Decrypt all PDFs in a directory using the given password and optionally store the password in the Mac OS system keychain

decrypt_pdfs

#! /bin/sh

# Check if qpdf is installed
installed=$(which qpdf &> /dev/null)
if [ $? -eq 1 ]; then
    echo >&2 "Please install qpdf first (brew install qpdf)"
    exit 1
fi

# Fetch the password from the keychain
password_entered=false
password=$(security 2> /dev/null find-generic-password -a login -s decrypt_pdfs -D "application password" -w)

# Prompt for password if not in keychain
if [ -z $password ]; then
    echo "Enter the password to decrypt PDFs:"
    read -s password
    password_entered=true
fi

# Make a folder called 'decrypted' unless it exists
mkdir -p decrypted

# Decrypt all .pdf files in the current directory
for file in *.pdf; do
    set -e
    echo "Decrypting $file"
    qpdf --decrypt --password="$password" "$file" "decrypted/$file"
done

# Save the password to the keychain
if [ $password_entered != false ]; then
    echo "Save password in keychain?"
    read yn
    case $yn in
        [Yy]* ) security add-generic-password -a login -l pdf_password -s decrypt_pdfs -T "" -w $password; break;;
        [Nn]* ) exit;;
        * ) echo "Please answer yes or no.";;
    esac
fi