiet)
{
    if (quiet)
        return module_get_symbol_quiet(module, symbol);

    return module_get_symbol(module, symbol);
}

static void module_free(struct module *module)
{
    if (module->deinit != NULL && module->initialized)
        module->deinit();
    /* dlclose()ing removes all symbols from valgrind's visibility.
       if GDB environment is set, don't actually unload the module
       (the GDB environment is used elsewhere too) */
    if (getenv("GDB") == NULL) {
        if (dlclose(module->handle) != 0)
            i_error("dlclose(%s) failed: %m", module->path);
    }
    i_free(module->path);
    i_free(module->name);
    i_free(module);
}

static bool
module_check_wrong_binary_dependency(const struct module_dir_load_settings *set,
                     struct module *module, const char **error_r)
{
    const char *symbol_name, *binary_dep, *const *names;
    string_t *errstr;

    if (set->binary_name == NULL)
        return TRUE;

    symbol_name = t_strconcat(module->name, "_binary_dependency", NULL);
    binary_dep = dlsym(module->handle, symbol_name);
    if (binary_dep == NULL)
        return TRUE;

    names = t_strsplit(binary_dep, " ");
    if (str_array_find(names, set->binary_name))
        return TRUE;

    errstr = t_str_new(128);
    str_printfa(errstr, "Can't load plugin %s: "
            "Plugin is intended to be used only by ", module->name);
    if (names[1] == NULL)
        str_printfa(errstr, "%s binary", binary_dep);
    else
        str_printfa(errstr, "binaries: %s", binary_dep);
    str_printfa(errstr, " (we're %s)", set->binary_name);
    *error_r = str_c(errstr);
    return FALSE;
}

static bool
module_check_missing_plugin_dependencies(const struct module_dir_load_settings *set,
                     struct module *module,
                     struct module *all_modules,
                     const char **error_r)
{
    const char **deps;
    struct module *m;
    string_t *errmsg;
    size_t len;

    deps = dlsym(module->handle,
             t_strconcat(module->name, "_dependencies", NULL));
    if (deps == NULL)
        return TRUE;

    for (; *deps != NULL; deps++) {
        len = strlen(*deps);
        for (m = all_modules; m != NULL; m = m->next) {
            if (strncmp(m->name, *deps, len) == 0 &&
                (m->name[len] == '\0' ||
                 strcmp(m->name+len, "_plugin") == 0))
                break;
        }
        if (m == NULL) {
            errmsg = t_str_new(128);
            str_printfa(errmsg, "Plugin %s must be loaded also",
                    *deps);
            if (set->setting_name != NULL) {
                str_printfa(errmsg,
                        " (you must set: %s=$%s %s)",
                        set->setting_name,
                        set->setting_name, *deps);
            }
            *error_r = str_c(errmsg);
            return FALSE;
        }
    }
    return TRUE;
}

static void *quiet_dlopen(const char *path, int flags)
{
#ifndef __OpenBSD__
    return dlopen(path, flags);
#else
    void *handle;
    int fd;

    /* OpenBSD likes to print all "undefined symbol" errors to stderr.
       Hide them by sending them to /dev/null. */
    fd = dup(STDERR_FILENO);
    if (fd == -1)
        i_fatal("dup() failed: %m");
    if (dup2(dev_null_fd, STDERR_FILENO) < 0)
        i_fatal("dup2() failed: %m");
    handle = dlopen(path, flags);
    if (dup2(fd, STDERR_FILENO) < 0)
        i_fatal("dup2() failed: %m");
    if (close(fd) < 0)
        i_error("close() failed: %m");
    return handle;
#endif
}

static bool versions_equal(const char *str1, const char *str2)
{
    while (*str1 == *str2) {
        if (*str1 == '\0' || *str1 == '(')
            return TRUE;
        str1++;
        str2++;
    }
    return FALSE;
}

static int
module_load(const char *path, const char *name,
        const struct module_dir_load_settings *set,
        struct module *all_modules,
        struct module **module_r, const char **error_r)
{
    void *handle;
    struct module *module;
    const char *const *module_version;

