WEBVTT 00:01.590 --> 00:11.450 We can use the Linux command, see harsh mod or change more to change permissions of the file or folder. 00:13.170 --> 00:19.680 Uh, this is the common thing that people use in this next year when a root user or the files owner 00:19.680 --> 00:21.460 can change permissions. 00:21.900 --> 00:28.630 In this lecture, we use a C judgment to change permission on hash. 00:28.680 --> 00:37.110 Get that he's seen that start using two different methods versus using numerical representation of permissions. 00:37.110 --> 00:39.360 And then we use a symbolic representation. 00:40.910 --> 00:48.500 Changing permissions with decimal notation, we can use a shortcut to refer now to permission by using 00:48.500 --> 00:56.030 a symbol, a single number to represent one, our double helix set of permissions. 00:56.480 --> 01:01.730 So like everything underlying the operating system, the permissions are represented in binary. 01:02.090 --> 01:07.250 So on and off switches are represented by one and zero, respectively. 01:08.150 --> 01:14.060 You can think of the RW X permissions on a string on off switches. 01:14.060 --> 01:23.480 So when all the emissions are granted, this equates in a one on one in binary and binary sit like this 01:23.480 --> 01:32.000 is them, then easily represented as one digit by converting it into a octal and each digit number system 01:32.000 --> 01:35.400 that starts with zero and ensuites seven. 01:36.230 --> 01:46.160 So and this represents a set of three binary digits, meaning we can represent an entire W P R W, except 01:46.160 --> 01:48.290 with one just the one digit. 01:48.520 --> 01:55.780 Uh, this can be zero one two three four five six seven eight seven, actually. 01:55.810 --> 01:57.200 Lastly, 7.8. 01:57.860 --> 01:58.970 So um. 02:02.670 --> 02:09.000 Here I will create a table here for a better understanding here. 02:09.420 --> 02:14.640 So in binary and here this is the binary here. 02:15.490 --> 02:17.910 Uh, octal, octal. 02:17.940 --> 02:23.030 And I will show you here is our W X. 02:24.720 --> 02:25.820 Our top picks. 02:26.320 --> 02:36.480 So the binary is zero, if binary zero zero zero octal is zero smell and RW, it's not read on or write 02:36.480 --> 02:37.710 nor execute yet. 02:38.640 --> 02:43.980 So if binary zero zero one here okodili, there's going to be one. 02:44.160 --> 02:46.550 And this can be not really. 02:46.560 --> 02:49.890 It's not right, but execute executable here. 02:50.400 --> 03:01.050 If binary is zero one zero and octal is two, then this means this is them not readable but readable 03:01.050 --> 03:03.330 and not executable here. 03:04.380 --> 03:10.830 And if binary zero one one and octal is three, then this means. 03:12.940 --> 03:22.000 This is not readable, but rewritable here and executable, if binary is one zero zero. 03:22.620 --> 03:24.880 And this man in octal for. 03:26.440 --> 03:27.010 So. 03:28.230 --> 03:34.650 This means this is not treated, is sexual readable, not rewritable, nor executable. 03:35.700 --> 03:44.340 And if there is one zero one, this means in Oakdale is five here and this is readable. 03:45.010 --> 03:47.010 Um, this is readable. 03:47.250 --> 03:48.180 Not right. 03:48.180 --> 03:50.520 Bill and executable here. 03:50.520 --> 03:52.260 And so readable. 03:52.440 --> 03:54.450 Not readable and executable. 03:55.620 --> 03:59.130 And here we have six and seven. 03:59.130 --> 04:09.000 Lastly, one one zero equals just six in October by a system here, and this is the readable writable 04:09.450 --> 04:10.770 executable here. 04:11.220 --> 04:20.360 But if the binary is one three one one one one, and this means in Oakdale, we have seven here. 04:21.070 --> 04:24.130 Um, and this is readable, right? 04:24.150 --> 04:26.490 Well and executable as well. 04:27.360 --> 04:31.380 So using this information, let's go through some examples. 04:31.980 --> 04:39.030 First, if you want to set only the read permission, we called off the table and look at the value 04:39.450 --> 04:39.990 for it. 04:39.990 --> 04:42.120 For example, this is the read permission. 04:42.820 --> 04:44.190 And this is the fourth. 04:44.580 --> 04:53.280 We can declare this using four or just read, write, execute, or we can declare it in binary. 04:53.640 --> 05:00.450 Next, if we want to set permission to write and execute, we could use the same methodology and look 05:00.450 --> 05:08.300 for what's said and what sets the W and what system is which is executable and write about. 05:09.180 --> 05:15.120 So as you can see here, no, we have our W X here. 05:15.570 --> 05:18.430 So we want just write about the exhibit unexcusable. 05:18.480 --> 05:21.000 And as you can see in Oakdale, this is them. 05:21.690 --> 05:22.080 Three. 05:22.740 --> 05:24.720 So the binary zero one one. 05:26.020 --> 05:26.440 So. 05:29.930 --> 05:35.540 Now we can, um, pass an argument here is a very short comment. 05:36.050 --> 05:36.620 Come in. 05:36.890 --> 05:43.700 So for example, let's, uh, create a new file or fear here of the Cuban section. 05:43.850 --> 05:44.210 OK. 05:44.860 --> 05:45.890 Uh, for example. 05:47.650 --> 05:51.810 Torch here, uh, it's um. 05:52.060 --> 05:53.160 Oh, what's? 05:54.590 --> 05:55.940 Polls while. 05:57.710 --> 06:00.710 Unless there, as you can see here, we create except for. 06:01.170 --> 06:02.830 While this is not enough. 06:03.350 --> 06:05.850 This has not incited any thing. 06:05.870 --> 06:08.690 There's just a file with zero lights here. 06:09.050 --> 06:21.140 So let's declare Ellis L.A. As you can see here, we have example file here, which is created by county. 06:21.740 --> 06:30.510 So let's cheng this permission to, uh uh, let's see how much seven seven four hash, actually. 06:31.260 --> 06:32.960 Example file. 06:34.820 --> 06:40.940 Unless L.A. and as you can see here, we changed these permissions it. 06:42.690 --> 06:43.080 So. 06:47.820 --> 06:58.640 Uh, you shall see R W here, R W X R W E S R e r on the left side of the this example file. 06:59.060 --> 07:04.430 So this confirms that that is, uh, see how someone can successfully change permission on the file 07:04.610 --> 07:10.160 to give the both the owner and the group ability to execute the file. 07:28.690 --> 07:36.610 So Europe's use of permission to protect users or groups files and directories from other users in the 07:36.610 --> 07:40.870 system can be used for offensive and defensive purposes. 07:41.380 --> 07:42.600 Little no, no. 07:43.120 --> 07:48.760 Now know how to manage these permissions and how to exploit weak points in the security system. 07:49.150 --> 07:51.680 In particular, Estudiantes guided.