Include process start time when doing polkit checks

Since PIDs can be reused, polkit prefers to be given
a (PID,start time) pair. If given a PID on its own,
it will attempt to lookup the start time in /proc/pid/stat,
though this is subject to races.

It is safer if the client app resolves the PID start
time itself, because as long as the app has the client
socket open, the client PID won't be reused.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 979e9c56a7aadf2dcfbddd1abfbad594b78b4468)

Conflicts:
	src/util/virprocess.c
	src/util/virstring.c
	src/util/virstring.h
	src/rpc/virnetserverclient.c
	src/rpc/virnetsocket.h
	src/util/viridentity.h

11 files changed, 171 insertions, 14 deletions

diff --git a/daemon/remote.c b/daemon/remote.c
index e879941fc0..90aa178fdc 100644
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -2372,6 +2372,7 @@ remoteDispatchAuthList(virNetServerPtr server ATTRIBUTE_UNUSED,
     uid_t callerUid;
     gid_t callerGid;
     pid_t callerPid;
+    unsigned long long timestamp;
 
     /* If the client is root then we want to bypass the
      * policykit auth to avoid root being denied if
@@ -2379,7 +2380,7 @@ remoteDispatchAuthList(virNetServerPtr server ATTRIBUTE_UNUSED,
      */
     if (auth == VIR_NET_SERVER_SERVICE_AUTH_POLKIT) {
         if (virNetServerClientGetUNIXIdentity(client, &callerUid, &callerGid,
-                                              &callerPid) < 0) {
+                                              &callerPid, &timestamp) < 0) {
             /* Don't do anything on error - it'll be validated at next
              * phase of auth anyway */
             virResetLastError();
@@ -2809,6 +2810,7 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
     pid_t callerPid = -1;
     gid_t callerGid = -1;
     uid_t callerUid = -1;
+    unsigned long long timestamp;
     const char *action;
     int status = -1;
     char *ident = NULL;
@@ -2834,7 +2836,7 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
     }
 
     if (virNetServerClientGetUNIXIdentity(client, &callerUid, &callerGid,
-                                          &callerPid) < 0) {
+                                          &callerPid, &timestamp) < 0) {
         goto authfail;
     }
 
@@ -2842,7 +2844,11 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
              (long long) callerPid, callerUid);
 
     virCommandAddArg(cmd, "--process");
-    virCommandAddArgFormat(cmd, "%lld", (long long) callerPid);
+    if (timestamp != 0) {
+        virCommandAddArgFormat(cmd, "%lld,%llu", (long long) callerPid, timestamp);
+    } else {
+        virCommandAddArgFormat(cmd, "%lld", (long long) callerPid);
+    }
     virCommandAddArg(cmd, "--allow-user-interaction");
 
     if (virAsprintf(&ident, "pid:%lld,uid:%d",
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index ed464798fd..dd44ba61c0 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1720,6 +1720,7 @@ virStorageFileResize;
 # util/virstring.h
 virStringFreeList;
 virStringJoin;
+virStringListLength;
 virStringSplit;
 
 
diff --git a/src/locking/lock_daemon.c b/src/locking/lock_daemon.c
index 97e5d749c2..bf0ee8124e 100644
--- a/src/locking/lock_daemon.c
+++ b/src/locking/lock_daemon.c
@@ -782,6 +782,7 @@ virLockDaemonClientNew(virNetServerClientPtr client,
     virLockDaemonClientPtr priv;
     uid_t clientuid;
     gid_t clientgid;
+    unsigned long long timestamp;
     bool privileged = opaque != NULL;
 
     if (VIR_ALLOC(priv) < 0) {
@@ -798,7 +799,8 @@ virLockDaemonClientNew(virNetServerClientPtr client,
     if (virNetServerClientGetUNIXIdentity(client,
                                           &clientuid,
                                           &clientgid,
-                                          &priv->clientPid) < 0)
+                                          &priv->clientPid,
+                                          &timestamp) < 0)
         goto error;
 
     VIR_DEBUG("New client pid %llu uid %llu",
diff --git a/src/rpc/virnetserverclient.c b/src/rpc/virnetserverclient.c
index 446e1e9168..8fec7e6758 100644
--- a/src/rpc/virnetserverclient.c
+++ b/src/rpc/virnetserverclient.c
@@ -618,12 +618,15 @@ int virNetServerClientGetFD(virNetServerClientPtr client)
 }
 
