HTTPS와 HTTP 차이, 맥 터미널로 인증서와 TLS 직접 확인해 보니

$ for d in solodevnote.com naver.com example.com; do echo "[$d]"; curl -sI http://$d | grep -iE '^HTTP|^location'; done
[solodevnote.com]
HTTP/1.1 301 Moved Permanently
Location: https://solodevnote.com/
[naver.com]
HTTP/1.1 301 Moved Permanently
location: https://www.naver.com/
[example.com]
HTTP/1.1 200 OK

$ for d in solodevnote.com naver.com ko.wikipedia.org; do printf '%s: ' $d; curl -sI https://$d | grep -i '^strict-transport-security' || echo '(없음)'; done
solodevnote.com: (없음)
naver.com: strict-transport-security: max-age=63072000; includeSubdomains
ko.wikipedia.org: strict-transport-security: max-age=106384710; includeSubDomains; preload

$ echo | openssl s_client -connect solodevnote.com:443 -servername solodevnote.com 2>/dev/null | openssl x509 -noout -subject -issuer -dates -text | grep -E 'subject=|issuer=|notBefore|notAfter|DNS:'
subject=CN=solodevnote.com
issuer=C=US, O=Google Trust Services, CN=WE1
notBefore=Sep 27 10:37:37 2026 GMT
notAfter=Dec 26 11:37:34 2026 GMT
                DNS:solodevnote.com, DNS:*.solodevnote.com

$ echo | openssl s_client -connect solodevnote.com:443 -servername solodevnote.com 2>/dev/null | grep -E '^New,|^Protocol:|^Verify return code'
curl -sv -o /dev/null https://solodevnote.com 2>&1 | grep -E 'SSL connection|ALPN'
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Protocol: TLSv1.3
Verify return code: 0 (ok)
* ALPN: curl offers h2,http/1.1
* SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256 / [blank] / UNDEF
* ALPN: server accepted h2

$ echo | openssl s_client -connect solodevnote.com:443 -servername solodevnote.com -showcerts 2>/dev/null | grep -E '^ *[0-9] s:|^ *i:'
 0 s:CN=solodevnote.com
   i:C=US, O=Google Trust Services, CN=WE1
 1 s:C=US, O=Google Trust Services, CN=WE1
   i:C=US, O=Google Trust Services LLC, CN=GTS Root R4
 2 s:C=US, O=Google Trust Services LLC, CN=GTS Root R4
   i:C=BE, O=GlobalSign nv-sa, OU=Root CA, CN=GlobalSign Root CA

$ ip=$(dig +short solodevnote.com | head -1); echo "IP $ip"
for n in solodevnote.com example.com; do printf 'SNI %s → ' $n; echo | openssl s_client -connect $ip:443 -servername $n 2>/dev/null | openssl x509 -noout -subject; done
printf 'SNI 없이 → '; echo | openssl s_client -connect $ip:443 2>&1 | grep -oE 'alert handshake failure|SSL alert number [0-9]+' | tr '\n' ' '; echo
IP 104.21.68.112
SNI solodevnote.com → subject=CN=solodevnote.com
SNI example.com → subject=CN=example.com
SNI 없이 → alert handshake failure SSL alert number 40

$ for u in http://example.com/ https://example.com/; do echo "$u"; for i in 1 2 3 4 5; do curl -s -o /dev/null -w '  DNS %{time_namelookup}s 연결 %{time_connect}s TLS %{time_appconnect}s 첫 바이트 %{time_starttransfer}s HTTP/%{http_version}\n' $u; done; done
http://example.com/
  DNS 0.002641s 연결 0.137089s TLS 0.000000s 첫 바이트 0.278439s HTTP/1.1
  DNS 0.003257s 연결 0.138771s TLS 0.000000s 첫 바이트 0.280221s HTTP/1.1
  DNS 0.002643s 연결 0.139064s TLS 0.000000s 첫 바이트 0.284200s HTTP/1.1
  DNS 0.003693s 연결 0.118578s TLS 0.000000s 첫 바이트 0.242387s HTTP/1.1
  DNS 0.002734s 연결 0.116992s TLS 0.000000s 첫 바이트 0.246281s HTTP/1.1
https://example.com/
  DNS 0.002522s 연결 0.121197s TLS 0.259231s 첫 바이트 0.390318s HTTP/2
  DNS 0.003081s 연결 0.121567s TLS 0.252977s 첫 바이트 0.380291s HTTP/2
  DNS 0.002545s 연결 0.122273s TLS 0.247918s 첫 바이트 0.374047s HTTP/2
  DNS 0.003532s 연결 0.142627s TLS 0.292143s 첫 바이트 0.439808s HTTP/2
  DNS 0.002401s 연결 0.133572s TLS 0.275059s 첫 바이트 0.412915s HTTP/2

