Envelope
Quick layer over python-gnupg, M2Crypto, smtplib, magic and email handling packages. Their common use cases merged into a single function. Want to sign a text and tired of forgetting how to do it right? You do not need to know everything about GPG or S/MIME, you do not have to bother with importing keys. Do not hassle with reconnecting to an SMTP server. Do not study various headers meanings to let your users unsubscribe via a URL. You insert a message, attachments and inline images and receive signed and/or encrypted output to the file or to your recipients' e-mail. Just single line of code. With the great help of the examples below.
Envelope("my message")
.subject("hello world")
.to("[email protected]")
.attach(file_contents, name="attached-file.txt")
.smtp("localhost", 587, "user", "pass", "starttls")
.signature()
.send()
# Inline image
Envelope("My inline image: <img src='cid:image.jpg' />")
.attach(path="image.jpg", inline=True)
# Load a message and read its attachments
Envelope.load(path="message.eml").attachments()
# in bash: envelope --load message.eml --attachments
Installation
-
Install with a single command from PyPi
pip3 install envelope
- Or install current GitHub master
pip3 install git+https://github.com/CZ-NIC/envelope.git
- Or just download the project and launch
python3 -m envelope
-
If planning to sign/encrypt with GPG, assure you have it on the system with
sudo apt install gpg
and possibly see Configure your GPG tutorial. -
If planning to use S/MIME, you should ensure some prerequisites:
sudo apt install swig build-essential python3-dev libssl-dev && pip3 install M2Crypto
-
If planning to send e-mails, prepare SMTP credentials or visit Configure your SMTP tutorial.
-
If your e-mails are to be received outside your local domain, visit DMARC section.
-
Package python-magic is used as a dependency. Due to a well-known name clash with the file-magic package, in case you need to use the latter, don't worry to run
pip uninstall python-magic && pip install file-magic
after installing envelope which is fully compatible with both projects.
Bash completion
- Run:
apt install bash-completion jq
- Copy: extra/envelope-autocompletion.bash to
/etc/bash_completion.d/
- Restart terminal
Usage
As an example, let's produce in three equal ways an output_file
with the GPG-encrypted "Hello world" content.
CLI
Launch as a CLI application in terminal, see envelope --help
envelope --message "Hello world" \
--output "/tmp/output_file" \
--from "[email protected]" \
--to "[email protected]" \
--encrypt-path "/tmp/remote_key.asc"
Module: fluent interface
Comfortable way to create the structure if your IDE supports autocompletion.
from envelope import Envelope
Envelope().message("Hello world")\
.output("/tmp/output_file")\
.from_("[email protected]")\
.to("[email protected]")\
.encrypt(key_path="/tmp/remote_key.asc")
Module: one-liner function
You can easily write a one-liner function that encrypts your code or sends an e-mail from within your application when imported as a module. See pydoc3 envelope
or documentation below.
from envelope import Envelope
Envelope(message="Hello world",
output="/tmp/output_file",
from_="[email protected]",
to="[email protected]",
encrypt="/tmp/remote_key.asc")
Documentation
Both envelope --help
for CLI arguments help and pydoc3 envelope
to see module arguments help should contain same information as here.
Command list
All parameters are optional.
- --param is used in CLI
- .param(value) denotes a positional argument
- .param(value=) denotes a keyword argument
- Envelope(param=) is a one-liner argument
Any attainable contents
Whenever any attainable contents is mentioned, we mean plain text, bytes or stream (ex: from open()
). In module interface, you may use a Path
object to the file. In CLI interface, additional flags are provided instead.
If the object is not accesible, it will immediately raise FileNotFoundError
.
Envelope().attach(path="file.jpg")
# Could not fetch file .../file.jpg
# FileNotFoundError: [Errno 2] No such file or directory: 'file.jpg'
Input / Output
-
message: Message / body text. If no string is set, message gets read. Besides, when "Content-Transfer-Encoding" is set to "base64" or "quoted-printable", it gets decoded (useful when quickly reading an EML file content
cat file.eml | envelope --message
).- --message: String. Empty to read.
- --input: (CLI only) Path to the message file. (Alternative to the
--message
parameter.) - .message(): Read current message in
str
. - .message(text): Set the message to any attainable contents.
- .message(path=None, alternative="auto", boundary=None)
path
: Path to the file.alternative
: "auto", "html", "plain" You may specify e-mail text alternative. Some e-mail readers prefer to display plain text version over HTML. By default, we try to determine content type automatically (see mime).print(Envelope().message("He<b>llo</b>").message("Hello", alternative="plain")) # (output shortened) # Content-Type: multipart/alternative; # boundary="===============0590677381100492396==" # # --===============0590677381100492396== # Content-Type: text/plain; charset="utf-8" # Hello # # --===============0590677381100492396== # Content-Type: text/html; charset="utf-8" # He<b>llo</b>
- boundary: When specifying alternative, you may set e-mail boundary if you do not wish a random one to be created.
