check_ssl_cert.1

.\" Process this file with
.\" groff -man -Tascii check_ssl_cert.1
.\"
.TH "check_ssl_cert" 1 "April, 2025" "2.92.0" "USER COMMANDS"
.SH NAME
check_ssl_cert \- checks the validity of X.509 certificates
.SH SYNOPSIS
.BR "check_ssl_cert " "-H host [OPTIONS]"
.br
.BR "check_ssl_cert " "-f file [OPTIONS]"
.SH DESCRIPTION
.B check_ssl_cert
A shell script (that can be used as a Nagios/Icinga plugin) to check an SSL/TLS connection
.SH ARGUMENTS
.TP
.BR "-f,--file" " file"
Local file path or URI. With -f you can not only pass a x509 certificate file but also a certificate revocation list (CRL) to check the validity period or a Java KeyStore file
.TP
.BR "-H,--host" " host"
server
.SH OPTIONS
.TP
.BR "-A,--noauth"
Ignore authority warnings (expiration only)
.TP
.BR "    --all"
Enable all the possible optional checks at the maximum level
.TP
.BR "    --all-local"
Enable all the possible optional checks at the maximum level (without SSL-Labs)
.TP
.BR "    --allow-empty-san"
Allow certificates without Subject Alternative Names (SANs)
.TP
.BR "-C,--clientcert" " path"
Use client certificate to authenticate
.TP
.BR "-c,--critical" " days"
Minimum number of days a certificate has to be valid to issue a critical status. Can be a floating point number, e.g., 0.5. Default: 15
.TP
.BR "   --check-chain"
The certificate chain cannot contain double or root certificates
.TP
.BR "   --check-ciphers" " grade"
Check the offered ciphers
.TP
.BR "   --check-ciphers-warnings"
Critical if nmap reports a warning for an offered cipher
.TP
.BR "   --check-http-headers"
Check the HTTP headers for best practices
.TP
.BR "   --check-ssl-labs-warn grade"
SSL Labs grade on which to warn
.TP
.BR "   --clientpass" " phrase"
Set passphrase for client certificate.
.TP
.BR "   --configuration" " file"
Read options from the specified file
.TP
.BR "   --crl"
Check revocation via CRL (requires --rootcert-file)
.TP
.BR "   --curl-bin" " path"
Path of the curl binary to be used
.TP
.BR "   --custom-http-header" " string"
Custom HTTP header sent when getting the cert example: 'X-Check-Ssl-Cert: Foobar=1'
.TP
.BR "   --dane"
Verify that valid DANE records exist (since OpenSSL 1.1.0)
.TP
.BR "   --dane 211"
Verify that a valid DANE-TA(2) SPKI(1) SHA2-256(1) TLSA record exists
.TP
.BR "   --dane 301"
Verify that a valid DANE-EE(3) Cert(0) SHA2-256(1) TLSA record exists
.TP
.BR "   --dane 302"
Verify that a valid DANE-EE(3) Cert(0) SHA2-512(2) TLSA record exists
.TP
.BR "   --dane 311"
Verify that a valid DANE-EE(3) SPKI(1) SHA2-256(1) TLSA record exists
.TP
.BR "   --dane 312"
Verify that a valid DANE-EE(3) SPKI(1) SHA2-512(1) TLSA record exists
.TP
.BR "   --date" " path"
Path of the date binary to be used
.TP
.BR "-d,--debug"
Produce debugging output (can be specified more than once)
.TP
.BR "   --debug-cert"
Store the retrieved certificates in the current directory
.TP
.BR "   --debug-file" " file"
Write the debug messages to file
.TP
.BR "   --debug-headers"
Store the retrieved HTLM headers in the headers.txt file
.TP
.BR "   --debug-time"
Write timing information in the debugging output
.TP
.BR "   --default-format"
Print the default output format and exit
.TP
.BR "   --dig-bin" " path"
Path of the dig binary to be used
.TP
.BR "   --do-not-resolve"
Do not check if the host can be resolved
.TP
.BR "   --dtls"
Use the DTLS protocol
.TP
.BR "   --dtls1"
Use the DTLS protocol 1.0
.TP
.BR "   --dtls1_2"
Use the DTLS protocol 1.2
.TP
.BR "-e,--email" " address"
Pattern (extended regular expression) to match the email address contained in the certificate. You can specify different addresses separated by a pipe (e.g., 'addr1|addr2')
.TP
.BR "   --ecdsa"
Signature algorithm selection: force ECDSA certificate
.TP
.BR "   --element" " number"
Check up to the N cert element from the beginning of the chain
.TP
.BR "   --file-bin" " path"
Path of the file binary to be used
.TP
.BR "   --fingerprint" " hash"
Pattern to match the fingerprint
.TP
.BR "   --fingerprint-alg" " algorithm"
Algorithm for fingerprint. Default sha1
.TP
.BR "   --first-element-only"
