qga: add ssh-{add,remove}-authorized-keys

Add new commands to add and remove SSH public keys from
~/.ssh/authorized_keys.

I took a different approach for testing, including the unit tests right
with the code. I wanted to overwrite the function to get the user
details, I couldn't easily do that over QMP. Furthermore, I prefer
having unit tests very close to the code, and unit files that are domain
specific (commands-posix is too crowded already). FWIW, that
coding/testing style is Rust-style (where tests can or should even be
part of the documentation!).

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1885332

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
*squashed in fix-ups for setting file ownership and use of QAPI
 conditionals for CONFIG_POSIX instead of stub definitions
*disable qga-ssh-test for now due to G_TEST_OPTION_ISOLATE_DIRS
 triggering leak detector in build-oss-fuzz
*fix disallowed g_assert* usage reported by checkpatch
Signed-off-by: Michael Roth <michael.roth@amd.com>

1 files changed, 407 insertions, 0 deletions

diff --git a/qga/commands-posix-ssh.c b/qga/commands-posix-ssh.c
new file mode 100644
index 0000000..f74d896
--- /dev/null
+++ b/qga/commands-posix-ssh.c
@@ -0,0 +1,407 @@
+ /*
+  * This work is licensed under the terms of the GNU GPL, version 2 or later.
+  * See the COPYING file in the top-level directory.
+  */
+#include "qemu/osdep.h"
+
+#include <glib-unix.h>
+#include <glib/gstdio.h>
+#include <locale.h>
+#include <pwd.h>
+
+#include "qapi/error.h"
+#include "qga-qapi-commands.h"
+
+#ifdef QGA_BUILD_UNIT_TEST
+static struct passwd *
+test_get_passwd_entry(const gchar *user_name, GError **error)
+{
+    struct passwd *p;
+    int ret;
+
+    if (!user_name || g_strcmp0(user_name, g_get_user_name())) {
+        g_set_error(error, G_UNIX_ERROR, 0, "Invalid user name");
+        return NULL;
+    }
+
+    p = g_new0(struct passwd, 1);
+    p->pw_dir = (char *)g_get_home_dir();
+    p->pw_uid = geteuid();
+    p->pw_gid = getegid();
+
+    ret = g_mkdir_with_parents(p->pw_dir, 0700);
+    g_assert(ret == 0);
+
+    return p;
+}
+
+#define g_unix_get_passwd_entry_qemu(username, err) \
+   test_get_passwd_entry(username, err)
+#endif
+
+static struct passwd *
+get_passwd_entry(const char *username, Error **errp)
+{
+    g_autoptr(GError) err = NULL;
+    struct passwd *p;
+
+    ERRP_GUARD();
+
+    p = g_unix_get_passwd_entry_qemu(username, &err);
+    if (p == NULL) {
+        error_setg(errp, "failed to lookup user '%s': %s",
+                   username, err->message);
+        return NULL;
+    }
+
+    return p;
+}
+
+static bool
+mkdir_for_user(const char *path, const struct passwd *p,
+               mode_t mode, Error **errp)
+{
+    ERRP_GUARD();
+
+    if (g_mkdir(path, mode) == -1) {
+        error_setg(errp, "failed to create directory '%s': %s",
+                   path, g_strerror(errno));
+        return false;
+    }
+
+    if (chown(path, p->pw_uid, p->pw_gid) == -1) {
+        error_setg(errp, "failed to set ownership of directory '%s': %s",
+                   path, g_strerror(errno));
+        return false;
+    }
+
+    if (chmod(path, mode) == -1) {
+        error_setg(errp, "failed to set permissions of directory '%s': %s",
+                   path, g_strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+static bool
+check_openssh_pub_key(const char *key, Error **errp)
+{
+    ERRP_GUARD();
+
+    /* simple sanity-check, we may want more? */
+    if (!key || key[0] == '#' || strchr(key, '\n')) {
+        error_setg(errp, "invalid OpenSSH public key: '%s'", key);
+        return false;
+    }
+
+    return true;
+}
+
+static bool
+check_openssh_pub_keys(strList *keys, size_t *nkeys, Error **errp)
+{
+    size_t n = 0;
+    strList *k;
+
+    ERRP_GUARD();
+
+    for (k = keys; k != NULL; k = k->next) {
+        if (!check_openssh_pub_key(k->value, errp)) {
+            return false;
