From fdd80eadcc2f147d0198d94b7b908764778184a2 Mon Sep 17 00:00:00 2001 From: Christian Cleberg Date: Mon, 29 Apr 2024 14:18:55 -0500 Subject: format line wrapping and fix escaped characters --- content/blog/2022-07-14-gnupg.md | 266 +++++++++++++++++++-------------------- 1 file changed, 126 insertions(+), 140 deletions(-) (limited to 'content/blog/2022-07-14-gnupg.md') diff --git a/content/blog/2022-07-14-gnupg.md b/content/blog/2022-07-14-gnupg.md index 9bd2e19..8daba99 100644 --- a/content/blog/2022-07-14-gnupg.md +++ b/content/blog/2022-07-14-gnupg.md @@ -7,33 +7,31 @@ draft = false # The History of GPG -[GNU Privacy Guard](https://gnupg.org/), also known as GnuPG and GPG, is -a free (\"free\" as in both speech and beer) software that fully -implements the OpenPGP Message Format documented in [RFC -4880](https://www.rfc-editor.org/rfc/rfc4880). +[GNU Privacy Guard](https://gnupg.org/), also known as GnuPG and GPG, is a free +("free" as in both speech and beer) software that fully implements the OpenPGP +Message Format documented in [RFC 4880](https://www.rfc-editor.org/rfc/rfc4880). -I won\'t go in-depth on the full history of the software in this post, -but it is important to understand that GPG is not the same as PGP -(Pretty Good Privacy), which is a different implementation of RFC 4880. -However, GPG was designed to interoperate with PGP. +I won't go in-depth on the full history of the software in this post, but it is +important to understand that GPG is not the same as PGP (Pretty Good Privacy), +which is a different implementation of RFC 4880. However, GPG was designed to +interoperate with PGP. GPG was originally developed in the late 1990s by [Werner -Koch](https://en.wikipedia.org/wiki/Werner_Koch) and has historically -been funded generously by the German government. +Koch](https://en.wikipedia.org/wiki/Werner_Koch) and has historically been +funded generously by the German government. -Now that we have all the high-level info out of the way, let\'s dive -into the different aspects of GPG and its uses. +Now that we have all the high-level info out of the way, let's dive into the +different aspects of GPG and its uses. # Encryption Algorithms GPG supports a wide range of different encryption algorithms, including -public-key, cipher, hash, and compression algorithms. The support for -these algorithms has grown since the adoption of the Libgcrypt library -in the 2.x versions of GPG. +public-key, cipher, hash, and compression algorithms. The support for these +algorithms has grown since the adoption of the Libgcrypt library in the 2.x +versions of GPG. -As you will be able to see below in an example of a full key generation -with the GPG command line tool, GPG recommends the following algorithms -to new users: +As you will be able to see below in an example of a full key generation with the +GPG command line tool, GPG recommends the following algorithms to new users: ```sh Please select what kind of key you want: @@ -45,77 +43,71 @@ Please select what kind of key you want: (10) ECC (sign only) ``` -I am not doing an in-depth explanation here in order to keep the focus -on GPG and not encryption algorithms. If you want a deep dive into -cryptography or encryption algorithms, please read my other posts: +I am not doing an in-depth explanation here in order to keep the focus on GPG +and not encryption algorithms. If you want a deep dive into cryptography or +encryption algorithms, please read my other posts: -- [AES Encryption](../aes-encryption/) (2018) -- [Cryptography Basics](../cryptography-basics/) (2020) +- [AES Encryption](../aes-encryption/) (2018) +- [Cryptography Basics](../cryptography-basics/) (2020) ## Vulnerabilities -As of 2022-07-14, there are a few different vulnerabilities associated -with GPG or the libraries it uses: - -- GPG versions 1.0.2--1.2.3 contains a bug where \"as soon as one - (GPG-generated) ElGamal signature of an arbitrary message is - released, one can recover the signer\'s private key in less than a - second on a PC.\" - ([Source](https://www.di.ens.fr/~pnguyen/pub_Ng04.htm)) -- GPG versions prior to 1.4.2.1 contain a false positive signature - verification bug. - ([Source](https://lists.gnupg.%20org/pipermail/gnupg-announce/2006q1/000211.html)) -- GPG versions prior to 1.4.2.2 cannot detect injection of unsigned - data. ( - [Source](https://lists.gnupg.org/pipermail/gnupg-announce/2006q1/000218.html)) -- Libgcrypt, a library used by GPG, contained a bug which enabled full - key recovery for RSA-1024 and some RSA-2048 keys. This was resolved - in a GPG update in 2017. - ([Source](https://lwn.net/Articles/727179/)) -- The [ROCA - Vulnerability](https://en.wikipedia.org/wiki/ROCA_vulnerability) - affects RSA keys generated by YubiKey 4 tokens. - ([Source](https://crocs.fi.