Verify just the first cert element, not the whole chain
.TP
.BR "   --force-dconv-date"
Force the usage of dconv for date computations
.TP
.BR "   --force-perl-date"
Force the usage of Perl for date computations
.TP
.BR "   --format" " FORMAT"
Format output template on success, for example: '%SHORTNAME% OK %CN% from %CA_ISSUER_MATCHED%'
.br
List of possible variables:
.br
- %CA_ISSUER_MATCHED%
.br
- %CHECKEDNAMES%
.br
- %CN%
.br
- %DATE%
.br
- %DAYS_VALID%
.br
- %DYSPLAY_CN%
.br
- %HOST%
.br
- %OCSP_EXPIRES_IN_HOURS%
.br
- %OPENSSL_COMMAND%
.br
- %PORT%
.br
- %SELFSIGNEDCERT%
.br
- %SHORTNAME%
.br
- %SIGALGO%
.br
- %SSL_LABS_HOST_GRADE%
.br
See --default-format for the default
.TP
.BR "   --grep-bin" " path"
Path of the grep binary to be used
.TP
.BR "-h,--help,-?"
This help message
.TP
.BR "   --http-headers-path" " path"
The path to be used to fetch HTTP headers
.TP
.BR "   --http-use-get"
Use GET instead of HEAD (default) for the HTTP related checks
.TP
.BR "-i,--issuer" " issuer"
Pattern (extended regular expression) to match the issuer of the certificate. You can specify different issuers separated by a pipe (e.g., 'issuer1|issuer2')
.TP
.BR "  --ignore-altnames"
Ignore alternative names when matching pattern specified in -n (or the host name)
.TP
.BR "  --ignore-connection-problems" " [state]"
In case of connection problems returns OK or the optional state
.TP
.BR "  --ignore-crl"
Ignore CRLs
.TP
.BR "  --ignore-dh"
Ignore too small DH keys
.TP
.BR "   --ignore-exp"
Ignore expiration date
.TP
.BR "   --ignore-http-headers"
Ignore checks on HTTP headers with --all and --all-local
.TP
.BR "   --ignore-host-cn"
Do not complain if the CN does not match the host name
.TP
.BR "   --ignore-incomplete-chain"
Do not check chain integrity
.TP
.BR "   --ignore-maximum-validity"
Ignore the certificate maximum validity
.TP
.BR "   --ignore-ocsp"
Do not check revocation with OCSP
.TP
.BR "   --ignore-ocsp-errors"
Continue if the OCSP status cannot be checked
.TP
.BR "   --ignore-ocsp-timeout"
Ignore OCSP result when timeout occurs while checking
.TP
.BR "   --ignore-sct"
Do not check for signed certificate timestamps (SCT)
.TP
.BR "   --ignore-sig-alg"
Do not check if the certificate was signed with SHA1 or MD5
.TP
.BR "   --ignore-ssl-labs-cache"
Force a new check by SSL Labs (see -L)
.TP
.BR "   --ignore-ssl-labs-errors"
Ignore errors if SSL Labs is not accessible or times out
.TP
.BR "   --ignore-tls-renegotiation"
Ignore the TLS renegotiation check
.TP
.BR "   --ignore-unexpected-eof"
Ignore unclean TLS shutdowns
.TP
.BR "   --inetproto protocol"
Force IP version 4 or 6
.TP
.BR "   --info"
Print certificate information
.TP
.BR "   --init-host-cache"
Initialize the host cache
.TP
.BR "   --issuer-cert-cache" " dir"
Directory where to store issuer certificates cache
.TP
.BR "   --jks-alias" " alias"
Alias name of the Java KeyStore entry (requires --file)
.TP
.BR "-K,--clientkey" " path"
Use client certificate key to authenticate
.TP
.BR "-L,--check-ssl-labs grade"
SSL Labs assessment (please check https://www.ssllabs.com/about/terms.html). Critical if the grade is lower than specified.
.TP
.BR "   --long-output" " list"
Append the specified comma separated (no spaces) list of attributes to the plugin output on additional lines.
Valid attributes are: enddate, startdate, subject, issuer, modulus, serial, hash, email, ocsp_uri and fingerprint. 'all' will include all the available attributes.
.TP
.BR "-m,--match" " name"
Pattern to match the CN or AltName (can be specified multiple times)
.TP
.BR "   --maximum-validity" " [days]"
The maximum validity of the certificate must not exceed 'days' (default 397). This check is automatic for HTTPS
.TP
.BR "   --nmap-bin" " path"
Path of the nmap binary to be used
.TP
.BR "   --nmap-with-proxy"
Allow nmap to be used with a proxy
.TP
.BR "   --no-perf"
Do not show performance data
.TP
.BR "   --no-proxy"
Ignore the http_proxy and https_proxy environment variables
.TP
.BR "   --no-proxy-curl"
Ignore the http_proxy and https_proxy environment variables for curl
.TP
