HOWTO: Restrict ssh access by IP Address and/or username

Opening SSH to the outside world is a security risk. Here is how to restrict SSH access to certain IP addresses on a machine.

Edit the /etc/hosts.allow file to include these lines, assuming your machine is on the 192.168.2.x nonrouting IP block, and you want to enable an external address of 217.40.111.121 IP block: Remember to add the period on the end of each incomplete IP number. If you have another complete IP address or range, add a space and that range on the end.
```
sshd,sshdfwd-X11: 192.168.2. 217.40.111.121
```
Edit your /etc/hosts.deny file to include this line:
```
sshd,sshdfwd-X11:ALL 
```
These lines refuse SSH connections from anyone not in the IP address blocks listed.

Additionally you can restrict SSH access by username.

Edit the /etc/ssh/sshd_config file and add the following lines

PermitRootLogin no
AllowUsers      user1 user2 user3 etc
PasswordAuthentication yes

Now restart the ssh daemon for these changes to take effect

service sshd restart

Published in Blogs

Building C Extension Libraries

In this article Barry Mavin, CEO and Chief Software Architect for Recital details how to Build C Extension Libraries to use with Recital.

Overview

It is possible to extend the functionaliy of Recital products using "Extension libraries" that can be written in C. These extension libraries, written using the Recital/SDK API, are dynamically loadable from all Recital 9 products. This includes:

Recital
Recital Server
Recital Web

Building C Extension Libraries

You can create C wrappers for virtually any native operating system function and access these from the Recital 4GL. Unlike traditional APIs which only handle the development of C functions that are callable from the 4GL, the Recital/SDK allows you to build Classes that are accessible from all Recital products. e.g. You could create a GUI framework for Linux that handles VFP system classes!

To deploy your C Extension Libraries, copy them to the following location:

Windows:

\Program Files\Recital\extensions

Linux/Unix:

/opt/recital/extensions

Please see the Recital/SDK API Reference documentation for further details.

Sample code

Listed below is the complete example of a C Extension Library.:

////////////////////////////////////////////////////////////////////////////////
#include "mirage_demo.h"  
      
////////////////////////////////////////////////////////////////////////////////
// Declare your functions and classes below as follows:
//
//    Recital Function Name, C Function Name, Type (Function or Class)
//
#define MAX_ELEMENTS    7
static  struct  API_SHARED_FUNCTION_TABLE api_function_table[MAX_ELEMENTS] = {
        {"schar",   "fnSamplesCharacter",   API_FUNCTION},
        {"stype",   "fnSamplesType",           API_FUNCTION},
        {"slog",    "fnSamplesLogical",        API_FUNCTION},
        {"snum",    "fnSamplesNumeric",    API_FUNCTION},
        {"sopen",   "fnSamplesOpen",         API_FUNCTION},
        {"myclass", "clsMyClass",               API_CLASS},
        {NULL,      NULL,                   -1}
};

////////////////////////////////////////////////////////////////////////////////
// Recital API initialization. This should be in only ONE of your C files
// **IT SHOULD NEVER BE EDITED OR REMOVED**  
INIT_API;


///////////////////////////////////////////////////////////////////////
// This is an example of passing a character parameter and returning one.
RECITAL_FUNCTION fnSamplesCharacter(void)
{
    char    *arg1;
    
    if (!_parse_parameters(PCOUNT, "C", &arg1)) { 
        ERROR(-1, "Incorrect parameters");
    }
    
    _retc(arg1);
}


///////////////////////////////////////////////////////////////////////
// This is an example of passing a numeric parameter and returning one.
RECITAL_FUNCTION fnSamplesNumeric(void)
{
    int arg1;
    
    if (!_parse_parameters(PCOUNT, "N", &arg1)) { 
        ERROR(-1, "Incorrect parameters");
    }
    