    *module_r = NULL;
    *error_r = NULL;

    if (set->ignore_dlopen_errors) {
        handle = quiet_dlopen(path, RTLD_GLOBAL | RTLD_NOW);
        if (handle == NULL) {
            if (set->debug) {
                i_debug("Skipping module %s, "
                    "because dlopen() failed: %s "
                    "(this is usually intentional, "
                    "so just ignore this message)",
                    name, dlerror());
            }
            return 0;
        }
    } else {
        handle = dlopen(path, RTLD_GLOBAL | RTLD_NOW);
        if (handle == NULL) {
            *error_r = t_strdup_printf("dlopen() failed: %s",
                           dlerror());
#ifdef RTLD_LAZY
            /* try to give a better error message by lazily loading
               the plugin and checking its dependencies */
            handle = dlopen(path, RTLD_LAZY);
            if (handle == NULL)
                return -1;
#else
            return -1;
#endif
        }
    }

    module = i_new(struct module, 1);
    module->path = i_strdup(path);
    module->name = i_strdup(name);
    module->handle = handle;

    module_version = set->abi_version == NULL ? NULL :
        get_symbol(module, t_strconcat(name, "_version", NULL), TRUE);
    if (module_version != NULL &&
        !versions_equal(*module_version, set->abi_version)) {
        *error_r = t_strdup_printf(
            "Module is for different ABI version %s (we have %s)",
            *module_version, set->abi_version);
        module_free(module);
        return -1;
    }

    /* get our init func */
    module->init = (void (*)(struct module *))
        get_symbol(module, t_strconcat(name, "_init", NULL),
               !set->require_init_funcs);
    module->deinit = (void (*)(void))
        get_symbol(module, t_strconcat(name, "_deinit", NULL),
               !set->require_init_funcs);

    if ((module->init == NULL || module->deinit == NULL) &&
        set->require_init_funcs) {
        *error_r = t_strdup_printf(
            "Module doesn't have %s function",
            module->init == NULL ? "init" : "deinit");
    } else if (!module_check_wrong_binary_dependency(set, module, error_r)) {
        /* failed */
    } else if (!module_check_missing_plugin_dependencies(set, module,
                                 all_modules, error_r)) {
        /* failed */
    }

    if (*error_r != NULL) {
        module->deinit = NULL;
        module_free(module);
        return -1;
    }

    if (set->debug)
        i_debug("Module loaded: %s", path);
    *module_r = module;
    return 1;
}

static int module_name_cmp(const char *const *n1, const char *const *n2)
{
    const char *s1 = *n1, *s2 = *n2;

    if (strncmp(s1, "lib", 3) == 0)
        s1 += 3;
    if (strncmp(s2, "lib", 3) == 0)
        s2 += 3;

    return strcmp(s1, s2);
}

static bool module_want_load(const struct module_dir_load_settings *set,
                 const char **names, const char *name)
{
    if (set->filter_callback != NULL) {
        if (!set->filter_callback(name, set->filter_context))
            return FALSE;
    }
    if (names == NULL)
        return TRUE;

    for (; *names != NULL; names++) {
        if (strcmp(*names, name) == 0) {
            *names = "";
            return TRUE;
        }
    }
    return FALSE;
}

static void check_duplicates(ARRAY_TYPE(const_string) *names,
                 const char *name, const char *dir)
{
    const char *const *names_p, *base_name, *tmp;
    unsigned int i, count;

    base_name = module_file_get_name(name);
    names_p = array_get(names, &count);
    for (i = 0; i < count; i++) {
        tmp = module_file_get_name(names_p[i]);

        if (strcmp(tmp, base_name) == 0)
            i_fatal("Multiple files for module %s: %s/%s, %s/%s",
                base_name, dir, name, dir, names_p[i]);
    }
}

struct module *module_dir_find(struct module *modules, const char *name)
{
    struct module *module;
    size_t len = strlen(name);

    for (module = modules; module != NULL; module = module->next) {
        if (strncmp(module->name, name, len) == 0) {
            if (module->name[len] == '\0' ||
                strcmp(module->name + len, "_plugin") == 0)
                return module;
        }
    }
    return NULL;
}

static bool module_is_loaded(struct module *modules, const char *name)
{
    return module_dir_find(modules, name) != NULL;
}

static void module_names_fix(const char **module_names)
{
    unsigned int i, j;

    if (module_names[0] == NULL)
        return;

    /* allow giving the module names also in non-base form.
       convert them in here. */
    for (i = 0; module_names[i] != NULL; i++)
        module_names[i] = module_file_get_name(module_names[i]);

