--- ../safeugid.diff	2019-10-02 13:37:13.191868203 +0200
+++ P	2019-10-02 13:36:09.036002978 +0200
@@ -0,0 +1,211 @@
+--- ./lib/rpmchroot.c.orig	2019-06-26 14:17:31.411985696 +0000
++++ ./lib/rpmchroot.c	2019-10-02 11:35:58.788024507 +0000
+@@ -126,6 +126,7 @@ int rpmChrootIn(void)
+ 
+ 	if (chdir("/") == 0 && chroot(rootState.rootDir) == 0) {
+ 	    rootState.chrootDone = 1;
++	    rpmugChroot(1);
+ 	} else {
+ 	    rpmlog(RPMLOG_ERR, _("Unable to change root directory: %m\n"));
+ 	    rc = -1;
+@@ -151,6 +152,7 @@ int rpmChrootOut(void)
+     } else if (rootState.chrootDone == 1) {
+ 	if (chroot(".") == 0 && fchdir(rootState.cwd) == 0) {
+ 	    rootState.chrootDone = 0;
++	    rpmugChroot(0);
+ 	} else {
+ 	    rpmlog(RPMLOG_ERR, _("Unable to restore root directory: %m\n"));
+ 	    rc = -1;
+--- ./lib/rpmug.c.orig	2019-06-26 14:17:31.418985685 +0000
++++ ./lib/rpmug.c	2019-10-02 11:35:58.788024507 +0000
+@@ -11,6 +11,47 @@
+ #include "lib/rpmug.h"
+ #include "debug.h"
+ 
++#if defined(__GLIBC__)
++
++static int inchroot;
++
++/*
++ * Unfortunatelly glibc caches nss/nscd data and there is no
++ * good way to flush those caches when we did a chroot(). Thus
++ * we need to parse /etc/passwd and /etc/group ourselfs.
++ */
++static int safe_lookup(const char * file, const char * name)
++{
++    FILE *fp;
++    int l;
++    char buf[4096], *p;
++
++    if (!name || !*name)
++	return -1;
++    l = strlen(name);
++    if ((fp = fopen(file, "r")) == 0)
++	return -1;
++    while ((p = fgets(buf, sizeof(buf), fp)) != 0) {
++	if (*p == '#')
++	    continue;
++	while (*p && (*p == ' ' || *p == '\t'))
++	    p++;
++	if (strncmp(p, name, l) != 0 || p[l] != ':')
++	    continue;
++	p = strchr(p + l + 1, ':');
++	if (!p)
++	    continue;
++	fclose(fp);
++	p++;
++	while (*p && (*p == ' ' || *p == '\t'))
++	    p++;
++	return atoi(p);
++    }
++    fclose(fp);
++    return -1;
++}
++#endif
++
+ /* 
+  * These really ought to use hash tables. I just made the
+  * guess that most files would be owned by root or the same person/group
+@@ -44,17 +85,28 @@ int rpmugUid(const char * thisUname, uid
+ 	    lastUnameAlloced = thisUnameLen + 10;
+ 	    lastUname = xrealloc(lastUname, lastUnameAlloced);	/* XXX memory leak */
+ 	}
+-	strcpy(lastUname, thisUname);
+ 
+-	pwent = getpwnam(thisUname);
+-	if (pwent == NULL) {
+-	    /* FIX: shrug */
+-	    endpwent();
++#if defined(__GLIBC__)
++	if (inchroot) {
++	    int uid =  safe_lookup("/etc/passwd", thisUname);
++	    if (uid < 0)
++		return -1;
++	    lastUid = uid;
++	} else
++#endif
++	{
+ 	    pwent = getpwnam(thisUname);
+-	    if (pwent == NULL) return -1;
++	    if (pwent == NULL) {
++		/* FIX: shrug */
++		endpwent();
++		pwent = getpwnam(thisUname);
++		if (pwent == NULL) return -1;
++	    }
++	    lastUid = pwent->pw_uid;
+ 	}
+ 
+-	lastUid = pwent->pw_uid;
++	strcpy(lastUname, thisUname);
++	lastUnameLen = thisUnameLen;
