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[Libvir] [RFC PATCH] Solaris least privilege



In the interests of giving a 'heads-up' I'm posting this patch. It
implements least-privilege on Solaris. The basic idea is that all
libvirt clients are forced to go through libvirtd, which verifies a
particular privilege. virtd itself runs with enough privilege to
interact with Xen.

This patch is:

 - not to be applied :)
 - only against 0.4.0
 - subject to further change
 - not yet reviewed, not even by myself (properly)

Nonetheless, comments are more than welcome.

regards
john

--- libvirt-0.4.0/qemud/remote.c	2007-12-12 05:30:49.000000000 -0800
+++ libvirt-new/qemud/remote.c	2008-04-10 12:52:18.059618661 -0700
@@ -434,6 +434,15 @@ remoteDispatchOpen (struct qemud_server 
     flags = args->flags;
     if (client->readonly) flags |= VIR_CONNECT_RO;
 
+#ifdef __sun
+    /*
+     * On Solaris, all clients are forced to go via virtd. As a result,
+     * virtd must indicate it really does want to connect to the
+     * hypervisor.
+     */
+    name = "xen:///";
+#endif
+
     client->conn =
         flags & VIR_CONNECT_RO
         ? virConnectOpenReadOnly (name)
--- libvirt-0.4.0/src/libvirt.c	2007-12-17 13:51:09.000000000 -0800
+++ libvirt-new/src/libvirt.c	2008-04-16 08:46:28.767087199 -0700
@@ -34,6 +34,7 @@
 
 #include "uuid.h"
 #include "test.h"
+#include "xen_internal.h"
 #include "xen_unified.h"
 #include "remote_internal.h"
 #include "qemu_driver.h"
@@ -202,8 +203,16 @@ virInitialize(void)
     if (qemudRegister() == -1) return -1;
 #endif
 #ifdef WITH_XEN
+    /*
+     * On Solaris, only initialize Xen if we're libvirtd.
+     */
+#ifdef __sun
+    if (geteuid() != 0 && xenHavePrivilege() &&
+        xenUnifiedRegister () == -1) return -1;
+#else
     if (xenUnifiedRegister () == -1) return -1;
 #endif
+#endif
 #ifdef WITH_OPENVZ
     if (openvzRegister() == -1) return -1;
 #endif
@@ -525,6 +534,16 @@ do_open (const char *name,
     if (STREQ (name, "xen://"))
         name = "xen:///";
 
+#ifdef __sun
+    /*
+     * If we're not libvirtd, force us to go via the daemon.
+     */
+    if (geteuid() == 0 || !xenHavePrivilege())
+        name = "remote+unix:///";
+    else if (STREQ (name, "xen:///") && xenUnifiedRegister () == -1)
+        return NULL;
+#endif
+
     if (!initialized)
         if (virInitialize() < 0)
 	    return NULL;
--- libvirt-0.4.0/qemud/qemud.c	2007-12-12 05:30:49.000000000 -0800
+++ libvirt-new/qemud/qemud.c	2008-04-17 17:16:47.075258251 -0700
@@ -60,6 +60,25 @@
 #include "mdns.h"
 #endif
 
+#ifdef __sun
+#include <ucred.h>
+#include <priv.h>
+
+#ifndef PRIV_VIRT_MANAGE
+#define PRIV_VIRT_MANAGE ((const char *)"virt_manage")
+#endif
+
+#ifndef PRIV_XVM_CONTROL
+#define PRIV_XVM_CONTROL ((const char *)"xvm_control")
+#endif
+
+#define PU_RESETGROUPS          0x0001  /* Remove supplemental groups */
+#define PU_CLEARLIMITSET        0x0008  /* L=0 */
+
+extern int __init_daemon_priv(int, uid_t, gid_t, ...);
+
+#endif
+
 static int godaemon = 0;        /* -d: Be a daemon */
 static int verbose = 0;         /* -v: Verbose mode */
 static int timeout = -1;        /* -t: Shutdown timeout */
@@ -668,11 +687,13 @@ static int qemudInitPaths(struct qemud_s
 
         unlink(sockname);
 
