mirror of
https://github.com/gchq/CyberChef.git
synced 2026-02-20 16:51:45 +01:00
Compare commits
13 Commits
| Author | SHA1 | Date | |
|---|---|---|---|
|
|
b5f6cedd30 | ||
|
|
c879af6860 | ||
|
|
22fe5a6ae7 | ||
|
|
57714c86a6 | ||
|
|
70cd375049 | ||
|
|
e27e1dd42f | ||
|
|
8ad18bc7db | ||
|
|
5893ac1a37 | ||
|
|
83c3ab97f9 | ||
|
|
9b6be140fa | ||
|
|
bda36e508a | ||
|
|
d2ea1273da | ||
|
|
3a2580fbc2 |
2
.github/workflows/master.yml
vendored
2
.github/workflows/master.yml
vendored
@@ -19,7 +19,7 @@ jobs:
|
||||
- name: Install
|
||||
run: |
|
||||
npm install
|
||||
export NODE_OPTIONS=--max_old_space_size=2048
|
||||
npm run setheapsize
|
||||
|
||||
- name: Lint
|
||||
run: npx grunt lint
|
||||
|
||||
2
.github/workflows/pull_requests.yml
vendored
2
.github/workflows/pull_requests.yml
vendored
@@ -18,7 +18,7 @@ jobs:
|
||||
- name: Install
|
||||
run: |
|
||||
npm install
|
||||
export NODE_OPTIONS=--max_old_space_size=2048
|
||||
npm run setheapsize
|
||||
|
||||
- name: Lint
|
||||
run: npx grunt lint
|
||||
|
||||
2
.github/workflows/releases.yml
vendored
2
.github/workflows/releases.yml
vendored
@@ -19,7 +19,7 @@ jobs:
|
||||
- name: Install
|
||||
run: |
|
||||
npm install
|
||||
export NODE_OPTIONS=--max_old_space_size=2048
|
||||
npm run setheapsize
|
||||
|
||||
- name: Lint
|
||||
run: npx grunt lint
|
||||
|
||||
@@ -13,6 +13,9 @@ All major and minor version changes will be documented in this file. Details of
|
||||
|
||||
## Details
|
||||
|
||||
### [9.27.0] - 2021-02-12
|
||||
- 'Fuzzy Match' operation added [@n1474335] | [8ad18b]
|
||||
|
||||
### [9.26.0] - 2021-02-11
|
||||
- 'Get Time' operation added [@n1073645] [@n1474335] | [#1045]
|
||||
|
||||
@@ -253,6 +256,7 @@ All major and minor version changes will be documented in this file. Details of
|
||||
|
||||
|
||||
|
||||
[9.27.0]: https://github.com/gchq/CyberChef/releases/tag/v9.27.0
|
||||
[9.26.0]: https://github.com/gchq/CyberChef/releases/tag/v9.26.0
|
||||
[9.25.0]: https://github.com/gchq/CyberChef/releases/tag/v9.25.0
|
||||
[9.24.0]: https://github.com/gchq/CyberChef/releases/tag/v9.24.0
|
||||
@@ -360,6 +364,8 @@ All major and minor version changes will be documented in this file. Details of
|
||||
[@dmfj]: https://github.com/dmfj
|
||||
[@mattnotmitt]: https://github.com/mattnotmitt
|
||||
|
||||
[8ad18b]: https://github.com/gchq/CyberChef/commit/8ad18bc7db6d9ff184ba3518686293a7685bf7b7
|
||||
|
||||
[#95]: https://github.com/gchq/CyberChef/pull/299
|
||||
[#173]: https://github.com/gchq/CyberChef/pull/173
|
||||
[#143]: https://github.com/gchq/CyberChef/pull/143
|
||||
|
||||
2
package-lock.json
generated
2
package-lock.json
generated
@@ -1,6 +1,6 @@
|
||||
{
|
||||
"name": "cyberchef",
|
||||
"version": "9.26.2",
|
||||
"version": "9.27.2",
|
||||
"lockfileVersion": 1,
|
||||
"requires": true,
|
||||
"dependencies": {
|
||||
|
||||
@@ -1,6 +1,6 @@
|
||||
{
|
||||
"name": "cyberchef",
|
||||
"version": "9.26.2",
|
||||
"version": "9.27.2",
|
||||
"description": "The Cyber Swiss Army Knife for encryption, encoding, compression and data analysis.",
|
||||
"author": "n1474335 <n1474335@gmail.com>",
|
||||
