Role-based access control used in MS Access - ms-access

I am currently working on a project were one of the requirements are to use the users windows login as their login for MS Access, where they would then click there role to gain access into the system. I have never done this before but I have set up a login screen in Access which pulls data from a table. I have code that successfully pulls the users windows login but I am having trouble after this. The table name is tblUser and the users are General User, HR, and Admin. Currently, In the table I have the roles assigned number with General User = 1, HR = 2, Admin = 3.
The Login Screen:
Log On
General User
HR
Admin
Code that pulls the user information:
Private Sub Form_Load()
Stop
Debug.Print Environ("UserName")
Debug.Print Environ$("ComputerName")
Dim strVar As String
Dim i As Long
For i = 1 To 255
strVar = Environ$(i)
If LenB(strVar) = 0& Then Exit For
Debug.Print strVar
Next
End Sub
Below is the code that I built for my login screen in the past. Through drawing everything out it seems as though it would be the same process but I am not to sure. Is there anything that I can do to the code below?
Private Sub btnLogin_Click()
Dim rs As Recordset
Set rs = CurrentDb.OpenRecordset("tblUser", dbOpenSnapshot, dbReadOnly)
rs.FindFirst "UserName='" & Me.txtUserName & "'"
If rs.NoMatch = True Then
Me.lblWrongUser.Visible = True
Me.txtUserName.SetFocus
Exit Sub
End If
Me.lblWrongUser.Visible = False
If rs!Password <> Nz(Me.txtPassword, "") Then
Me.lblWrongPass.Visible = True
Me.txtPassword.SetFocus
Exit Sub
End If
Me.lblWrongPass.Visible = False
If rs!EmployeeType_ID = 3 Then
Dim prop As Property
On Error GoTo SetProperty
Set prop = CurrentDb.CreateProperty("AllowBypassKey", dbBoolean, False)
CurrentDb.Properties.Append prop
SetProperty:
If MsgBox("Would you like to turn on the bypass key?", vbYesNo, "Allow Bypass") = vbYes Then
CurrentDb.Properties("AllowBypassKey") = True
Else
CurrentDb.Properties("AllowBypassKey") = False
End If
End If
DoCmd.OpenForm "frmPersonal_Information"
DoCmd.Close acForm, Me.Name
End Sub
I hope this is enough information for what I am trying to accomplish. If anymore information is needed please let me know. Thank you.

You do not need a login screen if the roles are tied to your Windows/Active Directory logins. You should make the assumption that the logged on user in Windows is legitimately using the workstation (and if that is not a safe assumption you need to look into your IT policies).
Access does not support roles and permissions. After accessing which user is currently logged on and getting their role from tblUser will have to:
Lock down the back end and especially access to the tables.
Lock down most of the user interface inherent to Access and only allow your front end forms to be used.
For each form of your front end manually make sure that whatever policies you wish to enforce are enforced using VBA.
Ultimately no matter what you do, somebody that knows how to use Access well can bypass any kind of lockdown you put in place. If you need to guard against more than casual curiosity and honest errors, you will need to combine Access with a much more robust DBMS like SQL server or MySQL.

