Ubuntu 20.04 - how to set lower SSL security level?

Question

I'd like to ask if there's a way to lower SSL security level to 1 on Ubuntu 20.04, since I'm receiving:

141A318A:SSL routines:tls_process_ske_dhe:dh key too small

when trying to curl the website.

Curl works if I add --ciphers 'DEFAULT:!DH' parameter, however, I am not able to fetch a website via my client app written in C#. The website also works when opened via browser.

According to bugs.launchpad.net the Ubuntu team set higher SSL security level on purpose.

In several places I came across an information that changing CipherString = DEFAULT@SECLEVEL=2 to 1 in openssl.cnf helps, but my config file did not have such a line at all and adding it had no effect.

I do not control the website server, so I am not able to change its security configuration.

Any ideas? Would installing some older openSSL package help?

Thanks in advance

EDIT: As for changes to my config file, I've added the following at the end:

system_default = system_default_sect 

[system_default_sect] 
MinProtocol = TLSv1.2
CipherString = DEFAULT@SECLEVEL=1 

Output from openssl version -a:

OpenSSL 1.1.1f 31 Mar 2020 built on: Mon Apr 20 11:53:50 2020 UTC
platform: debian-amd64
options: bn(64,64) rc4(16x,int) des(int) blowfish(ptr)
compiler: gcc -fPIC -pthread -m64 -Wa,--noexecstack -Wall -Wa,
--noexecstack -g -O2 -fdebug-prefix-map=/build/openssl-P_ODHM/openssl-1.1.1f=. 
-fstack-protector-strong -Wformat -Werror=format-security
-DOPENSSL_TLS_SECURITY_LEVEL=2 -DOPENSSL_USE_NODELETE
-DL_ENDIAN -DOPENSSL_PIC -DOPENSSL_CPUID_OBJ
-DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT
-DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m
-DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DKECCAK1600_ASM
-DRC4_ASM -DMD5_ASM -DAESNI_ASM -DVPAES_ASM -DGHASH_ASM
-DECP_NISTZ256_ASM -DX25519_ASM -DPOLY1305_ASM -DNDEBUG
-Wdate-time -D_FORTIFY_SOURCE=2
OPENSSLDIR: "/usr/lib/ssl" ENGINESDIR:
"/usr/lib/x86_64-linux-gnu/engines-1.1" Seeding source: os-specific

Answer 1

You don't have your config changes quite right. You need to add this to the beginning of your config file:

openssl_conf = default_conf

And then this to the end:

[ default_conf ]
ssl_conf = ssl_sect
[ssl_sect]
system_default = system_default_sect
[system_default_sect]
MinProtocol = TLSv1.2
CipherString = DEFAULT:@SECLEVEL=1

Note that if you prefer you can make changes to a local copy of the config file, and then ensure your process is started with the environment variable OPENSSL_CONF defined to point at the location of your config file:

export OPENSSL_CONF=/path/to/my/openssl.cnf

This way you can make changes without having to impact your entire system.

Note: To find the system's openssl.cnf file, run the following:

% openssl version -d

the run ls -l on the directory outputted to see where the openssl.cnf file is via its symlink in that directory as needed.

Answer 2

Edit openssl.conf file:

sudo nano /etc/ssl/openssl.cnf

Add this line at the top:

openssl_conf = openssl_init

And add these lines at the end:

[openssl_init]
ssl_conf = ssl_sect
[ssl_sect]
system_default = system_default_sect
[system_default_sect]
CipherString = DEFAULT@SECLEVEL=1

It works for me. :)

Ref: When I try to CURL a website I get SSL error

For the Laravel, also run

sudo service php7.4-fpm restart

Answer 3

The two solutions above were confusing for me.

