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Use regular expressions to verify password strength

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Release: 2018-05-25 09:52:25
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This time I will bring you the use of regular expressions to verify password strength, and what are the precautions for using regular expressions to verify password strength. The following is a practical case, let's take a look.

Preface

##When users register

, password regularization will be used test. To write a correct regular expression, you must first define the expression rules.

Option 1 (Simple) Assume that password verification is defined as follows:

    Shortest 6 digits, up to 16 digits {6,16}
  • can include lowercase letters [a-z] and uppercase letters [A-Z]
  • Can contain numbers [0-9]
  • Can contain underscores [_] and minus signs [-]
  • According to the above rules, it is easy The regular literal definition is given as follows:
var pattern = /^[\w_-]{6,16}$/;
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Scheme 1 AnalysisLiteral/ /

regular expression A literal is defined as a character contained between a pair of slashes (/), for example:

var pattern = /s$/;
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The above literal matches all strings ending with the letter "s".

Character class [ ]

Put characters in square brackets to form a character class. A character class can match any character it contains. Therefore, the regular expression /[abc]/ matches any of the letters "a", "b", or "c".

Character classes may use hyphens to represent

character ranges

. To match Latin lowercase letters use /[a-z]/ .

Character class \w

Character class \w matches any word composed of ASCII characters, equivalent to [a-zA-Z0-9].

[\w_-] means matching any Latin uppercase and lowercase letters, numbers plus underscores and minus signs.

Repeat {}

Use { } in regular expressions to represent the number of times an element repeats.

    {n,m} Match the previous item at least n times, but not more than m times
  • {n,} Match the previous item n times or more
  • {n} matches the previous item n times

  • [\w_-]{6,16} means matching any Latin uppercase and lowercase letters, numbers plus underscores and minus signs appearing at least 6 times and at most 16 times.

Matching position

^ Matches the beginning of the string, in multi-line retrieval, matches the beginning of a line

$ Matches the end of the string, in multiple lines During retrieval, match the end of a line

/^\w/ and match strings starting with uppercase and lowercase letters or numbers.

Option 1 testThe test results are given as follows:

var pattern = /^[\w_-]{6,16}$/;
pattern.test('123456') = true;
pattern.test('-ifat33') = true;
pattern.test('42du') = false;
pattern.test('du42du42du42du421') = false;
pattern.test('42du42@') = false;
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View source code

According to the test It can be seen from the results that Solution 1 only briefly limits the password and cannot guarantee the strength of the password and the security of the account.

Option 2 (Security) Assume that password verification is defined as follows:

    Shortest 6 digits, up to 16 digits {6,16}
  • must contain 1 number
  • must contain 2 lowercase letters
  • must contain 2 uppercase letters
  • must contain 1
  • special character

  • According to the above rules, it is easy to give the definition of regular literals as follows:
var pattern = /^.*(?=.{6,16})(?=.*\d)(?=.*[A-Z]{2,})(?=.*[a-z]{2,})(?=.*[!@#$%^&*?\(\)]).*$/;
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Analysis of scenario 2

Character class.

Character class. Represents any character except newlines and other Unicode line terminators.

Forward lookahead assertion (?= )

在符号“(?=” 和 “)” 之间加入一个表达式,它就是一个先行断言,用以说明圆括号内的表达式必须正确匹配。比如: /Java(?=\:)/ 只能匹配Java且后面有冒号的。

(?=.*[!@#$%^&*?\(\)])

该先行断言表示,必须包括一个特殊字符。上述表达式中的10个特殊字符为键盘1,2...0的上档键字符,也可以添加别的特殊字符。注意:如果添加字符是正则表达式中具有特殊含义的,需要在符号前加反斜线(\)转义。

方案2测试

给出测试结果如下:

var pattern = /^.*(?=.{6,16})(?=.*\d)(?=.*[A-Z]{2,})(?=.*[a-z]{2,})(?=.*[!@#$%^&*?\(\)]).*$/;
pattern.test('du42DU!') = true;
pattern.test('duDUd!') = false;
pattern.test('42dud!') = false;
pattern.test('42DUD!') = false;
pattern.test('42duDU') = false;
pattern.test('42duU(') = false;
pattern.test('42dUU!') = false;
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