2018-09-24 08:00:17 +00:00
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package fic
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import (
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2018-11-16 19:46:19 +00:00
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"bytes"
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"errors"
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"regexp"
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"time"
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"golang.org/x/crypto/blake2b"
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)
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// Flag represents a flag's challenge, stored as hash.
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type Flag struct {
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Id int64 `json:"id"`
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// IdExercice is the identifier of the underlying challenge
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IdExercice int64 `json:"idExercice"`
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// Label is the title of the flag as displayed to players
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Label string `json:"label"`
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// Help is a small piece of text that aims to add useful information like flag format, ...
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Help string `json:"help"`
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// IgnoreCase indicates if the case is sensitive to case or not
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IgnoreCase bool `json:"ignorecase"`
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// ValidatorRegexp extracts a subset of the player's answer, that will be checked.
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ValidatorRegexp *string `json:"validator_regexp"`
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// Checksum is the expected hashed flag
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Checksum []byte `json:"value"`
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}
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// GetFlags returns a list of flags comming with the challenge.
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func (e Exercice) GetFlags() ([]Flag, error) {
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if rows, err := DBQuery("SELECT id_flag, id_exercice, type, help, ignorecase, validator_regexp, cksum FROM exercice_flags WHERE id_exercice = ?", e.Id); err != nil {
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return nil, err
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} else {
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defer rows.Close()
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var flags = make([]Flag, 0)
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for rows.Next() {
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var k Flag
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k.IdExercice = e.Id
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if err := rows.Scan(&k.Id, &k.IdExercice, &k.Label, &k.Help, &k.IgnoreCase, &k.ValidatorRegexp, &k.Checksum); err != nil {
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return nil, err
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}
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flags = append(flags, k)
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}
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if err := rows.Err(); err != nil {
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return nil, err
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}
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return flags, nil
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}
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}
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// getHashedFlag calculates the expected checksum for the given raw_value.
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func getHashedFlag(raw_value []byte) [blake2b.Size]byte {
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hash := blake2b.Sum512(raw_value)
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return hash
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}
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// AddRawFlag creates and fills a new struct Flag, from a non-hashed flag, and registers it into the database.
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func (e Exercice) AddRawFlag(name string, help string, ignorecase bool, validator_regexp *string, raw_value []byte) (Flag, error) {
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if ignorecase {
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raw_value = bytes.ToLower(raw_value)
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}
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// Check that raw value passes through the regexp
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if validator_regexp != nil {
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if re, err := regexp.Compile(*validator_regexp); err != nil {
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return Flag{}, err
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} else if res := re.FindSubmatch(raw_value); res == nil {
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return Flag{}, errors.New("Expected flag doesn't pass through the validator_regexp")
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} else {
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raw_value = bytes.Join(res[1:], []byte("+"))
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}
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}
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hash := getHashedFlag(raw_value)
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return e.AddFlag(name, help, ignorecase, validator_regexp, hash[:])
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}
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// AddFlag creates and fills a new struct Flag, from a hashed flag, and registers it into the database.
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func (e Exercice) AddFlag(name string, help string, ignorecase bool, validator_regexp *string, checksum []byte) (Flag, error) {
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// Check the regexp compile
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if validator_regexp != nil {
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if _, err := regexp.Compile(*validator_regexp); err != nil {
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return Flag{}, err
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}
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}
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if res, err := DBExec("INSERT INTO exercice_flags (id_exercice, type, help, ignorecase, validator_regexp, cksum) VALUES (?, ?, ?, ?, ?, ?)", e.Id, name, help, ignorecase, validator_regexp, checksum); err != nil {
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return Flag{}, err
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} else if kid, err := res.LastInsertId(); err != nil {
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return Flag{}, err
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} else {
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return Flag{kid, e.Id, name, help, ignorecase, validator_regexp, checksum}, nil
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}
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}
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// Update applies modifications back to the database.
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func (k Flag) Update() (int64, error) {
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if k.ValidatorRegexp != nil {
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if _, err := regexp.Compile(*k.ValidatorRegexp); err != nil {
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return 0, err
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}
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}
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if res, err := DBExec("UPDATE exercice_flags SET id_exercice = ?, type = ?, help = ?, ignorecase = ?, validator_regexp = ?, cksum = ? WHERE id_flag = ?", k.IdExercice, k.Label, k.Help, k.IgnoreCase, k.ValidatorRegexp, k.Checksum, k.Id); err != nil {
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return 0, err
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} else if nb, err := res.RowsAffected(); err != nil {
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return 0, err
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} else {
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return nb, err
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}
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}
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// Delete the flag from the database.
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func (k Flag) Delete() (int64, error) {
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if _, err := DBExec("DELETE FROM exercice_files_deps WHERE id_flag = ?", k.Id); err != nil {
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return 0, err
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} else if res, err := DBExec("DELETE FROM exercice_flags WHERE id_flag = ?", k.Id); err != nil {
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return 0, err
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} else if nb, err := res.RowsAffected(); err != nil {
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return 0, err
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} else {
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return nb, err
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}
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}
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// WipeFlags deletes flags coming with the challenge.
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func (e Exercice) WipeFlags() (int64, error) {
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if _, err := DBExec("DELETE FROM exercice_files_deps WHERE id_flag IN (SELECT id_flag FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
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return 0, err
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} else if res, err := DBExec("DELETE FROM exercice_flags WHERE id_exercice = ?", e.Id); err != nil {
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return 0, err
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} else if nb, err := res.RowsAffected(); err != nil {
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return 0, err
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} else {
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return nb, err
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}
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}
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// Check if the given val is the expected one for this flag.
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func (k Flag) Check(val []byte) bool {
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if k.IgnoreCase {
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val = bytes.ToLower(val)
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}
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// Check that raw value passes through the regexp
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if k.ValidatorRegexp != nil {
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re := regexp.MustCompile(*k.ValidatorRegexp)
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if res := re.FindSubmatch(val); res != nil {
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val = bytes.Join(res[1:], []byte("+"))
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}
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}
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// Check that the value is not empty
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if len(val) == 0 {
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return false
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}
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hash := getHashedFlag(val)
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if len(k.Checksum) != len(hash) {
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return false
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}
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for i := range hash {
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if k.Checksum[i] != hash[i] {
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return false
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}
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}
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return true
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}
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// FoundBy registers in the database that the given Team solved the flag.
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func (k Flag) FoundBy(t Team) {
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DBExec("INSERT INTO flag_found (id_flag, id_team, time) VALUES (?, ?, ?)", k.Id, t.Id, time.Now())
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}
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