Replace password in connection string with regular expression in C#

Question

I'm trying to create a regular expression in C# that will replace the password of a connection string so that it is not shown when I display it on a page. The connection string password are somewhere in the string as PWD=password;

So far I have:

Regex.Replace(connStr, "PWD=.*;", "PWD=********");

This works to find the beginning of the pattern, but the problem is the wild card (.*) is also including the ; so the pattern is never terminated and the remainder of the string is replaced too. How can I say everthing but a ; in my RegEx?

Thanks.

Answer 1

You don't need to use RegEx for this - .NET has the built-in SqlConnectionStringBuilder class which you can use to get values from the connection string and change them.

Example code:

string conString = "Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword;";
var builder = new SqlConnectionStringBuilder(conString);

builder.Password = "********";

Console.WriteLine(builder.ToString());

Answer 2

You can use a non-greedy quantifier:

PWD=.*?;

Or exclude ;s:

PWD=[^;]*;

Answer 3

Here is the regex I'm using

(?<=Password=).+?(?=(;|'|"|$))

With positiv look behind to find the start of the password, positiv look ahead to find the end of the Password and a not greedy match Expression. The "Detektion Tokens" (Password= ;'"$) might differ in varios scenarios.

Testcases: https://regex101.com/

c# implementation

using System.Text.RegularExpressions;
private static Regex _regex = new Regex("(?<=Password=).+?(?=(;|'|\"|$))");
//...
var decryptPwdMatch = _regex.Match("some connectionstring for example");
//...

Answer 4

We came across this issue and a colleague came up with the following regex:

"(?i)(?:^|.*;)pwd=(\".*\"|.*?)(?:;|$)+?"

or

"(?i)(?:^|.*;)password=(\".*\"|.*?)(?:;|$)+?"

if there is password in it instead of pwd.

The Password matches with the following code:

            var regex = new Regex(mask);
            var password = string.Empty;
            var match = regex.Match(connectionString);
            if (match.Success && match.Groups.Count > 1)
            {
                password = match.Groups[1].Value;
            }

Answer 5

Lots of problems with the suggested solution. This is not pure Regex, but handles casing, white spaces and optional trailing separators (, or ;)

public static class StringExtensions
{
    public static string MaskField(this string str, string field, string mask = "***")
    {
        var separators = ",;";
        var sb = new StringBuilder();

        foreach (var keyValue in Regex.Split(str, $"(?<=[{separators}])"))
        {
            var temp = keyValue;
            var index = keyValue.IndexOf("=");
            if (index > 0)
            {
                var key = keyValue.Substring(0, index);
                if (string.Compare(key.Trim(), field.Trim(), true) == 0)
                {
                    var end = separators.Contains(keyValue.Last()) ? keyValue.Last().ToString() : "";
                    temp = key + "=" + mask + end;
                }
            }

            sb.Append(temp);
        }

        return sb.ToString();
    }
}