"homepage": "https://gchq.github.io/CyberChef",
|
||||
@@ -173,6 +173,8 @@
|
||||
"testuidev": "npx nightwatch --env=dev",
|
||||
"lint": "npx grunt lint",
|
||||
"postinstall": "npx grunt exec:fixCryptoApiImports",
|
||||
"newop": "node --experimental-modules src/core/config/scripts/newOperation.mjs"
|
||||
"newop": "node --experimental-modules src/core/config/scripts/newOperation.mjs",
|
||||
"getheapsize": "node -e 'console.log(`node heap limit = ${require(\"v8\").getHeapStatistics().heap_size_limit / (1024 * 1024)} Mb`)'",
|
||||
"setheapsize": "export NODE_OPTIONS=--max_old_space_size=2048"
|
||||
}
|
||||
}
|
||||
|
||||
@@ -895,8 +895,8 @@ class Utils {
|
||||
|
||||
while ((m = recipeRegex.exec(recipe))) {
|
||||
// Translate strings in args back to double-quotes
|
||||
args = m[2]
|
||||
.replace(/"/g, '\\"') // Escape double quotes // lgtm [js/incomplete-sanitization]
|
||||
args = m[2] // lgtm [js/incomplete-sanitization]
|
||||
.replace(/"/g, '\\"') // Escape double quotes
|
||||
.replace(/(^|,|{|:)'/g, '$1"') // Replace opening ' with "
|
||||
.replace(/([^\\]|(?:\\\\)+)'(,|:|}|$)/g, '$1"$2') // Replace closing ' with "
|
||||
.replace(/\\'/g, "'"); // Unescape single quotes
|
||||
|
||||
@@ -238,6 +238,7 @@
|
||||
"Pad lines",
|
||||
"Find / Replace",
|
||||
"Regular expression",
|
||||
"Fuzzy Match",
|
||||
"Offset checker",
|
||||
"Hamming Distance",
|
||||
"Convert distance",
|
||||
|
||||
@@ -148,4 +148,8 @@ export const ALPHABET_OPTIONS = [
|
||||
{name: "BinHex: !-,-0-689@A-NP-VX-Z[`a-fh-mp-r", value: "!-,-0-689@A-NP-VX-Z[`a-fh-mp-r"},
|
||||
{name: "ROT13: N-ZA-Mn-za-m0-9+/=", value: "N-ZA-Mn-za-m0-9+/="},
|
||||
{name: "UNIX crypt: ./0-9A-Za-z", value: "./0-9A-Za-z"},
|
||||
{name: "Atom128: /128GhIoPQROSTeUbADfgHijKLM+n0pFWXY456xyzB7=39VaqrstJklmNuZvwcdEC", value: "/128GhIoPQROSTeUbADfgHijKLM+n0pFWXY456xyzB7=39VaqrstJklmNuZvwcdEC"},
|
||||
{name: "Megan35: 3GHIJKLMNOPQRSTUb=cdefghijklmnopWXYZ/12+406789VaqrstuvwxyzABCDEF5", value: "3GHIJKLMNOPQRSTUb=cdefghijklmnopWXYZ/12+406789VaqrstuvwxyzABCDEF5"},
|
||||
{name: "Zong22: ZKj9n+yf0wDVX1s/5YbdxSo=ILaUpPBCHg8uvNO4klm6iJGhQ7eFrWczAMEq3RTt2", value: "ZKj9n+yf0wDVX1s/5YbdxSo=ILaUpPBCHg8uvNO4klm6iJGhQ7eFrWczAMEq3RTt2"},
|
||||
{name: "Hazz15: HNO4klm6ij9n+J2hyf0gzA8uvwDEq3X1Q7ZKeFrWcVTts/MRGYbdxSo=ILaUpPBC5", value: "HNO4klm6ij9n+J2hyf0gzA8uvwDEq3X1Q7ZKeFrWcVTts/MRGYbdxSo=ILaUpPBC5"}
|
||||
];
|
||||
|
||||
@@ -16,40 +16,72 @@
|
||||
* Anurag Awasthi - updated to 0.2.0
|
||||
*/
|
||||
|
||||
const SEQUENTIAL_BONUS = 15; // bonus for adjacent matches
|
||||
const SEPARATOR_BONUS = 30; // bonus if match occurs after a separator
|
||||
const CAMEL_BONUS = 30; // bonus if match is uppercase and prev is lower
|
||||
const FIRST_LETTER_BONUS = 15; // bonus if the first letter is matched
|
||||
export const DEFAULT_WEIGHTS = {
|
||||
sequentialBonus: 15, // bonus for adjacent matches
|
||||
separatorBonus: 30, // bonus if match occurs after a separator
|
||||
camelBonus: 30, // bonus if match is uppercase and prev is lower
|
||||
firstLetterBonus: 15, // bonus if the first letter is matched
|
||||
|
||||
const LEADING_LETTER_PENALTY = -5; // penalty applied for every letter in str before the first match