- .body(path=None): Alias of
.message
(withoutalternative
andboundary
parameter) - .text(path=None): Alias of
.message
(withoutalternative
andboundary
parameter) - Envelope(message=): Any attainable contents
Equivalents for setting a string (in Python and in Bash).
Envelope(message="hello") == Envelope().message("hello")
envelope --message "hello"
Equivalents for setting contents of a file (in Python and in Bash).
from pathlib import Path Envelope(message=Path("file.txt")) == Envelope(message=open("file.txt")) == Envelope.message(path="file.txt")
envelope --input file.txt
Envelope is sometimes able to handle wrong encoding or tries to print out a meaningful warning.
# Issue a warning when trying to represent a mal-encoded message. b ="β¬".encode("cp1250") # converted to bytes b'\x80' e = Envelope(b) repr(e) # WARNING: Cannot decode the message correctly, plain alternative bytes are not in Unicode. # Envelope(message="b'\x80'") # When trying to output a mal-encoded message, we end up with a ValueError exception. e.message() # ValueError: Cannot decode the message correctly, it is not in Unicode. b'\x80' # Setting up an encoding (even ex-post) solves the issue. e.header("Content-Type", "text/plain;charset=cp1250") e.message() # 'β¬'
-
output: Path to file to be written to (else the contents is returned).
- --output
- .output(output_file)
- Envelope(output=)
Recipients
- from: E-mail β needed to choose our key if encrypting.
- --from E-mail. Empty to read value.
- --no-from Declare we want to encrypt and never decrypt back.
- .from_(email): E-mail | False | None. If None, current
From
returned as an Address object (even an empty one). - Envelope(from_=): Sender e-mail or False to explicitly omit. When encrypting without sender, we do not use their key so that we will not be able to decipher again.
# These statements are identical. Envelope(from_="[email protected]") Envelope().from_("[email protected]") # This statement produces both From header and Sender header. Envelope(from_="[email protected]", headers=[("Sender", "[email protected]")]) # reading an Address object a = Envelope(from_="[email protected]").from_() a == "[email protected]", a.host == "example.com"
- to: E-mail or more in an iterable. When encrypting, we use keys of these identities. Multiple addresses may be given in a string, delimited by a comma (or semicolon). (The same is valid for
to
,cc
,bcc
andreply-to
.)- --to: One or more e-mail addresses. Empty to read.
$ envelope --to [email protected] [email protected] --message "hello" $ envelope --to [email protected] [email protected]
- .to(email_or_more): If None, current list of Addresses returned. If False or "", current list is cleared.
Envelope() .to("[email protected]") .to("[email protected], John <[email protected]>") .to(["[email protected]"]) .to() # ["[email protected]", "John <[email protected]>", "[email protected]"]
- Envelope(to=): E-mail or more in an iterable.
- --to: One or more e-mail addresses. Empty to read.
- cc: E-mail or more in an iterable. Multiple addresses may be given in a string, delimited by a comma (or semicolon). (The same is valid for
to
,cc
,bcc
andreply-to
.)- --cc: One or more e-mail addresses. Empty to read.
- .cc(email_or_more): If None, current list of Addresses returned. If False or "", current list is cleared.
Envelope() .cc("[email protected]") .cc("[email protected], John <[email protected]>") .cc(["[email protected]"]) .cc() # ["[email protected]", "John <[email protected]>", "[email protected]"]
- Envelope(cc=)
- bcc: E-mail or more in an iterable. Multiple addresses may be given in a string, delimited by a comma (or semicolon). (The same is valid for
to
,cc
,bcc
andreply-to
.) The header is not sent.- --bcc: One or more e-mail addresses. Empty to read.
- .bcc(email_or_more): If None, current list of Addresses returned. If False or "", current list is cleared.
- Envelope(bcc=)
- reply-to: E-mail or more in an iterable. Multiple addresses may be given in a string, delimited by a comma (or semicolon). (The same is valid for
to
,cc
,bcc
andreply-to
.) The field is not encrypted.- --reply-to: E-mail address or empty to read value.
- .reply_to(email_or_more): If None, current list of Addresses returned. If False or "", current list is cleared.
- Envelope(reply_to=)
- from_addr: SMTP envelope MAIL FROM address.
- --from-addr: E-mail address or empty to read value.
- .from_addr(email): E-mail or False. If None, current
SMTP envelope MAIL FROM
returned as an Address object (even an empty one). - .Envelope(from_addr=)
Sending
-
send: Send the message to the recipients by e-mail. True (blank in CLI) to send now or False to print out debug information.
- --send
- .send(send=True, sign=None, encrypt=None)
- send: True to send now. False (or 0/false/no in CLI) to print debug information.
- Returns the object back which converted to bool returns True if the message has been sent successfully.
