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Note : This is not really a question because I already found the answer but since I didn't find it easily here I will post it so that it can benefit others.

Question : How to read a concatenated PEM file as the one used by apache/mod_ssl directive SSLCACertificateFile ?

Answer (original) (source) :

cat $file|awk 'split_after==1{n++;split_after=0} /-----END CERTIFICATE-----/ {split_after=1} {print > "cert" n ".pem"}'

Answer 29/03/2016 :

Following @slugchewer answer, csplit might be a clearer option with :

csplit -f cert- $file '/-----BEGIN CERTIFICATE-----/' '{*}'
share|improve this question
This may be a dumb question, but why would I need to split my pem file? – Ashwani Agarwal Mar 26 at 8:06
@AshwaniAgarwal You want to split a PEM file when it contains several certificates and you wish to examine the certificates individually with tools such as openssl that take one certificate to analyze. – Law29 Mar 26 at 9:13
up vote 11 down vote accepted

This was previously answered on StackOverflow :

awk '
  split_after == 1 {n++;split_after=0}
  /-----END CERTIFICATE-----/ {split_after=1}
  {print > "cert" n ".pem"}' < $file

Edit 29/03/2016 : See @slugchewer answer

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Works on Linux only, fails on FreeBSD. – Michael-O Jan 7 '15 at 22:07
Inspired by this I've created an awk script that splits out certs and keys into separate files: – JinnKo Mar 23 '15 at 18:12

The awk snippet works for extracting the different parts, but you still need to know which section is the key / cert / chain. I needed to extract a specific section, and found this on the OpenSSL mailinglist:

# Extract key
openssl pkey -in foo.pem -out foo-key.pem

# Extract chain
openssl crl2pkcs7 -nocrl -certfile foo.pem |
  openssl pkcs7 -print_certs -out foo-chain.pem

# Extract cert
openssl x509 -in foo.pem -outform DER -out foo-cert.pem
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nice command set :) I'll keep it for future use, but in my use case above, I'm working with a cert-only file containing 50+ CA certs ==> no pkey nor chain – Cerber Mar 20 '15 at 12:42
I think this is superior to awk solution, let the openssl do the parsing + you get the conversion. – Rusty Mar 24 at 16:22

The split command is available on most systems, and its invocation is likely easier to remember.

If you have a file collection.pem that you want to split into individual-* files, use:

split -p "-----BEGIN CERTIFICATE-----" collection.pem individual-

If you don't have split, you could try csplit:

csplit -f individual- collection.pem '/-----BEGIN CERTIFICATE-----/' '{*}'
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Sorry, none of my systems (busybox, fedora, centos) show a -p option (nor the manpages I read) on split. Maybe you're using a special binary / package – Cerber Mar 25 at 10:25
@Cerber Could try csplit instead... (see edit above) – slugchewer Mar 26 at 5:33
works fine with csplit ! – Cerber Mar 29 at 8:52

Also worth noting that PEM files are just a collection of keys/certificates inside BEGIN/END blocks, so it's pretty easy to just cut/paste if it's just a single file with one or two interesting entities...

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If you want to get a single certificate out of a multi-certificate PEM bundle, try:

$ openssl crl2pkcs7 -nocrl -certfile INPUT.PEM | \
    openssl pkcs7 -print_certs | \
    awk '/subject.*,/END CERTIFICATE/'
  • The first two openssl commands will process a PEM file and and spit it back out with pre-pended "subject:" and "issuer:" lines before each cert. If your PEM is already formatted this way, all you need is the final awk command.
  • The awk command will spit out the individual PEM matching the CN (common name) string.

source1 , source2

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I don't see this in your source. Beside, PEM are Base64 encoded you won't find text like "subject", "CN", ... with awk – Cerber May 12 at 9:29
Yes, this doesn't work for every type of PEM. If you extract a P7B to PEM using openssl, it will have a subject line listed before each certificate. Or you can modify to any string you segment your PEM file with. – cmcginty May 12 at 9:54
Updated answer to handle when PEM does not contain "subject" – cmcginty May 13 at 1:22

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