.BR "   --no-proxy-s_client"
Ignore the http_proxy and https_proxy environment variables for openssl s_client
.TP
.BR "   --no-ssl2"
Disable SSL version 2
.TP
.BR "   --no-ssl3"
Disable SSL version 3
.TP
.BR "   --no-tls1"
Disable TLS version 1
.TP
.BR "   --no-tls1_1"
Disable TLS version 1.1
.TP
.BR "   --no-tls1_3"
Disable TLS version 1.3
.TP
.BR "   --no-tls1_2"
Disable TLS version 1.2
.TP
.BR "   --not-issued-by" " issuer"
Check that the issuer of the certificate does not match the given pattern
.TP
.BR "   --not-valid-longer-than" " days"
Critical if the certificate validity is longer than the specified period
.TP
.BR "-o,--org" " org"
Pattern to match the organization of the certificate
.TP
.BR "   --ocsp-critical" " hours"
Minimum number of hours an OCSP response has to be valid to issue a critical status
.TP
.BR "    --ocsp-warning" " hours"
Minimum number of hours an OCSP response has to be valid to issue a warning status
.TP
.BR "   --openssl" " path"
Path of the openssl binary to be used
.TP
.BR "-p,--port" " port"
TCP port (default 443)
.TP
.BR "--precision" " digits"
Number of decimal places for durations: defaults to 0 if critical or warning are integers, 2 otherwise
.TP
.BR "-P,--protocol" " protocol"
Use the specific protocol: dns, ftp, ftps, http, https (default), h2 (HTTP/2), h3 (HTTP/3), imap, imaps, irc, ircs, ldap, ldaps, mqtts, mysql, pop3, pop3s, postgres, sieve, sips, smtp, smtps, tds, xmpp, xmpp-server. ftp, imap, irc, ldap, pop3, postgres, sieve, smtp: switch to TLS using StartTLS.
.BR
These protocols switch to TLS using StartTLS: ftp, imap, irc, ldap, mysql, pop3, smtp.
.TP
.BR "   --path" " path"
Set the PATH variable to 'path'
.TP
.BR "   --password" " source"
Password source for a local certificate, see the PASS PHRASE ARGUMENTS section openssl(1)
.TP
.BR "   --prometheus"
Generate Prometheus/OpenMetrics output
.TP
.BR "   --proxy" " proxy"
Set http_proxy and the s_client -proxy option
.TP
.BR "   --python-bin" " path"
Path of the python binary to be used
.TP
.BR "   --quic"
Use QUIC
.TP
.BR "-q,--quiet"
Do not produce any output
.TP
.BR "-r,--rootcert" " cert"
Root certificate or directory to be used for certificate validation (passed to openssl's -CAfile or -CApath)
.TP
.BR "   --require-client-cert" " [list]"
The server must accept a client certificate. 'list' is an optional comma separated list of expected client certificate CAs
.TP
.BR "   --require-dnssec"
Require DNSSEC
.TP
.BR "   --require-http-header" " header"
Require the specified HTTP header (e.g., strict-transport-security)
.TP
.BR "   --require-no-http-header" " header"
Require the absence of the specified HTTP header (e.g., X-Powered-By)
.TP
.BR "   --require-no-ssl2"
Critical if SSL version 2 is offered
.TP
.BR "   --require-no-ssl3"
Critical if SSL version 3 is offered
.TP
.BR "   --require-no-tls1"
Critical if TLS 1 is offered
.TP
.BR "   --require-no-tls1_1"
Critical if TLS 1.1 is offered
.TP
.BR "   --require-no-tls1_2"
Critical if TLS 1.2 is offered
.TP
.BR "   --require-ocsp-stapling"
Require OCSP stapling
.TP
.BR "    --require-purpose" " usage"
Require the specified key usage (can be specified more then once)
.TP
.BR "    --require-purpose-critical"
The key usage must be critical
.TP
.BR "    --require-security-header" " header"
Require the specified HTTP security header (e.g., X-Frame-Options)
.TP
.BR "    --require-security-headers"
Require all the HTTP security headers:
  Content-Security-Policy
  Permissions-Policy
  Referrer-Policy
  strict-transport-security
  X-Content-Type-Options
  X-Frame-Options
.TP
.BR "   --resolve" " ip"
Provide a custom IP address for the specified host
.TP
.BR "   --resolve-over-http" " [server]"
Resolve the host over HTTP using Google or the specified server
.TP
.BR "   --rootcert-dir" " dir"
Root directory to be used for certificate validation (passed to openssl's -CApath)
overrides option -r,--rootcert
.TP
.BR "   --rootcert-file" " cert"
Root certificate to be used for certificate validation (passed to openssl's -CAfile)
overrides option -r,--rootcert
.TP
.BR "   --rsa"