- Envelope(send=)
$ envelope --to "[email protected]" --message "Hello world" --send 0 **************************************************************************************************** Have not been sent from - to [email protected] Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: 7bit MIME-Version: 1.0 Subject: From: To: [email protected] Date: Mon, 07 Oct 2019 16:13:37 +0200 Message-ID: <157045761791.29779.5279828659897745855@...> Hello world
-
subject: Mail subject. Gets encrypted with GPG, stays visible with S/MIME.
- --subject
- .subject(text=None, encrypt=None):
text
Subject text.encrypt
Text used instead of the real protected subject while PGP encrypting. False to not encrypt.- If neither parameter specified, current subject returned.
- Envelope(subject=)
- Envelope(subject_encrypted=)
-
date:
- .date(date)
str|False
Specify Date header (otherwise Date is added automatically). If False, the Date header will not be added automatically.
- .date(date)
-
smtp: SMTP server
- --smtp
- .smtp(host="localhost", port=25, user=, password=, security=, timeout=3, attempts=3, delay=3)
- Envelope(smtp=)
- Parameters:
host
May include hostname or any of the following input formats (ex: path to an INI file or adict
)security
If not set, automatically set tostarttls
for port 587 and totls
for port 465timeout
How many seconds should SMTP wait before timing out.attempts
How many times we try to send the message to an SMTP server.delay
How many seconds to sleep before re-trying a timed out connection.
- Input format may be in the following form:
None
default localhost server usedsmtplib.SMTP
objectlist
ortuple
havinghost, [port, [username, password, [security, [timeout, [attempts, [delay]]]]]]
parameters- ex:
envelope --smtp localhost 125 [email protected]
will set up host, port and username parameters
- ex:
dict
specifying {"host": ..., "port": ...}- ex:
envelope --smtp '{"host": "localhost"}'
will set up host parameter
- ex:
str
hostname or path to an INI file (existing file, ending at.ini
, with the section [SMTP])[SMTP] host = example.com port = 587
- Do not fear to pass the
smtp
in a loop, we make just a single connection to the server. If timed out, we attempt to reconnect once.
smtp = localhost, 25 for mail in mails: Envelope(...).smtp(smtp).send()
-
attachments
- --attach: Path to the attachment, followed by optional file name to be used and/or mime type. This parameter may be used multiple times.
envelope --attachment "/tmp/file.txt" "displayed-name.txt" "text/plain" --attachment "/tmp/another-file.txt"
- .attach(attachment=, mimetype=, name=, path=, inline=):
Envelope().attach(path="/tmp/file.txt").attach(path="/tmp/another-file.txt")
- Three different usages when specifying contents:
- .attach(attachment=, mimetype=, name=): You can put any attainable contents of a single attachment into attachment and optionally add mime type or displayed file name.
- .attach(mimetype=, name=, path=): You can specify path and optionally mime type or displayed file name.
- .attach(attachment=): You can put a list of attachments. The list may contain tuples:
contents [,mime type] [,file name] [, True for inline]
.
- .attach(inline=True|str): Specify content-id (CID) to reference the image from within HTML message body.
- True: Filename or attachment or path file name is set as CID.
- str: The attachment will get this CID.
from pathlib import Path Envelope().attach(Path("file.jpg"), inline=True) # <img src='cid:file.jpg' /> Envelope().attach(b"GIF89a\x03\x00\x03...", name="file.gif", inline=True) # <img src='cid:file.gif' /> Envelope().attach(Path("file.jpg"), inline="foo") # <img src='cid:foo' /> # Reference it like: .message("Hey, this is an inline image: <img src='cid:foo' />")
- Three different usages when specifying contents:
- Envelope(attachments=): Attachment or their list. Attachment is defined by any attainable contents, optionally in tuple with the file name to be used in the e-mail and/or mime type and/or True for being inline:
contents [,mime type] [,file name] [, True for inline]
Envelope(attachments=[(Path("/tmp/file.txt"), "displayed-name.txt", "text/plain"), Path("/tmp/another-file.txt")])
-
mime: Sets contents mime subtype: "auto" (default), "html" or "plain" for plain text. Maintype is always set to "text". Set maintype to "text". If a line is longer than 1000 characters, makes the message be transferred safely by bytes (otherwise these non-standard long lines might cause a transferring SMTP server to include line breaks and redundant spaces that might break up ex: DKIM signature). In case of
Content-Type
header put to the message, mime section functionality is skipped.- --mime SUBTYPE
- .mime(subtype="auto", nl2br="auto")
- nl2br: True will append
<br>
to every line break in the HTML message. "auto": line breaks are changed only if there is no<br
or<p
in the HTML message,
- nl2br: True will append
- Envelope(mime=)
-
headers: Any custom headers (these will not be encrypted with GPG nor S/MIME)
- --header name value (may be used multiple times)
- .header(name, value=None, replace=False)
value
If None, returns value of the header or its list if the header was used multiple times. (Note that To, Cc, Bcc and Reply-To headers always return list.)replace
If True, any header of thekey
name are removed first and ifval
is None, the header is deleted. Otherwise another header of the same name is appended.
