--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Sun Oct 19 22:33:43 2008 +0300
@@ -0,0 +1,14 @@
+
+XMSH_PATH=/home/xmsh
+XMSH_BIN_PATH=${XMSH_PATH}/bin/xmsh
+XMSH_ETC_DIR=${XMSH_PATH}/etc
+
+CFLAGS = -Wall -DXMSH_PATH=${XMSH_PATH}
+
+all: xmsh
+
+install:
+	/bin/cp ./xmsh ${XMSH_BIN_PATH}
+	/bin/chown root:root ${XMSH_BIN_PATH}
+	/bin/chmod u+s ${XMSH_BIN_PATH}
+	/bin/cp sshd_config ${XMSH_ETC_DIR}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sshd_config	Sun Oct 19 22:33:43 2008 +0300
@@ -0,0 +1,50 @@
+
+# what port to listen on 
+Port 2828
+
+# only allow members of the xmsh-users group and certain admins
+AllowGroups xmsh-users
+
+# use system hostkeys
+HostKey /etc/ssh/ssh_host_rsa_key
+HostKey /etc/ssh/ssh_host_dsa_key
+
+# runtime options
+PidFile /home/xmsh/run/sshd.pid
+
+# cosmetic options
+Banner /home/xmsh/etc/banner
+PrintLastLog yes
+PrintMotd no
+
+# Logging
+SyslogFacility AUTH
+LogLevel INFO
+
+# force some options
+Protocol 2
+UsePrivilegeSeparation yes
+
+# Authentication:
+LoginGraceTime 120
+StrictModes yes
+
+# behave like debian does
+PasswordAuthentication yes
+PubkeyAuthentication yes
+ChallengeResponseAuthentication no
+UsePAM no
+
+# disable most features
+AcceptEnv no
+AllowTcpForwarding no
+AuthorizedKeysFile no
+IgnoreRhosts yes
+IgnoreUserKnownHosts yes
+PermitRootLogin no
+PermitTunnel no
+PermitUserEnvironment no
+X11Forwarding no
+
+# By default no subsystems are defined
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xmsh.c	Sun Oct 19 22:33:43 2008 +0300
@@ -0,0 +1,184 @@
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <stdio.h>
+#include <string.h>
+#include <err.h>
+#include <ctype.h>
+#include <pwd.h>
+#include <errno.h>
+
+#ifndef XMSH_PATH
+#error must define XMSH_PATH
+#endif
+
+#define STRINGIFY(x) XSTRINGIFY(x)
+#define XSTRINGIFY(x) #x
+
+#define USERNAME_MAX 64
+#define VMNAME_MAX 64
+
+#define USERFILE_PATH_FMT (STRINGIFY(XMSH_PATH) "/users/%s")
+#define USERFILE_PATH_MAX 64 + USERNAME_MAX
+
+#define XM_PATH "/usr/sbin/xm"
+
+/*
+ * Parse command:
+ *  xmsh <cmd>
+ *  xmsh -c <cmd>
+ */
+char *parse_command (int argc, char **argv) {
+    if (argc == 2)
+        return argv[1];
+
+    else if (argc == 3 && strcmp(argv[1], "-c") == 0)
+        return argv[2];
+    
+    // fail
+    errx(EXIT_FAILURE, "usage: ssh [-t] <dom0> (list|reboot|console)");
+}
+
+/*
+ * Validate that the given command is legal
+ */
+void validate_command (const char *command) {
+    // strcmp against whitelist of commands
+    if (0
+        ||  (strcmp(command, "list") == 0)
+        ||  (strcmp(command, "reboot") == 0)
+        ||  (strcmp(command, "console") == 0)
+    )
+        return;
+    
+    // else fail
+    err(EXIT_FAILURE, "invalid command: %s", command);
+}
+
+/*
+ * Validate that the username is sane
+ */
+void validate_username (const char *c) {
+    if (!(*c))
+        errx(EXIT_FAILURE, "username length");
+
+    for (; *c; c++) {
+        if (!isalpha(*c) && *c != '-') {
+            break;
+        }
+    }
+
+    if (*c)
+        errx(EXIT_FAILURE, "username non-alpha");
+
+}   
+
+void validate_vmname (const char *c) {
+    if (!(*c))
+        errx(EXIT_FAILURE, "vmname length");
+
+    for (; *c; c++) {
+        if (!isprint(*c) || isspace(*c)) {
+            break;
+        }
+    }
+
+    if (*c)
+        errx(EXIT_FAILURE, "vmname non-print/space");
+}
+
+/*
+ * Get the real uid's username - i.e. the user who executed this file.
+ */
+void get_username (char buf[USERNAME_MAX]) {
+    uid_t uid;
+    struct passwd *passwd;
+
+    // get the real uid
+    uid = getuid();
+    
+    // get the passwd entry
+    if ((passwd = getpwuid(uid)) == NULL)
+        err(EXIT_FAILURE, "getpwuid");
+
+    if (passwd->pw_name == NULL)
+        errx(EXIT_FAILURE, "passwd->pw_name");
+
+    // fail too-long usernames
+    if (strlen(passwd->pw_name) >= USERNAME_MAX)
+        errx(EXIT_FAILURE, "strlen(passwd->pw_name) >= USERNAME_MAX");
+    
+    // copy the username to buf
+    strncpy(buf, passwd->pw_name, USERNAME_MAX);
+
+    // force zero-terminate
+    buf[USERNAME_MAX - 1] = '\0';
+    
+    // sanity-check username to be all-alpha
+    validate_username(buf);
+}
+
+/*
+ * Get the virtual machine name for the current user
+ */
+void get_vmname (const char *username, char buf[VMNAME_MAX]) {
+    // the path to the userfile
+    char path[USERFILE_PATH_MAX], *nl;
+    FILE *fh;
+    
+    // format the userfile path
+    if (snprintf(path, USERFILE_PATH_MAX, USERFILE_PATH_FMT, username) >= USERFILE_PATH_MAX)
+        errx(EXIT_FAILURE, "USERFILE_PATH_MAX");
+    
+    // open the userfile
+    if ((fh = fopen(path, "r")) == NULL) {
+        if (errno == ENOENT)
+            errx(EXIT_FAILURE, "no vm defined for user: %s", username);
+        else
+            err(EXIT_FAILURE, "fopen: %s", path);
+    }
+
+    // read the vmname
+    if (fgets(buf, VMNAME_MAX, fh) == NULL)
+        err(EXIT_FAILURE, "fgets: %s", path);
+    
+    // kill the newline
+    if ((nl = index(buf, '\n')))
+        *nl = '\0';
+    
+    // sanity-check the vmname
+    validate_vmname(buf);
+
+    // good
+}
+
+void __attribute__ ((noreturn)) xm_exec (const char *vmname, const char *command) {
+    const char *env[] = { NULL };
+    
+    // setuid to root
+    if (setuid(0))
+        err(EXIT_FAILURE, "setuid: 0");
+
+    // exec
+    execle(XM_PATH, "xm", command, vmname, NULL, env);
+
+    // if we're still here, an error has occured
+    err(EXIT_FAILURE, "%s: %s %s", XM_PATH, command, vmname);
+}
+
+int main (int argc, char **argv) {
+    char username[USERNAME_MAX], vmname[VMNAME_MAX], *command;
+
+    // get command
+    command = parse_command(argc, argv);
+
+    // get username
+    get_username(username);
+
+    // get vmname
+    get_vmname(username, vmname);
+
+    // execute xm
+    xm_exec(vmname, command);
+}
+