|
||||
const MAX_LEADING_LETTER_PENALTY = -15; // maximum penalty for leading letters
|
||||
const UNMATCHED_LETTER_PENALTY = -1;
|
||||
leadingLetterPenalty: -5, // penalty applied for every letter in str before the first match
|
||||
maxLeadingLetterPenalty: -15, // maximum penalty for leading letters
|
||||
unmatchedLetterPenalty: -1
|
||||
};
|
||||
|
||||
/**
|
||||
* Does a fuzzy search to find pattern inside a string.
|
||||
* @param {*} pattern string pattern to search for
|
||||
* @param {*} str string string which is being searched
|
||||
* @param {string} pattern pattern to search for
|
||||
* @param {string} str string which is being searched
|
||||
* @param {boolean} global whether to search for all matches or just one
|
||||
* @returns [boolean, number] a boolean which tells if pattern was
|
||||
* found or not and a search score
|
||||
*/
|
||||
export function fuzzyMatch(pattern, str) {
|
||||
export function fuzzyMatch(pattern, str, global=false, weights=DEFAULT_WEIGHTS) {
|
||||
const recursionCount = 0;
|
||||
const recursionLimit = 10;
|
||||
const matches = [];
|
||||
const maxMatches = 256;
|
||||
|
||||
return fuzzyMatchRecursive(
|
||||
pattern,
|
||||
str,
|
||||
0 /* patternCurIndex */,
|
||||
0 /* strCurrIndex */,
|
||||
null /* srcMatces */,
|
||||
matches,
|
||||
maxMatches,
|
||||
0 /* nextMatch */,
|
||||
recursionCount,
|
||||
recursionLimit
|
||||
);
|
||||
if (!global) {
|
||||
return fuzzyMatchRecursive(
|
||||
pattern,
|
||||
str,
|
||||
0 /* patternCurIndex */,
|
||||
0 /* strCurrIndex */,
|
||||
null /* srcMatches */,
|
||||
matches,
|
||||
maxMatches,
|
||||
0 /* nextMatch */,
|
||||
recursionCount,
|
||||
recursionLimit,
|
||||
weights
|
||||
);
|
||||
}
|
||||
|
||||
// Return all matches
|
||||
let foundMatch = true,
|
||||
score,
|
||||
idxs,
|
||||
strCurrIndex = 0;
|
||||
const results = [];
|
||||
|
||||
while (foundMatch) {
|
||||
[foundMatch, score, idxs] = fuzzyMatchRecursive(
|
||||
pattern,
|
||||
str,
|
||||
0 /* patternCurIndex */,
|
||||
strCurrIndex,
|
||||
null /* srcMatches */,
|
||||
matches,
|
||||
maxMatches,
|
||||
0 /* nextMatch */,
|
||||
recursionCount,
|
||||
recursionLimit,
|
||||
weights
|
||||
);
|
||||
if (foundMatch) results.push([foundMatch, score, [...idxs]]);
|
||||
strCurrIndex = idxs[idxs.length - 1] + 1;
|
||||
}
|
||||
return results;
|
||||
}
|
||||
|
||||
/**
|
||||
@@ -65,7 +97,8 @@ function fuzzyMatchRecursive(
|
||||
maxMatches,
|
||||
nextMatch,
|
||||
recursionCount,
|
||||
recursionLimit
|
||||
recursionLimit,
|
||||
weights
|
||||
) {
|
||||
let outScore = 0;
|
||||
|
||||
@@ -110,7 +143,8 @@ function fuzzyMatchRecursive(
|
||||
maxMatches,
|
||||
nextMatch,
|
||||
recursionCount,
|
||||
recursionLimit
|
||||
recursionLimit,
|
||||
weights
|
||||
);
|
||||
|
||||
if (matched) {
|
||||
@@ -134,16 +168,16 @@ function fuzzyMatchRecursive(
|
||||
outScore = 100;
|
||||
|
||||
// Apply leading letter penalty
|
||||
let penalty = LEADING_LETTER_PENALTY * matches[0];
|
||||
let penalty = weights.leadingLetterPenalty * matches[0];
|
||||
penalty =
|
||||
penalty < MAX_LEADING_LETTER_PENALTY ?
