X.509 Swiss Army Knife (x509sak) is a toolkit written in Python that acts as a boilerplate on top of OpenSSL to ease creation of X.509 certificates, certificate signing requests and CAs. It can automatically find CA chains and output them in a specifically desired format, graph CA hierarchies and more.
The tool is used similarly to OpenSSL in its syntax. The help page is meant to be comprehensive and self-explanatory. These are the currently available commands:
$ ./x509sak.py
Error: No command supplied.
Syntax: ./x509sak.py [command] [options]
Available commands:
Options vary from command to command. To receive further info, type
./x509sak.py [command] --help
buildchain Build a certificate chain
graph Graph a certificate pool
findcrt Find a specific certificate
createca Create a new certificate authority (CA)
createcsr Create a new certificate signing request (CSR) or
certificate
signcsr Make a certificate authority (CA) sign a crtificate
signing request (CSR) and output the certificate
revokecrt Revoke a specific certificate
genbrokenrsa Generate broken RSA keys for use in pentetration testing
dumpkey Dump a key in text form
forgecert Forge an X.509 certificate
x509sak requires Python3, pyasn1 and pyasn1_modules support. It also relies on OpenSSL. If you want graph support, then you also need to install the Graphviz package as well. Note that pyasn1_modules inside the Ubuntu tree (as of 3'2018, Ubuntu Artful MATE, v0.0.7-0.1) is broken and you'll need to use the version that pip3 installs (0.2.1 in my case).
The "buildchain" command is useful if you want to have a complete (or partial) certificate chain from a given leaf certfificate and a bundle of CAs. x509sak will figure out which of the CAs are appropriate (if any) and generate a chain in the order you want (root to leaf or leaf to root) including the certs you want (e.g., all certificates, all except root cert, etc.). This is useful if you have, for example, a webserver certificate and want to automatically find the chain of trust that you can use to deploy on your webserver.
usage: ./x509sak.py buildchain [-s path] [--inform {pem,der}]
[--order-leaf-to-root] [--allow-partial-chain]
[--dont-trust-crtfile]
[--outform {rootonly,intermediates,fullchain,all-except-root,multifile}]
[-o file] [-v] [--help]
crtfile
Build a certificate chain
positional arguments:
crtfile Certificate that a chain shall be build for, in PEM
format.
optional arguments:
-s path, --ca-source path
CA file (PEM format) or directory (containing
.pem/.crt files) to include when building the chain.
Can be specified multiple times to include multiple
locations.
--inform {pem,der} Specifies input file format for certificate. Possible
options are pem, der. Default is pem.
--order-leaf-to-root By default, certificates are ordered with the root CA
first and intermediate certificates following up to
the leaf. When this option is specified, the order is
inverted and go from leaf certificate to root.
--allow-partial-chain
When building the certificate chain, a full chain must
be found or the chain building fails. When this option
is specified, also partial chain matches are
permitted, i.e., not going up to a root CA. Note that
this can have undesired side effects when no root
certificates are found at all (the partial chain will
then consist of only the leaf certificate itself).
--dont-trust-crtfile When there's multiple certificates in the given
crtfile in PEM format, they're by default all added to
the truststore. With this option, only the leaf cert
is taken from the crtfile and they're not added to the
trusted pool.
--outform {rootonly,intermediates,fullchain,all-except-root,multifile}
Specifies what to write into the output file. Possible
options are rootonly, intermediates, fullchain, all-
except-root, multifile. Default is fullchain. When
specifying multifile, a %d format must be included in
the filename to serve as a template; typical printf-
style formatting can be used of course (e.g., %02d).
-o file, --outfile file
Specifies the output filename. Defaults to stdout.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
The graph utility can be used to plot multiple certificates and their certificate hierarchy. Some metadata is displayed within the graph as well. Here's an example of some certificates that I've plotted:
usage: ./x509sak.py graph [-f {dot,png,ps,pdf}] -o file [-v] [--help]
crtsource [crtsource ...]
Graph a certificate pool
positional arguments:
crtsource Certificate file (in PEM format) or directory
(conainting PEM-formatted .pem or .crt files) which
should be included in the graph.
optional arguments:
-f {dot,png,ps,pdf}, --format {dot,png,ps,pdf}
Specifies the output file format. Can be one of dot,
png, ps, pdf, defaults to None. When unspecified, the
file extension out the output file is used to
determine the file type.
