smtp.gmail.com from bash gives "Error in certificate: Peer's certificate issuer is not recognized."

Well it is not the one liner I wanted, but this is how to fetch and import a certificate from scratch:

# Create a certificate directory
~]$ mkdir certs

# Create a new database in the certs dir
~]$ certutil -N -d certs 

# Need now a chain certificate - May 18, 2015
~]$ wget https://www.geotrust.com/resources/root_certificates/certificates/GeoTrust_Global_CA.cer

# Need now a chain certificate part 2 - May 18, 2015
~]$ mv GeoTrust_Global_CA.cer certs/

# Fetch the certificate from Gmail, saving in the text file GMAILCERT
# Added the CA opion - May 18, 2015
~]$ echo -n | openssl s_client -connect smtp.gmail.com:465 -CAfile certs/GeoTrust_Global_CA.cer | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > GMAILCERT

# Import the new cert file into the new database in the new dir
~]$ certutil -A -n "Google Internet Authority" -t "C,," -d certs -i GMAILCERT 

# Double Check
~]$ certutil -L -d certs

Certificate Nickname                                         Trust Attributes
                                                             SSL,S/MIME,JAR/XPI

Google Internet Authority                                    C,,  

Yaa! and thanks to the answer on this ticket

This post needs to be updated again. I was having trouble with my mailx install on my CentOS 7 box. Mail would send but I was still receiving the "Error in certified: Peer's certificate issuer is not recognized." error.

I found the solution here, had to translate it though.

Here is a quick way to do it:

# Create a certificate directory
mkdir ~/.certs

# Create a new database in the certs dir (dont forget to enter your pass phrase!)
certutil -N -d ~/.certs 

# Create three files for the cert chain
touch ~/.certs/google ~/.certs/geotrust ~/.certs/equifax

# Copy the cert chain for smtp.google.com:465 over to my_certs file (don't forget the -showcerts option, CTRL + C to end this command)
openssl s_client -showcerts -connect smtp.gmail.com:465 > ~/.certs/my_certs

Now copy each certificate including the --BEGIN CERTIFICATE-- and --END CERTIFICATE-- and paste them into their respective files you created earlier (google, geotrust, equifax) and now save those files.

# Open your my_certs file you made earlier and copy the google cert (usually the first one)
nano ~/.certs/my_certs

# Open your google file, paste the google cert that you just copied, and save and close
nano ~/.certs/google

# Open your my_certs file you made earlier and copy the geotrust cert (usually the second one)
nano ~/.certs/my_certs

# Open your geotrust file, paste the geotrust cert that you just copied, and save and close
nano ~/.certs/geotrust

# Open your my_certs file you made earlier and copy the equifax cert (usually the third one)
nano ~/.certs/my_certs

# Open your equifax file, paste the equifax cert that you just copied, and save and close
nano ~/.certs/equifax

Now we have to import each of these certs into the db.

# Import the google cert into the db
certutil -A -n "Google Internet Authority" -t "TC,," -d ~/.certs -i ~/.certs/google

# Import the geotrust cert into the db
certutil -A -n "GeoTrust Global CA" -t "TC,," -d ~/.certs -i ~/.certs/geotrust

# Import the equifax cert into the db
certutil -A -n "Equifax Secure Certificate Authority" -t "TCP,," -d ~/.certs -i ~/.certs/equifax

# Double check to make sure everything imported correctly into the db
certutil -L -d ~/.certs

Example output:

Certificate Nickname                                         Trust Attributes
                                                             SSL,S/MIME,JAR/XPI

Google Internet Authority                                    CT,,
GeoTrust Global CA                                           CT,,
Equifax Secure Certificate Authority                         CT,,

Clean up time (optional)

# Remove all unnecessary files since the db has the certs :)
rm -rf ~/.certs/google ~/.certs/geotrust ~/.certs/equifax ~/.certs/my_certs

# Now run a test to make sure mailx is sending correctly now (don't forget to change [email protected] to the email address you'd like to send to)
echo "Your message" | mail -s "Message Subject" [email protected]

That should be it, you shouldn't receive the "Error in certified: Peer's certificate issuer is not recognized." error any more!

