From: Rich Felker <dalias@aerifal.cx>
Date: Fri, 24 Jun 2011 02:04:06 +0000 (-0400)
Subject: prepare support for LD_LIBRARY_PATH (checking suid/sgid safety)
X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=commitdiff_plain;h=b7f6e0c6f848b7a8c64b3f7b72014b48a9923729

prepare support for LD_LIBRARY_PATH (checking suid/sgid safety)

the use of this test will be much stricter than glibc and other
typical implementations; the environment will not be honored
whatsoever unless the program is confirmed non-suid/sgid by the aux
vector the kernel passed in. no fallback to slow syscall-based
checking is used if the kernel fails to provide the information; we
simply assume the worst (suid) in this case and refuse to honor
environment.
---

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 8ade0737..b308b875 100644
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -48,6 +48,7 @@ struct dso
 };
 
 static struct dso *head, *tail, *libc;
+static int trust_env;
 
 #define AUX_CNT 15
 #define DYN_CNT 34
@@ -373,6 +374,11 @@ void *__dynlink(int argc, char **argv, size_t *got)
 
 	/* At this point the standard library is fully functional */
 
+	/* Only trust user/env if kernel says we're not suid/sgid */
+	trust_env = (aux[0]&0x7800)==0x7800
+		&& aux[AT_UID]==aux[AT_EUID]
+		&& aux[AT_GID]==aux[AT_EGID];
+
 	head = tail = &app;
 	libc = &lib;
 	app.next = 0;