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doc: python bindings howto

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* Wrote the text description explaining each step in the most basic
  encryption operation.
* Will need to include additional examples for encrypting to multiple
  recipients using Context().encrypt instead of Context().op_encrypt.
This commit is contained in:
Ben McGinnes 2018-03-09 16:49:05 +11:00
parent 93252df9dc
commit 0168646394
1 changed files with 53 additions and 7 deletions
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lang/python/docs/GPGMEpythonHOWTOen.org
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@ -259,12 +259,51 @@
:CUSTOM_ID: howto-the-basics
:END:
The most frequently called features of any cryptographic library
will be the most fundamental tasks for enxryption software. In this
section we will look at how to programmatically encrypt data,
decrypt it, sign it and verify signatures.
** Encryption
:PROPERTIES:
:CUSTOM_ID: howto-basic-encryption
:END:
Encrypting to one key:
Encrypting is very straight forward. In the first example below
the message, =text=, is encrypted to a single recipient's key. In
the second example the message will be encrypted to multiple
recipients.
*** Encrypting to one key
:PROPERTIES:
:CUSTOM_ID: howto-basic-encryption-single
:END:
The text is then encapsulated in a GPGME Data object as =plain= and
the =cipher= object is created with another Data object. Then we
create the Context as =c= and set it to use the ASCII armoured
OpenPGP format. In later examples there will be alternative
methods of setting the OpenPGP output to be ASCII armoured.
Next we prepare a keylist object in our Context and follow it with
specifying the recipients as =r=. Note that the configuration in
one's =gpg.conf= file is honoured, so if you have the options set
to encrypt to one key or to a default key, that will be included
with this operation.
This is followed by a quick check to be sure that the recipient is
actually selected and that the key is available. Assuming it is,
the encryption can proceed, but if not a message will print stating
the key was not found.
The encryption operation is invoked within the Context with the
=c.op_encrypt= function, loading the recipien (=r=), the message
(=plain=) and the =cipher=. The =cipher.seek= uses =os.SEEK_SET=
to set the data to the correct byte format for GPGME to use it.
At this point we no longer need the plaintext material, so we
delete both the =text= and the =plain= objects. Then we write the
encrypted data out to a file, =secret_plans.txt.asc=.
#+begin_src python
import gpg
@ -296,13 +335,19 @@
cipher.seek(0, os.SEEK_SET)
del(text)
del(plain)
afile = open("secret_plans.org.asc", "wb")
afile = open("secret_plans.txt.asc", "wb")
afile.write(cipher.read())
afile.close()
except gpg.errors.GPGMEError as ex:
print(ex.getstring())
#+end_src
*** Encrypting to multiple keys
:PROPERTIES:
:CUSTOM_ID: howto-basic-encryption-multiple
:END:
** Decryption
:PROPERTIES:
:CUSTOM_ID: howto-basic-encryption
@ -316,10 +361,10 @@
import os.path
import gpg
if os.path.exists("/path/to/secret_plans.org.asc") is True:
ciphertext = "/path/to/secret_plans.org.asc"
elif os.path.exists("/path/to/secret_plans.org.gpg") is True:
ciphertext = "/path/to/secret_plans.org.gpg"
if os.path.exists("/path/to/secret_plans.txt.asc") is True:
ciphertext = "/path/to/secret_plans.txt.asc"
elif os.path.exists("/path/to/secret_plans.txt.gpg") is True:
ciphertext = "/path/to/secret_plans.txt.gpg"
else:
ciphertext = None
@ -327,7 +372,7 @@
afile = open(ciphertext, "rb")
plaintext = gpg.Context().decrypt(afile)
afile.close()
newfile = open("/path/to/secret_plans.org", "wb")
newfile = open("/path/to/secret_plans.txt", "wb")
newfile.write(plaintext[0])
newfile.close()
print(plaintext[0])
@ -338,6 +383,7 @@
pass
#+end_src
** Signing text
:PROPERTIES:
:CUSTOM_ID: howto-basic-signing