Adding checksum validation for cfssl cfssljson

docs/02-client-tools.md

@@ -16,6 +16,12 @@ curl -o cfssl https://pkg.cfssl.org/R1.2/cfssl_darwin-amd64
 curl -o cfssljson https://pkg.cfssl.org/R1.2/cfssljson_darwin-amd64
 ```
 
+Check if sha256sum match one provided at: https://pkg.cfssl.org/R1.2/SHA256SUMS
+
+```
+shasum -a 256 cfssl cfssljson
+```
+
 ```
 chmod +x cfssl cfssljson
 ```
@@ -38,6 +44,12 @@ wget -q --show-progress --https-only --timestamping \
   https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
 ```
 
+Check if sha256sum match one provided at: https://pkg.cfssl.org/R1.2/SHA256SUMS
+
+```
+sha256sum cfssl_linux-amd64 cfssljson_linux-amd64
+```
+
 ```
 chmod +x cfssl_linux-amd64 cfssljson_linux-amd64
 ```