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diff --git a/auth.c b/auth.c
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index b8d1040d..0134d694 100644
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--- a/auth.c
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+++ b/auth.c
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@@ -56,6 +56,7 @@
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 # include <paths.h>
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 #endif
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 #include <pwd.h>
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+#include <grp.h>
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 #ifdef HAVE_LOGIN_H
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 #include <login.h>
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 #endif
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@@ -2695,6 +2696,12 @@ subprocess(const char *tag, const char *command,
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 		}
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 		closefrom(STDERR_FILENO + 1);
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+		if (geteuid() == 0 &&
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+		    initgroups(pw->pw_name, pw->pw_gid) == -1) {
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+			error("%s: initgroups(%s, %u): %s", tag,
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+			    pw->pw_name, (u_int)pw->pw_gid, strerror(errno));
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+			_exit(1);
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+		}
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		/* Don't use permanently_set_uid() here to avoid fatal() */
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 		if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
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 			error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,