    /* @UNSAFE: drop duplicates */
    i_qsort(module_names, i, sizeof(*module_names), i_strcmp_p);
    for (i = j = 1; module_names[i] != NULL; i++) {
        if (strcmp(module_names[i-1], module_names[i]) != 0)
            module_names[j++] = module_names[i];
    }
    module_names[j] = NULL;
}

static bool
module_dir_is_all_loaded(struct module *old_modules, const char **module_names)
{
    unsigned int i;

    for (i = 0; module_names[i] != NULL; i++) {
        if (!module_is_loaded(old_modules, module_names[i]))
            return FALSE;
    }
    return TRUE;
}

static int
module_dir_load_real(struct module **_modules,
             const char *dir, const char **module_names,
             const struct module_dir_load_settings *set,
             char **error_r)
{
    DIR *dirp;
    struct dirent *d;
    const char *name, *p, *error, *const *names_p;
    struct module *modules, *module, **module_pos, *old_modules = *_modules;
    unsigned int i, count;
    ARRAY_TYPE(const_string) names;
    pool_t pool;
    int ret;

    *error_r = NULL;

    if (module_names != NULL) {
        if (module_dir_is_all_loaded(old_modules, module_names))
            return 0;
    }

    if (set->debug)
        i_debug("Loading modules from directory: %s", dir);

    dirp = opendir(dir);
    if (dirp == NULL) {
        *error_r = i_strdup_printf("opendir(%s) failed: %m", dir);
        if (module_names != NULL) {
            /* we were given a list of modules to load.
               we can't fail. */
            return -1;
        }
        return errno == ENOENT ? 0 : -1;
    }

    pool = pool_alloconly_create("module loader", 4096);
    p_array_init(&names, pool, 32);

    modules = NULL;
    for (errno = 0; (d = readdir(dirp)) != NULL; errno = 0) {
        name = d->d_name;

        if (name[0] == '.')
            continue;

        p = strstr(name, MODULE_SUFFIX);
        if (p == NULL || strlen(p) != 3)
            continue;

        T_BEGIN {
            check_duplicates(&names, name, dir);
        } T_END;

        name = p_strdup(pool, d->d_name);
        array_append(&names, &name, 1);
    }
    if (errno != 0)
        *error_r = i_strdup_printf("readdir(%s) failed: %m", dir);
    if (closedir(dirp) < 0 && *error_r == NULL)
        *error_r = i_strdup_printf("closedir(%s) failed: %m", dir);
    if (*error_r != NULL) {
        pool_unref(&pool);
        return -1;
    }

    array_sort(&names, module_name_cmp);
    names_p = array_get(&names, &count);

    modules = old_modules;
    module_pos = &modules;
    while (*module_pos != NULL)
        module_pos = &(*module_pos)->next;
    for (i = 0; i < count; i++) T_BEGIN {
        const char *path, *stripped_name, *suffixless_name;

        name = names_p[i];
        stripped_name = module_file_get_name(name);
        suffixless_name = module_name_drop_suffix(stripped_name);
        if (!module_want_load(set, module_names, suffixless_name) ||
            module_is_loaded(old_modules, suffixless_name))
            module = NULL;
        else {
            path = t_strconcat(dir, "/", name, NULL);
            ret = module_load(path, stripped_name, set, modules, &module, &error);
            if (ret >= 0)
                ;
            else if (module_names != NULL) {
                *error_r = i_strdup_printf("Couldn't load required plugin %s: %s",
                               path, error);
                i = count;
            } else {
                i_error("Couldn't load plugin %s: %s", path, error);
            }
        }

        if (module != NULL) {
            *module_pos = module;
            module_pos = &module->next;
        }
    } T_END;
    pool_unref(&pool);

    if (module_names != NULL && *error_r == NULL && !set->ignore_missing) {
        /* make sure all modules were found */
        for (; *module_names != NULL; module_names++) {
            if (**module_names != '\0') {
                *error_r = i_strdup_printf("Plugin '%s' not found from directory %s",
                    *module_names, dir);
                break;
            }
        }
    }
    *_modules = modules;
    return *error_r != NULL ? -1 : 0;
}

int module_dir_try_load_missing(struct module **modules,
                const char *dir, const char *module_names,
                const struct module_dir_load_settings *set,
                const char **error_r)
{
    char *error = NULL;
    int ret;