    _retni(arg1);
}


///////////////////////////////////////////////////////////////////////
// This is an example returns the data type of the parameter passed.
RECITAL_FUNCTION fnSamplesType(void)
{
    char    result[10];

    if (PCOUNT != 1) { 
        ERROR(-1, "Incorrect parameters");
    }
    
    switch (_parinfo(1)) {
        case API_CTYPE:
            strcpy(result, "Character");
            break;
        case API_NTYPE:
            strcpy(result, "Numeric");
            break;
        case API_LTYPE:
            strcpy(result, "Logical");
            break;
        case API_DTYPE:
            strcpy(result, "Date");
            break;
        case API_TTYPE:
            strcpy(result, "DateTime");
            break;
        case API_YTYPE:
            strcpy(result, "Currency");
            break;
        case API_ATYPE:
            strcpy(result, "Array");
            break;
        default:
            strcpy(result, "Unkown");
            break;
    }

    _retc(result);
}


///////////////////////////////////////////////////////////////////////
// This is an example returns "True" or False.
RECITAL_FUNCTION  fnSamplesLogical(void)
{
    char    result[10];
    int     arg1;
    
    if (!_parse_parameters(PCOUNT, "L", &arg1)) { 
        ERROR(-1, "Incorrect parameters");
    }
    
    if (arg1) strcpy(result, "True");
    else strcpy(result, "False");

    _retc(result);
}


///////////////////////////////////////////////////////////////////////
// This example opens a table.
RECITAL_FUNCTION fnSamplesOpen(void)
{
    char    *arg1;
    
    if (!_parse_parameters(PCOUNT, "C", &arg1)) { 
        ERROR(-1, "Incorrect parameters");
    }
    
    if (_parinfo(1) == API_CTYPE) {
        _retni(COMMAND(arg1));
    } else {
        _retni(-1);
    }
}

///////////////////////////////////////////////////////////////////////
// Define the MyClass CLASS using the API macros
///////////////////////////////////////////////////////////////////////
RECITAL_EXPORT int DEFINE_CLASS(clsMyClass)
{
    /*-------------------------------------*/ 
    /* Dispatch factory methods and return */
    /*-------------------------------------*/
    DISPATCH_FACTORY();
 
    /*---------------------------------*/
    /* Dispatch constructor and return */ 
    /*---------------------------------*/ 
    DISPATCH_METHOD(clsMyClass, Constructor);

    /*--------------------------------*/
    /* Dispatch destructor and return */
    /*--------------------------------*/
    DISPATCH_METHOD(clsMyClass, Destructor); 

    /*-----------------------------------*/
    /* Dispatch DEFINE method and return */
    /*-----------------------------------*/
    DISPATCH_METHOD(clsMyClass, Define);

    /*------------------------------*/
    /* Dispatch SET or GET PROPERTY */
    /* method for property NumValue */
    /* then return.                 */
    /*------------------------------*/
    DISPATCH_PROPSET(clsMyClass, NumValue);
    DISPATCH_PROPGET(clsMyClass, NumValue); 

    /*------------------------------*/
    /* Dispatch SET or GET PROPERTY */
    /* method for property LogValue */
    /* then return.                 */
    /*------------------------------*/
    DISPATCH_PROPSET(clsMyClass, LogValue);
    DISPATCH_PROPGET(clsMyClass, LogValue);

    /*-------------------------------*/
    /* Dispatch SET or GET PROPERTY  */
    /* method for property DateValue */
    /* then return.                 */
    /*-------------------------------*/
    DISPATCH_PROPSET(clsMyClass, DateValue);
    DISPATCH_PROPGET(clsMyClass, DateValue);

    /*-------------------------------*/
    /* Dispatch SET or GET PROPERTY  */
    /* method for property TimeValue */
    /* then return.                  */
    /*-------------------------------*/
    DISPATCH_PROPSET(clsMyClass, TimeValue);
    DISPATCH_PROPGET(clsMyClass, TimeValue);
 
    /*-------------------------------*/
    /* Dispatch SET or GET PROPERTY  */
    /* method for property CurrValue */
    /* then return.                  */
    /*-------------------------------*/
    DISPATCH_PROPSET(clsMyClass, CurrValue);
    DISPATCH_PROPGET(clsMyClass, CurrValue);

