I want to encrypt large files on linux with a bash script. When I was looking for methods to accomplish that, I thought about GPG and gave it a try. But when I ran some benchmarks I noticed that en-/decryption of large files takes very long.
Test scenario
I generated a 30GB large file filled with random content. Then I encrypted it with an RSA 4096 bit key. As I understand it, GPG is a hybird-encryption programm which encrypts sessions keys with the RSA Public Key. Therefore the en-/decryption should be done wihtin seconds or at least within a minute, as it uses these session keys to encrypt the actual data, isn't it? But here are the test results - I didnt bother decrypting the file with compressen turn on as it would take me another 2 - 3 hours...
System Specs:
GPG Version: 2.2.19
Arch Linux
Docker
Intel i7
My gpg keys were generated with a config file which contained the following values:
Key-Type: RSA
Key-Length: 4096
Subkey-Type: RSA
Subkey-Length: 4096
Name-Real: some-key-name
Name-Comment: some-key-comment
Expire-Date: 0
Passphrase: 123456789
For encryption i used the following commands:
gpg -q --output /outputFile.txt --recipient some-key-name --encrypt /inputFile.txt (with compression)
gpg -q --output /outputFile.txt -z 0 --recipient some-key-name --encrypt /inputFile.txt (without compression)
This command for decrypting the files:
gpg -q --pinentry-mode loopback --batch --passphrase 123456789 --output /decryptedFile.txt --decrypt /encryptedFile.txt
Test results
Encryption with compression turned on:
real 36m23.096s
user 14m54.920s
sys 2m31.870s
Encryption with compression turned off:
real 21m9.781s
user 1m39.590s
sys 2m20.980s
Decryption with compression turned off:
real 140m13.050s
user 5m5.340s
sys 16m33.020s
Questions
Am I missing something or am I using the tool in a wrong way?
Do you know a better way to encrypt large files with which uses an asymmetric encryption or at least uses it to encrypt the session keys?
PS
I googled very much and didn't find a applicable solution. I also read the man page and didn't find a hint what I might miss or did wrong. Also please be aware that I know that passing the password to gpg that way isn't the most secure way ;)
Related
I am working on a tool that sends out automated reports to our clients. This specific client wants the file to be encrypted and then signed. I have tried several different methods, with hours of searching, and have not had much luck. I know GPG signs then encrypts, but does anyone know if it is possible to swap the order? And if not does anyone know of any command line alternatives that can be run in a Linux container?
Example:
gpg --always-trust --batch --yes -s -u 'signee#email.com' -r 'receiver#email.com' -o 'test.txt.pgp' -e 'test.txt'
On verify :
gpg: verify signatures failed: Unexpected error
GPG doesn't seem to allow this in a single pass.
You have two options:
use a detached signing, then you'll need to send two files: one with encrypted data and second with the signature
encrypt data in first pass and then sign it in the second. However that would also need two steps on the receiving side: first verify signatures/unwrap data, then decrypt it.
Also it could be useful to ask client what exact format he expects to receive. Just example of gpg --list-packets report-file should be helpful.
I want to encrypt a file using a passphrase, which I did using gpg --gen-key to create a key (I used the default options) in the command line, and I also go this to work in an "automated" way without user interaction.
But, I'd like to specify the passphrase stored in a separate file. This is what I'm running now:
gpg --batch --gen-key "D:\Staging\FileContainingKeySettings.txt"
And what's in the file called "FileContainingKeySettings.txt" is this:
%echo Generating a default key
Key-Type: default
Subkey-Type: default
Name-Real: PBJ
Name-Comment: test
Name-Email: PBJ#pbj.com
Expire-Date: 0
Passphrase:blah
%commit
%echo done
So that works and generates the key.
Then I call this:
gpg --batch --yes -r PBJ --output D:\Staging\newEncryptedFile.txt --encrypt
D:\Staging\textfiletobeencrypted.csv
And this works too.
So now I have 1 problem and 1 question. The problem is that I need to specify the passphrase to reference a file that looks like this (but much longer):
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: BCPG v1.47
[encoding]
-----END PGP PUBLIC KEY BLOCK-----
instead of using the password where I wrote "blah"^, and I haven't found a way to do this online or from any other team members around me. How can I do that?
Question: I also notice now that the file I was sent containing the encryption key reads at the top
" -----BEGIN PGP PUBLIC KEY BLOCK-----"
...which says it uses PGP (but I am using gpg). I know that gpg and pgp are different and read about them, but can I even do what I'm trying to do using gpg to encrypt a file with a key that was apparently generated with pgp?
