HTTPS certificates don't work after generation with openssl

I ran the Espressif HTTPS Server example, with the provided certificates. I was able to successfully connect to the server accepting the warning in my browser (as expected).

Then, following the instructions contained in the above README file I issued in the certs folder:

openssl req -newkey rsa:2048 -nodes -keyout prvtkey.pem -x509 -days 3650 -out cacert.pem -subj "/CN=My own certificate"

and uploaded the new firmware to the ESP32. Now, I can't connect anymore. Firefox says:

SEC_ERROR_BAD_SIGNATURE

while Chrome says:

ERR_SSL_PROTOCOL_ERROR

on server side I get the following messages:

E (1059558) esp-tls-mbedtls: mbedtls_ssl_handshake returned -0x7780
E (1059558) esp_https_server: esp_tls_create_server_session failed
E (1059558) httpd: httpd_accept_conn: session creation failed
W (1059568) httpd: httpd_server: error accepting new connection

I RFTM and followed their instruction. What could prevent the creation of the secure connection with the certificate I generate using openssl?

Both certificates (mine and those provided by Expressif) are equal in lengths and headers.

Solution

After reading the comment of user President James K. Polk, I went deeper about the files generated by openssl and I discovered that the official docs of Expressif are wrong.

The README reports:

openssl req -newkey rsa:2048 -nodes -keyout prvtkey.pem -x509 -days 3650 -out cacert.pem -subj "/CN=ESP32 HTTPS server example"

but the CMakeLists.txt of the project contains:

idf_component_register(SRCS "main.c"
                    INCLUDE_DIRS "."
                    EMBED_TXTFILES "certs/servercert.pem"
                                   "certs/prvtkey.pem")

in fact, also the cert directories contains those files. Hence openssl created cacert.pem instead of servercert.pem.

The right command to issue is:

openssl req -newkey rsa:2048 -nodes -keyout prvtkey.pem -x509 -days 3650 -out servercert.pem -subj "/CN=ESP32 HTTPS server example"

This leads to the expected behavior.