From 7f1562fbf9262270b31d1007e400dd6605d81f99 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sun, 1 May 2016 18:56:11 -0700
Subject: Adding getresuid, getresuid, getresgid and setresgid.

* configure: Test for these functions.

* sysif.c (getresuid_wrap, getresgid_wrap, setresuid_wrap,
setresgid_wrap): New static function.
(sysif_init): Registered getresuid, setresgid, setresuid and
setresgid intrinsics.

* txr.1: Documented all four functions.
---
 configure | 26 ++++++++++++++++++++++++++
 sysif.c   | 45 +++++++++++++++++++++++++++++++++++++++++++++
 txr.1     | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 107 insertions(+)

diff --git a/configure b/configure
index e0759ab1..d78b791c 100755
--- a/configure
+++ b/configure
@@ -2193,6 +2193,32 @@ else
   printf "no\n"
 fi
 
+printf "Checking for {set,get}res{uid,gid} ... "
+
+cat > conftest.c <<!
+#include <sys/types.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+  uid_t ur, ue, us;
+  gid_t gr, ge, gs;
+  int gur = getresuid(&ur, &ue, &us);
+  int ggr = getresgid(&gr, &ge, &gs);
+  int sur = setresuid(0, 0, 0);
+  int sgr = setresgid(0, 0, 0);
+  return 0;
+}
+!
+
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_SETRESUID 1\n" >> $config_h
+  have_unistd=y
+else
+  printf "no\n"
+fi
+
 printf "Checking for setgroups ... "
 
 cat > conftest.c <<!
diff --git a/sysif.c b/sysif.c
index bc0dc822..cb0ae918 100644
--- a/sysif.c
+++ b/sysif.c
@@ -978,6 +978,44 @@ static val setgroups_wrap(val list)
 
 #endif
 
+#if HAVE_SETRESUID
+
+static val getresuid_wrap(void)
+{
+  uid_t r, e, s;
+  if (getresuid(&r, &e, &s) != 0)
+    uw_throwf(system_error_s, lit("getresuid failed: ~d/~s"),
+              num(errno), string_utf8(strerror(errno)), nao);
+  return list(num(r), num(e), num(s), nao);
+}
+
+static val getresgid_wrap(void)
+{
+  gid_t r, e, s;
+  if (getresgid(&r, &e, &s) != 0)
+    uw_throwf(system_error_s, lit("getresgid failed: ~d/~s"),
+              num(errno), string_utf8(strerror(errno)), nao);
+  return list(num(r), num(e), num(s), nao);
+}
+
+static val setresuid_wrap(val r, val e, val s)
+{
+  if (setresuid(c_num(r), c_num(e), c_num(s)) != 0)
+    uw_throwf(system_error_s, lit("setresuid failed: ~d/~s"),
+              num(errno), string_utf8(strerror(errno)), nao);
+  return t;
+}
+
+static val setresgid_wrap(val r, val e, val s)
+{
+  if (setresuid(c_num(r), c_num(e), c_num(s)) != 0)
+    uw_throwf(system_error_s, lit("setresuid failed: ~d/~s"),
+              num(errno), string_utf8(strerror(errno)), nao);
+  return t;
+}
+
+#endif
+
 #if HAVE_PWUID
 
 static val setpwent_wrap(void)
@@ -1542,6 +1580,13 @@ void sysif_init(void)
   reg_fun(intern(lit("setgroups"), user_package), func_n1(setgroups_wrap));
 #endif
 
+#if HAVE_SETRESUID
+  reg_fun(intern(lit("getresuid"), user_package), func_n0(getresuid_wrap));
+  reg_fun(intern(lit("getresgid"), user_package), func_n0(getresgid_wrap));
+  reg_fun(intern(lit("setresuid"), user_package), func_n3(setresuid_wrap));
+  reg_fun(intern(lit("setresgid"), user_package), func_n3(setresgid_wrap));
+#endif
+
 #if HAVE_PWUID
   reg_fun(intern(lit("setpwent"), user_package), func_n0(setpwent_wrap));
   reg_fun(intern(lit("endpwent"), user_package), func_n0(endpwent_wrap));
diff --git a/txr.1 b/txr.1
index 85e24742..6e43007f 100644
--- a/txr.1
+++ b/txr.1
@@ -37006,6 +37006,42 @@ is returned.
 On failure, it throws an exception of type
 .codn system-error .
 
+.coNP Functions @ getresuid and @ getresgid
+.synb
+.mets (getresuid)
+.mets (getresgid)
+.syne
+.desc
+These functions directly correspond to the POSIX C library functions
+of the same names available in some Unix operating systems.
+Each function retrieves a three element list of numeric IDs.
+The
+.code getresuid
+function retrieves the real, effective and saved user ID of
+the calling process.
+The
+.code getresgid
+function retrieves the real, effective and saved group ID of
+the calling process.
+
+.coNP Functions @ setresuid and @ setresgid
+.synb
+.mets (setresuid < real-uid < effective-uid << saved-uid )
+.mets (setresgid < real-gid < effective-gid << saved-gid )
+.syne
+.desc
+These functions directly correspond to the POSIX C library functions of the
+same names available in some Unix operating systems.  They change the real,
+effective and saved user ID or group ID, respectively, of the calling process.
+
+A value of -1 for any of the IDs specifies that the ID is not to be changed.
+
+Only privileged processes may arbitrarily change IDs to different values.
+
+Unprivileged processes are restricted in the following way:
+each of the new IDs that is replaced must have a new value which is equal to
+one of the existing three IDs.
+
 .SS* Unix Password Database
 
 .coNP Structure @ passwd
-- 
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