(in Windows)
UPDATE: Now I may have gotten this working, although I still have to validate by having the other person decrypt the message (it works fine when I decrypt it). Silly I didn't think of this code change earlier when I've actually tried this before...I simply changed my cmd call from this part:
gpg --batch --gen-key "D:\Staging\FileContainingKeySettings.txt"
to this instead, specifying the passphrase file location here instead:
gpg --batch --passphrase "D:\Staging\FileWithActualKey.txt --gen-key
"D:\Staging\FileContainingKeySettings.txt"
and I took the password line out of the file "FileContainingKeySettings" altogether. I haven't tested this by having the other person decrypt it yet on their end...I hope it worked. At least I didn't get error. But now when I run this line again to actually do encryption, it works:
gpg --batch --yes -r PBJ --output D:\Staging\newEncryptedFile.txt --encrypt
D:\Staging\textfiletobeencrypted.csv
The gpg software supports symmetric encryption out of the box. That means, it works with a password. But apart from protecting the content it is also important to ensure the Authentication of a message. The idea is to create a hashsum of the file itself together with the password used for encryption. According to [1] a popular “Message Authentication Code” is HMAC. After entering:
gpg --hmac --armor --symmetric --passphrase pwd1 file.txt
gpg: Invalid option "--hmac"
an error message occurs that the switch is not known by the software. How can i use the MAC authentication the right way?
You can't. The reason for the error message is that type of signature is not available with GPG. You'd be better off simply signing and encrypting the file with the standard GPG method. Even if you wanted to use symmetric encryption only, then the recipient would still need to use GPG to decrypt the file. The correct command would be:
gpg -o filename.txt.asc -sear $recipient_key filename.txt
This assumes you also always encrypt to your own key, otherwise the command would be:
gpg -o filename.txt.asc -sear $recipient_key -r $your_key filename.txt
If they don't have a key, you could still sign and encrypt to your own key only and then extract the session key so you could provide that for them to decrypt the file with it:
gpg -o filename.txt --show-session-key -d filename.txt.asc
Then the recipient would be able to decrypt with:
gpg -o filename.txt --override-session-key $session_key -d filename.txt.asc
If you really must use symmetric encryption only, however, you can do it in two setps.
First sign the file:
gpg -o filename.txt.asc -sa filename.txt
Then symmetrically encrypt that file:
gpg -o newfilename.asc -a -c filename.txt.asc
The recipient would then need to run the decryption command twice; first on the symmetrically encrypted file and then a second time on the file it decrypts.
The normal --verify option is only used for checking clearsigned files or files with detached signatures.
I would like to use GnuPG´s decrypt command without any user interation. The script's --passphrase-fd argument seems exactly what I need. But I don't know how it works - haven't found examples.
Could anyone give me an example of such a command, on both Windows and UNIX environments?
(FYI, I'm using GnuPG 2).
Thanks already :)
In order to use the gpg option --passphrase-fd in GnuPG v2, you must specify the --batch parameter. I will first explain how --passphrase-fd works, and then get to the examples.
--passphrase-fd tells GnuPG which file descriptor (-fd) to expect the passphrase to come from. The standard file descriptors are STDIN (0), STDOUT (1) and STDERR (2). For the context of this question, you would normally only be concerned about STDIN (0).
You didn't specify where you want the passphrase to come from, so I will demonstrate the usage of STDIN (standard in) in a variety of ways.
--passphrase-fd 0 tells GnuPG to retrieve the passphrase from input into the current shell; so for example if you want GnuPG to get the passphrase data in the very next line of console input, the command and output would be like so:
gpg2 --batch --passphrase-fd 0 --armor --decrypt /path/to/encrypted_file.pgp
<next line of input is passphrase followed by hitting enter>
gpg: encrypted with 1024-bit RSA key, ID EC18C175, created 2013-10-26
"testkey4321 (4321) <test#4321.com>"
this is a test... this is only a test...
In the above example, the passphrase was provided via file descriptor 0 (STDIN) - which we provided by entering it on the shells current standard input.
In the next example, we will tell GnuPG to retrieve the passphrase from input into the current shell that is actually the output of another command (echo, in this case, which merely "echos" what you tell it to):
echo "mypassphrase" | gpg2 --batch --passphrase-fd 0 --armor --decrypt /path/to/encrypted_file.pgp
gpg: encrypted with 1024-bit RSA key, ID EC18C175, created 2013-10-26
"testkey4321 (4321) <test#4321.com>"
this is a test... this is only a test...
