97 lines
3.9 KiB
Bash
Executable File
97 lines
3.9 KiB
Bash
Executable File
#!/bin/bash
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#
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# RSA private key, SSL certificate, Diffie-Hellman bits files
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# -------------------------------------------
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# Create an RSA private key, a self-signed SSL certificate, and some
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# Diffie-Hellman cipher bits, if they have not yet been created.
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#
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# The RSA private key and certificate are used for:
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#
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# * DNSSEC DANE TLSA records
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# * IMAP
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# * SMTP (opportunistic TLS for port 25 and submission on ports 465/587)
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# * HTTPS
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#
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# The certificate is created with its CN set to the PRIMARY_HOSTNAME. It is
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# also used for other domains served over HTTPS until the user installs a
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# better certificate for those domains.
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#
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# The Diffie-Hellman cipher bits are used for SMTP and HTTPS, when a
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# Diffie-Hellman cipher is selected during TLS negotiation. Diffie-Hellman
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# provides Perfect Forward Secrecy.
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source setup/functions.sh # load our functions
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source /etc/mailinabox.conf # load global vars
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# Show a status line if we are going to take any action in this file.
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if [ ! -f /usr/bin/openssl ] \
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|| [ ! -f $STORAGE_ROOT/ssl/ssl_private_key.pem ] \
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|| [ ! -f $STORAGE_ROOT/ssl/ssl_certificate.pem ] \
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|| [ ! -f $STORAGE_ROOT/ssl/dh4096.pem ]; then
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echo "Creating initial SSL certificate and perfect forward secrecy Diffie-Hellman parameters..."
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fi
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# Install openssl.
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apt_install openssl
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# Create a directory to store TLS-related things like "SSL" certificates.
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mkdir -p $STORAGE_ROOT/ssl
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# Generate a new private key.
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#
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# The key is only as good as the entropy available to openssl so that it
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# can generate a random key. "OpenSSL’s built-in RSA key generator ....
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# is seeded on first use with (on Linux) 32 bytes read from /dev/urandom,
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# the process ID, user ID, and the current time in seconds. [During key
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# generation OpenSSL] mixes into the entropy pool the current time in seconds,
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# the process ID, and the possibly uninitialized contents of a ... buffer
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# ... dozens to hundreds of times."
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#
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# A perfect storm of issues can cause the generated key to be not very random:
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#
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# * improperly seeded /dev/urandom, but see system.sh for how we mitigate this
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# * the user ID of this process is always the same (we're root), so that seed is useless
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# * zero'd memory (plausible on embedded systems, cloud VMs?)
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# * a predictable process ID (likely on an embedded/virtualized system)
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# * a system clock reset to a fixed time on boot
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#
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# Since we properly seed /dev/urandom in system.sh we should be fine, but I leave
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# in the rest of the notes in case that ever changes.
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if [ ! -f $STORAGE_ROOT/ssl/ssl_private_key.pem ]; then
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# Set the umask so the key file is never world-readable.
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(umask 077; hide_output \
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openssl genrsa -out $STORAGE_ROOT/ssl/ssl_private_key.pem 4096)
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fi
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# Generate a self-signed SSL certificate because things like nginx, dovecot,
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# etc. won't even start without some certificate in place, and we need nginx
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# so we can offer the user a control panel to install a better certificate.
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if [ ! -f $STORAGE_ROOT/ssl/ssl_certificate.pem ]; then
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# Generate a certificate signing request.
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CSR=/tmp/ssl_cert_sign_req-$$.csr
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hide_output \
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openssl req -new -key $STORAGE_ROOT/ssl/ssl_private_key.pem -out $CSR \
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-sha256 -subj "/CN=$PRIMARY_HOSTNAME"
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# Generate the self-signed certificate.
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CERT=$STORAGE_ROOT/ssl/$PRIMARY_HOSTNAME-selfsigned-$(date --rfc-3339=date | sed s/-//g).pem
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hide_output \
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openssl x509 -req -days 365 \
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-in $CSR -signkey $STORAGE_ROOT/ssl/ssl_private_key.pem -out $CERT
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# Delete the certificate signing request because it has no other purpose.
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rm -f $CSR
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# Symlink the certificate into the system certificate path, so system services
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# can find it.
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ln -s $CERT $STORAGE_ROOT/ssl/ssl_certificate.pem
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fi
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# We no longer generate Diffie-Hellman cipher bits. Following rfc7919 we use
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# a predefined finite field group, in this case ffdhe4096 from
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# https://raw.githubusercontent.com/internetstandards/dhe_groups/master/ffdhe4096.pem
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cp -f conf/dh4096.pem $STORAGE_ROOT/ssl/
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