+#ifndef __sun
         if (snprintf (roSockname, maxlen, "%s/run/libvirt/libvirt-sock-ro",
                       LOCAL_STATE_DIR) >= maxlen)
             goto snprintf_error;
 
         unlink(roSockname);
+#endif
 
         if (snprintf(server->logDir, PATH_MAX, "%s/log/libvirt/", LOCAL_STATE_DIR) >= PATH_MAX)
             goto snprintf_error;
@@ -1033,6 +1054,29 @@ static int qemudDispatchServer(struct qe
         return -1;
     }
 
+#ifdef __sun
+    {
+        ucred_t *ucred = NULL;
+        const priv_set_t *privs;
+
+        if (getpeerucred (fd, &ucred) == -1 ||
+            (privs = ucred_getprivset (ucred, PRIV_EFFECTIVE)) == NULL) {
+            if (ucred != NULL)
+                ucred_free (ucred);
+            close (fd);
+            return -1;
+        }
+
+        if (!priv_ismember (privs, PRIV_VIRT_MANAGE)) {
+            ucred_free (ucred);
+            close (fd);
+            return -1;
+        }
+
+        ucred_free (ucred);
+    }
+#endif /* __sun */
+
     /* Disable Nagle.  Unix sockets will ignore this. */
     setsockopt (fd, IPPROTO_TCP, TCP_NODELAY, (void *)&no_slow_start,
                 sizeof no_slow_start);
@@ -1864,6 +1908,10 @@ remoteReadConfigFile (struct qemud_serve
     if (auth_unix_rw == REMOTE_AUTH_POLKIT)
         unix_sock_rw_mask = 0777;
 #endif
+#ifdef __sun
+    unix_sock_rw_mask = 0666;
+#endif
+
     if (remoteConfigGetAuth(conf, "auth_unix_ro", &auth_unix_ro, filename) < 0)
         return -1;
     if (remoteConfigGetAuth(conf, "auth_tcp", &auth_tcp, filename) < 0)
@@ -1955,6 +2003,32 @@ remoteReadConfigFile (struct qemud_serve
     return -1;
 }
 
+#ifdef __sun
+static void
+qemudSetupPrivs (struct qemud_server *server)
+{
+    chown ("/var/run/libvirt", 60, 60);
+    chmod ("/var/run/libvirt", 0755);
+    chown ("/var/run/libvirt/libvirt-sock", 60, 60);
+    chmod ("/var/run/libvirt/libvirt-sock", 0666);
+    chown (server->logDir, 60, 60);
+
+    if (__init_daemon_priv (PU_RESETGROUPS | PU_CLEARLIMITSET,
+        60, 60, PRIV_XVM_CONTROL, NULL)) {
+        fprintf (stderr, "additional privileges are required\n");
+        exit (1);
+    }
+
+    if (priv_set (PRIV_OFF, PRIV_ALLSETS, PRIV_FILE_LINK_ANY, PRIV_PROC_INFO,
+        PRIV_PROC_SESSION, PRIV_PROC_EXEC, PRIV_PROC_FORK, NULL)) {
+        fprintf (stderr, "failed to set reduced privileges\n");
+        exit (1);
+    }
+}
+#else
+#define qemudSetupPrivs
+#endif
+
 /* Print command-line usage. */
 static void
 usage (const char *argv0)
@@ -2139,6 +2213,8 @@ int main(int argc, char **argv) {
         goto error2;
     }
 
+    qemudSetupPrivs(server);
+
     qemudRunLoop(server);
 
     qemudCleanup(server);
--- libvirt-0.4.0/src/xs_internal.c	2007-12-14 07:33:11.000000000 -0800
+++ libvirt-new/src/xs_internal.c	2008-04-10 09:54:38.676077954 -0700
@@ -31,7 +31,7 @@
 #include "driver.h"
 #include "xen_unified.h"
 #include "xs_internal.h"
-#include "xen_internal.h" /* for xenHypervisorCheckID */
+#include "xen_internal.h"
 
