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Self Signed Certificate with Custom Root CA

Create Root CA (Done once)

Create Root Key

Attention: this is the key used to sign the certificate requests, anyone holding this can sign certificates on your behalf. So keep it in a safe place!

openssl genrsa -des3 -out rootCA.key 4096

If you want a non password protected key just remove the -des3 option

Create and self sign the Root Certificate

openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.crt

Here we used our root key to create the root certificate that needs to be distributed in all the computers that have to trust us.

Create a certificate (Done for each server)

This procedure needs to be followed for each server/appliance that needs a trusted certificate from our CA

Create the certificate key

openssl genrsa -out 2048

Create the signing (csr)

The certificate signing request is where you specify the details for the certificate you want to generate. This request will be processed by the owner of the Root key (you in this case since you create it earlier) to generate the certificate.

Important: Please mind that while creating the signign request is important to specify the Common Name providing the IP address or domain name for the service, otherwise the certificate cannot be verified.

I will describe here two ways to gener

Method A (Interactive)

If you generate the csr in this way, openssl will ask you questions about the certificate to generate like the organization details and the Common Name (CN) that is the web address you are creating the certificate for, e.g

openssl req -new -key -out

Method B (One Liner)

This method generates the same output as Method A but it's suitable for use in your automation :) .

openssl req -new -sha256 -key -subj "/C=US/ST=CA/O=MyOrg, Inc./" -out

If you need to pass additional config you can use the -config parameter, here for example I want to add alternative names to my certificate.

openssl req -new -sha256 \
    -key \
    -subj "/C=US/ST=CA/O=MyOrg, Inc./" \
    -reqexts SAN \
    -config <(cat /etc/ssl/openssl.cnf \
        <(printf "\n[SAN]\,")) \

Verify the csr's content

openssl req -in -noout -text

Generate the certificate using the mydomain csr and key along with the CA Root key

openssl x509 -req -in -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out -days 500 -sha256

Verify the certificate's content

openssl x509 -in -text -noout
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yura833 commented Oct 13, 2023

Hi i am encouraging error like this:

So i am using reverse proxy for my web server and want ssl certificate to be included in my nginx config file so i followed this
guide here that creates ssl certificate and did these steps to create csr:
openssl genrsa -des3 -out rootCA.key 4096

openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.crt

openssl genrsa -out 2048

openssl req -new -sha256
-key SERVER.key
-subj "/C=US/ST=North Carolina/O=ORG/OU=ORG_UNIT/"
-reqexts SAN
-config <(cat /etc/ssl/openssl.cnf <(printf "\n[SAN]\"))
-out SERVER.csr
then i used this for signing certifiacte for my web server:
openssl x509 -req -extfile <(printf "subjectAltName=DNS:YOUR_DOMAIN_NAME") -days 120 -in SERVER.csr -CA rootCA.crt -CAkey root_rsa.key -CAcreateserial -out SERVER.crt -sha256

and everything looked fine btw i am using swarm, and when i try to connect to server i get 502 bad gateway and after using curl i get this error:

curl: (35) OpenSSL/3.1.3: error:0A00010B:SSL routines::wrong version number

inside my container logs it shows this:
failed (SSL: error:0A00010B:SSL routines::wrong version number) while SSL handshaking to upstream, client:, server: , request: "GET / HTTP/1.1", upstream

does anyone have idea what can i do here ?

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I followed your guide but cannot verify created certificate with root CA

openssl verify -CAfile rootCA.crt C = AU, ST = Some-State, O = Internet Widgits Pty Ltd error 18 at 0 depth lookup: self signed certificate error verification failed

@notariuss you should use: openssl verify -CAfile C:\ca-cert.pem C:\mycert.pem

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