Signature algorithm selection: force RSA certificate
.TP
.BR "   --security-level" " number"
Set the security level to specified value. See SSL_CTX_set_security_level(3) for a description of what each level means
.TP
.BR "-s,--selfsigned"
Allow self-signed certificates
.TP
.BR "   --serial" " serialnum"
Pattern to match the serial number
.TP
.BR "--skip-element" " number"
Skip checks on the Nth cert element (can be specified multiple times)
.TP
.BR "   --sni" " name"
Set the TLS SNI (Server Name Indication) extension in the ClientHello message to 'name'
.TP
.BR "   --ssl2"
Force SSL version 2
.TP
.BR "   --ssl3"
Force SSL version 3
.TP
.BR "-t,--timeout" " seconds"
Timeout after the specified time (defaults to 120 seconds)
.TP
.BR "   --temp" " dir"
Directory where to store the temporary files
.TP
.BR "   --terse"
Terse output (also see --verbose)
.TP
.BR "   --tls1"
Force TLS version 1
.TP
.BR "   --tls1_1"
Force TLS version 1.1
.TP
.BR "   --tls1_2"
Force TLS version 1.2
.TP
.BR "   --tls1_3"
Force TLS version 1.3
.TP
.BR "-u,--url" " URL"
HTTP request URL
.TP
.BR "   --user-agent" " string"
User agent that shall be used for HTTPS connections
.TP
.BR "-v,--verbose"
Verbose output (can be specified more than once)
.TP
.BR "-V,--version"
Version
.TP
.BR "-w,--warning" " days"
Minimum number of days a certificate has to be valid to issue a warning status. Might be a floating point number, e.g., 0.5. Default: 20
.TP
.BR "   --xmpphost" " name"
Specify the host for the 'to' attribute of the stream element
.TP
.BR "-4"
Force IPv4
.TP
.BR "-6"
Force IPv6
.SH DEPRECATED OPTIONS
.TP
.BR "   --altnames"
Match the pattern specified in -n with alternate names too (enabled by default)
.TP
.BR "-n,--cn" " name"
Pattern to match the CN or AltName (can be specified multiple times)
.TP
.BR "   --curl-user-agent" " string"
User agent that curl shall use to obtain the issuer cert
.TP
.BR "-d,--days" " days"
Minimum number of days a certificate has to be valid (see --critical and --warning)
.TP
.BR "-N,--host-cn"
Match CN with the host name (enabled by default)
.TP
.BR "   --no_ssl2"
Disable SSLv2 (deprecated use --no-ssl2)
.TP
.BR "   --no_ssl3"
Disable SSLv3 (deprecated use --no-ssl3)
.TP
.BR "    --no_tls1"
Disable TLSv1 (deprecated use --no-tls1)
.TP
.BR "   --no_tls1_1"
Disable TLSv1.1 (deprecated use --no-tls1_1)
.TP
.BR "   --no_tls1_2"
Disable TLSv1.1 (deprecated use --no-tls1_2)
.TP
.BR "   --no_tls1_3"
Disable TLSv1.1 (deprecated use --no-tls1_3)
.TP
.BR "   --ocsp"
Check revocation via OCSP (enabled by default)
.TP
.BR "   --require-hsts"
Require HTTP Strict Transport Security (deprecated use --require-security-header strict-transport-security)
.TP
.BR "    --require-security-headers-path" " path"
the path to be used to fetch HTTP security headers
.TP
.BR "   --require-san"
Require the presence of a Subject Alternative Name extension
.TP
.BR "   --require-x-frame-options [path]"
Require the presence of the X-Frame-Options HTTP header. 'path' is the optional path to be used in the URL to check for the header (deprecated use --require-security-header X-Frame-Options and --require-security-headers-path path)
.TP
.BR "-S,--ssl" " version"
Force SSL version (2,3) (see: --ssl2 or --ssl3)

.SH CONFIGURATION

Command line options can be specified in a configuration file (${HOME}/.check_ssl_certrc). For example

  $ cat ${HOME}/.check_ssl_certrc
  --verbose
  --critical 20
  --warning 40

Options specified in the configuration file are read before processing the arguments and can be overridden.

.SH NOTES
If the host has multiple certificates and the installed openssl version supports the -servername option it is possible to specify the TLS SNI (Server Name Identificator) with the -N (or --host-cn) option.

.SH "EXIT STATUS"
check_ssl_cert returns a zero exist status if it finds no errors, 1 for warnings, 2 for a critical errors and 3 for unknown problems
.SH BUGS
Please report bugs to:
https://github.com/matteocorti/check_ssl_cert/issues

.SH "EXAMPLE"
check_ssl_cert --host github.com --all-local

.SH "SEE ALSO"
openssl(1), openssl-x509(1)