Commod0re
commented
8 years ago Ah, this is a case of PGPy not having support for partial packet lengths just yet (see #95), but it is something I am planning to implement for the next release.
Depending on how you invoke gpg, it will chunk the data packets using partial packet length headers so it can stream the encrypt/decrypt operations while still receiving input. That looks to be what has happened here:
% pgpdump 161.asc
Old: Public-Key Encrypted Session Key Packet(tag 1)(268 bytes)
New version(3)
Key ID - 0x3E46A25F81612D05
Pub alg - RSA Encrypt or Sign(pub 1)
RSA m^e mod n(2046 bits) - ...
-> m = sym alg(1 byte) + checksum(2 bytes) + PKCS-1 block type 02
New: Symmetrically Encrypted and MDC Packet(tag 18)(4096 bytes) partial start
Ver 1
Encrypted data [sym alg is specified in pub-key encrypted session key]
(plain text + MDC SHA1(20 bytes))
New: (86 bytes) partial endI generated a similar file (but slightly larger) and tested a bit like so:
% stat -c "%s" data.txt
8200
% wc -l data.txt
1025 data.txt
% # the options I used here were used to skip compression and encrypt with
% # just a passphrase for easier demonstration purposes
% gpg --armor --symmetric --cipher-algo AES --compress-algo 0 data.txt
% pgpdump data.txt.asc
Old: Symmetric-Key Encrypted Session Key Packet(tag 3)(13 bytes)
New version(4)
Sym alg - AES with 128-bit key(sym 7)
Iterated and salted string-to-key(s2k 3):
Hash alg - SHA1(hash 2)
Salt - bf 72 81 ce 4f a1 38 eb
Count - 31457280(coded count 238)
New: Symmetrically Encrypted and MDC Packet(tag 18)(8258 bytes)
Ver 1
Encrypted data [sym alg is specified in sym-key encrypted session key]
(plain text + MDC SHA1(20 bytes))
% # now I'll pipe the contents of data.txt into gpg instead,
% # which will cause it to stream
% cat data.txt | gpg --armor --symmetric --cipher-algo AES --compress-algo 0 > piped-data.txt.asc
% pgpdump piped-data.txt.asc
Old: Symmetric-Key Encrypted Session Key Packet(tag 3)(13 bytes)
New version(4)
Sym alg - AES with 128-bit key(sym 7)
Iterated and salted string-to-key(s2k 3):
Hash alg - SHA1(hash 2)
Salt - b9 18 9b e3 79 21 34 27
Count - 31457280(coded count 238)
New: Symmetrically Encrypted and MDC Packet(tag 18)(8192 bytes) partial start
Ver 1
Encrypted data [sym alg is specified in sym-key encrypted session key]
(plain text + MDC SHA1(20 bytes))
New: (58 bytes) partial endI was able to force it to not use partial packets by adding the --set-filesize option like so:
% cat data.txt | gpg --armor --symmetric --cipher-algo AES --compress-algo 0 --set-filesize 8200 > piped-sf-data.txt.asc
gpg: Note: --set-filesize is not for normal use!
% pgpdump piped-sf-data.txt.asc
Old: Symmetric-Key Encrypted Session Key Packet(tag 3)(13 bytes)
New version(4)
Sym alg - AES with 128-bit key(sym 7)
Iterated and salted string-to-key(s2k 3):
Hash alg - SHA1(hash 2)
Salt - c3 c8 2e 8b 60 54 1e fe
Count - 31457280(coded count 238)
New: Symmetrically Encrypted and MDC Packet(tag 18)(8250 bytes)
Ver 1
Encrypted data [sym alg is specified in sym-key encrypted session key]
(plain text + MDC SHA1(20 bytes))Since partial packet support is on the roadmap, I'll close this issue for now.
seddonym
I've run into a similar issue as reported here: https://github.com/SecurityInnovation/PGPy/issues/160. I think it's might have different causes so I'm reporting it as a separate bug.
The bug is that I get the same
NotImplementedErrorwhen I runPGPMessage.from_blob()on messages that are not very short. For example:This raises the following exception:
This is a message that consists of 1,000 lines of random 7 digit integers, one on each line. I have no problems with loading a message that is just 100 lines.