%20muni.cz/_media/public/papers/nemec_roca_ccs17_preprint.pdf)) -- The [SigSpoof Attack](https://en.wikipedia.org/wiki/SigSpoof) allows - an attacker to spoof digital signatures. - ([Source](https://arstechnica.%20com/information-technology/2018/06/decades-old-pgp-bug-allowed-hackers-to-spoof-just-about-anyones-signature/)) -- Libgcrypt 1.9.0 contains a severe flaw related to a heap buffer - overflow, fixed in Libgcrypt 1.9.1 - ([Source](https://web.archive.%20org/web/20210221012505/https://www.theregister.com/2021/01/29/severe_libgcrypt_bug/)) +As of 2022-07-14, there are a few different vulnerabilities associated with GPG +or the libraries it uses: + +- GPG versions 1.0.2--1.2.3 contains a bug where "as soon as one + (GPG-generated) ElGamal signature of an arbitrary message is released, one can + recover the signer's private key in less than a second on a PC." + ([Source](https://www.di.ens.fr/~pnguyen/pub_Ng04.htm)) +- GPG versions prior to 1.4.2.1 contain a false positive signature verification + bug. + ([Source](https://lists.gnupg.%20org/pipermail/gnupg-announce/2006q1/000211.html)) +- GPG versions prior to 1.4.2.2 cannot detect injection of unsigned data. ( + [Source](https://lists.gnupg.org/pipermail/gnupg-announce/2006q1/000218.html)) +- Libgcrypt, a library used by GPG, contained a bug which enabled full key + recovery for RSA-1024 and some RSA-2048 keys. This was resolved in a GPG + update in 2017. ([Source](https://lwn.net/Articles/727179/)) +- The [ROCA Vulnerability](https://en.wikipedia.org/wiki/ROCA_vulnerability) + affects RSA keys generated by YubiKey 4 tokens. + ([Source](https://crocs.fi.%20muni.cz/_media/public/papers/nemec_roca_ccs17_preprint.pdf)) +- The [SigSpoof Attack](https://en.wikipedia.org/wiki/SigSpoof) allows an + attacker to spoof digital signatures. + ([Source](https://arstechnica.%20com/information-technology/2018/06/decades-old-pgp-bug-allowed-hackers-to-spoof-just-about-anyones-signature/)) +- Libgcrypt 1.9.0 contains a severe flaw related to a heap buffer overflow, + fixed in Libgcrypt 1.9.1 + ([Source](https://web.archive.%20org/web/20210221012505/https://www.theregister.com/2021/01/29/severe_libgcrypt_bug/)) ### Platforms -Originally developed as a command-line program for \*nix systems, GPG -now has a wealth of front-end applications and libraries available for -end-users. However, the most recommended programs remain the same: +Originally developed as a command-line program for *nix systems, GPG now has a +wealth of front-end applications and libraries available for end-users. However, +the most recommended programs remain the same: -- [GnuPG](https://gnupg.org) for Linux (depending on distro) -- [Gpg4win](https://gpg4win.org) for Windows -- [GPGTools](https://gpgtools.org) for macOS +- [GnuPG](https://gnupg.org) for Linux (depending on distro) +- [Gpg4win](https://gpg4win.org) for Windows +- [GPGTools](https://gpgtools.org) for macOS # Creating a Key Pair -In order to create a GPG key pair, a user would first need to install -GPG on their system. If we\'re assuming that the user is on Fedora -Linux, they would execute the following: +In order to create a GPG key pair, a user would first need to install GPG on +their system. If we're assuming that the user is on Fedora Linux, they would +execute the following: ```sh sudo dnf install gpg ``` -Once installed, a user can create a new key pair with the following -command(s): +Once installed, a user can create a new key pair with the following command(s): ```sh gpg --full-generate-key ``` -GPG will walk the user through an interactive setup that asks for an -algorithm preference, expiration date, name, and email to associate with -this key. +GPG will walk the user through an interactive setup that asks for an algorithm +preference, expiration date, name, and email to associate with this key. -See the following example key set-up for a default key generation using -the GnuPG command-line interface: +See the following example key set-up for a default key generation using the +GnuPG command-line interface: ```sh gpg (GnuPG) 2.3.6; Copyright (C) 2021 Free Software Foundation, Inc. @@ -178,66 +170,63 @@ interface. As noted in RFC 4880, the general functions of OpenPGP