2018-05-15 03:13:16 +00:00
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE dita PUBLIC "-//OASIS//DTD DITA Composite//EN" "ditabase.dtd">
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2018-05-15 03:50:14 +00:00
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<dita xml:lang="en-GB">
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2018-05-15 03:13:16 +00:00
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<topic id="topic_wmg_tjz_5db">
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<title>Encrypting to Multiple Keys</title>
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<body>
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<p>Encrypting to multiple keys essentially just expands upon the key selection process
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and the recipients from the previous examples.</p>
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<p>The following example encrypts a message (<codeph>text</codeph>) to everyone with an email
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address on the <codeph>gnupg.org </codeph>domain,<fn>You probably don't really want to do
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this. Searching the keyservers for "gnupg.org" produces over 400 results, the majority of
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which aren't actually at the gnupg.org domain, but just included a comment regarding the
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project in their key somewhere.</fn> but does <i>not</i> encrypt to a default key or other
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key which is configured to normally encrypt to.</p>
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<p>
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<codeblock id="enc2-1" outputclass="language-python">import gpg
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text = b"""Oh look, another test message.
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The same rules apply as with the previous example and more likely
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than not, the message will actually be drawn from reading the
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contents of a file or, maybe, from entering data at an input()
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prompt.
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Since the text in this case must be bytes, it is most likely that
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the input form will be a separate file which is opened with "rb"
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as this is the simplest method of obtaining the correct data
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format.
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"""
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c = gpg.Context(armor=True)
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rpattern = list(c.keylist(pattern="@gnupg.org", secret=False))
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logrus = []
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for i in range(len(rpattern)):
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if rpattern[i].can_encrypt == 1:
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logrus.append(rpattern[i])
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ciphertext, result, sign_result = c.encrypt(text, recipients=logrus, sign=False,
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always_trust=True)
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with open("secret_plans.txt.asc", "wb") as f:
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f.write(ciphertext)
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</codeblock>
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</p>
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<p>All it would take to change the above example to sign the message and also encrypt the
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message to any configured default keys would be to change the <codeph>c.encrypt</codeph>
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line to this:</p>
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<p>
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<codeblock id="enc2-2" outputclass="language-python">ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
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always_trust=True,
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add_encrypt_to=True)
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</codeblock>
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</p>
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<p>The only keyword arguments requiring modification are those for which the default values
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are changing. The default value of <codeph>sign</codeph> is <codeph>True</codeph>, the
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default of <codeph>always_trust</codeph> is <codeph>False</codeph>, the default of
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<codeph>add_encrypt_to</codeph> is <codeph>False</codeph>.</p>
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<p>If <codeph>always_trust</codeph> is not set to <codeph>True</codeph> and any of the
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recipient keys are not trusted (e.g. not signed or locally signed) then the encryption will
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raise an error. It is possible to mitigate this somewhat with something more like this:</p>
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<p>
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<codeblock id="enc2-3" outputclass="language-python">import gpg
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with open("secret_plans.txt.asc", "rb") as f:
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text = f.read()
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c = gpg.Context(armor=True)
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rpattern = list(c.keylist(pattern="@gnupg.org", secret=False))
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logrus = []
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for i in range(len(rpattern)):
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if rpattern[i].can_encrypt == 1:
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logrus.append(rpattern[i])
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try:
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ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
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add_encrypt_to=True)
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except gpg.errors.InvalidRecipients as e:
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for i in range(len(e.recipients)):
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for n in range(len(logrus)):
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if logrus[n].fpr == e.recipients[i].fpr:
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logrus.remove(logrus[n])
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else:
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pass
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try:
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ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
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add_encrypt_to=True)
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except:
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pass
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with open("secret_plans.txt.asc", "wb") as f:
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f.write(ciphertext)
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</codeblock>
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</p>
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<p>This will attempt to encrypt to all the keys searched for, then remove invalid recipients
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if it fails and try again.</p>
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</body>
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</topic>
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</dita>
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