Envelope().header("X-Mailer", "my-app").header("X-Mailer") # "my-app" Envelope().header("Generic-Header", "1") \ .header("Generic-Header", "2") \ .header("Generic-Header") # ["1", "2"]
- Envelope(headers=[(name, value)])
Equivalent headers:
envelope --header X-Mailer my-app
Envelope(headers=[("X-Mailer", "my-app")]) Envelope().header("X-Mailer", "my-app")
Specific headers
These helpers are available via fluent interface.
-
.list_unsubscribe(uri=None, one_click=False, web=None, email=None): You can specify either url, email or both.
- .list_unsubscribe(uri): We try to determine whether this is e-mail and prepend brackets and 'https:'/'mailto:' if needed. Ex:
[email protected]?subject=unsubscribe
,example.com/unsubscribe
,<https://example.com/unsubscribe>
- .list_unsubscribe(email=): E-mail address. Ex:
[email protected]
,mailto:[email protected]
- .list_unsubscribe(web=, one_click=False): Specify URL. Ex:
example.com/unsubscribe
,http://example.com/unsubscribe
. Ifone_click=True
, rfc8058 List-Unsubscribe-Post header is added. This says user can unsubscribe with a single click that is realized by a POST request in order to prevent e-mail scanner to access the unsubscribe page by mistake. A 'https' url must be present.
# These will produce: # List-Unsubscribe: <https://example.com/unsubscribe> Envelope().list_unsubscribe("example.com/unsubscribe") Envelope().list_unsubscribe(web="example.com/unsubscribe") Envelope().list_unsubscribe("<https://example.com/unsubscribe>") # This will produce: # List-Unsubscribe: <https://example.com/unsubscribe>, <mailto:[email protected]?subject=unsubscribe> Envelope().list_unsubscribe("example.com/unsubscribe", mail="[email protected]?subject=unsubscribe")
- .list_unsubscribe(uri): We try to determine whether this is e-mail and prepend brackets and 'https:'/'mailto:' if needed. Ex:
-
.auto_submitted:
- .auto_submitted(val="auto-replied"): Direct response to another message by an automatic process.
- .auto_submitted.auto_generated(): automatic (often periodic) processes (such as UNIX "cron jobs") which are not direct responses to other messages
- .auto_submitted.no(): message was originated by a human
Envelope().auto_submitted() # mark message as automatic
Envelope().auto_submitted.no() # mark message as human produced
Cipher standard method
Note that if neither gpg nor smime is specified, we try to determine the method automatically.
- gpg: True to prefer GPG over S/MIME or home path to GNUPG rings (otherwise default ~/.gnupg is used)
- --gpg [path]
- .gpg(gnugp_home=True)
- Envelope(gpg=True)
- .smime: Prefer S/MIME over GPG
- --smime
- .smime()
- Envelope(smime=True)
Signing
- sign: Sign the message.
key
parameter- GPG:
- Blank (CLI) or True (module) for user default key
- "auto" for turning on signing if there is a key matching to the "from" header
- key ID/fingerprint
- e-mail address of the identity whose key is to be signed with
- Any attainable contents with the key to be signed with (will be imported into keyring)
- S/MIME: Any attainable contents with key to be signed with. May contain signing certificate as well.
- GPG:
- --sign key: (for
key
see above) - --sign-path: Filename with the From's private key. (Alternative to the
sign
parameter.) - --passphrase: Passphrase to the key if needed.
- --attach-key: GPG: Blank for appending public key to the attachments when sending.
- --cert: S/MIME: Certificate contents if not included in the key.
- --cert-path: S/MIME: Filename with the From's private cert if cert not included in the key. (Alternative to the
cert
parameter.) - .sign(key=True, passphrase=, attach_key=False, cert=None, key_path=None): Sign now (and you may specify the parameters). (For
key
see above.) - .signature(key=True, passphrase=, attach_key=False, cert=None, key_path=None): Sign later (when launched with .sign(), .encrypt() or .send() functions
- Envelope(sign=key): (for
key
see above) - Envelope(passphrase=): Passphrase to the signing key if needed.
- Envelope(attach_key=): If true, append GPG public key as an attachment when sending.