You just need two blocks of modifications in /usr/lib/ssl/openssl.cnf as documented with this diff:

     rcsdiff ./openssl.cnf 
    ===================================================================
    RCS file: ./openssl.cnf,v
    retrieving revision 1.1
    diff -r1.1 ./openssl.cnf
    13a14,15
    > openssl_conf = default_conf
    > 
    350a353,362
    > 
    > [default_conf]
    > ssl_conf = ssl_sect
    > 
    > [ssl_sect]
    > system_default = system_default_sect
    > 
    > [system_default_sect]
    > MinProtocol = TLSv1.2
    > CipherString = DEFAULT@SECLEVEL=1

For cut&paste:

openssl_conf = default_conf

[default_conf]
ssl_conf = ssl_sect
[ssl_sect]
system_default = system_default_sect
[system_default_sect]
MinProtocol = TLSv1.2
CipherString = DEFAULT@SECLEVEL=1

Answer 4

Update: the previous answer seems to work if you extract the default configuration from the deb file by downloading it on https://packages.ubuntu.com/search?keywords=openssl&searchon=names.

Update 2: in fact the previous answer did not work for me because I had a wrong config file using [system_default_sect] instead of [ssl_default_sect]. It seems to be an error that I copy-pasted from https://wiki.debian.org/ContinuousIntegration/TriagingTips/openssl-1.1.1. It is possible to use the name system_default_sect to be consistent with Debian, you just need to use it everywhere instead of ssl_default_sect.

Original answer:

The previous answer was not working for me on Ubuntu 20.04 so I used the config file from my Debian LXC container on Ubuntu and changed SECLEVEL=2 to SECLEVEL=1.

I saved the file as /etc/ssl/openssl_custom.cnf and then used the command shared in the previous answer to load another config file when you need to:

export OPENSSL_CONF=/etc/ssl/openssl_custom.cnf

Here is the full config file that worked for me (you can also extract the default configuration from the deb file by downloading it on https://packages.debian.org/stable/openssl):