are as follows: -- digital signatures -- encryption -- compression -- Radix-64 conversion -- key management and certificate services +- digital signatures +- encryption +- compression +- Radix-64 conversion +- key management and certificate services -From this, you can probably gather that the main use of GPG is for -encrypting data and/or signing the data with a key. The purpose of -encrypting data with GPG is to ensure that no one except the intended -recipient(s) can access the data. +From this, you can probably gather that the main use of GPG is for encrypting +data and/or signing the data with a key. The purpose of encrypting data with GPG +is to ensure that no one except the intended recipient(s) can access the data. -Let\'s explore some specific GPG use-cases. +Let's explore some specific GPG use-cases. ## Email -One of the more popular uses of GPG is to sign and/or encrypt emails. -With the use of a GPG keypair, you can encrypt a message, its subject, -and even the attachments within. - -The first process, regarding the signing of a message without any -encryption, is generally used to provide assurance that an email is -truly coming from the sender that the message claims. When I send an -email, and it\'s signed with my public key, the recipient(s) of the -message can verify that the message was signed with my personal key. - -The second process, regarding the actual encryption of the message and -its contents, works by using a combination of the sender\'s keys and the -recipient\'s keys. This process may vary slightly by implementation, but -it most commonly uses asymmetric cryptography, also known as public-key -cryptography. In this version of encryption, the sender\'s private key -to sign the message and a combination of the sender\'s keys and the -recipient\'s public key to encrypt the message. - -If two people each have their own private keys and exchange their public -keys, they can send encrypted messages back and forth with GPG. This is -also possible with symmetric cryptography, but the process differs since -there are no key pairs. - -Implementation of email encryption varies greatly between email clients, -so you will need to reference your email client\'s documentation to -ensure you are setting it up correctly for that specific client. +One of the more popular uses of GPG is to sign and/or encrypt emails. With the +use of a GPG keypair, you can encrypt a message, its subject, and even the +attachments within. + +The first process, regarding the signing of a message without any encryption, is +generally used to provide assurance that an email is truly coming from the +sender that the message claims. When I send an email, and it's signed with my +public key, the recipient(s) of the message can verify that the message was +signed with my personal key. + +The second process, regarding the actual encryption of the message and its +contents, works by using a combination of the sender's keys and the +recipient's keys. This process may vary slightly by implementation, but it most +commonly uses asymmetric cryptography, also known as public-key cryptography. In +this version of encryption, the sender's private key to sign the message and a +combination of the sender's keys and the recipient's public key to encrypt the +message. + +If two people each have their own private keys and exchange their public keys, +they can send encrypted messages back and forth with GPG. This is also possible +with symmetric cryptography, but the process differs since there are no key +pairs. + +Implementation of email encryption varies greatly between email clients, so you +will need to reference your email client's documentation to ensure you are +setting it up correctly for that specific client. ## File Encryption -As noted in the section above regarding emails, GPG enables users to be -able to send a message to each other if they are both set-up with GPG -keys. In this example, I am going to show how a user could send a file -called `example_file.txt` to another user via the -recipient\'s email. +As noted in the section above regarding emails, GPG enables users to be able to +send a message to each other if they are both set-up with GPG keys. In this +example, I am going to show how a user could send a file called +`example_file.txt` to another user via the recipient's email. -The sender would find the file they want to send and execute the -following command: +The sender would find the file they want to send and execute the following +command: ```sh gpg --encrypt --output example_file.txt.gpg --recipient \ recipient@example.com example_file.txt ``` -Once received, the recipient can decrypt the file with the following -command: +Once received, the recipient can decrypt the file with the following command: ```sh gpg --decrypt --output example_file.txt example_file.txt.gpg @@ -245,29 +234,28 @@ gpg --decrypt --output example_file.txt example_file.txt.gpg ## Ownership Signatures -One important aspect of GPG, especially for developers, is the ability -to sign data without encrypting it. For example, developers often sign -code changes when they commit the changes back to a central repository, -in order to display ownership of who made the changes. This allows other -users to look at a code change and determine that the change was valid. +One important aspect of GPG, especially for developers, is the ability to sign +data without encrypting it. For example, developers often sign code changes when +they commit the changes back to a central repository, in order to display +ownership of who made the changes. This allows other users to look at a code +change and determine that the change was valid. -In order to do this using [Git](https://git-scm.com), the developer -simply needs to alter the `git commit` command to include the -`-S` flag. Here\'s an example: +In order to do this using [Git](https://git-scm.com), the developer simply needs +to alter the `git commit` command to include the `-S` flag. Here's an example: ```sh git commit -S -m "my commit message" ``` -As an expansion of the example above, Git users can configure their -environment with a default key to use by adding their GPG signature: +As an expansion of the example above, Git users can configure their environment +with a default key to use by adding their GPG signature: ```sh git config --global user.signingkey XXXXXXXXXXXXXXXX ``` -If you\'re not sure what your signature is, you can find it titled -`sig` in the output of this command: +If you're not sure what your signature is, you can find it titled `sig` in the +output of this command: ```sh gpg --list-signatures @@ -275,12 +263,11 @@ gpg --list-signatures ## File Integrity -When a person generates a signature for data, they are allowing users -the ability to verify the signature on that data in the future to ensure -the data has not been corrupted. This is most common with software -applications hosted on the internet - developers provide signatures so -that users can verify a website was not hijacked and download links -replaced with dangerous software. +When a person generates a signature for data, they are allowing users the +ability to verify the signature on that data in the future to ensure the data +has not been corrupted. This is most common with software applications hosted on +the internet - developers provide signatures so that users can verify a website +was not hijacked and download links replaced with dangerous software. In order to verify signed data, a user needs to have: @@ -288,9 +275,8 @@ In order to verify signed data, a user needs to have: 2. A signature file 3. The public GPG key of the signer -Once the signer\'s public key is imported on the user\'s system, and -they have the data and signature, they can verify the data with the -following commands: +Once the signer's public key is imported on the user's system, and they have +the data and signature, they can verify the data with the following commands: ```sh # If the signature is attached to the data @@ -302,13 +288,13 @@ gpg --verify [signature-file] [original-file] ### Finding Public Keys -In order to use GPG with others, a user needs to know the other user(s) -keys. This is easy to do if the user knows the other user(s) in person, -but may be hard if the relationship is strictly digital. Luckily, there -are a few options. The first option is to look at a user\'s web page or -social pages if they have them. +In order to use GPG with others, a user needs to know the other user(s) keys. +This is easy to do if the user knows the other user(s) in person, but may be +hard if the relationship is strictly digital. Luckily, there are a few options. +The first option is to look at a user's web page or social pages if they have +them. Otherwise, the best option is to use a keyserver, such as: -- [pgp.mit.edu](https://pgp.mit.edu) -- [keys.openpgp.org](https://keys.openpgp.org) +- [pgp.mit.edu](https://pgp.mit.edu) +- [keys.openpgp.org](https://keys.openpgp.org) -- cgit v1.2.3-70-g09d2