Related

Access VBA login application

I am writing this little login validation application as a step of my VBA learning process. The application should check whether the login name is "sa" and the password is "XEL". The application should allow the user to enter the username and password for a maximum of three times. If in the all of the three attempts, a wrong usename and password is entered, the application should display an error and close. And blow is my code:
Private Sub Command6_Click()
Me.Text0.SetFocus
cID = Text0.Text
Me.Text4.SetFocus
cPswd = Text4.Text
For i = 1 To 3
validpswd = False
If cID = "sa" And cPswd = "XEL" Then
validpswd = True
MsgBox "Successful"
Exit For
Else
MsgBox "Try again"
Exit For
End If
Next i
'MsgBox ("byebye")
'DoCmd.Close acForm, "Used Car Sales", acSaveYes
End Sub
Now it does the checking/validating part. But it doesn't do the three times max limitation, I am kind of confused as how to put the last message box code and close command into the whole code blocks. Any helps are appreciated.
Thank you very much.
What I see wrong is you are having them type in the username/password then click a button. That button then checks to see if the username/password matches the predefined values three times in a row. That is a problem because the user wouldn't be able to actually try three times.
To fix it, you create a Module/Form level variable and initialize it in the form load to 0. then you check in the button click if that variable is greater than 2. If it is, then you run your close procedure. If it isnt, then it checks your username and password to see if they are correct, if they aren't then it increments the Module level variable by 1. Example below.
EDIT: added a check since it doesn't quite catch it after the 3rd try. Feels a bit ugly, but it works.
EDIT2: Dyslexia moment, fixed the greater then, less then signs for the if statements and the associated values
Dim Tries as Long
Private Sub Form_Load()
Tries = 0
End Sub
Private Sub Command6_Click()
If Tries < 3 Then
cID = Text0.Text
cPswd = Text4.Text
validpswd = False
If cID = "sa" And cPswd = "XEL" Then
validpswd = True
MsgBox "Successful"
Else
Tries = Tries + 1
If Tries > 2 Then
MsgBox ("byebye")
DoCmd.Close acForm, "Used Car Sales", acSaveYes
else
MsgBox "Try again"
end if
End If
'MsgBox ("byebye")
'DoCmd.Close acForm, "Used Car Sales", acSaveYes
End If
End Sub
Thanks all. This is what I did eventually. I am sure there is other better way to do this and please comment to let me know as well
If try < 3 Then
If cID <> "sa" Or cPswd <> "XEL" Then
try = try + 1
MsgBox "Try again"
Else
MsgBox "Successful"
try = 0
End If
If try = 3 Then
MsgBox ("Too many tries")
DoCmd.Close acForm, "Login Test", acSaveYes
End If
End If

Deleting record on Continuous form in MS Access using acCmdDeleteRecord

I have continuous form with just 2 fields and a button.
Design View
'
Form View
Below is the code for Delete Button.
Private Sub cmdDelete_Click()
DoCmd.RunCommand acCmdDeleteRecord
Debug.Print "IDWeb - " & Me.IDWeb
'Here I Execute a Web API to Delete Data based on Me.IDWeb
End Sub
The Problem - Web API does not get the Me.IDWeb Value . SOme times the IDWeb is captured correctly, sometimes not.
Edit1 : I tried the code below. But still the problem exists.
I guess the users can be on another record when they deleted the current record. Hence the issue. But the record is currently deleted in MS Access. Only the problem is Me.IDWeb is NOT captured correctly, and hence my web API is getting failed.
Private Sub cmdDelete_Click()
Me.WebType.SetFocus
If Me.IDWeb = "" Or Me.IDWeb = vbNull Or Me.IDWeb = vbNullString Then
MsgBox "No Record Selected"
Else
DoCmd.RunCommand acCmdSelectRecord
DoCmd.RunCommand acCmdDeleteRecord
Debug.Print "IDWeb - " & Me.IDWeb
'Here I execute my Web API to Delete based on Me.IDWeb
End If
End Sub
The solution was to first get Me.IDWeb and store it in a variable,
then run acCmdDeleteRecord afterwards.
Personally, I don't use DoCmd. You are trying to get the IdWeb of a deleted record.
Assuming your IDWeb is a number (if not use the appropriate data type), the following should work
Dim lngIdWeb as long
lngIdWeb = nz(Me.IdWeb, 0)
If lngIdWeb > 0 Then
Me.RecordsetClone.FindFirst "IdWeb = " & lngIdWeb
If Not Me.RecordsetClone.NoMatch Then
Me.RecordsetClone.Delete
End If
Debug.Print "IdWeb - " & lngIdWeb
End If

