qga: add guest-set-user-password command

Add a new 'guest-set-user-password' command for changing the password
of guest OS user accounts. This command is needed to enable OpenStack
to support its API for changing the admin password of guests running
on KVM/QEMU. It is not practical to provide a command at the QEMU
level explicitly targetting administrator account password change
only, since different guest OS have different names for the admin
account. While UNIX systems use 'root', Windows systems typically
use 'Administrator' and even that can be renamed. Higher level apps
like OpenStack have the ability to figure out the correct admin
account name since they have info that QEMU/libvirt do not.

The command accepts either the clear text password string, encoded
in base64 to make it 8-bit safe in JSON:

$ echo -n "123456" | base64
MTIzNDU2
$ virsh -c qemu:///system  qemu-agent-command f21x86_64 \
   '{ "execute": "guest-set-user-password",
      "arguments": { "crypted": false,
                     "username": "root",
                     "password": "MTIzNDU2" } }'
  {"return":{}}

Or a password that has already been run though a crypt(3) like
algorithm appropriate for the guest, again then base64 encoded:

$ echo -n '$6$n01A2Tau$e...snip...DfMOP7of9AJ1I8q0' | base64
JDYkb...snip...YT2Ey
$ virsh -c qemu:///system  qemu-agent-command f21x86_64 \
   '{ "execute": "guest-set-user-password",
      "arguments": { "crypted": true,
                     "username": "root",
                     "password": "JDYkb...snip...YT2Ey" } }'

NB windows support is desirable, but not implemented in this
patch.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index f6f3e3c..57409d0 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -1875,6 +1875,108 @@ int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList *vcpus, Error **errp)
     return processed;
 }
 
+void qmp_guest_set_user_password(const char *username,
+                                 const char *password,
+                                 bool crypted,
+                                 Error **errp)
+{
+    Error *local_err = NULL;
+    char *passwd_path = NULL;
+    pid_t pid;
+    int status;
+    int datafd[2] = { -1, -1 };
+    char *rawpasswddata = NULL;
+    size_t rawpasswdlen;
+    char *chpasswddata = NULL;
+    size_t chpasswdlen;
+
+    rawpasswddata = (char *)g_base64_decode(password, &rawpasswdlen);
+    rawpasswddata = g_renew(char, rawpasswddata, rawpasswdlen + 1);
+    rawpasswddata[rawpasswdlen] = '\0';
+
+    if (strchr(rawpasswddata, '\n')) {
+        error_setg(errp, "forbidden characters in raw password");
+        goto out;
+    }
+
+    if (strchr(username, '\n') ||
+        strchr(username, ':')) {
+        error_setg(errp, "forbidden characters in username");
+        goto out;
+    }
+
+    chpasswddata = g_strdup_printf("%s:%s\n", username, rawpasswddata);
+    chpasswdlen = strlen(chpasswddata);
+
+    passwd_path = g_find_program_in_path("chpasswd");
+
+    if (!passwd_path) {
+        error_setg(errp, "cannot find 'passwd' program in PATH");
+        goto out;
+    }
+
+    if (pipe(datafd) < 0) {
+        error_setg(errp, "cannot create pipe FDs");
+        goto out;
+    }
+
+    pid = fork();
+    if (pid == 0) {
+        close(datafd[1]);
+        /* child */
+        setsid();
+        dup2(datafd[0], 0);
+        reopen_fd_to_null(1);
+        reopen_fd_to_null(2);
+
+        if (crypted) {
+            execle(passwd_path, "chpasswd", "-e", NULL, environ);
+        } else {
+            execle(passwd_path, "chpasswd", NULL, environ);
+        }
+        _exit(EXIT_FAILURE);
+    } else if (pid < 0) {
+        error_setg_errno(errp, errno, "failed to create child process");
+        goto out;
+    }
+    close(datafd[0]);
+    datafd[0] = -1;
+
+    if (qemu_write_full(datafd[1], chpasswddata, chpasswdlen) != chpasswdlen) {
+        error_setg_errno(errp, errno, "cannot write new account password");
+        goto out;
+    }
+    close(datafd[1]);
+    datafd[1] = -1;
+
+    ga_wait_child(pid, &status, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto out;
+    }
+
+    if (!WIFEXITED(status)) {
+        error_setg(errp, "child process has terminated abnormally");
+        goto out;
+    }
+
+    if (WEXITSTATUS(status)) {
+        error_setg(errp, "child process has failed to set user password");
+        goto out;
+    }
+
+out:
+    g_free(chpasswddata);
+    g_free(rawpasswddata);
+    g_free(passwd_path);
+    if (datafd[0] != -1) {
+        close(datafd[0]);
+    }
+    if (datafd[1] != -1) {
+        close(datafd[1]);
+    }
+}
+
 #else /* defined(__linux__) */
 
 void qmp_guest_suspend_disk(Error **errp)
@@ -1910,6 +2012,14 @@ int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList *vcpus, Error **errp)
     return -1;
 }
 
+void qmp_guest_set_user_password(const char *username,
+                                 const char *password,
+                                 bool crypted,
+                                 Error **errp)
+{
+    error_set(errp, QERR_UNSUPPORTED);
+}
+
 #endif
 
 #if !defined(CONFIG_FSFREEZE)