+        }
+        n++;
+    }
+
+    if (nkeys) {
+        *nkeys = n;
+    }
+    return true;
+}
+
+static bool
+write_authkeys(const char *path, const GStrv keys,
+               const struct passwd *p, Error **errp)
+{
+    g_autofree char *contents = NULL;
+    g_autoptr(GError) err = NULL;
+
+    ERRP_GUARD();
+
+    contents = g_strjoinv("\n", keys);
+    if (!g_file_set_contents(path, contents, -1, &err)) {
+        error_setg(errp, "failed to write to '%s': %s", path, err->message);
+        return false;
+    }
+
+    if (chown(path, p->pw_uid, p->pw_gid) == -1) {
+        error_setg(errp, "failed to set ownership of directory '%s': %s",
+                   path, g_strerror(errno));
+        return false;
+    }
+
+    if (chmod(path, 0600) == -1) {
+        error_setg(errp, "failed to set permissions of '%s': %s",
+                   path, g_strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+static GStrv
+read_authkeys(const char *path, Error **errp)
+{
+    g_autoptr(GError) err = NULL;
+    g_autofree char *contents = NULL;
+
+    ERRP_GUARD();
+
+    if (!g_file_get_contents(path, &contents, NULL, &err)) {
+        error_setg(errp, "failed to read '%s': %s", path, err->message);
+        return NULL;
+    }
+
+    return g_strsplit(contents, "\n", -1);
+
+}
+
+void
+qmp_guest_ssh_add_authorized_keys(const char *username, strList *keys,
+                                  Error **errp)
+{
+    g_autofree struct passwd *p = NULL;
+    g_autofree char *ssh_path = NULL;
+    g_autofree char *authkeys_path = NULL;
+    g_auto(GStrv) authkeys = NULL;
+    strList *k;
+    size_t nkeys, nauthkeys;
+
+    ERRP_GUARD();
+
+    if (!check_openssh_pub_keys(keys, &nkeys, errp)) {
+        return;
+    }
+
+    p = get_passwd_entry(username, errp);
+    if (p == NULL) {
+        return;
+    }
+
+    ssh_path = g_build_filename(p->pw_dir, ".ssh", NULL);
+    authkeys_path = g_build_filename(ssh_path, "authorized_keys", NULL);
+
+    authkeys = read_authkeys(authkeys_path, NULL);
+    if (authkeys == NULL) {
+        if (!g_file_test(ssh_path, G_FILE_TEST_IS_DIR) &&
+            !mkdir_for_user(ssh_path, p, 0700, errp)) {
+            return;
+        }
+    }
+
+    nauthkeys = authkeys ? g_strv_length(authkeys) : 0;
+    authkeys = g_realloc_n(authkeys, nauthkeys + nkeys + 1, sizeof(char *));
+    memset(authkeys + nauthkeys, 0, (nkeys + 1) * sizeof(char *));
+
+    for (k = keys; k != NULL; k = k->next) {
+        if (g_strv_contains((const gchar * const *)authkeys, k->value)) {
+            continue;
+        }
+        authkeys[nauthkeys++] = g_strdup(k->value);
+    }
+
+    write_authkeys(authkeys_path, authkeys, p, errp);
+}
+
+void
+qmp_guest_ssh_remove_authorized_keys(const char *username, strList *keys,
+                                     Error **errp)
+{
+    g_autofree struct passwd *p = NULL;
+    g_autofree char *authkeys_path = NULL;
+    g_autofree GStrv new_keys = NULL; /* do not own the strings */
+    g_auto(GStrv) authkeys = NULL;
+    GStrv a;
+    size_t nkeys = 0;
+
+    ERRP_GUARD();
+
+    if (!check_openssh_pub_keys(keys, NULL, errp)) {
+        return;
+    }
+
+    p = get_passwd_entry(username, errp);
+    if (p == NULL) {
+        return;
+    }
+
+    authkeys_path = g_build_filename(p->pw_dir, ".ssh",
+                                     "authorized_keys", NULL);
+    if (!g_file_test(authkeys_path, G_FILE_TEST_EXISTS)) {
+        return;
+    }
+    authkeys = read_authkeys(authkeys_path, errp);
+    if (authkeys == NULL) {
+        return;
+    }
+
+    new_keys = g_new0(char *, g_strv_length(authkeys) + 1);
+    for (a = authkeys; *a != NULL; a++) {
+        strList *k;
+
+        for (k = keys; k != NULL; k = k->next) {
+            if (g_str_equal(k->value, *a)) {
+                break;
+            }
+        }
+        if (k != NULL) {
+            continue;
+        }
+