-o file, --outfile file
Specifies the output filename. Mandatory argument.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
When looking for a bunch of certificates (some of which might be in PEM format) by their authoritative hash (i.e., the SHA256 hash over their DER-representation), findcrt can help you out. You specify a bunch of certificates and the hash prefix you're looking for and x509sak will show it to you.
usage: ./x509sak.py findcrt [-h hash] [-v] [--help] crtsource [crtsource ...]
Find a specific certificate
positional arguments:
crtsource Certificate file (in PEM format) or directory
(conainting PEM-formatted .pem or .crt files) which
should be included in the search.
optional arguments:
-h hash, --hashval hash
Find only certificates with a particular hash prefix.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
Creating a CA structure that can be used with "openssl ca" is tedious. The "createca" command does exactly this for you in one simple command. The created OpenSSL config file directly works with "openssl ca" for manual operation but can also be used with other x509sak commands (e.g., creating or revoking certificates). x509sak takes care that you have all the necessary setup files in place (index, serial, etc.) and can just as easily create intermediate CAs as it can create root CAs.
usage: ./x509sak.py createca [-k keyspec] [-p capath] [-s subject] [-d days]
[-h alg] [--serial serial] [-f] [-v] [--help]
capath
Create a new certificate authority (CA)
positional arguments:
capath Directory to create the new CA in.
optional arguments:
-k keyspec, --keytype keyspec
Private key type to generate for the new CA. Defaults
to ecc:secp384r1.
-p capath, --parent-ca capath
Parent CA directory. If omitted, CA certificate will
be self-signed.
-s subject, --subject-dn subject
CA subject distinguished name. Defaults to /CN=Root
CA.
-d days, --validity-days days
Number of days that the newly created CA will be valid
for. Defaults to 365 days.
-h alg, --hashfnc alg
Hash function to use for signing. Defaults to sha256.
--serial serial Serial number to use for root CA certificate.
Randomized by default.
-f, --force By default, the capath will not be overwritten if it
already exists. When this option is specified the
complete directory will be erased before creating the
new CA.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
The "createcsr" command can (as the name suggests) create CSRs, but also can directly generate CRTs that are signed by a previously created CA. The advantage over using OpenSSL manually is that the API is quite simple to configure the certificate manually for most cases (e.g., webserver certificates with X.509 Subject Alternative Name set), but also is flexible enough for custom stuff by including your custom extensions directly into the extension file configuration used by OpenSSL.
usage: ./x509sak.py createcsr [-k keyspec]
[-t {rootca,ca,tls-server,tls-client}]
[-s subject] [-d days] [-h alg] [--san-dns FQDN]
[--san-ip IP] [--extension key=value] [-f]
[-c capath] [-v] [--help]
in_key_filename out_filename
Create a new certificate signing request (CSR) or certificate
positional arguments:
in_key_filename Filename of the input private key.
out_filename Filename of the output certificate signing request or
certificate.
optional arguments:
-k keyspec, --keytype keyspec
Private key type to generate for the certificate or
CSR. By default, it is assumed the private key has
created beforehand.
-t {rootca,ca,tls-server,tls-client}, --template {rootca,ca,tls-server,tls-client}
Template to use for determining X.509 certificate
extensions. Can be one of rootca, ca, tls-server, tls-
client. By default, no extensions are included except
for SAN.
-s subject, --subject-dn subject
Certificate/CSR subject distinguished name. Defaults
to /CN=New Cert.
-d days, --validity-days days
When creating a certificate, number of days that the
certificate will be valid for. Defaults to 365 days.
-h alg, --hashfnc alg
Hash function to use for signing when creating a
certificate. Defaults to the default hash function
specified in the CA config.
--san-dns FQDN Subject Alternative DNS name to include in the
certificate or CSR. Can be specified multiple times.
--san-ip IP Subject Alternative IP address to include in the
certificate or CSR. Can be specified multiple times.
--extension key=value
Additional certificate X.509 extension to include on
top of the extensions in the template and by the SAN
parameters. Can be specified multiple times.
-f, --force Overwrite the output file if it already exists.
-c capath, --create-crt capath
Instead of creating a certificate signing request,
directly create a certificate instead. Needs to supply
the CA path that should issue the certificate.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
The signcsr command allows you to turn a CSR into a certificate by signing it by a CA private key.
usage: ./x509sak.py signcsr [-t {rootca,ca,tls-server,tls-client}]
[-s subject] [--san-dns FQDN] [--san-ip IP]
[-d days] [-h alg] [-f] [-v] [--help]
capath in_csr_filename out_crt_filename
Make a certificate authority (CA) sign a crtificate signing request (CSR) and
output the certificate
positional arguments:
capath Directory of the signing CA.
in_csr_filename Filename of the input certificate signing request.
out_crt_filename Filename of the output certificate.
optional arguments:
-t {rootca,ca,tls-server,tls-client}, --template {rootca,ca,tls-server,tls-client}
Template to use for determining X.509 certificate
extensions. Can be one of rootca, ca, tls-server, tls-
client. By default, no extensions are included except
for SAN.