 #ifdef __linux__
 #define XEN_HYPERVISOR_SOCKET "/proc/xen/privcmd"
@@ -344,11 +344,11 @@ xenStoreOpen(virConnectPtr conn,
 
     if (priv->xshandle == NULL) {
 	/*
-         * not being able to connect via the socket as a normal user
-         * is rather normal, this should fallback to the proxy (or
-         * remote) mechanism.
+	 * not being able to connect via the socket as an unprivileged
+	 * user is rather normal, this should fallback to the proxy (or
+	 * remote) mechanism.
 	 */
-        if (getuid() == 0) {
+        if (!xenHavePrivilege()) {
 	    virXenStoreError(NULL, VIR_ERR_NO_XEN, 
 				 _("failed to connect to Xen Store"));
 	}
--- libvirt-0.4.0/src/xen_internal.c	2007-12-12 05:30:49.000000000 -0800
+++ libvirt-new/src/xen_internal.c	2008-04-10 10:28:41.363704244 -0700
@@ -28,6 +28,15 @@
 #include <errno.h>
 #include <sys/utsname.h>
 
+#ifdef __sun
+#include <priv.h>
+
+#ifndef PRIV_XVM_CONTROL
+#define PRIV_XVM_CONTROL ((const char *)"xvm_control")
+#endif
+
+#endif
+
 #include "xs_internal.h"
 #include "stats_linux.h"
 #include "xend_internal.h"
@@ -3259,6 +3268,21 @@ xenHypervisorGetVcpuMax(virDomainPtr dom
     return maxcpu;
 }
 
+/**
+ * xenHavePrivilege()
+ *
+ * Return true if the current process should be able to connect to Xen.
+ */
+int
+xenHavePrivilege()
+{
+#ifdef __sun
+	return priv_ineffect (PRIV_XVM_CONTROL);
+#else
+	return getuid () == 0;
+#endif
+}
+
 #endif /* WITH_XEN */
 /*
  * vim: set tabstop=4:
--- libvirt-0.4.0/src/xen_internal.h	2007-12-05 12:33:02.000000000 -0800
+++ libvirt-new/src/xen_internal.h	2008-04-10 09:34:16.379186656 -0700
@@ -98,6 +98,9 @@ int	xenHypervisorNodeGetCellsFreeMemory(
 					  unsigned long long *freeMems,
 					  int startCell,
 					  int maxCells);
+
+int	xenHavePrivilege(void);
+
 #ifdef __cplusplus
 }
 #endif
--- libvirt-0.4.0/src/xen_unified.c	2007-12-12 05:30:49.000000000 -0800
+++ libvirt-new/src/xen_unified.c	2008-04-10 15:10:53.653298774 -0700
@@ -266,8 +266,8 @@ xenUnifiedOpen (virConnectPtr conn, xmlU
             priv->xendConfigVersion > 2)
             continue;
 
-        /* Ignore proxy for root */
-        if (i == XEN_UNIFIED_PROXY_OFFSET && getuid() == 0)
+        /* Ignore proxy if we have privilege */
+        if (i == XEN_UNIFIED_PROXY_OFFSET && xenHavePrivilege())
             continue;
 
         if (drivers[i]->open) {
@@ -282,10 +282,10 @@ xenUnifiedOpen (virConnectPtr conn, xmlU
 #endif
         }
 
-        /* If as root, then all drivers must succeed.
-           If non-root, then only proxy must succeed */
+        /* If privileged, then all drivers must succeed.
+           If unprivileged, then only proxy must succeed */
         if (!priv->opened[i] &&
-            (getuid() == 0 || i == XEN_UNIFIED_PROXY_OFFSET)) {
+            (xenHavePrivilege() || i == XEN_UNIFIED_PROXY_OFFSET)) {
             for (j = 0; j < i; ++j)
                 if (priv->opened[j]) drivers[j]->close (conn);
             free (priv);
@@ -1266,6 +1266,12 @@ static virDriver xenUnifiedDriver = {
 int
 xenUnifiedRegister (void)
 {
+    static int driver_priority = 0;
+    static int xen_initialized = 0;
+
+    if (xen_initialized)
+        return driver_priority;
+
     /* Ignore failures here. */
     (void) xenHypervisorInit ();
     (void) xenProxyInit ();
@@ -1273,7 +1279,9 @@ xenUnifiedRegister (void)
     (void) xenStoreInit ();
     (void) xenXMInit ();
 