|
||||
MAX_LEADING_LETTER_PENALTY :
|
||||
penalty < weights.maxLeadingLetterPenalty ?
|
||||
weights.maxLeadingLetterPenalty :
|
||||
penalty;
|
||||
outScore += penalty;
|
||||
|
||||
// Apply unmatched penalty
|
||||
const unmatched = str.length - nextMatch;
|
||||
outScore += UNMATCHED_LETTER_PENALTY * unmatched;
|
||||
outScore += weights.unmatchedLetterPenalty * unmatched;
|
||||
|
||||
// Apply ordering bonuses
|
||||
for (let i = 0; i < nextMatch; i++) {
|
||||
@@ -152,7 +186,7 @@ function fuzzyMatchRecursive(
|
||||
if (i > 0) {
|
||||
const prevIdx = matches[i - 1];
|
||||
if (currIdx === prevIdx + 1) {
|
||||
outScore += SEQUENTIAL_BONUS;
|
||||
outScore += weights.sequentialBonus;
|
||||
}
|
||||
}
|
||||
|
||||
@@ -165,15 +199,15 @@ function fuzzyMatchRecursive(
|
||||
neighbor !== neighbor.toUpperCase() &&
|
||||
curr !== curr.toLowerCase()
|
||||
) {
|
||||
outScore += CAMEL_BONUS;
|
||||
outScore += weights.camelBonus;
|
||||
}
|
||||
const isNeighbourSeparator = neighbor === "_" || neighbor === " ";
|
||||
if (isNeighbourSeparator) {
|
||||
outScore += SEPARATOR_BONUS;
|
||||
outScore += weights.separatorBonus;
|
||||
}
|
||||
} else {
|
||||
// First letter
|
||||
outScore += FIRST_LETTER_BONUS;
|
||||
outScore += weights.firstLetterBonus;
|
||||
}
|
||||
}
|
||||
|
||||
@@ -102,6 +102,26 @@ class FromBase64 extends Operation {
|
||||
flags: "i",
|
||||
args: ["./0-9A-Za-z", true]
|
||||
},
|
||||
{
|
||||
pattern: "^\\s*(?:[A-Z=\\d\\+/]{4}){5,}(?:[A-Z=\\d\\+/]{2}CC|[A-Z=\\d\\+/]{3}C)?\\s*$",
|
||||
flags: "i",
|
||||
args: ["/128GhIoPQROSTeUbADfgHijKLM+n0pFWXY456xyzB7=39VaqrstJklmNuZvwcdEC", true]
|
||||
},
|
||||
{
|
||||
pattern: "^\\s*(?:[A-Z=\\d\\+/]{4}){5,}(?:[A-Z=\\d\\+/]{2}55|[A-Z=\\d\\+/]{3}5)?\\s*$",
|
||||
flags: "i",
|
||||
args: ["3GHIJKLMNOPQRSTUb=cdefghijklmnopWXYZ/12+406789VaqrstuvwxyzABCDEF5", true]
|
||||
},
|
||||
{
|
||||
pattern: "^\\s*(?:[A-Z=\\d\\+/]{4}){5,}(?:[A-Z=\\d\\+/]{2}22|[A-Z=\\d\\+/]{3}2)?\\s*$",
|
||||
flags: "i",
|
||||
args: ["ZKj9n+yf0wDVX1s/5YbdxSo=ILaUpPBCHg8uvNO4klm6iJGhQ7eFrWczAMEq3RTt2", true]
|
||||
},
|
||||
{
|
||||
pattern: "^\\s*(?:[A-Z=\\d\\+/]{4}){5,}(?:[A-Z=\\d\\+/]{2}55|[A-Z=\\d\\+/]{3}5)?\\s*$",
|
||||
flags: "i",
|
||||
args: ["HNO4klm6ij9n+J2hyf0gzA8uvwDEq3X1Q7ZKeFrWcVTts/MRGYbdxSo=ILaUpPBC5", true]
|
||||
}
|
||||
];
|
||||
}
|
||||
|
||||
|
||||
121
src/core/operations/FuzzyMatch.mjs
Normal file
121
src/core/operations/FuzzyMatch.mjs
Normal file
@@ -0,0 +1,121 @@
|
||||
/**
|
||||
* @author n1474335 [n1474335@gmail.com]
|
||||
* @copyright Crown Copyright 2021
|
||||
* @license Apache-2.0
|
||||
*/
|
||||
|
||||
import Operation from "../Operation.mjs";
|
||||
import {fuzzyMatch, calcMatchRanges, DEFAULT_WEIGHTS} from "../lib/FuzzyMatch.mjs";
|
||||
import Utils from "../Utils.mjs";
|
||||
|
||||
/**
|
||||
* Fuzzy Match operation
|
||||
*/
|
||||