how to write a script to look for and correct invalid entries in a table

First off I'd like to make perfectly clear that my knowledge of Access and VBA is extremely limited at best. I have an employee database system that due to it's age has been prone to small data corruption issues and controls breaking due to differences between 2003/2007 and 2010. While I've managed to hash out the bulk of the problems, one that has me especially concered is the script we're using to manage access to the database. The system is split between two files, a frontend where users can access the database and a backend file that contains all of the tables.
The issue I have is in the frontend form that handles the logon for the users. The way the access system is set up is the user enters their SSN, then the script finds their SSN in the table and if it exists looks if an access checkbox is checked. If they have access, they're directed to the main menu, if not they get a denied message. What I've found though is for some reason or another, if an entry in the personnel table has an incomplete SSN, the script breaks and anyone can gain access to the database.
There's a query that runs in the frontend that looks at the master personnel table and pulls just the first two columns, SSAN and Access.
The form itself has a visible text box, "Text8", and a hidden Combo Box "Combo4". Combo4 uses the previously mentioned query for the row source (SELECT qryAccess.SSAN FROM qryAccess;), while Text8 is where the user enters their SSN.
Here's the code right now:
Option Compare Database
Private Sub Combo4_AfterUpdate()
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
Private Sub Text8_AfterUpdate()
Me![Combo4] = Me![Text8]
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
Like I said before, as long as every entry for the SSNs is a full 9-digits, this system works. However, if for some reason the entry is not the full 9 like I just found in my database (and no, I have no idea what caused that to happen, there is an input mask in place, 000-00-0000;;_), this system breaks. You could type in "abc" for the SSN and gain access to the database.
How can I write a small script that pre-checks the table for SSN entries that don't fit the 9-digit format that is set, and if it finds them, resets them to an unused number, such as 000000000, 000000001, etc?
Also, if you have any suggestions on how to streamline the existing code, I'd be more than happy to take them.
Add this function to you application
Public Function IsValidSSN(ByVal SSN As String) As Boolean
'Determines if SSN is a valid social security number
'requires SSN to be in either "#########" or "###-##-####" format
IsValidSSN = (SSN Like "###-##-####") Or _
SSN Like ("#########")
End Function
Also change your function to this:
Private Sub Combo4_AfterUpdate()
' Find the record that matches the control.
If IsValidSSN(Me![Combo4]) Then
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
Else
DoCmd.OpenForm "frmDenied"
End IF
End Sub
Private Sub Text8_AfterUpdate()
Me![Combo4] = Me![Text8]
If IsValidSSN(Me![Text8]) Then
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
EDIT
Also why are you using a combobox to enter a SSN? You can use input mask on text box. Also I would highly suggest that you convert your system to some other identification other than SSN because it is easily passable to get past this code to look at the table containing everyones SSN, by holding down shift when opening the application. As for streamlining your code just remove that combobox altogether. If they are typing it into a textbox there is no need to put it into a hidden combobox.
You have a text field, SSAN, and with that input mask the dashes are not included in the stored values. So valid values would be 9 digit strings.
If that is correct, you can use a query to identify any invalid stored values.
SELECT y.SSAN, Len(SSAN) AS LenghtOfSSAN
FROM YourTable AS y
WHERE Len(SSAN)<>9 OR y.SSAN ALike '%[!0-9]%';
That query will return rows where SSAN includes < or > 9 characters, and any values which include characters other than digits.
Note the ALike keyword tells the db engine to expect ANSI wild card characters.  If you prefer Access' * wild card instead, change it to Like '*[!0-9]*'
Once you fix the stored values, add a Validation rule for that SSAN field (Like "#########") to require all values consist of 9 digits.
Since it looks like this became more of a "How do I find the user" than "How do I fix the existing entries", let me throw my hat into the ring.
Unless I completely misunderstand this, the existing (and accepted answer) function is HORRIBLE. You can do this all much more efficiently and with less code. First of all, delete Combo4. No need for it. Then do this:
Private Sub Text8_AfterUpdate()
Dim X as Integer
X = DLookup("Access", "qryAccess", "SSAN = '" & Me!Text8 & "'")
If Nz(X) = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
That's all you need. If the user's SSN was stored incorrectly, he's gonna be denied. 7 digits, 8 digits, doesn't make a difference. Only exact matches get through. That is, assuming 0 = False and 1 = True, which should be the default anyway.