 int virNetServerClientGetUNIXIdentity(virNetServerClientPtr client,
-                                      uid_t *uid, gid_t *gid, pid_t *pid)
+                                      uid_t *uid, gid_t *gid, pid_t *pid,
+                                      unsigned long long *timestamp)
 {
     int ret = -1;
     virObjectLock(client);
     if (client->sock)
-        ret = virNetSocketGetUNIXIdentity(client->sock, uid, gid, pid);
+        ret = virNetSocketGetUNIXIdentity(client->sock,
+                                          uid, gid, pid,
+                                          timestamp);
     virObjectUnlock(client);
     return ret;
 }
diff --git a/src/rpc/virnetserverclient.h b/src/rpc/virnetserverclient.h
index 325f5d9c4e..053b54484d 100644
--- a/src/rpc/virnetserverclient.h
+++ b/src/rpc/virnetserverclient.h
@@ -97,7 +97,8 @@ int virNetServerClientSetIdentity(virNetServerClientPtr client,
 const char *virNetServerClientGetIdentity(virNetServerClientPtr client);
 
 int virNetServerClientGetUNIXIdentity(virNetServerClientPtr client,
-                                      uid_t *uid, gid_t *gid, pid_t *pid);
+                                      uid_t *uid, gid_t *gid, pid_t *pid,
+                                      unsigned long long *timestamp);
 
 void *virNetServerClientGetPrivateData(virNetServerClientPtr client);
 
diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
index 93980d65d4..7ad25e32eb 100644
--- a/src/rpc/virnetsocket.c
+++ b/src/rpc/virnetsocket.c
@@ -1097,31 +1097,41 @@ int virNetSocketGetPort(virNetSocketPtr sock)
 int virNetSocketGetUNIXIdentity(virNetSocketPtr sock,
                                 uid_t *uid,
                                 gid_t *gid,
-                                pid_t *pid)
+                                pid_t *pid,
+                                unsigned long long *timestamp)
 {
     struct ucred cr;
     socklen_t cr_len = sizeof(cr);
+    int ret = -1;
+
     virObjectLock(sock);
 
     if (getsockopt(sock->fd, SOL_SOCKET, SO_PEERCRED, &cr, &cr_len) < 0) {
         virReportSystemError(errno, "%s",
                              _("Failed to get client socket identity"));
-        virObjectUnlock(sock);
-        return -1;
+        goto cleanup;
     }
 
+    if (virProcessGetStartTime(cr.pid, timestamp) < 0)
+        goto cleanup;
+
     *pid = cr.pid;
     *uid = cr.uid;
     *gid = cr.gid;
 
+    ret = 0;
+
+cleanup:
     virObjectUnlock(sock);
-    return 0;
+    return ret;
 }
 #elif defined(LOCAL_PEERCRED)
+
 int virNetSocketGetUNIXIdentity(virNetSocketPtr sock,
                                 uid_t *uid,
                                 gid_t *gid,
-                                pid_t *pid)
+                                pid_t *pid,
+                                unsigned long long *timestamp ATTRIBUTE_UNUSED)
 {
     struct xucred cr;
     socklen_t cr_len = sizeof(cr);
@@ -1145,7 +1155,8 @@ int virNetSocketGetUNIXIdentity(virNetSocketPtr sock,
 int virNetSocketGetUNIXIdentity(virNetSocketPtr sock ATTRIBUTE_UNUSED,
                                 uid_t *uid ATTRIBUTE_UNUSED,
                                 gid_t *gid ATTRIBUTE_UNUSED,
-                                pid_t *pid ATTRIBUTE_UNUSED)
+                                pid_t *pid ATTRIBUTE_UNUSED,
+                                unsigned long long *timestamp ATTRIBUTE_UNUSED)
 {
     /* XXX Many more OS support UNIX socket credentials we could port to. See dbus ....*/
     virReportSystemError(ENOSYS, "%s",
diff --git a/src/rpc/virnetsocket.h b/src/rpc/virnetsocket.h
index 13583f846c..e04a67a543 100644
--- a/src/rpc/virnetsocket.h
+++ b/src/rpc/virnetsocket.h
@@ -113,7 +113,8 @@ int virNetSocketGetPort(virNetSocketPtr sock);
 int virNetSocketGetUNIXIdentity(virNetSocketPtr sock,
                                 uid_t *uid,
                                 gid_t *gid,
-                                pid_t *pid);
+                                pid_t *pid,
+                                unsigned long long *timestamp);
 
 int virNetSocketSetBlocking(virNetSocketPtr sock,
                             bool blocking);
diff --git a/src/util/virprocess.c b/src/util/virprocess.c
index a492bd11f7..4202d9c5d7 100644
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -29,12 +29,20 @@
 #include <sys/wait.h>
 #include <sched.h>
 
+#ifdef __FreeBSD__
+# include <sys/param.h>
+# include <sys/sysctl.h>
+# include <sys/user.h>
+#endif
+
+#include "viratomic.h"
 #include "virprocess.h"
 #include "virerror.h"
 #include "viralloc.h"
 #include "virfile.h"
 #include "virlog.h"
 #include "virutil.h"
+#include "virstring.h"
 