#
# OpenSSL example configuration file.
# This is mostly being used for generation of certificate requests.
#
Note that you can include other files from the main configuration
file using the .include directive.
#.include filename
This definition stops the following lines choking if HOME isn't
defined.
HOME                    = .
Extra OBJECT IDENTIFIER info:
#oid_file               = $ENV::HOME/.oid
oid_section             = new_oids
System default
openssl_conf = default_conf
To use this configuration file with the "-extfile" option of the
"openssl x509" utility, name here the section containing the
X.509v3 extensions to use:
extensions            =
(Alternatively, use a configuration file that has only
X.509v3 extensions in its main [= default] section.)
[ new_oids ]
We can add new OIDs in here for use by 'ca', 'req' and 'ts'.
Add a simple OID like this:
testoid1=1.2.3.4
Or use config file substitution like this:
testoid2=${testoid1}.5.6
Policies used by the TSA examples.
tsa_policy1 = 1.2.3.4.1
tsa_policy2 = 1.2.3.4.5.6
tsa_policy3 = 1.2.3.4.5.7
####################################################################
[ ca ]
default_ca      = CA_default            # The default ca section
####################################################################
[ CA_default ]
dir             = ./demoCA              # Where everything is kept
certs           = $dir/certs            # Where the issued certs are kept
crl_dir         = $dir/crl              # Where the issued crl are kept
database        = $dir/index.txt        # database index file.
#unique_subject = no                    # Set to 'no' to allow creation of
                                        # several certs with same subject.
new_certs_dir   = $dir/newcerts         # default place for new certs.
certificate     = $dir/cacert.pem       # The CA certificate
serial          = $dir/serial           # The current serial number
crlnumber       = $dir/crlnumber        # the current crl number
                                        # must be commented out to leave a V1 CRL
crl             = $dir/crl.pem          # The current CRL
private_key     = $dir/private/cakey.pem# The private key
x509_extensions = usr_cert              # The extensions to add to the cert
Comment out the following two lines for the "traditional"
(and highly broken) format.
name_opt        = ca_default            # Subject Name options
cert_opt        = ca_default            # Certificate field options
Extension copying option: use with caution.
copy_extensions = copy
Extensions to add to a CRL. Note: Netscape communicator chokes on V2 CRLs
so this is commented out by default to leave a V1 CRL.
crlnumber must also be commented out to leave a V1 CRL.
crl_extensions        = crl_ext
default_days    = 365                   # how long to certify for
default_crl_days= 30                    # how long before next CRL
default_md      = default               # use public key default MD
preserve        = no                    # keep passed DN ordering
A few difference way of specifying how similar the request should look
For type CA, the listed attributes must be the same, and the optional
and supplied fields are just that :-)
policy          = policy_match
For the CA policy
[ policy_match ]
countryName             = match
stateOrProvinceName     = match
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional
For the 'anything' policy
At this point in time, you must list all acceptable 'object'
types.
[ policy_anything ]
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional
####################################################################
[ req ]
default_bits            = 2048
default_keyfile         = privkey.pem
distinguished_name      = req_distinguished_name
attributes              = req_attributes
x509_extensions = v3_ca # The extensions to add to the self signed cert
Passwords for private keys if not present they will be prompted for
input_password = secret
output_password = secret
This sets a mask for permitted string types. There are several options.
default: PrintableString, T61String, BMPString.
pkix   : PrintableString, BMPString (PKIX recommendation before 2004)
utf8only: only UTF8Strings (PKIX recommendation after 2004).
nombstr : PrintableString, T61String (no BMPStrings or UTF8Strings).
MASK:XXXX a literal mask value.
WARNING: ancient versions of Netscape crash on BMPStrings or UTF8Strings.
string_mask = utf8only
req_extensions = v3_req # The extensions to add to a certificate request
[ req_distinguished_name ]
countryName                     = Country Name (2 letter code)
countryName_default             = AU
countryName_min                 = 2
countryName_max                 = 2
stateOrProvinceName             = State or Province Name (full name)
stateOrProvinceName_default     = Some-State
localityName                    = Locality Name (eg, city)
0.organizationName              = Organization Name (eg, company)
0.organizationName_default      = Internet Widgits Pty Ltd
we can do this but it is not needed normally :-)
#1.organizationName             = Second Organization Name (eg, company)
#1.organizationName_default     = World Wide Web Pty Ltd
organizationalUnitName          = Organizational Unit Name (eg, section)
#organizationalUnitName_default =
commonName                      = Common Name (e.g. server FQDN or YOUR name)
commonName_max                  = 64
emailAddress                    = Email Address
emailAddress_max                = 64
SET-ex3                       = SET extension number 3
[ req_attributes ]
challengePassword               = A challenge password
challengePassword_min           = 4
challengePassword_max           = 20
unstructuredName                = An optional company name
[ usr_cert ]
These extensions are added when 'ca' signs a request.
This goes against PKIX guidelines but some CAs do it and some software
requires this to avoid interpreting an end user certificate as a CA.
basicConstraints=CA:FALSE
Here are some examples of the usage of nsCertType. If it is omitted
