go - 如何使用mxk/go-imap查找附件并下载？

Question

这几天一直在努力解决这个问题。我正在尝试下载邮箱中所有电子邮件的图像附件。

在这里和那里调查发现这个 mxk/go-imap/issues/17 BODYSTRUCTURE图书馆的作者给出了一些提示，但老实说，我无法围绕 RFC 3501 思考我应该如何使用他的图书馆的 As* 功能，正如我所见，导航不会与像数组一样迭代字段并在找到嵌入的“数组”时进行一些递归没有任何不同。

我已经能够将这段代码放在一起，使用 TLS 连接到 IMAP 服务器，并获取所有打印每个字段的电子邮件，请原谅代码中嵌入的西类牙语。

package main

import (
    "crypto/tls"
    "log"
    "time"

    "github.com/mxk/go-imap/imap"
)

func main() {
    client, err := imap.DialTLS("imapserver.com:993", &tls.Config{
        ServerName:         "imapserver.com",
        InsecureSkipVerify: false,
    })

    if client.State() == imap.Login {
        _, err = client.Login("myemail@imapserver.com", "mypassword:)")
        if err != nil {
            log.Fatalf("no se pudo iniciar sesion: %s", err)
        }
    }
    defer client.Logout(30 * time.Second)
    log.Printf("Conectado")
    // lista correo en la bandeja de entrada
    client.Select("INBOX", true)
    log.Printf("Seleccionado: %s", client.Mailbox)
    set, _ := imap.NewSeqSet("")
    set.Add("1:*")

    cmd, err := client.Fetch(set, "FLAGS", "INTERNALDATE", "RFC822.SIZE", "ENVELOPE", "BODYSTRUCTURE")
    if err != nil {
        log.Fatalf("no se pudo hacer FETCH: %s", err)
    }
    log.Println("Mensajes mas recientes:")
    for cmd.InProgress() {
        // espera por la siguiente respuesta
        client.Recv(-1)

        for _, respuesta := range cmd.Data {
            message := respuesta.MessageInfo()
            log.Printf("= %d\n", message.Seq)
            for _, k := range imap.AsList(message.Attrs["BODYSTRUCTURE"]) {
                log.Printf("== %#v\n", k)
            }
        }
    }
}

这位美女将打印以下内容:

2019/03/16 22:30:45 Conectado
2019/03/16 22:30:45 Seleccionado: --- "INBOX" ---
ReadOnly:     true
Flags:        (\Answered \Deleted \Draft \Flagged \Seen)
PermFlags:    ()
Messages:     2
Recent:       0
Unseen:       1
UIDNext:      85
UIDValidity:  1542111171
UIDNotSticky: false
2019/03/16 22:30:45 Mensajes mas recientes:
2019/03/16 22:30:45 = 1
2019/03/16 22:30:45 == "\"text\""
2019/03/16 22:30:45 == "\"plain\""
2019/03/16 22:30:45 == []imap.Field{"\"charset\"", "\"utf-8\""}
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == "\"base64\""
2019/03/16 22:30:45 == 0x6a
2019/03/16 22:30:45 == 0x3
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 = 1
2019/03/16 22:30:45 == "\"text\""
2019/03/16 22:30:45 == "\"plain\""
2019/03/16 22:30:45 == []imap.Field{"\"charset\"", "\"utf-8\""}
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == "\"base64\""
2019/03/16 22:30:45 == 0x6a
2019/03/16 22:30:45 == 0x3
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 = 2
2019/03/16 22:30:45 == []imap.Field{"\"text\"", "\"plain\"", []imap.Field{"\"charset\"", "\"utf-8\""}, imap.Field(nil), imap.Field(nil), "\"base64\"", 0x66, 0x1, imap.Field(nil), imap.Field(nil), imap.Field(nil), imap.Field(nil)}
2019/03/16 22:30:45 == []imap.Field{"\"image\"", "\"jpeg\"", []imap.Field{"\"name\"", "\"Screenshot_20190315-090210.jpg\""}, imap.Field(nil), imap.Field(nil), "\"base64\"", 0xfd0b2, imap.Field(nil), []imap.Field{"\"attachment\"", []imap.Field{"\"filename\"", "\"Screenshot_20190315-090210.jpg\"", "\"size\"", "\"757415\""}}, imap.Field(nil), imap.Field(nil)}
2019/03/16 22:30:45 == "\"mixed\""
2019/03/16 22:30:45 == []imap.Field{"\"boundary\"", "\"--_com.android.email_70037410718460\""}
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 = 1
2019/03/16 22:30:45 == "\"text\""
2019/03/16 22:30:45 == "\"plain\""
2019/03/16 22:30:45 == []imap.Field{"\"charset\"", "\"utf-8\""}
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == "\"base64\""
2019/03/16 22:30:45 == 0x6a
2019/03/16 22:30:45 == 0x3
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 = 2
2019/03/16 22:30:45 == []imap.Field{"\"text\"", "\"plain\"", []imap.Field{"\"charset\"", "\"utf-8\""}, imap.Field(nil), imap.Field(nil), "\"base64\"", 0x66, 0x1, imap.Field(nil), imap.Field(nil), imap.Field(nil), imap.Field(nil)}
2019/03/16 22:30:45 == []imap.Field{"\"image\"", "\"jpeg\"", []imap.Field{"\"name\"", "\"Screenshot_20190315-090210.jpg\""}, imap.Field(nil), imap.Field(nil), "\"base64\"", 0xfd0b2, imap.Field(nil), []imap.Field{"\"attachment\"", []imap.Field{"\"filename\"", "\"Screenshot_20190315-090210.jpg\"", "\"size\"", "\"757415\""}}, imap.Field(nil), imap.Field(nil)}
2019/03/16 22:30:45 == "\"mixed\""
2019/03/16 22:30:45 == []imap.Field{"\"boundary\"", "\"--_com.android.email_70037410718460\""}
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>
2019/03/16 22:30:45 == <nil>

Answer 1

你应该选择一个更新的库，你选择的库已经 4 年没有任何贡献了。这里有一个例子 https://github.com/emersion/go-imap png 和 gif 库。

package main

import (
    "io"
    "io/ioutil"
    "log"

    "github.com/emersion/go-imap"
    "github.com/emersion/go-imap/client"
    "github.com/emersion/go-message"
)

func main() {
    log.Println("Connecting to server...")

    c, err := client.DialTLS("xxxxxxxxx", nil)
    if err != nil {
        log.Fatal(err)
    }

    log.Println("Connected")

    defer c.Logout()

    if err := c.Login("xxxxxxxxxxxxx", "xxxxxxxxxx"); err != nil {
        log.Fatal(err)
    }
    log.Println("Logged in")

    mbox, err := c.Select("INBOX", false)
    if err != nil {
        log.Fatal(err)
    }

    seqset := new(imap.SeqSet)
    seqset.AddRange(1, mbox.Messages)

    messages := make(chan *imap.Message, 10)
    done := make(chan error, 1)
    go func() {
        done <- c.Fetch(seqset, []imap.FetchItem{imap.FetchRFC822}, messages)
    }()

    for msg := range messages {
        for _, r := range msg.Body {
            entity, err := message.Read(r)
            if err != nil {
                log.Fatal(err)
            }

            multiPartReader := entity.MultipartReader()

            for e, err := multiPartReader.NextPart(); err != io.EOF; e, err = multiPartReader.NextPart() {
                kind, params, cErr := e.Header.ContentType()
                if cErr != nil {
                    log.Fatal(cErr)
                }

                if kind != "image/png" && kind != "image/gif" {
                    continue
                }

                c, rErr := ioutil.ReadAll(e.Body)
                if rErr != nil {
                    log.Fatal(rErr)
                }

                log.Printf("Dump file %s", params["name"])

                if fErr := ioutil.WriteFile("/tmp/"+params["name"], c, 0777); fErr != nil {
                    log.Fatal(fErr)
                }
            }
        }
    }

    if err := <-done; err != nil {
        log.Fatal(err)
    }

    log.Println("Done")
}