Notes:

You might have noticed that I changed the dir from /certs to ~/.certs. mailx runs as root so I just made these changes as root/. "~/" means HOME directory put it all together ~/.certs means /root/.certs/. I'm sure you knew that but hey just in case you never know who might be reading this!

Just in case you need this, here is the configuration options I added to the bottom of /etc/mail.rc

# /etc/mail.rc options added to the bottom
set smtp-use-starttls
set smtp-auth=login
set smtp=smtp://smtp.gmail.com:587
set from="[email protected](Web01 Server)"
set [email protected]
set smtp-auth-password=your.pass
set ssl-verify=ignore
set nss-config-dir=/root/.certs

Make sure to change your.from.user, your.smtp.user, and your.pass to their respective variables.

I created a little script, based on the replies in this thread, that will automatically pull, parse, and install the current gmail smtp certs. It should be able to handle it if the number of certs changes again.

Here's a pastebin with syntax highlighting as well

#!/bin/bash

# This script pulls ssl certs for using gmail smtp. Adapted from the following config explaination:
# https://serverfault.com/questions/498588/smtp-gmail-com-from-bash-gives-error-in-certificate-peers-certificate-issuer

certdirectory="/home/user/.certs"

# Functions

fail() {
    ec=$?
    [ "${ec}" == "0" ] && ec=1
    echo -e "FAILED[code=$ec]: $@"
    exit $ec
}

warn(){
echo -e "WARNING $@"
}

cleanup() {
  rm allgcert* || warn "Cleanup of files errored"
  rm gcert* || warn "Cleanup of files errored"
}

failclean() {
  cleanup
  fail "$@"
}

# Count number of certs currently being used (can change from time to time)
numcerts=$(echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | grep -c "i:")

# Create the certs directory if it does not exist
mkdir -p $certdirectory || fail "Unable to create certificates directory"

# Pull certs to a local file for parsing
echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > allgcert || failclean "Unable to pull certs from smtp.gmail.com"

# Parses certs output based on the number of certs, and outputs to individual files
if (($numcerts > 1)) ; then
  # Pulls the first cert out as it needs one extra line
  sed '1,27!d' allgcert > gcert1
  # For subsequent certs, it multiplies the cert number by the number of lines in the file where it should exist
  for i in $(seq 2 $numcerts) ; do
    sed "$((2 + (((($i - 1)) * 26))))"','"$((1 + (($i * 26))))"'!d' allgcert > gcert${i}
  done
fi

# Parses out certificate issuer names for installation
echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | grep i: | sed -e 's,.*=,,' > allgcertnames || failclean "Unable to output parsed names for certificates"

for i in $(seq 1 $numcerts) ; do
  certutil -A -n "$(sed -n ${i}p allgcertnames)" -t "TC,," -d $certdirectory -i gcert${i} || failclean "Unable to import certificates to database"
done

cleanup

@pyr0ball, just updated little changes in your script and thanks for sharing nice approach :)

#!/bin/bash
certdirectory="/root/.certs"
fail() {
    ec=$?
    [ "${ec}" == "0" ] && ec=1
    echo -e "FAILED[code=$ec]: $@"
    exit $ec
}

cleanup() {
  rm /tmp/allgcert* || warn "Cleanup of files errored"
  rm /tmp/gcert* || warn "Cleanup of files errored"
}

failclean() {
  cleanup
  fail "$@"
}

numcerts=$(echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | grep -c "i:")
mkdir -p $certdirectory || fail "Unable to create certificates directory"
echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > /tmp/allgcert || failclean "Unable to pull certs from smtp.gmail.com"
awk '/-----BEGIN CERTIFICATE-----/,/-----END CERTIFICATE-----/{if(/-----BEGIN CERTIFICATE-----/){a++}; out="/tmp/gcert"a".crt"; print > out}' /tmp/allgcert
echo -n | openssl s_client -showcerts -connect smtp.gmail.com:465 | grep i: | sed -e 's,.*=,,' > /tmp/allgcertnames || failclean "Unable to output parsed names for certificates"

for i in $(seq 1 $numcerts) ; do
  certutil -A -n "$(sed -n ${i}p /tmp/allgcertnames)" -t "TC,," -d $certdirectory -i /tmp/gcert${i}.crt || failclean "Unable to import certificates to database"
done

cleanup