Test SSL cert for a domain before flipping DNS

curl https://some.domain.net --resolve some.domain.net:443:

Where is the current IP address where the cert we are testing is located.

JSON & friends

CFN EBS volume tagging

If you want to tag EC2 instance root volume based on the EC2 instance tag, you can use something like this.


  • This is script that runs post-stack creation.
  • Stack creates a single instance
  • We are using CFN Outputs to get the InstanceID

# Known variables

# Get Instance ID from $STACKNAME
INSTANCEID=$(aws cloudformation describe-stacks --stack-name $STACKNAME | jq -r '.Stacks[].Outputs[].OutputValue')

# Get Volume ID from $INSTANCEID
VOLUMEID=$(aws ec2 describe-instances --instance-ids $INSTANCEID | jq -r '.Reservations[].Instances[].BlockDeviceMappings[].Ebs.VolumeId')

# Get the tag value based on the key we already know. 
# Use of "--arg" is of interest here. Basically, we assign a JQ variable $TAGKEY with the bash variable $TAGKEY. 
# This is because the JQ expression is in single quotes, and we wouldn't be able to bash-substitute within the brackets.
TAGVALUE=$(aws ec2 describe-instances --instance-ids $INSTANCEID | jq -r --arg TAGKEY $TAGKEY '.Reservations[].Instances[].Tags[] | select(.Key == $TAGKEY) | .Value' )

# Create tag on the volume 
aws ec2 create-tags --resources $VOLUMEID --tags "[ { \"Key\" : \"$TAGKEY\" , \"Value\" : \"$TAGVALUE\" } ]"

Fine grained CloudTrail parsing with custom output

Parse large amounts of CT logs:

cd month1
find . -name '*.gz' | while read line
    zcat "$line" |
        jq '.Records[] |
            select(.requestParameters.roleName == "NAME-OF-THE-ROLE-I-WAS-INTERESTED-IN")'
done > out.txt

Note: I did the above for both months in parallel as CPU (core) was the bottleneck. Doing it for the larger month alone (984MB) took almost 12 minutes.

After this, I parsed individual out.txt files in a few different ways until I was happy with outputting only PutRolePolicy or DeleteRolePolicy, and formatted the output a little bit, in a way it was presentable to the customer:

cat out.txt| jq '
    select(.eventName ## "PutRolePolicy" or .eventName "DeleteRolePolicy") |
            Policy: .requestParameters.policyName ,
            Time: .eventTime ,
            Action: .eventName,
            ARN: .userIdentity.arn
        } '

’'’Similar to above’’’, but in one step and using a jq argument (import shell variable). Use case: “Who removed rules from “sg-xxxxxxxx”:

cd month1


find . -name '*.gz' | while read line
    zcat "$line" |
        jq --arg SG $SG '.Records[] |
            select(.requestParameters.groupId == $SG) |
            select(.eventName ## "RevokeSecurityGroupEgress" or .eventName "RevokeSecurityGroupIngress") |
                GroupId: .requestParameters.groupId ,
                Time: .eventTime ,
                Action: .eventName,
                ARN: .userIdentity.arn
            } '

Adding values via JQ

Script that parses a JSON, structures it im key: value structure where value is integer. A friend needed to put a sum at the bottom. My last line in this JQ is what did what he wanted:



            select((.key|match("-(str1|str2|str3|(st3(4|5|6)))@literalsuffix")) and (.value["total"] > 0))
            {"key" : .key,"value" : .value["total"]}
        from_entries | 
        . + {"Total" : (. |add) }

curl -s "$URL" | jq "$FILTER"

Example output:

  "str1@literalsuffix": 12,
  "str2@literalsuffix": 12,
  "str3@literalsuffix": 12,
  "str4@literalsuffix": 12,
  "str5@literalsuffix": 12,
  "str6@literalsuffix": 12,
  "Total": 72

Filter AWS IP ranges by service & region(s)

Requires JQ 1.5: https://github.com/stedolan/jq/releases

curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq -r '
                .prefixes[] |
                select ( 
                         (.service | match("EC2")) and 
                         (.region | match("us-east-1|us-west-2")) 
                       ) |

Filter then catenate all CloudTrail gzip logs into one text file with output time sorted

find . -name '*.gz' | while read line
    zcat "$line"  | jq '.Records[]
    select(.userIdentity.arn == "arn:aws:sts::000000000000:assumed-role/Something/someguy@whatever.com" )
done | jq -s ' sort_by(.eventTime) '

Finding highest offenders

Again, in this example, we try to do as much as possible on each iteration of .gz files to avoid crashing the desktop


echo "Processing highest API offenders"
find . -name '*.gz' | while read line
    zcat "$line"  | jq '.Records[]
    (.eventSource + "-" + .eventName)
done | sort | uniq -c | sort -n

Recursively search json structure for a value of desired keyname

For example, we might have keys “volumeId” in different places throughout our input JSON. If we want to grab all such entries, we can do something like this (CloudTrail parse example):

find . -name '*.gz' | while read line


    zcat "$line" |

        jq '

            .Records[] |

            select(..|.volumeId? )


done  | jq -s ' sort_by(.eventTime) ' > output.txt

Note: This is an expensive operation (~4-5 x more time than when directly checking for a value on a specific key location)

Database stuff

MySQL Basics

Useful MySQL commands

When creating MySQL users, make sure that your .mysql_history file does not log anything. There are two ways:

  • Permanently: ln -s /dev/null $HOME/.mysql_history
  • Temporarily: MYSQL_HISTFILE=/dev/null && mysql <your parameters here>

And now for some general tips:

# List all users
SELECT User, Host FROM mysql.user;

# Create user
CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';

# Show Grants
SHOW GRANTS FOR 'jeffrey'@'localhost';

# Grant all perms to db1 DB and it's tables:
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';

# Grant select on table invoice of db2:
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';

# No privileges for all databases/tables with rate limiting
GRANT USAGE ON *.* TO 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;

# Grant, require SSL
GRANT USAGE ON *.* TO 'jeffrey'@'%' REQUIRE SSL ; 

# Common permissions
GRANT SELECT, INSERT, UPDATE, DELETE, CREATE ON `db_jeffrey`.* TO 'jeffrey'@'%' ;

# Change user password
SET PASSWORD FOR user@'host' = PASSWORD('somepass');

SSL for MySQL (RDS example)

mkdir -p "$MyPath"
wget http://s3.amazonaws.com/rds-downloads/rds-combined-ca-bundle.pem -O "$MyPath/rds-ssl-ca-cert.pem"
mysql --ssl_ca="$MyPath/rds-ssl-ca-cert.pem" --ssl-verify-server-cert -h <hostname> -P <port> -u <username> -p
# You'll be prompted for the password

MySQL workbench also supports SSL. When creating a connection go to the Advanced tab and just fill in the CA field. Relevant RDS doc


AWS CLI basics


aws cloudformation update-stack \
--template-body file://~/Desktop/cfn/ASG-LifeCycle-DelayFirstInstance.cform  \
--capabilities CAPABILITY_IAM \
--parameters file://~/Desktop/cfn/ASG-LifeCycle-DelayFirstInstance.params  \
--stack-name asjdaad4233

Example Parameters file

        "ParameterKey": "InstanceAmi",
        "ParameterValue": "ami-xxxxxxx"
        "ParameterKey": "InstanceType",
        "ParameterValue": "t2.micro"


Create a deployment with AWS CLI


aws deploy create-deployment \
--application-name "$APP" \
--deployment-group-name "$DG" \
--github-location commitId="$COMMIT",repository="$REPO"