the certificate can be used for anything except object signing.
This is OK for an SSL server.
nsCertType                    = server
For an object signing certificate this would be used.
nsCertType = objsign
For normal client use this is typical
nsCertType = client, email
and for everything including object signing:
nsCertType = client, email, objsign
This is typical in keyUsage for a client certificate.
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
This will be displayed in Netscape's comment listbox.
nsComment                       = "OpenSSL Generated Certificate"
PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer
This stuff is for subjectAltName and issuerAltname.
Import the email address.
subjectAltName=email:copy
An alternative to produce certificates that aren't
deprecated according to PKIX.
subjectAltName=email:move
Copy subject details
issuerAltName=issuer:copy
#nsCaRevocationUrl              = http://www.domain.dom/ca-crl.pem
#nsBaseUrl
#nsRevocationUrl
#nsRenewalUrl
#nsCaPolicyUrl
#nsSslServerName
This is required for TSA certificates.
extendedKeyUsage = critical,timeStamping
[ v3_req ]
Extensions to add to a certificate request
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
[ v3_ca ]
Extensions for a typical CA
PKIX recommendation.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid:always,issuer
basicConstraints = critical,CA:true
Key usage: this is typical for a CA certificate. However since it will
prevent it being used as an test self-signed certificate it is best
left out by default.
keyUsage = cRLSign, keyCertSign
Some might want this also
nsCertType = sslCA, emailCA
Include email address in subject alt name: another PKIX recommendation
subjectAltName=email:copy
Copy issuer details
issuerAltName=issuer:copy
DER hex encoding of an extension: beware experts only!
obj=DER:02:03
Where 'obj' is a standard or added object
You can even override a supported extension:
basicConstraints= critical, DER:30:03:01:01:FF
[ crl_ext ]
CRL extensions.
Only issuerAltName and authorityKeyIdentifier make any sense in a CRL.
issuerAltName=issuer:copy
authorityKeyIdentifier=keyid:always
[ proxy_cert_ext ]
These extensions should be added when creating a proxy certificate
This goes against PKIX guidelines but some CAs do it and some software
requires this to avoid interpreting an end user certificate as a CA.
basicConstraints=CA:FALSE
Here are some examples of the usage of nsCertType. If it is omitted
the certificate can be used for anything except object signing.
This is OK for an SSL server.
nsCertType                    = server
For an object signing certificate this would be used.
nsCertType = objsign
For normal client use this is typical
nsCertType = client, email
and for everything including object signing:
nsCertType = client, email, objsign
This is typical in keyUsage for a client certificate.
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
This will be displayed in Netscape's comment listbox.
nsComment                       = "OpenSSL Generated Certificate"
PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer
This stuff is for subjectAltName and issuerAltname.
Import the email address.
subjectAltName=email:copy
An alternative to produce certificates that aren't
deprecated according to PKIX.
subjectAltName=email:move
Copy subject details
issuerAltName=issuer:copy
#nsCaRevocationUrl              = http://www.domain.dom/ca-crl.pem
#nsBaseUrl
#nsRevocationUrl
#nsRenewalUrl
#nsCaPolicyUrl
#nsSslServerName
This really needs to be in place for it to be a proxy certificate.
proxyCertInfo=critical,language:id-ppl-anyLanguage,pathlen:3,policy:foo
####################################################################
[ tsa ]
default_tsa = tsa_config1       # the default TSA section
[ tsa_config1 ]
These are used by the TSA reply generation only.
dir             = ./demoCA              # TSA root directory
serial          = $dir/tsaserial        # The current serial number (mandatory)
crypto_device   = builtin               # OpenSSL engine to use for signing
signer_cert     = $dir/tsacert.pem      # The TSA signing certificate
                                        # (optional)
certs           = $dir/cacert.pem       # Certificate chain to include in reply
                                        # (optional)
signer_key      = $dir/private/tsakey.pem # The TSA private key (optional)
signer_digest  = sha256                 # Signing digest to use. (Optional)
default_policy  = tsa_policy1           # Policy if request did not specify it
                                        # (optional)
other_policies  = tsa_policy2, tsa_policy3      # acceptable policies (optional)
digests     = sha1, sha256, sha384, sha512  # Acceptable message digests (mandatory)
accuracy        = secs:1, millisecs:500, microsecs:100  # (optional)
clock_precision_digits  = 0     # number of digits after dot. (optional)
ordering                = yes   # Is ordering defined for timestamps?
                                # (optional, default: no)
tsa_name                = yes   # Must the TSA name be included in the reply?
                                # (optional, default: no)
ess_cert_id_chain       = no    # Must the ESS cert id chain be included?
                                # (optional, default: no)
ess_cert_id_alg         = sha1  # algorithm to compute certificate
                                # identifier (optional, default: sha1)
[default_conf]
ssl_conf = ssl_sect
[ssl_sect]
system_default = system_default_sect
[system_default_sect]
MinProtocol = TLSv1.2
CipherString = DEFAULT@SECLEVEL=1

Answer 5

For any system add at the top of openssl.cnf:

openssl_conf = default_conf

and at end of openssl.cnf:

• For Debian add:

  [system_default_sect]
  MinProtocol = TLSv1.0
  CipherString = DEFAULT@SECLEVEL=2
  

• For Ubuntu 20.04 add:

  [system_default_sect]
  MinProtocol = TLSv1    #important !
  CipherString = DEFAULT@SECLEVEL=2 # in my case works good with very old software