+     }
+ 
+     *uid = lastUid;
+@@ -87,18 +139,29 @@ int rpmugGid(const char * thisGname, gid
+ 	    lastGnameAlloced = thisGnameLen + 10;
+ 	    lastGname = xrealloc(lastGname, lastGnameAlloced);	/* XXX memory leak */
+ 	}
+-	strcpy(lastGname, thisGname);
+ 
+-	grent = getgrnam(thisGname);
+-	if (grent == NULL) {
+-	    /* FIX: shrug */
+-	    endgrent();
++#if defined(__GLIBC__)
++	if (inchroot) {
++	    int gid =  safe_lookup("/etc/group", thisGname);
++	    if (gid < 0)
++		return -1;
++	    lastGid = gid;
++	} else
++#endif
++	{
+ 	    grent = getgrnam(thisGname);
+ 	    if (grent == NULL) {
+-		return -1;
++		/* FIX: shrug */
++		endgrent();
++		grent = getgrnam(thisGname);
++		if (grent == NULL) {
++		    return -1;
++		}
+ 	    }
++	    lastGid = grent->gr_gid;
+ 	}
+-	lastGid = grent->gr_gid;
++	strcpy(lastGname, thisGname);
++	lastGnameLen = thisGnameLen;
+     }
+ 
+     *gid = lastGid;
+@@ -110,7 +173,7 @@ const char * rpmugUname(uid_t uid)
+ {
+     static uid_t lastUid = (uid_t) -1;
+     static char * lastUname = NULL;
+-    static size_t lastUnameLen = 0;
++    static size_t lastUnameAlloced = 0;
+ 
+     if (uid == (uid_t) -1) {
+ 	lastUid = (uid_t) -1;
+@@ -127,9 +190,9 @@ const char * rpmugUname(uid_t uid)
+ 
+ 	lastUid = uid;
+ 	len = strlen(pwent->pw_name);
+-	if (lastUnameLen < len + 1) {
+-	    lastUnameLen = len + 20;
+-	    lastUname = xrealloc(lastUname, lastUnameLen);
++	if (lastUnameAlloced < len + 1) {
++	    lastUnameAlloced = len + 20;
++	    lastUname = xrealloc(lastUname, lastUnameAlloced);
+ 	}
+ 	strcpy(lastUname, pwent->pw_name);
+ 
+@@ -141,7 +204,7 @@ const char * rpmugGname(gid_t gid)
+ {
+     static gid_t lastGid = (gid_t) -1;
+     static char * lastGname = NULL;
+-    static size_t lastGnameLen = 0;
++    static size_t lastGnameAlloced = 0;
+ 
+     if (gid == (gid_t) -1) {
+ 	lastGid = (gid_t) -1;
+@@ -158,9 +221,9 @@ const char * rpmugGname(gid_t gid)
+ 
+ 	lastGid = gid;
+ 	len = strlen(grent->gr_name);
+-	if (lastGnameLen < len + 1) {
+-	    lastGnameLen = len + 20;
+-	    lastGname = xrealloc(lastGname, lastGnameLen);
++	if (lastGnameAlloced < len + 1) {
++	    lastGnameAlloced = len + 20;
++	    lastGname = xrealloc(lastGname, lastGnameAlloced);
+ 	}
+ 	strcpy(lastGname, grent->gr_name);
+ 
+@@ -192,3 +255,16 @@ void rpmugFree(void)
+     rpmugUname(-1);
+     rpmugGname(-1);
+ }
++
++void rpmugChroot(int in)
++{
++    /* tell libc to drop caches / file descriptors */
++    endpwent();
++    endgrent();
++    /* drop our own caches */
++    rpmugUid(NULL, NULL);
++    rpmugGid(NULL, NULL);
++#if defined(__GLIBC__)
++    inchroot = in;
++#endif
++}
+--- ./lib/rpmug.h.orig	2019-06-26 14:17:31.418985685 +0000
++++ ./lib/rpmug.h	2019-10-02 11:35:58.788024507 +0000
+@@ -15,4 +15,6 @@ int rpmugInit(void);
+ 
+ void rpmugFree(void);
+ 
++void rpmugChroot(int in);
++
+ #endif /* _RPMUG_H */