How to see who is using my Access database over the network?

I actually have 2 questions:
1. How might I see who is using my Access database?
E.g: There is someone with an Access database opened and it created the .ldb file, I would like to see a list of who opened that database (it could be more than one person).
2. How might I see who is using a linked table?
E.g: I have 10 different Access databases, and all of them are using a same linked table. I would like to see who is using that linked table.
I don't even know if it's really possible, but I really appreciate your help!
For you information: The main problem is that lots of people use the same Access in the same network drive, so when I need to change it I have to kick them all out, but I never know who is actually using it.
Update: Rather than reading and parsing the .ldb/.lacdb file, a better approach would be to use the "User Roster" feature of the Access OLEDB provider as described in the Knowledge Base article
https://support.microsoft.com/en-us/kb/285822
and in the other SO question
Get contents of laccdb file through VBA
Original answer:
I put together the following a while ago. It looked promising but then I discovered that computers are not immediately removed from the lock file when they disconnect. Instead, Jet/ACE seems to (internally) mark them as inactive: If ComputerA disconnects and then ComputerB connects, ComputerB overwrites ComputerA's entry in the lock file.
Still, it does provide a list of sorts. I'm posting it here in case somebody can offer some suggestions for refinement.
I created two tables in my back-end database:
Table: [CurrentConnections]
computerName Text(255), Primary Key
Table: [ConnectionLog]
computerName Text(255), Primary Key
userName Text(255)
A VBA Module in my back-end database contained the following code to read (a copy of) the lock file and update the [CurrentConnections] table:
Public Sub GetCurrentlyConnectedMachines()
Dim cdb As DAO.Database, rst As DAO.Recordset
Dim fso As Object '' FileSystemObject
Dim lck As Object '' ADODB.Stream
Dim lockFileSpec As String, lockFileExt As String, tempFileSpec As String
Dim buffer() As Byte
Set cdb = CurrentDb
cdb.Execute "DELETE FROM CurrentConnections", dbFailOnError
Set rst = cdb.OpenRecordset("SELECT computerName FROM CurrentConnections", dbOpenDynaset)
lockFileSpec = Application.CurrentDb.Name
If Right(lockFileSpec, 6) = ".accdb" Then
lockFileExt = ".laccdb"
Else
lockFileExt = ".ldb"
End If
lockFileSpec = Left(lockFileSpec, InStrRev(lockFileSpec, ".", -1, vbBinaryCompare) - 1) & lockFileExt
'' ADODB.Stream cannot open the lock file in-place, so copy it to %TEMP%
Set fso = CreateObject("Scripting.FileSystemObject") '' New FileSystemObject
tempFileSpec = fso.GetSpecialFolder(2) & "\" & fso.GetTempName
fso.CopyFile lockFileSpec, tempFileSpec, True
Set lck = CreateObject("ADODB.Stream") '' New ADODB.Stream
lck.Type = 1 '' adTypeBinary
lck.Open
lck.LoadFromFile tempFileSpec
Do While Not lck.EOS
buffer = lck.Read(32)
rst.AddNew
rst!computerName = DecodeSZ(buffer)
rst.Update
buffer = lck.Read(32) '' skip accessUserId, (almost) always "Admin"
Loop
lck.Close
Set lck = Nothing
rst.Close