 #define VIR_FROM_THIS VIR_FROM_NONE
 
@@ -605,3 +613,112 @@ int virProcessSetNamespaces(size_t nfdlist ATTRIBUTE_UNUSED,
     return -1;
 }
 #endif /* ! HAVE_SETNS */
+
+#ifdef __linux__
+/*
+ * Port of code from polkitunixprocess.c under terms
+ * of the LGPLv2+
+ */
+int virProcessGetStartTime(pid_t pid,
+                           unsigned long long *timestamp)
+{
+    char *filename = NULL;
+    char *buf = NULL;
+    char *tmp;
+    int ret = -1;
+    int len;
+    char **tokens = NULL;
+
+    if (virAsprintf(&filename, "/proc/%llu/stat",
+                    (unsigned long long)pid) < 0) {
+        virReportOOMError();
+        return -1;
+    }
+
+    if ((len = virFileReadAll(filename, 1024, &buf)) < 0)
+        goto cleanup;
+
+    /* start time is the token at index 19 after the '(process name)' entry - since only this
+     * field can contain the ')' character, search backwards for this to avoid malicious
+     * processes trying to fool us
+     */
+
+    if (!(tmp = strrchr(buf, ')'))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Cannot find start time in %s"),
+                       filename);
+        goto cleanup;
+    }
+    tmp += 2; /* skip ') ' */
+    if ((tmp - buf) >= len) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Cannot find start time in %s"),
+                       filename);
+        goto cleanup;
+    }
+
+    tokens = virStringSplit(tmp, " ", 0);
+
+    if (virStringListLength(tokens) < 20) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Cannot find start time in %s"),
+                       filename);
+        goto cleanup;
+    }
+
+    if (virStrToLong_ull(tokens[19],
+                         NULL,
+                         10,
+                         timestamp) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Cannot parse start time %s in %s"),
+                       tokens[19], filename);
+        goto cleanup;
+    }
+
+    ret = 0;
+
+cleanup:
+    virStringFreeList(tokens);
+    VIR_FREE(filename);
+    VIR_FREE(buf);
+    return ret;
+}
+#elif defined(__FreeBSD__)
+int virProcessGetStartTime(pid_t pid,
+                           unsigned long long *timestamp)
+{
+    struct kinfo_proc p;
+    int mib[4];
+    size_t len = 4;
+
+    sysctlnametomib("kern.proc.pid", mib, &len);
+
+    len = sizeof(struct kinfo_proc);
+    mib[3] = pid;
+
+    if (sysctl(mib, 4, &p, &len, NULL, 0) < 0) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to query process ID start time"));
+        return -1;
+    }
+
+    *timestamp = (unsigned long long)p.ki_start.tv_sec;
+
+    return 0;
+
+}
+#else
+int virProcessGetStartTime(pid_t pid,
+                           unsigned long long *timestamp)
+{
+    static int warned = 0;
+    if (virAtomicIntInc(&warned) == 1) {
+        VIR_WARN("Process start time of pid %llu not available on this platform",
+                 (unsigned long long)pid);
+        warned = true;
+    }
+    *timestamp = 0;
+    return 0;
+}
+#endif
diff --git a/src/util/virprocess.h b/src/util/virprocess.h
index 53475d3cc3..149d451a61 100644
--- a/src/util/virprocess.h
+++ b/src/util/virprocess.h
@@ -47,6 +47,9 @@ int virProcessGetAffinity(pid_t pid,
                           virBitmapPtr *map,
                           int maxcpu);
 
+int virProcessGetStartTime(pid_t pid,
+                           unsigned long long *timestamp);
+
 int virProcessGetNamespaces(pid_t pid,
                             size_t *nfdlist,
                             int **fdlist);
diff --git a/src/util/virstring.c b/src/util/virstring.c
index 0420ca37f9..1fc24de9a1 100644
--- a/src/util/virstring.c
+++ b/src/util/virstring.c
@@ -166,3 +166,13 @@ void virStringFreeList(char **strings)
     }
     VIR_FREE(strings);
 }
+
+size_t virStringListLength(char **strings)
+{
+    size_t i = 0;
+
+    while (strings && strings[i])
+        i++;
+
+    return i;
+}
diff --git a/src/util/virstring.h b/src/util/virstring.h
index a569fe080a..d68ed2f689 100644
--- a/src/util/virstring.h
+++ b/src/util/virstring.h
@@ -35,4 +35,6 @@ char *virStringJoin(const char **strings,
 
 void virStringFreeList(char **strings);
 
+size_t virStringListLength(char **strings);
+
 #endif /* __VIR_STRING_H__ */