class FuzzyMatch extends Operation {
|
||||
|
||||
/**
|
||||
* FuzzyMatch constructor
|
||||
*/
|
||||
constructor() {
|
||||
super();
|
||||
|
||||
this.name = "Fuzzy Match";
|
||||
this.module = "Default";
|
||||
this.description = "Conducts a fuzzy search to find a pattern within the input based on weighted criteria.<br><br>e.g. A search for <code>dpan</code> will match on <code><b>D</b>on't <b>Pan</b>ic</code>";
|
||||
this.infoURL = "https://wikipedia.org/wiki/Fuzzy_matching_(computer-assisted_translation)";
|
||||
this.inputType = "string";
|
||||
this.outputType = "html";
|
||||
this.args = [
|
||||
{
|
||||
name: "Search",
|
||||
type: "binaryString",
|
||||
value: ""
|
||||
},
|
||||
{
|
||||
name: "Sequential bonus",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.sequentialBonus,
|
||||
hint: "Bonus for adjacent matches"
|
||||
},
|
||||
{
|
||||
name: "Separator bonus",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.separatorBonus,
|
||||
hint: "Bonus if match occurs after a separator"
|
||||
},
|
||||
{
|
||||
name: "Camel bonus",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.camelBonus,
|
||||
hint: "Bonus if match is uppercase and previous is lower"
|
||||
},
|
||||
{
|
||||
name: "First letter bonus",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.firstLetterBonus,
|
||||
hint: "Bonus if the first letter is matched"
|
||||
},
|
||||
{
|
||||
name: "Leading letter penalty",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.leadingLetterPenalty,
|
||||
hint: "Penalty applied for every letter in the input before the first match"
|
||||
},
|
||||
{
|
||||
name: "Max leading letter penalty",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.maxLeadingLetterPenalty,
|
||||
hint: "Maxiumum penalty for leading letters"
|
||||
},
|
||||
{
|
||||
name: "Unmatched letter penalty",
|
||||
type: "number",
|
||||
value: DEFAULT_WEIGHTS.unmatchedLetterPenalty
|
||||
},
|
||||
];
|
||||
}
|
||||
|
||||
/**
|
||||
* @param {string} input
|
||||
* @param {Object[]} args
|
||||
* @returns {html}
|
||||
*/
|
||||
run(input, args) {
|
||||
const searchStr = args[0];
|
||||
const weights = {
|
||||
sequentialBonus: args[1],
|
||||
separatorBonus: args[2],
|
||||
camelBonus: args[3],
|
||||
firstLetterBonus: args[4],
|
||||
leadingLetterPenalty: args[5],
|
||||
maxLeadingLetterPenalty: args[6],
|
||||
unmatchedLetterPenalty: args[7]
|
||||
};
|
||||
const matches = fuzzyMatch(searchStr, input, true, weights);
|
||||
|
||||
if (!matches) {
|
||||
return "No matches.";
|
||||
}
|
||||
|
||||
let result = "", pos = 0, hlClass = "hl1";
|
||||
matches.forEach(([matches, score, idxs]) => {
|
||||
const matchRanges = calcMatchRanges(idxs);
|
||||
|
||||
matchRanges.forEach(([start, length], i) => {
|
||||
result += Utils.escapeHtml(input.slice(pos, start));
|
||||
if (i === 0) result += `<span class="${hlClass}">`;