- Envelope(cert=): S/MIME: Any attainable contents
Encrypting
-
encrypt: Recipient GPG public key or S/MIME certificate to be encrypted with.
key
parameter- GPG:
- Blank (CLI) or True (module) to force encrypt with the user default keys (identities in the "from", "to", "cc" and "bcc" headers)
- "auto" for turning on encrypting if there is a matching key for every recipient
- key ID/fingerprint
- e-mail address of the identity whose key is to be encrypted with
- Any attainable contents with the key to be encrypted with (will be imported into keyring)
- an iterable with the identities specified by key ID / fingerprint / e-mail address / raw key data
- S/MIME any attainable contents with a certificate to be encrypted with or more in an iterable
- GPG:
- --encrypt [key]: (for
key
see above) Put 0/false/no to disableencrypt-path
. - --encrypt-path (CLI only): Filename(s) with the recipient's public key(s). (Alternative to the
encrypt
parameter.) - .encrypt(key=True, sign=, key_path=):
sign
See signing, ex: you may specify boolean or default signing key ID/fingerprint or "auto" for GPG or any attainable contents with an S/MIME key + signing certificate.key_path
: Key/certificate contents (alternative to thekey
parameter)
- .encryption(key=True, key_path=): Encrypt later (when launched with .sign(), .encrypt() or .send() functions. If needed, in the parameters specify any attainable contents with GPG encryption key or S/MIME encryption certificate.
- Envelope(encrypt=key): (for
key
see above)
# message gets encrypted for multiple S/MIME certificates envelope --smime --encrypt-path recipient1.pem recipient2.pem --message "Hello" # message gets encrypted with the default GPG key envelope --message "Encrypted GPG message!" --subject "Secret subject will not be shown" --encrypt --from [email protected] --to [email protected] # message not encrypted for the sender (from Bash) envelope --message "Encrypted GPG message!" --subject "Secret subject will not be shown" --encrypt [email protected] [email protected] --from [email protected] --to [email protected] [email protected]
# message not encrypted for the sender (from Python) Envelope() .message("Encrypted GPG message!") .subject("Secret subject will not be shown") .from_("[email protected]") .to(("[email protected]", "[email protected]")) .encrypt(("[email protected]", "[email protected]"))
GPG notes
- If the GPG encryption fails, it tries to determine which recipient misses the key.
- By default, GPG encrypts with the key of the from header recipient too.
- Key ID/fingerprint is internally ignored right now, GPG decides itself which key is to be used.
Supportive
- .recipients(): Return set of all recipients β
To
,Cc
,Bcc
- .recipients(clear=True): All
To
,Cc
andBcc
recipients are removed and theEnvelope
object is returned.
- .recipients(clear=True): All
- attachments: Access the list of attachments.
- --attachments [NAME] Get the list of attachments or a contents of the one specified by
NAME
- .attachments(name=None, inline=None)
- name (str): The name of the only desired attachment to be returned.
- inline (bool): Filter inline/enclosed attachments only.
- Attachment object has the attributes .name file name, .mimetype, .data raw data
- if casted to str/bytes, its raw .data are returned
- --attachments [NAME] Get the list of attachments or a contents of the one specified by
- .copy(): Return deep copy of the instance to be used independently.
factory = Envelope().cc("[email protected]").copy
e1 = factory().to("[email protected]")
e2 = factory().to("[email protected]").cc("[email protected]") #
print(e1.recipients()) # {'[email protected]', '[email protected]'}
print(e2.recipients()) # {'[email protected]', '[email protected]', '[email protected]'}
-
Read message and subject by .message() and .subject()
-
preview: Returns the string of the message or data as a human-readable text. Ex: whilst we have to use quoted-printable (as seen in str), here the output will be plain text.
- --preview
- .preview()
-
check: Check all e-mail addresses and SMTP connection and return True/False if succeeded. Tries to find SPF, DKIM and DMARC DNS records depending on the From's domain and print them out.
- --check
- .check(check_mx=True, check_smtp=True)
check_mx
E-mail addresses can be checked for MX record, not only for their format.check_smtp
We try to connect to the SMTP host.
$ envelope --smtp localhost 25 --from [email protected] --check SPF found on the domain example.com: v=spf1 -all See: dig -t SPF example.com && dig -t TXT example.com DKIM found: ['v=DKIM1; g=*; k=rsa; p=...'] Could not spot DMARC. Trying to connect to the SMTP... Check succeeded.
-
.as_message(): Generates an email.message.Message object.
e = Envelope("hello").as_message() print(type(e), e.get_payload()) # <class 'email.message.EmailMessage'> hello\n
Note: due to a bug in a standard Python library python/cpython#99533 and #19 you void GPG when you access the message this way wihle signing an attachment with a name longer than 34 chars.
-
load: Parse any attainable contents (including email.message.Message) like an EML file to build an Envelope object.
- It can decrypt the message and parse its (inline or enclosed) attachments.
- Note that if you will send this reconstructed message, you might not probably receive it due to the Message-ID duplication. Delete at least Message-ID header prior to re-sending.
- (static) .load(message, *, path=None, key=None, cert=None, gnupg_home=None)
- message: Any attainable contents
- path: Path to the file, alternative to the
message
- key, cert: Specify when decrypting an S/MIME message (may be bundled together to the
key
) - gnupg_home: Path to the GNUPG_HOME or None if the environment default should be used.
