CVE-2016-6494 (C++, published 2016-10-03T18:59Z)
Description: value: The client in MongoDB uses world-readable permissions on .dbshell history files, which might allow local users to obtain sensitive information by reading these files.
Severity: LOW (CVSS v3 base score: 5.5)
Weakness: CWE-200 \u2014 Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
Repository: https://github.com/mongodb/mongo
Files changed:
jstests/noPassthrough/shell_history.js
src/mongo/shell/linenoise.cpp
Commit message: SERVER-25335 avoid group and other permissions when creating .dbshell history file


Vulnerable code:
    FILE* fp = fopen(filename, "wt");
    fclose(fp);

Fixed code:
// Test that when running the shell for the first time creates the ~/.dbshell file, and it has
// appropriate permissions (where relevant).

(function() {
    "use strict";

    // Use dataPath because it includes the trailing "/" or "\".
    var tmpHome = MongoRunner.dataPath;
    // Ensure it exists and is a dir (eg. if running without resmoke.py and /data/db doesn't exist).
    mkdir(tmpHome);
    removeFile(tmpHome + ".dbshell");

    var args = [];
    var cmdline = "mongo --nodb";
    var redirection = "";
    var env = {};
    if (_isWindows()) {
        args.push("cmd.exe");
        args.push("/c");

        // Input is set to NUL.  The output must also be redirected to NUL, otherwise running the
        // jstest manually has strange terminal IO behaviour.
        redirection = "< NUL > NUL";

        // USERPROFILE set to the tmp homedir.
        // Since NUL is a character device, isatty() will return true, which means that .mongorc.js
        // will be created in the HOMEDRIVE + HOMEPATH location, so we must set them also.
        if (tmpHome.match("^[a-zA-Z]:")) {
            var tmpHomeDrive = tmpHome.substr(0, 2);
            var tmpHomePath = tmpHome.substr(2);
        } else {
            var _pwd = pwd();
            assert(_pwd.match("^[a-zA-Z]:"), "pwd must include drive");
            var tmpHomeDrive = _pwd.substr(0, 2);
            var tmpHomePath = tmpHome;
        }
        env = {USERPROFILE: tmpHome, HOMEDRIVE: tmpHomeDrive, HOMEPATH: tmpHomePath};

    } else {
        args.push("sh");
        args.push("-c");

        // Use the mongo shell from the current dir, same as resmoke.py does.
        // Doesn't handle resmoke's --mongo= option.
        cmdline = "./" + cmdline;

        // Set umask to 0 prior to running the shell.
        cmdline = "umask 0 ; " + cmdline;

        // stdin is /dev/null.
        redirection = "< /dev/null";

        // HOME set to the tmp homedir.
        if (!tmpHome.startsWith("/")) {
            tmpHome = pwd() + "/" + tmpHome;
        }
        env = {HOME: tmpHome};
    }

    // Add redirection to cmdline, and add cmdline to args.
    cmdline += " " + redirection;
    args.push(cmdline);
    jsTestLog("Running args:\n    " + tojson(args) + "\nwith env:\n    " + tojson(env));
    var pid = _startMongoProgram({args, env});
    var rc = waitProgram(pid);

    assert.eq(rc, 0);

    var files = listFiles(tmpHome);
    jsTestLog(tojson(files));

    var findFile = function(baseName) {
        for (var i = 0; i < files.length; i++) {
            if (files[i].baseName === baseName) {
                return files[i];
            }
        }
        return undefined;
    };

    var targetFile = ".dbshell";
    var file = findFile(targetFile);

    assert.neq(typeof(file), "undefined", targetFile + " should exist, but it doesn't");
    assert.eq(file.isDirectory, false, targetFile + " should not be a directory, but it is");
    assert.eq(file.size, 0, targetFile + " should be empty, but it isn't");

    if (!_isWindows()) {
        // On Unix, check that the file has the correct mode (permissions).
        // The shell has no way to stat a file.
        // There is no stat utility in POSIX.
        // `ls -l` is POSIX, so this is the best that we have.
        // Check for exactly "-rw-------".
        clearRawMongoProgramOutput();
        var rc = runProgram("ls", "-l", file.name);
        assert.eq(rc, 0);
        var output = rawMongoProgramOutput();
        var fields = output.split(" ");
        // First field is the prefix, second field is the `ls -l` permissions.
        assert.eq(fields[1], "-rw-------", targetFile + " has bad permissions");
    }

})();
    FILE* fp;
#if _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
    int fd = open(filename, O_CREAT, S_IRUSR | S_IWUSR);
    if (fd == -1) {
        // report errno somehow?
        return -1;
    }
    fp = fdopen(fd, "wt");
#else
    fp = fopen(filename, "wt");
#endif  // _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
    fclose(fp);  // Also causes fd to be closed.