pass=${pass:‐123456}

这是一个在Bash脚本中的语句，它的作用是将变量pass的值设置为-123456。在这个语句中，pass是一个变量，:是一个分隔符，-123456是要赋给pass变量的值。
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相关问题

给下面这段代码加上加盐处理<?php $user = $_POST['username']; $pass = $_POST['password']; if($user && $pass){ $db = new PDO('mysql:host=localhost;dbname=php_wish', 'root', 'root'); $pre = $db->prepare('select * from user where username=:user limit 1'); $pre->execute(['user' => $user]); if($pre->rowCount() > 0){ echo "用户已存在！<br>"; echo "<a href='reg.php'>返回注册页</a>"; } else{ $pre = $db->prepare('insert into user (username, password) values (:user, :pass)'); $pre->execute(['user' => $user, 'pass' => $pass]); echo "注册成功！<br>"; echo "<a href='login.php'>前往登录页</a>"; // print_r($pre->errorInfo()); } } else { echo "注册失败！<br>"; echo "<a href='reg.php'>返回注册页</a>"; }

好的，以下是加盐处理后的代码：

$user = $_POST['username'];
$pass = $_POST['password'];

if($user && $pass){
    $db = new PDO('mysql:host=localhost;dbname=php_wish', 'root', 'root');
    $pre = $db->prepare('select * from user where username=:user limit 1');
    $pre->execute(['user' => $user]);
    if($pre->rowCount() > 0){
        echo "用户已存在！<br>";
        echo "<a href='reg.php'>返回注册页</a>";
    }
    else{
        // 加盐处理
        $salt = '123456'; // 自定义盐值
        $password = md5($pass . $salt); // 加盐后的密码
        $pre = $db->prepare('insert into user (username, password, salt) values (:user, :pass, :salt)');
        $pre->execute(['user' => $user, 'pass' => $password, 'salt' => $salt]);
        
        echo "注册成功！<br>";
        echo "<a href='login.php'>前往登录页</a>";
        // print_r($pre->errorInfo());
    }
}
else {
    echo "注册失败！<br>";
    echo "<a href='reg.php'>返回注册页</a>";
}

在这里，我们加入了加盐处理，即在用户输入的密码后面加上一个自定义的盐值（在这里使用了字符串“123456”作为盐值），然后再对该字符串进行 MD5 加密，最终得到加盐后的密码。同时，我们还在数据库中增加了一个字段“salt”，用于保存盐值，以备后续验证时使用。这样，即使黑客获取了数据库中的密码信息，由于不知道盐值，也无法轻易地破解出用户的真实密码。

start_addr=0x05877000 #end_addr=0x3ffff000 end_addr=0x05877002 data_write=0x55AA55AA data_read=$(printf "%08x" $data_write) count=0 match_count=0 for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do echo $data_write | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') #percent=$(echo "scale=2; ($addr - $start_addr) * 100 / ($end_addr - $start_addr)" | bc) # echo -ne "Writing: $percent%\r" done # echo $data for ((addr=$start_addr; addr<$end_addr; addr+=4)); do data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') if [ "$data_write" == "$data_read" ]; then match_count=$((match_count+1)) fi count=$((count+1)) # percent=$(echo "scale=2; $count * 100 / (($end_addr - $start_addr) / 4)" | bc) # echo -ne "Reading: $percent%\r" done #echo $data echo $data_read echo $data_write 如果data_read=55aa55aa，data_write=0x55AA55AA,那么该如何修改程序才能让程序输出PASS

要让程序输出PASS，需要将match_count与count进行比较。如果它们相等，说明所有写入的数据都被正确地读回，程序就可以输出PASS。因此，可以在第一个循环中，将写入数据的值改为data_read，即：

echo $data_read | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul

然后，在第二个循环中，添加一个判断语句，如果match_count等于count，则输出PASS，如下所示：

if [ $match_count -eq $count ]; then
    echo "PASS"
fi

完整代码如下：

start_addr=0x05877000
end_addr=0x3ffff000
data_write=0x55AA55AA
data_read=$(printf "%08x" $data_write)
count=0
match_count=0

for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do
    echo $data_read | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul
done

for ((addr=$start_addr; addr<$end_addr; addr+=4)); do
    data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"')
    if [ "$data_read" == "$data" ]; then
        match_count=$((match_count+1))
    fi
    count=$((count+1))
done

if [ $match_count -eq $count ]; then
    echo "PASS"
fi