nginx

[PELock@…]

I found an interesting bug in my logs

2022/11/07 18:30:47 [crit] 319012#319012: *39814 SSL_do_handshake() failed (SSL: error:14201044:SSL routines:tls_choose_sigalg:internal error) while SSL handshaking, client: 138.246.253.5, server: 0.0.0.0:443

[Maxim Dounin]

The "internal error" in the SSL part of per the message suggests it's an internal error in the OpenSSL library you are using.

Seems to be fixed here (that is, upgrading to OpenSSL 3.0.x should help, and basically the bug is an incorrect error code being reported):
​https://github.com/openssl/openssl/commit/a70535f84902b8d86c16ef3fe9d570b96fa5cfce

And this issue seems to be related:
​https://github.com/openssl/openssl/issues/15484

The fix and the issue suggest that the bug manifests itself when SHA-1 signatures are disabled on the server for some reason.

Upgrading OpenSSL to the latest version should help, this seems to be fixed in OpenSSL 3.0.x. There might be other bugs though.

For older OpenSSL versions, it is likely caused by non-default SSL configuration either in nginx or in the OS itself.

Could you please provide more details about your configuration, in particular:

• the OS you are using;
• exact version of the OpenSSL library you are using (should be shown by "nginx -V", unfortunately you've omitted it in the ticket details);
• OS-level OpenSSL configuration, the /etc/ssl/openssl.cnf file;
• nginx configuration, most notably ssl_* settings.

?

[PELock@…]

1. Debian GNU/Linux 11 (bullseye)

2. nginx version: nginx/1.23.2

built by gcc 10.2.1 20210110 (Debian 10.2.1-6)
built with OpenSSL 1.1.1n 15 Mar 2022
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-compat --with-file-aio --with-threads --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-cc-opt='-g -O2 -ffile-prefix-map=/data/builder/debuild/nginx-1.23.2/debian/debuild-base/nginx-1.23.2=. -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fPIC' --with-ld-opt='-Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'

3. /etc/ssl/openssl.cnf

#
# 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=2

4. SSL config for the domain

listen 443 ssl http2;
listen [::]:443 ssl http2;

ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem;

# Remember this setting for 365 days
#add_header Strict-Transport-Security max-age=31536000;
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains;" always;

# config to don't allow the browser to render the page inside an frame or iframe
# and avoid clickjacking en.wikipedia.org/wiki/Clickjacking
# if you need to allow [i]frames, you can use SAMEORIGIN or even set an uri with ALLOW-FROM uri
# developer.mozilla.org/en-US/docs/HTTP/X-Frame-Options
add_header X-Frame-Options SAMEORIGIN;

# when serving user-supplied content, include a X-Content-Type-Options: nosniff header along with the Content-Type: header,
# to disable content-type sniffing on some browsers.
# owasp.org/index.php/List_of_useful_HTTP_headers
# currently suppoorted in IE > 8 blogs.msdn.com/b/ie/archive/2008/09/02/ie8-security-part-vi-beta-2-update.aspx
# msdn.microsoft.com/en-us/library/ie/gg622941(v=vs.85).aspx
# 'soon' on Firefox bugzilla.mozilla.org/show_bug.cgi?id=471020
add_header X-Content-Type-Options nosniff;

# enable session resumption to improve https performance
# vincent.bernat.im/en/blog/2011-ssl-session-reuse-rfc5077.html

ssl_session_cache shared:SSL:20m;
ssl_session_timeout 1d;

# ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AE>
# ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-S>

# kompatybilne z .NET 2.0
ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES>
# enables server-side protection from BEAST attacks

# is-beast-still-a-threat.html
ssl_prefer_server_ciphers on;

# improve-seo-https-nginx
ssl_session_tickets on;

#ssl_protocols TLSv1.3 TLSv1.2;
#ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;

# enable ocsp stapling (mechanism by which a site can convey certificate revocation information to visitors in a privacy-preserving, scalable manner)
ssl_stapling on;
ssl_stapling_verify on;

# Cloudflare resolver
resolver 1.1.1.1 1.0.0.1 [2606:4700:4700::1111] [2606:4700:4700::1001];

[Maxim Dounin]

Thanks for the details.

Your system uses @SECLEVEL=2 (see CipherString = DEFAULT@SECLEVEL=2 in openssl.cnf), which is set by Debian package of OpenSSL. Security level 2 disables default RSA+SHA1 signature algorithm, which only provides 80 bits of security. Accordingly, as long as a client connects via TLSv1.2 and does not provide a list of supported signature algorithms, this results in failed connection and the "internal error" logged instead of a meaningful one due to the bug in OpenSSL.

Reverting security level to 1 via @SECLEVEL=1 in ssl_ciphers might be a way to resolve this, so nginx will be able to talk to such clients. Alternatively, upgrading to OpenSSL 3.0.x should fix the error message.

[Maxim Dounin]

See also #2501.