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[libvirt] [v0.9.12-maint 7/9] Include process start time when doing polkit checks



From: "Daniel P. Berrange" <berrange redhat com>

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)
Signed-off-by: Eric Blake <eblake redhat com>

Conflicts:
	src/libvirt_private.syms - not backported
	src/locking/lock_daemon.c - not backported
	src/rpc/virnetserverclient.c
	src/rpc/virnetsocket.c
	src/rpc/virnetsocket.h
	src/util/viridentity.h - not backported
	src/util/virprocess.c
	src/util/virprocess.h
	src/util/virstring.c
	src/util/virstring.h

Most conflicts were contextual (this patch adds new functions,
but upstream intermediate patches not backported here also added
new features, and the resolution was picking out just the portions
needed by this commit).  virnetsocket.c also had slightly
different locking semantics.
---
 daemon/remote.c              |  12 +++--
 src/rpc/virnetserverclient.c |   8 ++-
 src/rpc/virnetserverclient.h |   3 +-
 src/rpc/virnetsocket.c       |  19 +++++--
 src/rpc/virnetsocket.h       |   3 +-
 src/util/virprocess.c        | 118 +++++++++++++++++++++++++++++++++++++++++++
 src/util/virprocess.h        |   3 ++
 src/util/virstring.c         |  11 ++++
 src/util/virstring.h         |   2 +
 9 files changed, 167 insertions(+), 12 deletions(-)

diff --git a/daemon/remote.c b/daemon/remote.c
index 435f663..c65e4e4 100644
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -2119,6 +2119,7 @@ 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
@@ -2126,7 +2127,7 @@ 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();
@@ -2554,6 +2555,7 @@ 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;
@@ -2579,7 +2581,7 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
     }

     if (virNetServerClientGetUNIXIdentity(client, &callerUid, &callerGid,
-                                          &callerPid) < 0) {
+                                          &callerPid, &timestamp) < 0) {
         goto authfail;
     }

@@ -2587,7 +2589,11 @@ 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/rpc/virnetserverclient.c b/src/rpc/virnetserverclient.c
index 3838136..73aa28d 100644
--- a/src/rpc/virnetserverclient.c
+++ b/src/rpc/virnetserverclient.c
@@ -448,16 +448,20 @@ 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;
     virNetServerClientLock(client);
     if (client->sock)
-        ret = virNetSocketGetUNIXIdentity(client->sock, uid, gid, pid);
+        ret = virNetSocketGetUNIXIdentity(client->sock,
+                                          uid, gid, pid,
+                                          timestamp);
     virNetServerClientUnlock(client);
     return ret;
 }

+
 bool virNetServerClientIsSecure(virNetServerClientPtr client)
 {
     bool secure = false;
diff --git a/src/rpc/virnetserverclient.h b/src/rpc/virnetserverclient.h
index 154a160..9fc05c2 100644
--- a/src/rpc/virnetserverclient.h
+++ b/src/rpc/virnetserverclient.h
@@ -71,7 +71,8 @@ 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 virNetServerClientRef(virNetServerClientPtr client);

diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
index e82f375..1b4f894 100644
--- a/src/rpc/virnetsocket.c
+++ b/src/rpc/virnetsocket.c
@@ -828,31 +828,40 @@ 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;
+
     virMutexLock(&sock->lock);

     if (getsockopt(sock->fd, SOL_SOCKET, SO_PEERCRED, &cr, &cr_len) < 0) {
         virReportSystemError(errno, "%s",
                              _("Failed to get client socket identity"));
-        virMutexUnlock(&sock->lock);
-        return -1;
+        goto cleanup;
     }

+    if (virProcessGetStartTime(cr.pid, timestamp) < 0)
+        goto cleanup;
+
     *pid = cr.pid;
     *uid = cr.uid;
     *gid = cr.gid;

+    ret = 0;
+
+cleanup:
     virMutexUnlock(&sock->lock);
-    return 0;
+    return ret;
 }
 #else
 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 5ba7c8f..4eaf951 100644
--- a/src/rpc/virnetsocket.h
+++ b/src/rpc/virnetsocket.h
@@ -89,7 +89,8 @@ 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 ac78f1d..f05f8f3 100644
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -26,11 +26,19 @@
 #include <errno.h>
 #include <sys/wait.h>

+#ifdef __FreeBSD__
+# include <sys/param.h>
+# include <sys/sysctl.h>
+# include <sys/user.h>
+#endif
+
+#include "viratomic.h"
 #include "virprocess.h"
 #include "virterror_internal.h"
 #include "memory.h"
 #include "logging.h"
 #include "util.h"
+#include "virstring.h"
 #include "ignore-value.h"
 #define virReportError(code, ...)                                      \
     virReportErrorHelper(VIR_FROM_NONE, code, __FILE__,                 \
@@ -239,3 +247,113 @@ int virProcessKill(pid_t pid, int sig)
     return kill(pid, sig);
 #endif
 }
+
+
+#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 048a73c..30ca21f 100644
--- a/src/util/virprocess.h
+++ b/src/util/virprocess.h
@@ -39,4 +39,7 @@ virProcessWait(pid_t pid, int *exitstatus)
 int virProcessKill(pid_t pid, int sig);


+int virProcessGetStartTime(pid_t pid,
+                           unsigned long long *timestamp);
+
 #endif /* __VIR_PROCESS_H__ */
diff --git a/src/util/virstring.c b/src/util/virstring.c
index 1917e9a..92289eb 100644
--- a/src/util/virstring.c
+++ b/src/util/virstring.c
@@ -166,3 +166,14 @@ 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 a569fe0..d68ed2f 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__ */
-- 
1.8.3.1


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