[libvirt] [PATCH 2/3] new virSetUIDGID() utility function

[Laine Stump]

virSetUIDGID() sets both the real and effective group and user of the
process, and additionally calls initgroups() to assure that the
process joins all the auxiliary groups that the given uid is a member
of.
---
 src/libvirt_private.syms |    1 +
 src/util/util.c          |   63 ++++++++++++++++++++++++++++++++++++++++++++++
 src/util/util.h          |    2 +
 3 files changed, 66 insertions(+), 0 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 0e3033d..befecc1 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -853,6 +853,7 @@ virRun;
 virRunWithHook;
 virSetCloseExec;
 virSetNonBlock;
+virSetUIDGID;
 virSkipSpaces;
 virStrToDouble;
 virStrToLong_i;
diff --git a/src/util/util.c b/src/util/util.c
index 7d3377b..a0ab28d 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -2811,6 +2811,60 @@ int virGetGroupID(const char *name,
     return 0;
 }
 
+
+/* Set the real and effective uid and gid to the given values, and call
+ * initgroups so that the process has all the assumed group membership of
+ * that uid. return 0 on success, -1 on failure.
+ */
+int
+virSetUIDGID(uid_t uid, gid_t gid)
+{
+    if (gid > 0) {
+        if (setregid(gid, gid) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot change to '%d' group"), gid);
+            return -1;
+        }
+    }
+
+    if (uid > 0) {
+        struct passwd pwd, *pwd_result;
+        char *buf = NULL;
+        size_t bufsize;
+
+        bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
+        if (bufsize == -1)
+            bufsize = 16384;
+
+        if (VIR_ALLOC_N(buf, bufsize) < 0) {
+            virReportOOMError();
+            return -1;
+        }
+        getpwuid_r(uid, &pwd, buf, bufsize, &pwd_result);
+        if (!pwd_result) {
+            virReportSystemError(errno,
+                                 _("cannot getpwuid_r(%d)"), uid);
+            VIR_FREE(buf);
+            return -1;
+        }
+        if (initgroups(pwd.pw_name, pwd.pw_gid) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot initgroups(\"%s\", %d)"),
+                                 pwd.pw_name, pwd.pw_gid);
+            VIR_FREE(buf);
+            return -1;
+        }
+        VIR_FREE(buf);
+
+        if (setreuid(uid, uid) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot change to uid to '%d'"), uid);
+            return -1;
+        }
+    }
+    return 0;
+}
+
 #else /* HAVE_GETPWUID_R */
 
 char *
@@ -2849,6 +2903,15 @@ int virGetGroupID(const char *name ATTRIBUTE_UNUSED,
 
     return 0;
 }
+
+int
+virSetUIDGID(uid_t uid ATTRIBUTE_UNUSED,
+             gid_t gid ATTRIBUTE_UNUSED)
+{
+    virUtilError(VIR_ERR_INTERNAL_ERROR,
+                 "%s", _("virSetUIDGID is not available"));
+    return -1;
+}
 #endif /* HAVE_GETPWUID_R */
 
 
diff --git a/src/util/util.h b/src/util/util.h
index ef4fc13..989962f 100644
--- a/src/util/util.h
+++ b/src/util/util.h
@@ -93,6 +93,8 @@ int virPipeReadUntilEOF(int outfd, int errfd,
                         char **outbuf, char **errbuf);
 int virFork(pid_t *pid);
 
+int virSetUIDGID(uid_t uid, gid_t gid);
+
 int virFileReadLimFD(int fd, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK;
 
 int virFileReadAll(const char *path, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK;
-- 
1.7.3.4