+        new_keys[nkeys++] = *a;
+    }
+
+    write_authkeys(authkeys_path, new_keys, p, errp);
+}
+
+
+#ifdef QGA_BUILD_UNIT_TEST
+#if GLIB_CHECK_VERSION(2, 60, 0)
+static const strList test_key2 = {
+    .value = (char *)"algo key2 comments"
+};
+
+static const strList test_key1_2 = {
+    .value = (char *)"algo key1 comments",
+    .next = (strList *)&test_key2,
+};
+
+static char *
+test_get_authorized_keys_path(void)
+{
+    return g_build_filename(g_get_home_dir(), ".ssh", "authorized_keys", NULL);
+}
+
+static void
+test_authorized_keys_set(const char *contents)
+{
+    g_autoptr(GError) err = NULL;
+    g_autofree char *path = NULL;
+    int ret;
+
+    path = g_build_filename(g_get_home_dir(), ".ssh", NULL);
+    ret = g_mkdir_with_parents(path, 0700);
+    g_assert(ret == 0);
+    g_free(path);
+
+    path = test_get_authorized_keys_path();
+    g_file_set_contents(path, contents, -1, &err);
+    g_assert(err == NULL);
+}
+
+static void
+test_authorized_keys_equal(const char *expected)
+{
+    g_autoptr(GError) err = NULL;
+    g_autofree char *path = NULL;
+    g_autofree char *contents = NULL;
+
+    path = test_get_authorized_keys_path();
+    g_file_get_contents(path, &contents, NULL, &err);
+    g_assert(err == NULL);
+
+    g_assert(g_strcmp0(contents, expected) == 0);
+}
+
+static void
+test_invalid_user(void)
+{
+    Error *err = NULL;
+
+    qmp_guest_ssh_add_authorized_keys("", NULL, &err);
+    error_free_or_abort(&err);
+
+    qmp_guest_ssh_remove_authorized_keys("", NULL, &err);
+    error_free_or_abort(&err);
+}
+
+static void
+test_invalid_key(void)
+{
+    strList key = {
+        .value = (char *)"not a valid\nkey"
+    };
+    Error *err = NULL;
+
+    qmp_guest_ssh_add_authorized_keys(g_get_user_name(), &key, &err);
+    error_free_or_abort(&err);
+
+    qmp_guest_ssh_remove_authorized_keys(g_get_user_name(), &key, &err);
+    error_free_or_abort(&err);
+}
+
+static void
+test_add_keys(void)
+{
+    Error *err = NULL;
+
+    qmp_guest_ssh_add_authorized_keys(g_get_user_name(),
+                                      (strList *)&test_key2, &err);
+    g_assert(err == NULL);
+
+    test_authorized_keys_equal("algo key2 comments");
+
+    qmp_guest_ssh_add_authorized_keys(g_get_user_name(),
+                                      (strList *)&test_key1_2, &err);
+    g_assert(err == NULL);
+
+    /*  key2 came first, and should'nt be duplicated */
+    test_authorized_keys_equal("algo key2 comments\n"
+                               "algo key1 comments");
+}
+
+static void
+test_remove_keys(void)
+{
+    Error *err = NULL;
+    static const char *authkeys =
+        "algo key1 comments\n"
+        /* originally duplicated */
+        "algo key1 comments\n"
+        "# a commented line\n"
+        "algo some-key another\n";
+
+    test_authorized_keys_set(authkeys);
+    qmp_guest_ssh_remove_authorized_keys(g_get_user_name(),
+                                         (strList *)&test_key2, &err);
+    g_assert(err == NULL);
+    test_authorized_keys_equal(authkeys);
+
+    qmp_guest_ssh_remove_authorized_keys(g_get_user_name(),
+                                         (strList *)&test_key1_2, &err);
+    g_assert(err == NULL);
+    test_authorized_keys_equal("# a commented line\n"
+                               "algo some-key another\n");
+}
+
+int main(int argc, char *argv[])
+{
+    setlocale(LC_ALL, "");
+
+    g_test_init(&argc, &argv, G_TEST_OPTION_ISOLATE_DIRS, NULL);
+
+    g_test_add_func("/qga/ssh/invalid_user", test_invalid_user);
+    g_test_add_func("/qga/ssh/invalid_key", test_invalid_key);
+    g_test_add_func("/qga/ssh/add_keys", test_add_keys);
+    g_test_add_func("/qga/ssh/remove_keys", test_remove_keys);
+
+    return g_test_run();
+}
+#else
+int main(int argc, char *argv[])
+{
+    g_test_message("test skipped, needs glib >= 2.60");
+    return 0;
+}
+#endif /* GLIB_2_60 */
+#endif /* BUILD_UNIT_TEST */