Envelope.load("Subject: testing message").subject() # "testing message"
- bash
- allows use blank
--subject
or--message
flags to display the - --load FILE
$ envelope --load email.eml Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit MIME-Version: 1.0 Subject: testing message Message body $ envelope --load email.eml --subject testing message
- (bash) piped in content, envelope executable used with no argument
$ echo "Subject: testing message" | envelope Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit MIME-Version: 1.0 Subject: testing message $ cat email.eml | envelope $ envelope < email.eml
- allows use blank
-
smtp_quit(): As Envelope tends to re-use all the SMTP instances, you may want to quit them explicitly. Either call this method to the Envelope class to close all the cached connections or to an Envelope object to close only the connection it currently uses.
e = Envelope().smtp(server1).smtp(server2) e.smtp_quit() # called on an instance β closes connection to `server2` only Envelope.smtp_quit() # called on the class β closes both connections
Address
Any e-mail address encountered is internally converted to an Address(str)
object that can be imported from the envelope
package. You can safely access following str
properties:
.name
β the real name.address
β the e-mail address.host
β its domain.user
β the user name part of the e-mail
from envelope import Address
a = Address("John <[email protected]>")
a.name == "John", a.address == "[email protected]", a.host == "example.com", a.user == "person"
Empty object works too. For example, if the From
header is not set, we get an empty Address object. Still it is safe to access its properties.
a = Envelope.load("Empty message").from_()
bool(a) is False, a.host == ""
Address() == Address("") == "", Address().address == ""
Method .casefold()
returns casefolded Address
object which is useful for comparing with strings whereas comparing with other Address
object casefolds automatically
a = Address("John <[email protected]>")
c = a.casefold()
a is not c, a == c, a.name == "john", a.name != c.name
Method .is_valid(check_mx=False)
returns boolean if the format is valid. When check_mx
set to True
, MX server is inquired too.
Since the Address
is a subclass of str
, you can safely join such objects.
", ".join([a, a]) # "John <[email protected]>, "John <[email protected]>"
a + " hello" # "John <[email protected]> hello"
Address objects are equal if their e-mail address are equal. (Their real names might differ.) Address object is equal to a string if the string contains its e-mail address or the whole representation.
"[email protected]" == Address("John <[email protected]>") == "John <[email protected]>" # True
Concerning to
, cc
, bcc
and reply-to
, multiple addresses may always be given in a string, delimited by comma (or semicolon). The .get(address:bool, name:bool)
method may be called on an Address
object to filter the desired information.
e = (Envelope()
.to("[email protected]")
.to("[email protected], John <[email protected]>")
.to(["[email protected]"]))
[str(x) for x in e.to()] # ["[email protected]", "John <[email protected]>", "[email protected]"]
[x.get(address=False) for x in e.to()] # ["", "John", ""]
[x.get(name=True) for x in e.to()] # ["[email protected]", "John", "[email protected]"]
# return an address if no name given
[x.get(address=True) for x in e.to()] # ["[email protected]", "[email protected]", "[email protected]"]
# addresses only
For some exotic cases, Address tends to do the parsing job better than the underlying standard library (see the bug report from 2004).
from email.utils import parseaddr
from envelope import Address
parseaddr("[email protected] <[email protected]>")
# ('', '[email protected]') -> empty name and wrong address
Address("[email protected] <[email protected]>").address
# '[email protected]' -> the right address
Experimental
Since we tend to keep the API simple and do the least amount of backward incompatible changes, it is hard to decide the right way. Your suggestions are welcome! Following methods have no stable API, hence their name begins with an underscore.
_report()
: Accessingmultipart/report
.
Currently only XARF is supported in the moment. You may directly access the fields, without any additional json
parsing.
if xarf := Envelope.load(path="xarf.eml")._report():
print(xarf['SourceIp']) # '192.0.2.1'
Envelope object
Converting object to str or bool
When successfully signing, encrypting or sending, object is resolvable to True and signed text / produced e-mail could be obtained via str().
o = Envelope("message", sign=True)
str(o) # signed text
bool(o) # True
Object equality
Envelope object is equal to a str
, bytes
or another Envelope
if their bytes
are the same.
# Envelope objects are equal
sign = {"message": "message", "sign": True}
Envelope(**sign) == Envelope(**sign) # True
bytes(Envelope(**sign)) # because their bytes are the same
# b'-----BEGIN PGP SIGNED MESSAGE-----\nHash: SHA512\n\nmessage\n-----BEGIN PGP SIGNATURE-----\n\niQEzBAEBCgAdFiE...\n-----END PGP SIGNATURE-----\n'
# however, result of a PGP encrypting produces always a different output
encrypt = {"message": "message", "encrypt": True, "from_": False, "to": "[email protected]"}
Envelope(**encrypt) != Envelope(**encrypt) # Envelope objects are not equal
Examples
Signing and encrypting
Sign the message.
