IMAP security information storage

As the dissemination of information technologies, the issue of security becomes important. And work has to be different aspects and relative to different developments. Here, for example, IMAP security - what is it? How reliable is the Internet Message Access Protocol? What advantages it has, why it was developed, what versions and mechanism of work exist - here is a brief retelling of the contents of the article that you are currently acquainting with.

What is IMAP?

Security of correspondence is important due to the fact that it can contain valuable information. This protocol is used at the application level to provide access to e-mail data only to those who must receive it. It was developed on the basis of TCP and uses 143 ports for its needs. IMAP gives the user the ability to work with mail that is on some central server. A program using this protocol performs the necessary actions in such a way that the impression is created that all correspondence is on the user's computer. With a large amount of traffic, a special IMAP server can be used. Manipulation of letters does not require a permanent transfer to the recipient of files in which there is content. But this is not the only protocol that is used in mail services. For example, SMTP is used to send a message, because the sending command to IMAP can not fully guarantee the security. There are known vulnerabilities.

Why was the IMAP protocol developed?

It was developed as an alternative to POP3. It all started because of the drawbacks of the latter. So, it does not have the ability to manage, move and store messages on the server. That's why the IMAP protocol was developed, which offers the possibility to receive e-mail in different places thanks to the data saving on the remote server.

Advantages over POP3

Why did you use this protocol? The fact is that IMAP mail offers, in addition to the above, a number of other advantages:

1. The connection is not disconnected while the user interface is active .
2. Messages are downloaded only if there are appropriate requirements from the client.
3. It can simultaneously access several people, and each of them can monitor all changes made.
4. The client can create, change the name and delete boxes, and move messages between them. Also, if you have the IMAP 4 Access Control List extension, you can change the permissions.
5. You can track the status of the message itself (it was read, deleted, sent a response, and more). Data about such actions are called flags and they are stored on servers.
6. Message search is always performed on the server and there is an explicit extension mechanism.

Messages and their attributes

IMAP security provides work exclusively with messages, and they do not need any packages with special headers. Each of them has its own attributes. They can be determined individually or together with others. At the moment there are six versions of IMAP protocols, but almost always only the last one is used.

UID

Each message receives its 32-bit code. A unique identifier is added to it. Together, they form a 64-bit sequence, which is necessary to identify the message. This is IMAP security. The later it came, the more important the UID is. This parameter is used as a response code when you select a mailbox. It does not change during one session or between them. If the technical conditions require editing this parameter, then the UID must necessarily be larger than before. For data transfer, the same IMAP port is used.

Sequence number of the message

It starts with one. The number of each subsequent message is increased by 1, in comparison with the previous ones. An important difference from a mailbox is that it can change during one connection session: for example, when you completely delete a message.

Message flags

This attribute looks like a list in which there is a zero or more named tokens that are associated with the underlying information. IMAP 4.1 introduced two types of flags. They can act temporarily (throughout the session), or be permanent. The system name is the flag whose name is defined in the protocol specification. All of these must begin with a \. At the moment, such system flags have been defined:

1. \ Seen - the message was read;
2. \ Answered - the response was sent;
3. \ Recent - the message appeared during the current session;
4. \ Draft - was marked as a draft;
5. \ Flagged - the user marked this message as important;
6. \ Deleted - deleted.

Internal date and time of the message

How is it determined which values should be in these parameters? If the message was delivered using the SMTP protocol, then the time and date of the final destination are taken. If you use the copy command, the sender's parameters are used. You can specify both your time and date - for this you should use the append command.

Interaction between client and server

When using IMAP, a connection is established based on the client-server principle. So, the first one sends all received commands from itself, and the second sends the requested data, as well as information about the execution of the request. All messages have a form of lines, which ends with a special sequence. The implementation of all procedures begins with the commands of the client. They are recognized thanks to a special prefix-identifier (which is a short alphanumeric string), which is called a label. Each team has its own unique number.

There may be two cases where the data sent by the client is not complete. The first - the argument of the command is provided with a code that previously determined the number of octets that is in the trod. The second is that you need a response from the server. In both cases, the client receives a request to continue the command, which necessarily begins with a character such as +. If a certain type of data begins to arrive, the transfer must be completed, otherwise it will not be possible to start a new process. Reading, parsing, highlighting of parameters and transfer to the server of data is carried out by a protocol receiver. When the processing of the command is completed, the client is sent a response with this notification. Information that does not indicate completion of the instruction execution is prefixed with *. It is called an unmarked response. It is practicable to send these servers as a response to a customer request or on their own initiative. Their format does not depend on the reason why they were sent.

And what about popular services like Gmail? IMAP settings for ordinary users are not available, but they can be made if you send a message through a special client. But this is purely only for outgoing letters.

And for what are the responses really necessary? They report the successful / unsuccessful execution of information. The response always applies the same label that the client command used, which started the procedure. Therefore, multithreading of data transmission is possible, and they will not be confused with themselves. To clarify the situation, three types of response from the server were developed:

1. Successful execution.
2. Failure.
3. Protocol error IMAP (occurs when an unknown command is applied, or the server recognized that there is a problem with the syntax).

The peculiarity of the client is that he should always be ready to process any response that comes to him. The data must be written in such a way that the client can use them directly, without having to send clarifying requests to the server. You can see this in Gmail. IMAP settings can be edited or changed due to mail clients with wide functionality.

Conclusion

This security protocol significantly improves the reliability of data transmission, and it can provide significant guarantees that a third party can not access information. But this does not mean that someone else can not read the letter. Potentially vulnerable remains the server, and the user can because of low knowledge about the cunning of scammers to personally send them all the data necessary to access the mail.