Another example that dumps the contents of a file that contains the passphrase to STDIN -
cat /path/to/file_with_passphrase | gpg2 --batch --passphrase-fd 0 --armor --decrypt /path/to/encrypted_file.pgp
gpg: encrypted with 1024-bit RSA key, ID EC18C175, created 2013-10-26
"testkey4321 (4321) <test#4321.com>"
this is a test... this is only a test...
In summary, --passphrase-fd just tells GnuPG that you want to feed it the requisite passphrase via a standard file descriptor; the difference between GnuPG v2 and GnuPG is merely the --batch parameter.
The above examples should work the same in Windows and *nix environments, with the only difference being that in Windows - depending on your configuration and version - you will have to replace cat with type in order to dump the contents of a file to STDIN.
kylehuff's answer still wouldn't work for me, with gpupg still popping up a password prompt.
According to https://wiki.archlinux.org/index.php/GnuPG#Unattended_passphrase with gnupg version 2.1.0 and higher, you need to do additional steps to support --passphrase-fd
First, edit the gpg-agent configuration to allow loopback pinentry mode:
~/.gnupg/gpg-agent.conf
allow-loopback-pinentry
Restart the gpg-agent process if it is running to let the change take effect.
Second, either the application needs to be updated to include a commandline parameter to use loopback mode like so:
$ gpg --pinentry-mode loopback ...
Using GPG4win/gpg 2.2.3: to use the passphrase-fd 0 and bypass the prompt, I can confirm that the following works:
--pinentry-mode loopback
As I've had to recently figure this out myself I thought it might be worth chiming in.
The answer by kylehuff is very good if you're decryping files, however, if you've need of input/output redirection, such as piping, here's an example of using a non-0 file descriptor to pass the passphrase.
#!/usr/bin/env bash
# Set some variables for easy modding
Var_fd='9'
Var_pass_location="/path/to/passphrase.file"
Var_gpg_decrypt_opts="--passphrase-fd ${Var_fd} --decrypt"
Var_output_location="out.txt"
Arr_string=( "$#" )
# Open file descriptor and shove the passphrase file into it
exec ${Var_fd}<${Var_pass_location}
# Pipe input array though gpg and append to output file
cat <<<"${Arr_string[*]}" | $(which gpg) ${Var_gpg_decrypt_opts} >> ${Var_output_location}
# Do not forget to close the file descriptor
exec ${Var_fd}>&-
Do be warned, outside of special use cases, that saving your private keys passphrase is generally seen as a bad idea or bad security practice. -Also please don't forget to close the descriptor when finished so that your passphrase isn't accessible via that method anymore.- Often I've seen advised in these use cases to use specifically non-passphrase protected keys but that's totally your choose. If you like the above code then you may want to also checkout the script I debugged for key generation either unattended or attended because it covers even less commonly used gpg file descriptor options.
Edits/updates
So I've been debugging the bulk decryption operations and have evidence to show that file descriptors seem to close automatically or perhaps it's auto closed by GnuPG. Check build 152 all the way at the bottom of the raw logs, just before diff checks, you'll find that the first block of encrypted data ate the passphrase leaving the next two blocks of data without a valid passphrase. The related scripts in this operation are ; first the script_decrypt.sh build script sets the test key's passphrase to file descriptor 9 as shown in above examples, then the Helper script is called such that it'll make use of that file descriptor... it's a funky use case but the moral of the story seems to be that what ever bulk decryption operations you plan to implement with GnuPG file descriptors will likely need to follow the steps outlined above as a whole function to properly have the file descriptors reopened. I'll be rewriting the helper script over the next few pushes so check the Travis-CI build logs greater than 152 to find if I've a solution to where file descriptors get closed...
... so that only took two tries to get things working, see the difference in build 154 both the encrypted file and raw input log match. As hypothesised the file descriptors get dumped after first usage by either GnuPG or a sub shell, thus the passphrase needs to be assigned before every decrypt command for bulk decryption to happen.
Hope this was valuable to y'all.
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I am running next command within a crontab to encrypt a file and I don't want a keyboard interaction
echo "PASSPHRASE" | gpg --passphrase-fd 0 -r USER --encrypt FILENAME.TXT
but I have this answer:
gpg: C042XXXX: There is no assurance this key belongs to the named user
pub 40XXX/C042XXXX 2012-01-11 Name LastName. (comment) <user#email.com>
Primary key fingerprint: XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX
Subkey fingerprint: XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX
It is NOT certain that the key belongs to the person named
in the user ID. If you *really* know what you are doing,
you may answer the next question with yes.
