Protocolos de E-mail

Diogo Rodrigues LopesPaulo Vitor Bischof

Agenda

1. Introdução;2. História;3. Funcionamento;4. Protocolos Seguros;5. Considerações finais;

SMTP

• Protocolo padrão de envio de E-mail• Criado em 1982, na Universidade do Sul da

Califórnia por Jon Postel• Envia o e-mail do client para o server

SMTP SyntaxCOMMAND DESCRIPTION

HELO <domain> (Hello) Connect to the server as specified in <domain>MAIL FROM:<reverse-path>

Tell the server the sender’s identity as specified in <reverse-path> [Mail-parameters]

RCPT TO:<forward-path>

(Recipient) Tell the server the intended recipient’s identity as specified in [Rcpt-parameters] <forward-path>

DATA Convey the message body to the serverRSET (Reset) Reset the server connectionVRFY <string> (Verify) Ask the receiver to confirm that a user has been

identifiedEXPN <string> (Expand) Ask the receiver to confirm that a mailing list has

been identifiedHELP [<string>] Obtain help informationNOOP [<string>] (No operation) Indicate no operation, but signify the sender is

still connected (i.e.,“alive”)QUIT Close the server connection

POP

• Criado em 1984• Protocolo de leitura• Copia as mensagens do server para o client• Possui problemas de sincronização, pois foi

projetado para deletar as mensagens do servidor

POPCOMMAND DESCRIPTION

BASIC COMMANDS FROM RFC 918 USER <name> Set usernamePASS <password> Set passwordSTAT Check the status of the mailbox, typically retrieves

number of messagesLIST [msg] List messages in the mailbox; Optional argument for

message [msg]RETR <msg> Retrieve message <msg>DELE <msg> Delete message <msg>QUIT QuitNOOP No operationRSET Reset

POPCOMMAND DESCRIPTION

OPTIONAL COMMANDS FROM RFC 1939 TOP <msg> <n> Retrieve the top <n> lines of message <msg>UIDL [msg] Retrieve unique id for [msg]APOP <name> <digest> A more robust form of authentication than

USER/PASSEXTENSION COMMAND FROM RFC 2449 CAPA Retrieve a list of capabilities supported by the

POP3 server

IMAP

• Criado em 1988, para solucionar problemas conhecidos do protocolo POP.

• Possui mais recursos que o POP• Solucionou a sincronização de E-mail entre server e clients.

• Permite pesquisar e-mails no servidor

IMAPCOMMAND DESCRIPTION

NOOP Perform no operationSTARTTLS Establish confidentiality and integrity protectionAUTHENTICATE <type> Choose authentication method LOGIN <user> <passwd> Login with username and password LOGOUT Logout the current userSELECT <mailbox> Select the desired mailbox to accessEXAMINE <mailbox> Same as SELECT except opens mailbox for read-onlyCREATE <mailbox> Create a mailbox with the name <mailbox>DELETE <mailbox> Delete selected mailboxRENAME <mailbox> <newmailbox>

Rename mailbox

SUBSCRIBE <mailbox> Subscribe to selected mailboxUNSUBSCRIBE <mailbox> Unsubscribe from selected mailbox

IMAPCOMMAND DESCRIPTION

LIST <reference> [pattern] List contents of current reference based on an optional pattern

LSUB <reference> [pattern] List a set of mailboxes matching the patternSTATUS <mailbox> <item> Show the status of specific items in the selected

mailboxAPPEND <mailbox> [flags] <msg> Append a message to the selected mailboxCHECK Perform a checkpoint on the currently selected mailboxCLOSE Close the currently selected mailboxEXPUNGE Expunge deleted messages from the mailboxSEARCH <criteria> Search the mailbox based on certain criteriaFETCH <message> <item> Fetch the specified item from the selected messageSTORE <message> <item> <newvalue>

Update the selected item in a message

COPY <message> <mailbox> Copy a message to the provided mailboxUID <command> [args] Perform an operation on a message based on its UIDCAPABILITY Query the server for its capabilities

Protocolos Seguros

• Surgiram na década de 90• PGP• SSL• TLS

Considerações finais

• Posso usar SSL ou TLS?• PGP ainda existe?• Qual protocolo devo configurar no meu

smartphone?• Se usar SSL a NSA pode ler meu e-mail?

Referência bibliográfica

KUROSE, James F. Redes de Computadores e a Internet – 5ª Edição.

TANENBAUM, Andrew S.; Redes de Computadores - 5ª Edição. Pearson Education do Brasil, 2011.

Obrigado

Diogo Rodrigues LopesPaulo Vitor Bischof