$ echo | openssl s_client -connect solodevnote.com:443 -servername solodevnote.com 2>/dev/null | openssl x509 -noout -enddate -checkend 2592000; echo "종료 코드 $?"
notAfter=Dec 26 11:37:34 2026 GMT
Certificate will not expire
종료 코드 0

$ openssl req -x509 -newkey rsa:2048 -nodes -keyout key.pem -out cert.pem -days 1 -subj '/CN=localhost' -addext 'subjectAltName=DNS:localhost' 2>/dev/null && ls key.pem cert.pem
openssl x509 -in cert.pem -noout -subject -issuer -dates -text | grep -E 'subject=|issuer=|notAfter|DNS:'
openssl x509 -in cert.pem -noout -checkend 172800; echo "종료 코드 $?"
cert.pem
key.pem
subject=CN=localhost
issuer=CN=localhost
notAfter=Nov  3 02:07:42 2026 GMT
                DNS:localhost
Certificate will expire
종료 코드 1

$ openssl s_server -accept 18443 -cert cert.pem -key key.pem -www >/dev/null 2>&1 &
pid=$!; sleep 1
curl -sS https://localhost:18443/ -o /dev/null; code=$?
kill $pid; exit $code
curl: (60) SSL certificate problem: self signed certificate
More details here: https://curl.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.

$ openssl s_server -accept 18443 -cert cert.pem -key key.pem -www >/dev/null 2>&1 &
pid=$!; sleep 1
echo '[--cacert cert.pem]'; curl -sS --cacert cert.pem https://localhost:18443/ -o /dev/null -w 'HTTP %{http_code}\n'
echo '[이름이 다른 주소 wrong.test]'; curl -sS --cacert cert.pem --resolve wrong.test:18443:127.0.0.1 https://wrong.test:18443/ -o /dev/null; echo "종료 코드 $?"
echo '[-k]'; curl -sSk https://localhost:18443/ -o /dev/null -w 'HTTP %{http_code}\n'
kill $pid
[--cacert cert.pem]
HTTP 200
[이름이 다른 주소 wrong.test]
curl: (60) SSL: no alternative certificate subject name matches target host name 'wrong.test'
More details here: https://curl.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
종료 코드 60
[-k]
HTTP 200

$ claude --model opus -p "맥 터미널에서 solodevnote.com의 HTTPS 상태를 점검하는 셸 명령을 3줄만 출력해: 1) http로 접속했을 때 상태 코드와 Location, 2) 인증서 만료일, 3) Strict-Transport-Security 헤더(없으면 '없음' 출력). 설명이나 코드 블록 표시는 붙이지 마." < /dev/null > check.sh && cat check.sh && zsh -f check.sh
curl -sI http://solodevnote.com | grep -iE '^(HTTP/|location:)'
echo | openssl s_client -connect solodevnote.com:443 -servername solodevnote.com 2>/dev/null | openssl x509 -noout -enddate
curl -sI https://solodevnote.com | grep -i '^strict-transport-security:' || echo '없음'
HTTP/1.1 301 Moved Permanently
Location: https://solodevnote.com/
notAfter=Dec 26 11:37:34 2026 GMT
없음

$ openssl version && curl --version | head -1
OpenSSL 4.1.0 23 Oct 2026 (Library: OpenSSL 4.1.0 23 Oct 2026)
curl 8.7.1 (x86_64-apple-darwin26.0) libcurl/8.7.1 (SecureTransport) LibreSSL/3.3.6 zlib/1.2.12 nghttp2/1.69.0