1 files changed, 145 insertions, 0 deletions
diff --git a/su/su.cpp b/su/su.cpp
new file mode 100644
index 00000000..ee1526ef
--- /dev/null
+++ b/su/su.cpp
@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <error.h>
+#include <getopt.h>
+#include <paths.h>
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <private/android_filesystem_config.h>
+
+void pwtoid(const char* tok, uid_t* uid, gid_t* gid) {
+    struct passwd* pw = getpwnam(tok);
+    if (pw) {
+        if (uid) *uid = pw->pw_uid;
+        if (gid) *gid = pw->pw_gid;
+    } else {
+        char* end;
+        errno = 0;
+        uid_t tmpid = strtoul(tok, &end, 10);
+        if (errno != 0 || end == tok) error(1, errno, "invalid uid/gid '%s'", tok);
+        if (uid) *uid = tmpid;
+        if (gid) *gid = tmpid;
+    }
+}
+
+void extract_uidgids(const char* uidgids, uid_t* uid, gid_t* gid, gid_t* gids, int* gids_count) {
+    char *clobberablegids;
+    char *nexttok;
+    char *tok;
+    int gids_found;
+
+    if (!uidgids || !*uidgids) {
+        *gid = *uid = 0;
+        *gids_count = 0;
+        return;
+    }
+
+    clobberablegids = strdup(uidgids);
+    strcpy(clobberablegids, uidgids);
+    nexttok = clobberablegids;
+    tok = strsep(&nexttok, ",");
+    pwtoid(tok, uid, gid);
+    tok = strsep(&nexttok, ",");
+    if (!tok) {
+        /* gid is already set above */
+        *gids_count = 0;
+        free(clobberablegids);
+        return;
+    }
+    pwtoid(tok, NULL, gid);
+    gids_found = 0;
+    while ((gids_found < *gids_count) && (tok = strsep(&nexttok, ","))) {
+        pwtoid(tok, NULL, gids);
+        gids_found++;
+        gids++;
+    }
+    if (nexttok && gids_found == *gids_count) {
+        fprintf(stderr, "too many group ids\n");
+    }
+    *gids_count = gids_found;
+    free(clobberablegids);
+}
+
+int main(int argc, char** argv) {
+    uid_t current_uid = getuid();
+    if (current_uid != AID_ROOT && current_uid != AID_SHELL) error(1, 0, "not allowed");
+
+    // Handle -h and --help.
+    ++argv;
+    if (*argv && (strcmp(*argv, "--help") == 0 || strcmp(*argv, "-h") == 0)) {
+        fprintf(stderr,
+                "usage: su [UID[,GID[,GID2]...]] [COMMAND [ARG...]]\n"
+                "\n"
+                "Switch to WHO (default 'root') and run the given command (default sh).\n"
+                "\n"
+                "where WHO is a comma-separated list of user, group,\n"
+                "and supplementary groups in that order.\n"
+                "\n");
+        return 0;
+    }
+
+    // The default user is root.
+    uid_t uid = 0;
+    gid_t gid = 0;
+
+    // If there are any arguments, the first argument is the uid/gid/supplementary groups.
+    if (*argv) {
+        gid_t gids[10];
+        int gids_count = sizeof(gids)/sizeof(gids[0]);
+        extract_uidgids(*argv, &uid, &gid, gids, &gids_count);
+        if (gids_count) {
+            if (setgroups(gids_count, gids)) {
+                error(1, errno, "setgroups failed");
+            }
+        }
+        ++argv;
+    }
+
+    if (setgid(gid)) error(1, errno, "setgid failed");
+    if (setuid(uid)) error(1, errno, "setuid failed");
+
+    // Reset parts of the environment.
+    setenv("PATH", _PATH_DEFPATH, 1);
+    unsetenv("IFS");
+    struct passwd* pw = getpwuid(uid);
+    if (pw) {
+        setenv("LOGNAME", pw->pw_name, 1);
+        setenv("USER", pw->pw_name, 1);
+    } else {
+        unsetenv("LOGNAME");
+        unsetenv("USER");
+    }
+
+    // Set up the arguments for exec.
+    char* exec_args[argc + 1];  // Having too much space is fine.
+    size_t i = 0;
+    for (; *argv != NULL; ++i) {
+      exec_args[i] = *argv++;
+    }
+    // Default to the standard shell.
+    if (i == 0) exec_args[i++] = const_cast<char*>("/system/bin/sh");
+    exec_args[i] = NULL;
+
+    execvp(exec_args[0], exec_args);
+    error(1, errno, "failed to exec %s", exec_args[0]);
+}