    T_BEGIN {
        const char **arr = NULL;

        if (module_names != NULL) {
            arr = t_strsplit_spaces(module_names, ", ");
            module_names_fix(arr);
        }

        ret = module_dir_load_real(modules, dir, arr, set, &error);
    } T_END;
    *error_r = t_strdup(error);
    i_free(error);
    return ret;
}

struct module *
module_dir_load_missing(struct module *old_modules,
            const char *dir, const char *module_names,
            const struct module_dir_load_settings *set)
{
    struct module *new_modules = old_modules;
    const char *error;

    if (module_dir_try_load_missing(&new_modules, dir, module_names,
                    set, &error) < 0) {
        if (module_names != NULL)
            i_fatal("%s", error);
        else
            i_error("%s", error);
    }
    return new_modules;
}

void module_dir_init(struct module *modules)
{
    struct module *module;

    for (module = modules; module != NULL; module = module->next) {
        if (!module->initialized) {
            module->initialized = TRUE;
            if (module->init != NULL) T_BEGIN {
                module->init(module);
            } T_END;
        }
    }
}

void module_dir_deinit(struct module *modules)
{
    struct module *module, **rev;
    unsigned int i, count = 0;

    for (module = modules; module != NULL; module = module->next) {
        if (module->deinit != NULL && module->initialized)
            count++;
    }

    if (count == 0)
        return;

    /* @UNSAFE: deinitialize in reverse order */
    T_BEGIN {
        rev = t_new(struct module *, count);
        for (i = 0, module = modules; i < count; ) {
            if (module->deinit != NULL && module->initialized) {
                rev[count-i-1] = module;
                i++;
            }
            module = module->next;
        }

        for (i = 0; i < count; i++) {
            module = rev[i];

            module->deinit();
            module->initialized = FALSE;
        }
    } T_END;
}

void module_dir_unload(struct module **modules)
{
    struct module *module, *next;

    /* Call all modules' deinit() first, so that they may still call each
       others' functions. */
    module_dir_deinit(*modules);

    for (module = *modules; module != NULL; module = next) {
        next = module->next;
        module_free(module);
    }

    *modules = NULL;
}

#else

#ifndef MODULE_SUFFIX
#  define MODULE_SUFFIX ".so" /* just to avoid build failure */
#endif

struct module *
module_dir_load_missing(struct module *old_modules ATTR_UNUSED,
            const char *dir ATTR_UNUSED,
            const char *module_names,
            const struct module_dir_load_settings *set ATTR_UNUSED)
{
#define NO_SUPPORT_ERRSTR "Dynamically loadable module support not built in"
    if (module_names == NULL)
        i_error(NO_SUPPORT_ERRSTR);
    else {
        i_fatal(NO_SUPPORT_ERRSTR", can't load plugins: %s",
            module_names);
    }
    return NULL;
}

void module_dir_init(struct module *modules ATTR_UNUSED)
{
}

void module_dir_deinit(struct module *modules ATTR_UNUSED)
{
}

void module_dir_unload(struct module **modules ATTR_UNUSED)
{
}

struct module *module_dir_find(struct module *modules ATTR_UNUSED,
                   const char *name ATTR_UNUSED)
{
    return NULL;
}

void *module_get_symbol(struct module *module ATTR_UNUSED,
            const char *symbol ATTR_UNUSED)
{
    return NULL;
}

void *module_get_symbol_quiet(struct module *module ATTR_UNUSED,
                  const char *symbol ATTR_UNUSED)
{
    return NULL;
}

#endif

struct module *module_dir_load(const char *dir, const char *module_names,
                   const struct module_dir_load_settings *set)
{
    return module_dir_load_missing(NULL, dir, module_names, set);
}

const char *module_file_get_name(const char *fname)
{
    const char *p;

    /* [lib][nn_]name(.so) */
    if (strncmp(fname, "lib", 3) == 0)
        fname += 3;

    for (p = fname; *p != '\0'; p++) {
        if (*p < '0' || *p > '9')
            break;
    }
    if (*p == '_')
        fname = p + 1;

    p = strstr(fname, MODULE_SUFFIX);
    if (p == NULL)
        return fname;

    return t_strdup_until(fname, p);
}

static const char *module_name_drop_suffix(const char *name)
{
    size_t len;

    len = strlen(name);
    if (len > 7 && strcmp(name + len - 7, "_plugin") == 0)
        name = t_strndup(name, len - 7);
    return name;
}

const char *module_get_plugin_name(struct module *module)
{
    return module_name_drop_suffix(module->name);
}