|
||||
pos = start + length;
|
||||
result += `<b>${Utils.escapeHtml(input.slice(start, pos))}</b>`;
|
||||
});
|
||||
result += "</span>";
|
||||
hlClass = hlClass === "hl1" ? "hl2" : "hl1";
|
||||
});
|
||||
|
||||
result += Utils.escapeHtml(input.slice(pos, input.length));
|
||||
|
||||
return result;
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
export default FuzzyMatch;
|
||||
@@ -185,7 +185,7 @@ class RegularExpression extends Operation {
|
||||
* @param {boolean} captureGroups - Display each of the capture groups separately
|
||||
* @returns {string}
|
||||
*/
|
||||
function regexList (input, regex, displayTotal, matches, captureGroups) {
|
||||
function regexList(input, regex, displayTotal, matches, captureGroups) {
|
||||
let output = "",
|
||||
total = 0,
|
||||
match;
|
||||
@@ -225,7 +225,7 @@ function regexList (input, regex, displayTotal, matches, captureGroups) {
|
||||
* @param {boolean} displayTotal
|
||||
* @returns {string}
|
||||
*/
|
||||
function regexHighlight (input, regex, displayTotal) {
|
||||
function regexHighlight(input, regex, displayTotal) {
|
||||
let output = "",
|
||||
title = "",
|
||||
hl = 1,
|
||||
|
||||
@@ -725,7 +725,7 @@ class App {
|
||||
this.progress = 0;
|
||||
this.autoBake();
|
||||
|
||||
this.updateTitle(false, null, true);
|
||||
this.updateTitle(true, null, true);
|
||||
}
|
||||
|
||||
|
||||
|
||||
@@ -100,7 +100,7 @@ class ControlsWaiter {
|
||||
const includeRecipe = document.getElementById("save-link-recipe-checkbox").checked;
|
||||
const includeInput = document.getElementById("save-link-input-checkbox").checked;
|
||||
const saveLinkEl = document.getElementById("save-link");
|
||||
const saveLink = this.generateStateUrl(includeRecipe, includeInput, recipeConfig);
|
||||
const saveLink = this.generateStateUrl(includeRecipe, includeInput, null, recipeConfig);
|
||||
|
||||
saveLinkEl.innerHTML = Utils.escapeHtml(Utils.truncate(saveLink, 120));
|
||||
saveLinkEl.setAttribute("href", saveLink);
|
||||
@@ -128,11 +128,13 @@ class ControlsWaiter {
|
||||
includeRecipe = includeRecipe && (recipeConfig.length > 0);
|
||||
|
||||
// If we don't get passed an input, get it from the current URI
|
||||
if (input === null) {
|
||||
if (input === null && includeInput) {
|
||||
const params = this.app.getURIParams();
|
||||
if (params.input) {
|
||||
includeInput = true;
|
||||
input = params.input;
|
||||
} else {
|
||||
includeInput = false;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
@@ -6,7 +6,7 @@
|
||||
|
||||
import HTMLOperation from "../HTMLOperation.mjs";
|
||||
import Sortable from "sortablejs";
|
||||
import {fuzzyMatch, calcMatchRanges} from "../../core/lib/FuzzySearch.mjs";
|
||||
import {fuzzyMatch, calcMatchRanges} from "../../core/lib/FuzzyMatch.mjs";
|
||||
|
||||
|
||||
/**
|
||||
|
||||
Reference in New Issue
Block a user