Envelope(message="Hello world", sign=True)
Sign the message loaded from a file by standard pathlib library
from pathlib import Path
Envelope(message=Path("/tmp/message.txt"), sign=True)
Sign the message got from a file-stream
with open("/tmp/message.txt") as f:
Envelope(message=f, sign=True)
Sign and encrypt the message so that's decryptable by keys for [email protected] and [email protected] (that should already be loaded in the keyring).
Envelope(message="Hello world", sign=True,
encrypt=True,
from_="[email protected]",
to="[email protected]")
Sign and encrypt the message so that's decryptable by keys for [email protected] and [email protected] (that get's imported to the keyring from the file).
Envelope(message="Hello world", sign=True,
encrypt=Path("/tmp/remote_key.asc"),
from_="[email protected]",
to="[email protected]")
Sign the message via different keyring.
Envelope(message="Hello world", sign=True, gnupg="/tmp/my-keyring/")
Sign the message with a key that needs passphrase.
Envelope(message="Hello world", sign=True, passphrase="my-password")
Sign a message with signing by default turned previously on and having a default keyring path. Every factory
call will honour these defaults.
factory = Envelope().signature(True).gpg("/tmp/my-keyring").copy
factory().(message="Hello world")
Sending
Send an e-mail via module call.
Envelope(message="Hello world", send=True)
Send an e-mail via CLI and default SMTP server localhost on port 25.
envelope --to "[email protected]" --message "Hello world" --send
Send while having specified the SMTP server host, port, username, password.
envelope --to "[email protected]" message "Hello world" --send --smtp localhost 123 username password
Send while having specified the SMTP server through a dictionary.
envelope --to "[email protected]" --message "Hello world" --send --smtp '{"host": "localhost", "port": "123"}'
Send while having specified the SMTP server via module call.
Envelope(message="Hello world", to="[email protected]", send=True, smtp={"host":"localhost"})
Attachment
You can attach a file in many different ways. Pick the one that suits you the best.
Envelope(attachment=Path("/tmp/file.txt")) # file name will be 'file.txt'
with open("/tmp/file.txt") as f:
Envelope(attachment=f) # file name will be 'file.txt'
with open("/tmp/file.txt") as f:
Envelope(attachment=(f, "filename.txt"))
Envelope().attach(path="/tmp/file.txt", name="filename.txt")
Inline images
The only thing you have to do is to set the inline=True
parameter of the attachment. Then, you can reference the image from within your message, with the help of cid
keyword. For more details, see attachments in the Sending section.
(Envelope()
.attach(path="/tmp/file.jpg", inline=True)
.message("Hey, this is an inline image: <img src='cid:file.jpg' />"))
Complex example
Send an encrypted and signed message (GPG) via the default SMTP server, via all three interfaces.
# CLI interface
envelope --message "Hello world" --from "[email protected]" --to "[email protected]" --subject "Test" --sign --encrypt -a /tmp/file.txt -a /tmp/file2 application/gzip zipped-file.zip --send
from pathlib import Path
from envelope import Envelope
# fluent interface
Envelope().message("Hello world").from_("[email protected]").to("[email protected]").subject("Test").signature().encryption().attach(path="/tmp/file.txt").attach(Path("/tmp/file2"), "application/gzip", "zipped-file.zip").send()
# one-liner interface
Envelope("Hello world", "[email protected]", "[email protected]", "Test", sign=True, encrypt=True, attachments=[(Path("/tmp/file.txt"), (Path("/tmp/file2"), "application/gzip", "zipped-file.zip")], send=True)
In the condition [email protected] private key for signing, [email protected] public key for encrypting and open SMTP server on localhost:25 are available, change --send
to --send 0
(or .send()
to .send(False)
or send=True
to send=False
) to investigate the generated message that may be similar to the following output:
****************************************************************************************************
Have not been sent from [email protected] to [email protected]
Encrypted subject: Test
Encrypted message: b'Hello world'
Subject: Encrypted message
MIME-Version: 1.0
Content-Type: multipart/encrypted; protocol="application/pgp-encrypted";
boundary="===============8462917939563016793=="
From: [email protected]
To: [email protected]
Date: Tue, 08 Oct 2019 16:16:18 +0200
Message-ID: <157054417817.4405.938581433237601455@promyka>
--===============8462917939563016793==
Content-Type: application/pgp-encrypted
Version: 1
--===============8462917939563016793==
Content-Type: application/octet-stream; name="encrypted.asc"
Content-Description: OpenPGP encrypted message
Content-Disposition: inline; filename="encrypted.asc"
-----BEGIN PGP MESSAGE-----
hQMOAyx1c9zl1h4wEAv+PmtwjQDt+4XCn8YQJ6d7kyrp2R7xzS3PQwOZ7e+HWJjY
(...)