Use this key anyway? (y/N)
As David intimated, the problem here is that gpg doesn't trust the public key you're using to encrypt. You could sign the key as he explained.
An alternative--especially if the key might be changing occasionally--would be to tack on --trust-model always to your gpg command.
Here's the relevant bit from the man page:
--trust-model pgp|classic|direct|always|auto
Set what trust model GnuPG should follow. The models are:
pgp This is the Web of Trust combined with trust signatures as used in
PGP 5.x and later. This is the default trust model when creating a
new trust database.
classic
This is the standard Web of Trust as used in PGP 2.x and earlier.
direct Key validity is set directly by the user and not calculated via
the Web of Trust.
always Skip key validation and assume that used keys are always fully
trusted. You generally won't use this unless you are using some
external validation scheme. This option also suppresses the
"[uncertain]" tag printed with signature checks when there is no
evidence that the user ID is bound to the key.
auto Select the trust model depending on whatever the internal trust
database says. This is the default model if such a database
already exists.
Here is my solution, based on gpg2 (but I bet you can apply similar technique to gpg)
$ gpg2 --edit-key {recipient email address}
> trust
> 5 (select 5 if you ultimately trust the key)
> save
This will tell gpg2 to trust the key fully, so that you can encrypt without prompt
The hack approach:
echo -n PASSPHRASE > phrase
chmod 400 phrase #Make sure ONLY the user running the cron job can read the phrase
yes | gpg --passphrase-fd 3 --recipient USER --encrypt FILENAME.txt 3<phrase
The underlying problem is that the key you have for USER isn't signed. If you trust it, you can sign it with
gpg --edit-key USER sign
It will probably ask a couple questions, depending on your configuration. Do this once, then you should be good to go in your crontab. I'd still recommend using the solution I proposed, putting the passphrase in a separate file and making it only readable by the one user that command runs as. If you do that, you can kill the yes |, and just have the encrypt line.
Use this command, it will help you
echo "PASSPHRASE" | gpg --passphrase-fd 0 --always-trust -r USER --encrypt FILENAME.TX
I was running into this too. I couldn't get sign-key to do anything interesting. Here's what I did:
create a gpg key:
gpg --gen-key
get long key ID (result is in 5th column):
gpg --list-keys --with-colon name#domain.tld
Add trusted key line to ~/gnupg/gpg.conf
trusted-key 16DIGITALPHANUMERICKEYID
gpg line in backup script:
gpg -e -r name#domain.tld backup_file.tgz
Debugging cron:
I'm also capturing cron dubugging output by sending stdout and stderr to a log file in the cron command line. It's helpful to know
I assume that like me, a lot of people come here for the 'without keyboard interaction' part of the question. With gpg2 and gpg-agent it got quite complicated to sign/encrypt/decrypt stuff without any keyboard interaction. Here is how you would create a signature when your plaintext private key passphrase is saved in a text file:
cat something_so_sign.xzy | gpg \
--passphrase-file "plaintext_passphrase.txt" \
--batch \
--pinentry-mode loopback \
-bsa
Change -b -s -a depending on your needs. The other switches are mandatory. You may also just use --passphrase 'SECRET'. As already pointed out, be careful with that. Plaintext textfiles are not that much better of course.
Or sign the key (after you veryfied the fingerprint, of course):
gpg --sign-key <recipient email address>
After that you fully trust the key.
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
When you create a certificate first time with your email-id select fully trusted certificate then whenever you encrypt any file will not ask question like.... for more information open image in above link.
It is NOT certain that the key belongs to the person named in the user
ID. If you really know what you are doing, you may answer the next
question with yes.
Use this key anyway? (y/N)
A different approach:
This solution will work without user input.
To deny access to sensitive data (rather than encrypt it using third-party's keys), I upload *ONLY my PUBLIC key to the server I want to protect data on and use that key to encrypt with. This negates the need for an interactive prompt to supply a password facilitating automation and best of all, the PRIVATE key is apart from the public server.
gpg --batch --yes --trust-model always -r $YOURPUBKEYEMAILADDRESS -e ./file.txt
However, if NOT encrypting with your own public key, the use of the switch --trust-model always is a bit ropey. Anyway, a different way of solving the problem of denying access to data. HTH- Terrence Houlahan