    /*-------------------------------*/
    /* Dispatch SET or GET PROPERTY  */
    /* method for property CharValue */
    /* then return.                  */
    /*-------------------------------*/
    DISPATCH_PROPSET(clsMyClass, CharValue); 
    DISPATCH_PROPGET(clsMyClass, CharValue);

    /*------------------------------*/
    /* Dispatch SET or GET PROPERTY */ 
    /* method for property ObjValue */ 
    /* then return.                 */
    /*------------------------------*/
    DISPATCH_PROPSET(clsMyClass, ObjValue);
    DISPATCH_PROPGET(clsMyClass, ObjValue);

    /*-----------------------------------*/
    /* If message not found return error */
    /*-----------------------------------*/
    OBJECT_RETERROR("Unknown message type");
}

////////////////////////////////////////////////////////////////////////////////
// Define METHOD handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_METHOD(clsMyClass, Constructor) 
{
        struct example_data *objectDataArea;

        /* Allocate memory for objects objectData area */
        objectDataArea = (struct example_data *) 
           malloc(sizeof(struct example_data));
        if (objectDataArea == NULL) return(-1);
    
        /* Assign the default property values */
        strcpy(objectDataArea->prop_charvalue, "Test API object");
        objectDataArea->prop_numvalue = 15.2827;
        objectDataArea->prop_logvalue = 'F';
        strcpy(objectDataArea->prop_datevalue, DATE_DATE());
        strcpy(objectDataArea->prop_timevalue, DATE_DATETIME());
        strcpy(objectDataArea->prop_currvalue, "15.2827");
        strcpy(objectDataArea->object_name, "APIobject");
        objectDataArea->prop_objvalue 
             = OBJECT_NEW(objectDataArea->object_name, "exception", NULL);
    
        /* Set the object objectData area */
        OBJECT_SETDATA((char *)objectDataArea);
    
        return(0);
}
  
DEFINE_METHOD(clsMyClass, Destructor) 
{
        struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

        if (objectData != NULL) {
            if (objectData->prop_objvalue != NULL) 
              OBJECT_DELETE(objectData->prop_objvalue);
            free(objectData);
            objectData = NULL;
        }
        return(0);
}

DEFINE_METHOD(clsMyClass, Define) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct      API_EXPRESSION result;
    char        buffer[512];
    int         rc;

/* Check the object class */
    OBJECT_GETPROPERTY(objectData->prop_objvalue, "class", buffer);
    rc = OBJECT_GETARG(buffer, &result);
    if (result.errno == 0 && result.type == 'C' 
        && strcmp(result.character, "Exception") == 0) { 
        switch (OBJECT_GETARGC()) {
            case 1: 
                rc = OBJECT_GETPARAMETER(1, &result);
                if (result.errno == 0 && result.type == 'C') {
                    OBJECT_SETARG(buffer, &result);
                    rc = OBJECT_SETPROPERTY(objectData->prop_objvalue,
                         "message", buffer);
                }
                break;
            case 2: 
                rc = OBJECT_GETPARAMETER(2, &result);
                if (result.errno == 0 && result.type == 'N') {
                    OBJECT_SETARG(buffer, &result);
                    rc = OBJECT_SETPROPERTY(objectData->prop_objvalue,
                         "errorno", buffer);
                }
         }
    }

    result.type = 'L';
    result.logical = (rc == 0 ? 'T' : 'F');  
    OBJECT_RETRESULT(&result);
}

////////////////////////////////////////////////////////////////////////////////
// Define GET property handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_PROPERTYGET(clsMyClass, NumValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('N', objectData->prop_numvalue);
}

DEFINE_PROPERTYGET(clsMyClass, LogValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('L', objectData->prop_logvalue);
}  

DEFINE_PROPERTYGET(clsMyClass, DateValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('D', objectData->prop_datevalue);
}