Set rst = Nothing
Set cdb = Nothing
fso.DeleteFile tempFileSpec
Set fso = Nothing
End Sub
Private Function DecodeSZ(buf() As Byte) As String
Dim b As Variant, rt As String
rt = ""
For Each b In buf
If b = 0 Then
Exit For '' null terminates the string
End If
rt = rt & Chr(b)
Next
DecodeSZ = rt
End Function
The following code in the Main_Menu form of the front-end database updated the [ConnectionLog] table
Private Sub Form_Load()
Dim cdb As DAO.Database, rst As DAO.Recordset
Dim wshNet As Object '' WshNetwork
Set wshNet = CreateObject("Wscript.Network")
Set cdb = CurrentDb
Set rst = cdb.OpenRecordset("SELECT * FROM ConnectionLog", dbOpenDynaset)
rst.FindFirst "ComputerName=""" & wshNet.computerName & """"
If rst.NoMatch Then
rst.AddNew
rst!computerName = wshNet.computerName
Else
rst.Edit
End If
rst!userName = wshNet.userName
rst.Update
Set wshNet = Nothing
End Sub
Finally, the following form in the back-end database listed [its best guess at] the current connections
It is a "continuous forms" form whose Record Source is
SELECT CurrentConnections.computerName, ConnectionLog.userName
FROM CurrentConnections LEFT JOIN ConnectionLog
ON CurrentConnections.computerName = ConnectionLog.computerName
ORDER BY ConnectionLog.userName;
and the code-behind is simply
Private Sub Form_Load()
UpdateFormData
End Sub
Private Sub cmdRefresh_Click()
UpdateFormData
End Sub
Private Sub UpdateFormData()
GetCurrentlyConnectedMachines
Me.Requery
End Sub
Easy. Open the .ldb file in notepad (or any text editor) and you can see the machine names.
RE: How might I see who is using my Access database?
•E.g: There is someone with an Access database opened and it created the .ldb file, I would like to see a list of who opened that database (it could be more than one person).
Just happened across this while looking for something else, and I thought I might share what I do for this. Note that this assumes that the host computer (the computer on which the database file resides) uses file sharing to provide access to the file.
You will need to be on the host computer, or have authority to connect to that machine.
click Start
right-click My Computer and select Manage
if you're not on the host computer, right-click 'Computer Management' and enter the host's name
Expand 'Shared Folders' and click on 'Open Files'
At the right is the list of currently open files with the username for each current user
I agree with Gord's Original answer. I used this code on my database, it seems that there is a way around computers not being taken out of CurrentConnections upon exit of the DB.
I placed this on my main menu form because it is always open until the user exits. I used the unload event on my form to get this to work, and it works awesome! Here is my code
p.s. Ignore SetWarnings I just have that on so the user doesn't have to click through prompts.
Private Sub Form_Unload(Cancel As Integer)
Dim wshNet As Object
Dim deleteSQL As String
Set wshNet = CreateObject("WScript.Network")
DoCmd.SetWarnings False
deleteSQL = "DELETE tblCurrentConnections.* " & _
"FROM tblCurrentConnections WHERE[computerName] = '" & wshNet.computerName & "';"
DoCmd.RunSQL deleteSQL
DoCmd.SetWarnings True
End Sub