-s subject, --subject-dn subject
Certificate's subject distinguished name. Defaults to
the subject given in the CSR.
--san-dns FQDN Subject Alternative DNS name to include in the
certificate. Can be specified multiple times.
--san-ip IP Subject Alternative IP address to include in the CRT.
Can be specified multiple times.
-d days, --validity-days days
Number of days that the newly created certificate will
be valid for. Defaults to 365 days.
-h alg, --hashfnc alg
Hash function to use for signing. Defaults to the
default hash function specified in the CA config.
-f, --force Overwrite the output certificate file if it already
exists.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
With revokecrt it's possible to easily revoke a certificate that you've previous generated. Simply specify the CA and the certificate that you want to revoke and you're set.
usage: ./x509sak.py revokecrt [-v] [--help] capath crt_filename
Revoke a specific certificate
positional arguments:
capath CA which created the certificate.
crt_filename Filename of the output certificate.
optional arguments:
-v, --verbose Increase verbosity level. Can be specified multiple times.
--help Show this help page.
With genbrokenrsa it is possible to generate deliberately malformed or odd RSA keys. For example, RSA keys with a custom value for the public exponent e, or RSA keys which have a very small exponent d (e.g, 3) and a correspondingly large exponent e. Note that keys generated by this tool are exclusively for testing purposes and may not, under any circumstances, be used for actual cryptographic applications. They are not secure.
usage: ./x509sak.py genbrokenrsa [-d path] [-b bits] [-e exp] [--switch-e-d]
[--accept-unusable-key] [-o file] [-f] [-v]
[--help]
Generate broken RSA keys for use in pentetration testing
optional arguments:
-d path, --prime-db path
Prime database directory. Defaults to . and searches
for files called primes_{bitlen}.txt in this
directory.
-b bits, --bitlen bits
Bitlength of primes p/q to choose. Note that the
modulus bitlength will be twice of that because it is
the product of two primes (n = pq). Defaults to 2048
bits.
-e exp, --public-exponent exp
Public exponent e (or d in case --switch-e-d is
specified) to use. Defaults to 0x10001. Will be
randomly chosen from 2..n-1 if set to -1.
--switch-e-d Swtich e with d when generating keypair.
--accept-unusable-key
Disregard integral checks, such as if gcd(e, phi(n))
== 1 before inverting e. Might lead to an unusable key
or might fail altogether.
-o file, --outfile file
Output filename. Defaults to broken_rsa.key.
-f, --force Overwrite output file if it already exists instead of
bailing out.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
The dumpkey facility can be used to dump the public/private key parameters of a given PEM keyfile into Python-code for further processing.
usage: ./x509sak.py dumpkey [-t {rsa,ecc}] [-p] [-v] [--help] key_filename
Dump a key in text form
positional arguments:
key_filename Filename of the input key file in PEM format.
optional arguments:
-t {rsa,ecc}, --key-type {rsa,ecc}
Type of private key to import. Can be one of rsa, ecc,
defaults to rsa. Disregarded for public keys and
determined automatically.
-p, --public-key Input is a public key, not a private key.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
With the forgecert tool you can forge a certificate chain. The input PEM file must begin with a self-signed root certificate and each following certificate must descend from its predecessor. The functionality is rather simplistic currently. The purpose is to create certificates which look and feel like their "original" counterparts, but are obviously fakes. This is for white hat testing of implementations.
usage: ./x509sak.py forgecert [--key_template path] [--cert_template path]
[-r] [-f] [-v] [--help]
crt_filename
Forge an X.509 certificate
positional arguments:
crt_filename Filename of the input certificate or certificates PEM
format.
optional arguments:
--key_template path Output template for key files. Should contain '%d' to
indicate element in chain. Defaults to
'forged_%02d.key'.
--cert_template path Output template for certificate files. Should contain
'%d' to indicate element in chain. Defaults to
'forged_%02d.crt'.
-r, --recalculate-keyids
By default, Subject Key Identifier and Authority Key
Identifier X.509 extensions are kept as-is in the
forged certificates. Specifying this will recalculate
the IDs to fit the forged keys.
-f, --force Overwrite key/certificate files.
-v, --verbose Increase verbosity level. Can be specified multiple
times.
--help Show this help page.
GNU GPL-3.
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