RQ8QtLLEza+rs+1lgcPgdBZEHFpYpgDb0AUvYg9d
=YuqI
-----END PGP MESSAGE-----
--===============8462917939563016793==--
Related affairs
Sending an e-mail does not mean it will be received. Sending it successfully through your local domain does not mean a public mailbox will accept it as well. If you are not trustworthy enough, your e-mail may not even appear at the recipient's spam bin, it can just be discarded without notice.
Configure your SMTP
It is always easier if you have an account on an SMTP server the application is able to send e-mails with. If it is not the case, various SMTP server exist but as a quick and non-secure solution, I've tested bytemark/smtp docker image that allows you to start up a SMTP server by a single line.
docker run --network=host --restart always -d bytemark/smtp # starts open port 25 on localhost
envelope --message "SMTP test" --from [your e-mail] --to [your e-mail] --smtp localhost 25 --send
Choose ciphering method
Configure your GPG
In order to sign messages, you need a private key. Let's pretend a usecase when your application will run under www-data
user and GPG sign messages through the keys located at: /var/www/.gnupg
. You have got a SMTP server with an e-mail account the application may use.
ls -l $(tty) # see current TTY owner
sudo chown www-data $(tty) # if creating the key for a different user and generation fails, changing temporarily the ownership of the terminal might help (when handling passphrase, the agent opens the controlling terminal rather than using stdin/stdout for security purposes)
GNUPGHOME=/var/www/.gnupg sudo -H -u www-data gpg --full-generate-key # put application e-mail you are able to send e-mails from
# sudo chown [USER] $(tty) # you may set back the TTY owner
GNUPGHOME=/var/www/.gnupg sudo -H -u www-data gpg --list-secret-keys # get key ID
GNUPGHOME=/var/www/.gnupg sudo -H -u www-data gpg --send-keys [key ID] # now the world is able to pull the key from a global webserver when they receive an e-mail from you
GNUPGHOME=/var/www/.gnupg sudo -H -u www-data gpg --export [APPLICATION_EMAIL] | curl -T - https://keys.openpgp.org # prints out the link you can verify your key with on `keys.openpgp.org` (ex: used by default by Thunderbird Enigmail; standard --send-keys method will not verify the identity information here, hence your e-mail would not be searchable)
GNUPGHOME=/var/www/.gnupg sudo -H -u www-data envelope --message "Hello world" --subject "GPG signing test" --sign [key ID] --from [application e-mail] --to [your e-mail] --send # you now receive e-mail and may import the key and set the trust to the key
It takes few hours to a key to propagate. If the key cannot be imported in your e-mail client because not found on the servers, try in the morning again or check the online search form at http://hkps.pool.sks-keyservers.net. Put your fingerprint on the web or on the business card then so that everybody can check your signature is valid.
Configure your S/MIME
If you are supposed to use S/MIME, you would probably be told where to take your key and certificate from. If planning to try it all by yourself, generate your certificate.pem
.
- Either: Do you have private key?
openssl req -key YOUR-KEY.pem -nodes -x509 -days 365 -out certificate.pem # will generate privkey.pem alongside
- Or: Do not you have private key?
openssl req -newkey rsa:1024 -nodes -x509 -days 365 -out certificate.pem # will generate privkey.pem alongside
Now, you may sign a message with your key and certificate. (However, the messages will not be trustworthy because no authority signed the certificate.) Give your friend the certificate so that they might verify the message comes from you. Receive a certificate from a friend to encrypt them a message with.
envelope --message "Hello world" --subject "S/MIME signing test" --sign-path [key file] --cert-path [certificate file] --from [application e-mail] --to [your e-mail] --send # you now receive e-mail
DNS validation tools
This is just a short explanation on these anti-spam mechanisms so that you can take basic notion what is going on.
Every time, the receiver should ask the From's domain these questions over DNS.
SPF
The receiver asks the sender's domain: Do you allow the senders IP/domain to send the e-mail on your behalf? Is the IP/domain the mail originates from enlisted as valid in the DNS of the SMTP envelope MAIL FROM address domain?
Check your domain on SPF:
dig -t TXT example.com
SPF technology is tied to the SMTP envelope MAIL FROM address which is specified with the .from_addr
method and then stored into the Return-Path header by the receiving server, and it has nothing in common with the headers like From .from_
, Reply-To .reply_to
, or Sender .header("Sender")
.
DKIM
The receiver asks the sender's domain: Give me the public key so that I may check the hash in the e-mail header that assert the message was composed by your private key. So that the e-mail comes trustworthy from you and nobody modified it on the way.
Check your domain on DKIM:
dig -t TXT [selector]._domainkey.example.com
You can obtain the selector
from an e-mail message you received. Check the line DKIM-Signature
and the value of the param s
.
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=example.com; s=default;
DMARC
What is your policy concerning SPF and DKIM? What abuse address do you have?
Check your domain on DMARC:
dig -t TXT _dmarc.example.com