-    return virRegisterDriver (&xenUnifiedDriver);
+    driver_priority = virRegisterDriver (&xenUnifiedDriver);
+    xen_initialized = 1;
+    return driver_priority;
 }
 
 #endif /* WITH_XEN */
--- libvirt-0.4.0/src/xend_internal.c	2007-12-17 15:05:27.000000000 -0800
+++ libvirt-new/src/xend_internal.c	2008-04-10 09:45:10.262989682 -0700
@@ -42,7 +42,7 @@
 #include "uuid.h"
 #include "xen_unified.h"
 #include "xend_internal.h"
-#include "xen_internal.h" /* for DOM0_INTERFACE_VERSION */
+#include "xen_internal.h"
 #include "xs_internal.h" /* To extract VNC port & Serial console TTY */
 
 /* required for cpumap_t */
@@ -235,7 +235,7 @@ do_connect(virConnectPtr xend)
 	 * is rather normal, this should fallback to the proxy (or
 	 * remote) mechanism.
 	 */
-	if ((getuid() == 0) || (xend->flags & VIR_CONNECT_RO)) {
+	if (xenHavePrivilege() || (xend->flags & VIR_CONNECT_RO)) {
 	    virXendError(xend, VIR_ERR_INTERNAL_ERROR,
 			 "failed to connect to xend");
         }
--- libvirt-0.4.0/src/virsh.c	2007-12-07 07:00:48.000000000 -0800
+++ libvirt-new/src/virsh.c	2008-04-16 08:44:35.668718168 -0700
@@ -36,6 +36,7 @@
 #include <sys/stat.h>
 #include <inttypes.h>
 #include <test.h>
+#include <signal.h>
 
 #include <libxml/parser.h>
 #include <libxml/tree.h>
@@ -50,6 +51,7 @@
 #include "console.h"
 
 static char *progname;
+static int sigpipe;
 
 #ifndef TRUE
 #define TRUE 1
@@ -202,9 +204,6 @@ typedef struct __vshControl {
     virConnectPtr conn;         /* connection to hypervisor (MAY BE NULL) */
     vshCmd *cmd;                /* the current command */
     char *cmdstr;               /* string with command */
-#ifndef __MINGW32__
-    uid_t uid;                  /* process owner */
-#endif /* __MINGW32__ */
     int imode;                  /* interactive mode? */
     int quiet;                  /* quiet mode */
     int debug;                  /* print debug messages? */
@@ -464,12 +463,8 @@ static vshCmdOptDef opts_console[] = {
 static int
 cmdConsole(vshControl * ctl, vshCmd * cmd)
 {
-    xmlDocPtr xml = NULL;
-    xmlXPathObjectPtr obj = NULL;
-    xmlXPathContextPtr ctxt = NULL;
     virDomainPtr dom;
     int ret = FALSE;
-    char *doc;
 
     if (!vshConnectionUsability(ctl, ctl->conn, TRUE))
         return FALSE;
@@ -477,37 +472,16 @@ cmdConsole(vshControl * ctl, vshCmd * cm
     if (!(dom = vshCommandOptDomain(ctl, cmd, "domain", NULL)))
         return FALSE;
 
-    doc = virDomainGetXMLDesc(dom, 0);
-    if (!doc)
-        goto cleanup;
-
-    xml = xmlReadDoc((const xmlChar *) doc, "domain.xml", NULL,
-                     XML_PARSE_NOENT | XML_PARSE_NONET |
-                     XML_PARSE_NOWARNING);
-    free(doc);
-    if (!xml)
-        goto cleanup;
-    ctxt = xmlXPathNewContext(xml);
-    if (!ctxt)
-        goto cleanup;
+    ret = vshConsole(dom);
 
-    obj = xmlXPathEval(BAD_CAST "string(/domain/devices/console/@tty)", ctxt);
-    if ((obj != NULL) && ((obj->type == XPATH_STRING) &&
-                          (obj->stringval != NULL) && (obj->stringval[0] != 0))) {
-        if (vshRunConsole((const char *)obj->stringval) == 0)
-            ret = TRUE;
-    } else {
+    if (ret == 0) {
         vshPrintExtra(ctl, _("No console available for domain\n"));
+    } else if (ret == -1) {
+        fprintf(stderr, _("unable to open console: %s\n"),
+                strerror(errno));
     }
-    xmlXPathFreeObject(obj);
 