DEFINE_PROPERTYGET(clsMyClass, TimeValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('T', objectData->prop_timevalue);
}

DEFINE_PROPERTYGET(clsMyClass, CurrValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('Y', objectData->prop_currvalue);
}

DEFINE_PROPERTYGET(clsMyClass, CharValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('C', objectData->prop_charvalue);
}

DEFINE_PROPERTYGET(clsMyClass, ObjValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();

    if (objectData == NULL) return(-1);

    OBJECT_RETPROPERTY('O', objectData->prop_objvalue);
} 


////////////////////////////////////////////////////////////////////////////////
// Define SET property handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_PROPERTYSET(clsMyClass, NumValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;

    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'N') {
        objectData->prop_numvalue = result.number;
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

DEFINE_PROPERTYSET(clsMyClass, LogValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;

    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'L') {
        objectData->prop_logvalue = result.logical;
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

DEFINE_PROPERTYSET(clsMyClass, DateValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;
    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'D') {
        strcpy(objectData->prop_datevalue, DATE_DTOS(result.date));
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

DEFINE_PROPERTYSET(clsMyClass, TimeValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;

    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'T') {
        strcpy(objectData->prop_timevalue, DATE_TTOS(result.datetime));
        rc = OBJECT_SUCCESS;
    }

    return(rc); 
}

DEFINE_PROPERTYSET(clsMyClass, CurrValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;

    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'Y') {
        strcpy(objectData->prop_currvalue, CURR_YTOS(result.currency));
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

DEFINE_PROPERTYSET(clsMyClass, CharValue)  
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    struct API_EXPRESSION result;
    int rc = OBJECT_ERROR;

    OBJECT_GETVALUE(&result);
    if (result.errno == 0 && result.type == 'C') {
        strcpy(objectData->prop_currvalue, result.character);
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

DEFINE_PROPERTYSET(clsMyClass, ObjValue) 
{
    struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
    OBJECT  objvalue;
    int rc = OBJECT_ERROR;

    if (OBJECT_GETTYPE() == 'O') {
        objvalue = OBJECT_GETOBJECT(); 
        objectData->prop_objvalue = OBJECT_ASSIGN(objvalue, objectData->object_name);
        rc = OBJECT_SUCCESS;
    }

    return(rc);
}

Published in Blogs

Finally IE9 will support rounded corners

And apparently IE9 will support rounded corners.
http://kbala.com/ie-9-supports-corner-radius/

Published in Blogs

What is the best way to learn Recital?

The best way to learn Recital is to build some applications. The developers of Recital have written a book "Recital Essentials" which you can read here.

Published in Blogs

Handling binary objects in Recital

In this article Chris Mavin, explains and details how to Store and Retrieve Binary Objects in a Recital Database.

Published in Blogs

How to configure Recital Server to authenticate against Kerberos

By default Recital uses PAM to authenticate users. It is also possible to tell PAM to use Kerberos. Simply replace the existing entries in the /etc/pam.d/recital file with the ones below:

auth       sufficient   pam_krb5.so try_first_pass
auth       sufficient   pam_unix.so shadow nullok try_first_pass
account    required     pam_unix.so broken_shadow
account    [default=bad success=ok user_unknown=ignore] pam_krb5.so

Published in Blogs

Working with triggers in the Recital Database Server

In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to work with Triggers in the Recital Database Server.

Overview

A trigger is a special kind of stored procedure that runs when you modify data in a specified table using one or more of the data modification operations: UPDATE, INSERT, or DELETE.

Triggers can query other tables and can include complex SQL statements. They are primarily useful for enforcing complex business rules or requirements. For example, you can control whether to allow a new order to be inserted based on a customer's current account status.

Triggers are also useful for enforcing referential and data integrity.