Does it degrade performance to use subforms in MS Access?

I am considering the use of a tab control on a parent form for which I would like to have around 20 tabs. Each tab I am considering the use of one or two separate sub forms. Each sub form will have varied complexity in coded logic. By taking this approach will I severally reduce the performance of my application? I am currently using this in MS Access 2003. I will expect an average of 15 users at any given time on the various forms.
Thoughts?
Yes, performance will be degraded slightly for each subform. One or three isn't too bad but twenty is definitely going to cause you performance issues.
Once you have the subform working to your satisfaction either save the Record Source as a query and give it a name or save the query SQL string. Then either paste the query name or the query SQL string in the VBA code in the tab control change event.
Private Sub TabCtl_Change()
On Error GoTo TabCtl_Change_Error
Select Case Me.TabCtl.Value
Case Me.pagPartsConsumed.PageIndex
If Me.PartsConsumedsbf.Form.RecordSource <> "Equipment - Parts Consumed sbf" Then _
Me.PartsConsumedsbf.Form.RecordSource = "Equipment - Parts Consumed sbf"
....
Now just to ensure that I don't accidentally leave some subform recordsources filled in slowing down the app on startup I check to see if the file the code is running is an MDB (instead of an MDE. The function is below) then display a message telling me I have to remove the recordsource.
If Not tt_IsThisAnMDE Then
If Me.PartsConsumedsbf.Form.RecordSource <> "" Then _
MsgBox "Record source of Equipment - Parts Consumed sbf not empty"
...
End If
Public Function tt_IsThisAnMDE()
On Error GoTo tagError
Dim dbs As Database
Set dbs = CurrentDb
Dim strMDE As String
On Error Resume Next
strMDE = dbs.Properties("MDE")
If Err = 0 And strMDE = "T" Then
' This is an MDE database.
tt_IsThisAnMDE = True
Else
tt_IsThisAnMDE = False
End If
Exit Function
tagError:
Call LogError(Application.CurrentObjectName, "")
Exit Function
End Function
Also in the form unload event I clear the Recourd Source as well.
Private Sub Form_Unload(Cancel As Integer)
On Error GoTo Form_Unload_Error
Me.PartsConsumedsbf.Form.RecordSource = ""
....
BTW I almost always would put each subform on a seperate tab. Also that many tab entries gets visusally unwieldy. When I had a similar question my fellow Access MVPs suggested using a listbox along the left hand side to control which subform is viewable.
Also each combo box and list box will also slightly degrade the performance. So if you have those on a subform then consider similar logic.
In addition to adding recordsets at runtime, I would generally only use one or two tabs and a number of controls to load various subforms into a subform control.
The text for the On Click event of the control might be:
=WhichPage([Form],"lblLocations")
Where WhichPage is a function with the following lines, amongst others:
Function WhichPage(frm, Optional LabelName = "")
<..>
Select Case LabelName
Case "lblLocations"
frm("sfrmAll").SourceObject = "sfrmLocations"
<...>
If necessary, the link child and link master fields can be changed at runtime. The link master field is best set to the name of a control, rather than a field, to avoid errors.
Me.sfrmAll.LinkChildFields = "LocationKey"
Me.sfrmAll.LinkMasterFields = "txtLocationKey"
To expand on Remou's answer...here is a sub I wrote that dynamically loads a form into a subform control. You pass in the name of the form in the call and it will load it into the subform of the Main form. The arguments map to the arguments of Docmd.OpenForm method of Access. If the main form that is hosting the subform control is not open...it just does a regular open of the form. Otherwise it loads it into the subform control. If a where clause was passed in it is used to filter the subform.
Public Sub MyOpenForm(FormName As String, _
Optional View As AcFormView = acNormal, _
Optional FilterName As String = vbNullString, _
Optional WhereCondition As String = vbNullString, _
Optional DataMode As AcFormOpenDataMode, _
Optional WindowMode As AcWindowMode, _
Optional OpenArgs As String)
On Error GoTo PROC_ERR
Dim frm As Form
Dim strNewForm As String
Dim strCurrentForm As String
Dim strNewTable As String
Dim fDoNotFilter As Boolean
Dim strActionText As String
Dim strID As String
If Not IsLoaded("frmMain") Then
DoCmd.OpenForm FormName:=FormName, View:=View, FilterName:=FilterName, WhereCondition:=WhereCondition, DataMode:=DataMode, WindowMode:=WindowMode, OpenArgs:=OpenArgs
Else
strCurrentForm = Forms![frmMain]![sfrMyForm].SourceObject
If strCurrentForm <> FormName Then
Forms![frmMain]![sfrMyForm].SourceObject = vbNullString
Forms![frmMain]![sfrMyForm].SourceObject = FormName
End If
If WhereCondition <> vbNullString Then
Forms![frmMain]![sfrMyForm].Form.Filter = WhereCondition
Forms![frmMain]![sfrMyForm].Form.FilterOn = True
End If
End If
PROC_EXIT:
Exit Sub
PROC_ERR:
MsgBox Err.Description
Resume PROC_EXIT
End Sub