- cleanup:
-    if (ctxt)
-        xmlXPathFreeContext(ctxt);
-    if (xml)
-        xmlFreeDoc(xml);
-    virDomainFree(dom);
-    return ret;
+    return ret == 1;
 }
 
 #else /* __MINGW32__ */
@@ -4523,22 +4497,11 @@ vshInit(vshControl * ctl)
     if (ctl->conn)
         return FALSE;
 
-#ifndef __MINGW32__
-    ctl->uid = getuid();
-#endif
-
     vshOpenLogFile(ctl);
 
     /* set up the library error handler */
     virSetErrorFunc(NULL, virshErrorHandler);
 
-#ifndef __MINGW32__
-    /* Force a non-root, Xen connection to readonly */
-    if ((ctl->name == NULL ||
-         !strcasecmp(ctl->name, "xen")) && ctl->uid != 0)
-         ctl->readonly = 1;
-#endif
-
     ctl->conn = virConnectOpenAuth(ctl->name,
                                    virConnectAuthPtrDefault,
                                    ctl->readonly ? VIR_CONNECT_RO : 0);
@@ -5021,12 +4984,21 @@ vshParseArgv(vshControl * ctl, int argc,
     return TRUE;
 }
 
-int
+static void sigpipe_handler(int sig)
+{
+    sigpipe = 1;
+    /*
+     * Force readline() to exit.
+     */
+    close(STDIN_FILENO);
+}
+
 main(int argc, char **argv)
 {
     vshControl _ctl, *ctl = &_ctl;
     char *defaultConn;
     int ret = TRUE;
+    struct sigaction sig_action;
 
     if (!setlocale(LC_ALL, "")) {
         perror("setlocale");
@@ -5059,6 +5031,12 @@ main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
+    sig_action.sa_handler = sigpipe_handler;
+    sig_action.sa_flags = 0;
+    sigemptyset(&sig_action.sa_mask);
+
+    sigaction(SIGPIPE, &sig_action, NULL);
+
     if (!vshInit(ctl)) {
         vshDeinit(ctl);
         exit(EXIT_FAILURE);
@@ -5098,6 +5076,13 @@ main(int argc, char **argv)
             fputc('\n', stdout);        /* line break after alone prompt */
     }
 
+    /*
+     * If the connection over a socket failed abruptly, it's probably
+     * due to not having the right privileges.
+     */
+    if (sigpipe)
+        vshError(ctl, TRUE, _("failed to connect (insufficient privileges?)"));
+
     vshDeinit(ctl);
     exit(ret ? EXIT_SUCCESS : EXIT_FAILURE);
 }
--- libvirt-0.4.0/src/console.c	2007-12-07 07:00:48.000000000 -0800
+++ libvirt-new/src/console.c	2008-04-16 16:34:15.533322609 -0700
@@ -34,6 +34,11 @@
 #include <errno.h>
 #include <unistd.h>
 #include <signal.h>
+#include <stdlib.h>
+
+#include <libxml/parser.h>
+#include <libxml/tree.h>
+#include <libxml/xpath.h>
 
 #include "console.h"
 #include "internal.h"
@@ -59,8 +64,10 @@ cfmakeraw (struct termios *attr)
 }
 #endif /* !HAVE_CFMAKERAW */
 
-int vshRunConsole(const char *tty) {
-    int ttyfd, ret = -1;
+static int 
+vshDirectConsole(int ttyfd)
+{
+    int ret = -1;
     struct termios ttyattr, rawattr;
     void (*old_sigquit)(int);
     void (*old_sigterm)(int);
@@ -68,14 +75,6 @@ int vshRunConsole(const char *tty) {
     void (*old_sighup)(int);
     void (*old_sigpipe)(int);
 
