1 files changed, 155 insertions, 0 deletions

diff --git a/other/ssharp/uidswap.c b/other/ssharp/uidswap.c
new file mode 100644
index 0000000..3b264cf
--- /dev/null
+++ b/other/ssharp/uidswap.c
@@ -0,0 +1,155 @@
+/*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ * Code for uid-swapping.
+ *
+ * As far as I am concerned, the code I have written for this software
+ * can be used freely for any purpose.  Any derived versions of this
+ * software must be clearly marked as such, and if the derived work is
+ * incompatible with the protocol description in the RFC file, it must be
+ * called by a name other than "ssh" or "Secure Shell".
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: uidswap.c,v 1.16 2001/04/20 16:32:22 markus Exp $");
+
+#include "log.h"
+#include "uidswap.h"
+
+/*
+ * Note: all these functions must work in all of the following cases:
+ *    1. euid=0, ruid=0
+ *    2. euid=0, ruid!=0
+ *    3. euid!=0, ruid!=0
+ * Additionally, they must work regardless of whether the system has
+ * POSIX saved uids or not.
+ */
+
+#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
+/* Lets assume that posix saved ids also work with seteuid, even though that
+   is not part of the posix specification. */
+#define SAVED_IDS_WORK_WITH_SETEUID
+/* Saved effective uid. */
+static uid_t    saved_euid = 0;
+static gid_t    saved_egid = 0;
+#endif
+
+/* Saved effective uid. */
+static int      privileged = 0;
+static int      temporarily_use_uid_effective = 0;
+static gid_t    saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
+static int      saved_egroupslen = -1, user_groupslen = -1;
+
+/*
+ * Temporarily changes to the given uid.  If the effective user
+ * id is not root, this does nothing.  This call cannot be nested.
+ */
+void
+temporarily_use_uid(struct passwd *pw)
+{
+        /* Save the current euid, and egroups. */
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+        saved_euid = geteuid();
+        saved_egid = getegid();
+        debug("temporarily_use_uid: %d/%d (e=%d)",
+            pw->pw_uid, pw->pw_gid, saved_euid);
+        if (saved_euid != 0) {
+                privileged = 0;
+                return;
+        }
+#else
+        if (geteuid() != 0) {
+                privileged = 0;
+                return;
+        }
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+
+        privileged = 1;
+        temporarily_use_uid_effective = 1;
+        saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);                           
+        if (saved_egroupslen < 0)
+                fatal("getgroups: %.100s", strerror(errno));
+
+        /* set and save the user's groups */
+        if (user_groupslen == -1) {
+                if (initgroups(pw->pw_name, pw->pw_gid) < 0)
+                        fatal("initgroups: %s: %.100s", pw->pw_name,
+                            strerror(errno));
+                user_groupslen = getgroups(NGROUPS_MAX, user_groups);                           
+                if (user_groupslen < 0)
+                        fatal("getgroups: %.100s", strerror(errno));
+        }
+#ifndef HAVE_CYGWIN
+        /* Set the effective uid to the given (unprivileged) uid. */
+        if (setgroups(user_groupslen, user_groups) < 0)
+                fatal("setgroups: %.100s", strerror(errno));
+#endif /* !HAVE_CYWIN */
+#ifndef SAVED_IDS_WORK_WITH_SETEUID
+        /* Propagate the privileged gid to all of our gids. */
+        if (setgid(getegid()) < 0)
+                debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
+        /* Propagate the privileged uid to all of our uids. */
+        if (setuid(geteuid()) < 0)
+                debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+        if (setegid(pw->pw_gid) < 0)
+                fatal("setegid %u: %.100s", (u_int) pw->pw_gid,
+                    strerror(errno));
+        if (seteuid(pw->pw_uid) == -1)
+                fatal("seteuid %u: %.100s", (u_int) pw->pw_uid,
+                    strerror(errno));
+}
+
+/*
+ * Restores to the original (privileged) uid.
+ */
+void
+restore_uid(void)
+{
+        debug("restore_uid");
+        /* it's a no-op unless privileged */
+        if (!privileged)
+                return;
+        if (!temporarily_use_uid_effective)
+                fatal("restore_uid: temporarily_use_uid not effective");
+
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+        /* Set the effective uid back to the saved privileged uid. */
+        if (seteuid(saved_euid) < 0)
+                fatal("seteuid %u: %.100s", (u_int) saved_euid, 
+                    strerror(errno));
+        if (setegid(saved_egid) < 0)
+                fatal("setegid %u: %.100s", (u_int) saved_egid, 
+                    strerror(errno));
+#else /* SAVED_IDS_WORK_WITH_SETEUID */
+        /*
+         * We are unable to restore the real uid to its unprivileged value.
+         * Propagate the real uid (usually more privileged) to effective uid
+         * as well.
+         */
+        setuid(getuid());
+        setgid(getgid());
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+
+#ifndef HAVE_CYGWIN
+        if (setgroups(saved_egroupslen, saved_egroups) < 0)
+                fatal("setgroups: %.100s", strerror(errno));
+#endif /* !HAVE_CYGWIN */
+        temporarily_use_uid_effective = 0;
+}
+
+/*
+ * Permanently sets all uids to the given uid.  This cannot be
+ * called while temporarily_use_uid is effective.
+ */
+void
+permanently_set_uid(struct passwd *pw)
+{
+        if (temporarily_use_uid_effective)
+                fatal("restore_uid: temporarily_use_uid effective");
+        if (setgid(pw->pw_gid) < 0)
+                fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno));
+        if (setuid(pw->pw_uid) < 0)
+                fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno));
+}