Triggers can be used with any data source that is handled natively by the Recital Database Engine. This includes Recital, FoxPro, FoxBASE, Clipper, dBase, CISAM, and RMS data,

Creating and Editing Triggers

To create a new Trigger, right-click the Procedures node in the Databases tree of the Project Explorer and choose Create. To modify an existing Trigger select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it, or select Modify from the context menu. By convertion we recommend that you name your Stored Procedures beginning with "sp_xxx_", user-defined functions with "f_xxx_", and Triggers with "dt_xxx_", where xxx is the name of the table that they are associated with.

Associating Triggers with a Table

Once you have written your Triggers as detailed above you can associate them with the operations performed on a Table by selecting the Table tab.

The Tables tab allows you to select a Trigger procedure by clicking on the small button at the right of the Text field.

Types of Triggers

As can be seen from the Tables tab detailed below, The Recital Database Server handles 6 distinct types of Triggers.

Open Trigger

The Open Trigger is called after is a table is opened but before any operations are performed on it. You can use this trigger to record a log of table usage or provide a programmable means of checing security. If the Trigger procedure returns .F. (false), then the table is not opened. You can use a TRY...CATCH block around the associated command to inform the user.

Close Trigger

The Close Trigger is called just prior to a table being closed. In this trigger you may find it useful to get transaction counts by using the IOSTATS() built-in 4GL function, and record these values in a transaction log.

Update Trigger

The Update Trigger is called prior to a record update operation being performed. You can use this trigger to perform complex application or data specific validation. If the Trigger procedure returns .F. (false), then the record is not updated. You can use inform the user from within the Trigger procedure the reason that the data cannot be updated.

Delete Trigger

The Delete Trigger is called prior to a record delete operation being performed. You can use this trigger to perform complex application or data specific validation such as cross-table lookups e.g. attempting to delete a customer recortd when there are still open orders for that specific customer. If the Trigger procedure returns .F. (false), then the record is not deleted.

Insert Trigger

The Insert Trigger is called prior to a record insert (append) operation being performed. You can use this trigger to perform such tasks as setting up default values of columns within the record. If the Trigger procedure returns .F. (false), then the record is not inserted.

Rollback Trigger

The RollbackTrigger is called prior to a rollback operation being performed from within a form. If the Trigger procedure returns .F. (false), then the record is not rolled back to its original state.

Testing the Trigger

To test run the Trigger, select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it. Once the Database Administrator is displayed, click the Run button to run the Trigger.

Published in Blogs

Increase memory allocation for Eclipse CDT on linux

If you use Eclipse Ganymede with large projects on linux you may run out of memory. To prevent this happening, you can specify the amount of memory to be allocated to Eclipse in the eclipse.ini file which is located in the eclipse directory.

Specifying this seems to reslove the problem:

-Xmx512m
-XX:MaxPermSize=512m

Published in Blogs

Recital Data Validation: dynamic list of choices

Each Recital table can have one or more data dictionaries to provide a central repository for constraints and other metadata.

Here's how to set up field validation based on dynamic values from another table.

Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.

open database southwind
alter table products add constraint;
 (categoryid set check rlookup(products.categoryid,categories))

The rlookup() function checks whether an expression exists in the index (master or specified) of the specified table . An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.

If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.

Published in Blogs

Using Recital with PHP

This article describes how to use Recital with PHP.

Published in Blogs

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HOWTO: Restrict ssh access by IP Address and/or username

Building C Extension Libraries

Overview

Building C Extension Libraries

Sample code

Finally IE9 will support rounded corners

What is the best way to learn Recital?

Handling binary objects in Recital

How to configure Recital Server to authenticate against Kerberos

Working with triggers in the Recital Database Server

Overview

Creating and Editing Triggers

Associating Triggers with a Table

Types of Triggers

Open Trigger

Close Trigger

Update Trigger

Delete Trigger

Insert Trigger

Rollback Trigger

Testing the Trigger

Increase memory allocation for Eclipse CDT on linux

Recital Data Validation: dynamic list of choices

Using Recital with PHP

More...

HOWTO: How to colorize code in your joomla articles with geshi

HOWTO: Using more than 4GB of memory on centos 5.3

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