-
-    /* We do not want this to become the controlling TTY */
-    if ((ttyfd = open(tty, O_NOCTTY | O_RDWR)) < 0) {
-        fprintf(stderr, _("unable to open tty %s: %s\n"),
-                tty, strerror(errno));
-        return -1;
-    }
-
     /* Put  STDIN into raw mode so that stuff typed
        does not echo to the screen (the TTY reads will
        result in it being echoed back already), and
@@ -174,7 +173,7 @@ int vshRunConsole(const char *tty) {
         }
     }
  done:
-    ret = 0;
+    ret = 1;
 
  cleanup:
 
@@ -195,6 +194,106 @@ int vshRunConsole(const char *tty) {
     return ret;
 }
 
+/*
+ * Attempt to access the domain via 'xenconsole', which may have
+ * additional privilege to reach the console.
+ */
+static int
+vshXenConsole(int id)
+{
+    char arg[100];
+    char *argv[3];
+    pid_t pid;
+
+    if ((pid = fork()) < 0) {
+        return -1;
+    } else if (pid) {
+        int wstat;
+
+        if (waitpid(pid, &wstat, 0) < 0)
+            return -1;
+
+        if (WIFSIGNALED(wstat))
+            return -1;
+        if (WIFEXITED(wstat) && WEXITSTATUS(wstat))
+            return -1;
+
+        return 1;
+    }
+
+    /* child */
+
+    if (snprintf(arg, 100, "%d", id) < 0)
+        return -1;
+
+    argv[0] = "/usr/lib/xen/bin/xenconsole";
+    argv[1] = arg;
+    argv[2] = NULL;
+
+    if (execv("/usr/lib/xen/bin/xenconsole", argv))
+        fprintf(stderr, _("failed to run xenconsole: %s\n"),
+            strerror(errno));
+    _exit(1);
+}
+
+/*
+ * Returns 0 if no console is available, 1 if the console was accessed
+ * successfully, or -1 on error.
+ */
+int vshConsole(virDomainPtr dom)
+{
+    xmlDocPtr xml = NULL;
+    xmlXPathObjectPtr obj = NULL;
+    xmlXPathContextPtr ctxt = NULL;
+    char *doc;
+    int ttyfd;
+    int ret = -1;
+
+    doc = virDomainGetXMLDesc(dom, 0);
+    if (!doc)
+        goto cleanup;
+
+    xml = xmlReadDoc((const xmlChar *) doc, "domain.xml", NULL,
+                     XML_PARSE_NOENT | XML_PARSE_NONET |
+                     XML_PARSE_NOWARNING);
+    free(doc);
+    if (!xml)
+        goto cleanup;
+    ctxt = xmlXPathNewContext(xml);
+    if (!ctxt)
+        goto cleanup;
+
+    obj = xmlXPathEval(BAD_CAST "string(/domain/devices/console/@tty)", ctxt);
+    if (obj == NULL || obj->type != XPATH_STRING || obj->stringval == NULL ||
+        obj->stringval[0] == '\0') {
+        ret = 0;
+        goto cleanup;
+    }
+
+    /* We do not want this to become the controlling TTY */
+    ttyfd = open((char *)obj->stringval, O_NOCTTY | O_RDWR);
+
+    if (ttyfd != -1) {
+        ret = vshDirectConsole(ttyfd);
+        goto cleanup;
+    } else if (errno != EACCES) {
+        fprintf(stderr, _("unable to open tty %s: %s\n"),
+            obj->stringval, strerror(errno));
+    } else {
+        ret = vshXenConsole(virDomainGetID(dom));
+    }
+
+ cleanup:
+    if (obj)
+        xmlXPathFreeObject(obj);
+    if (ctxt)
+        xmlXPathFreeContext(ctxt);
+    if (xml)
+        xmlFreeDoc(xml);
+    virDomainFree(dom);
+    return ret;
+}
+
 #endif /* !__MINGW32__ */
 
 /*
--- libvirt-0.4.0/src/console.h	2007-12-07 07:00:48.000000000 -0800
+++ libvirt-new/src/console.h	2008-04-16 08:49:20.165071296 -0700
@@ -25,11 +25,13 @@
 
 #ifndef __MINGW32__
 
+#include "libvirt/libvirt.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-    int vshRunConsole(const char *tty);
+int vshConsole(virDomainPtr dom);
 
 #ifdef __cplusplus
 }


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