angler-fishThe Vulnerability History Project

CVE-2012-1101
aka Systemd Service Overload

A vulnerability in the Debian OS allowed a user to abuse a command within systemctl to create an arbitrary entry into the Linux systems service manager. By overloading the service list, the manager would fail during the login/boot phase of Debian resulting in a denial of service.


In the original bug report from 2011, the systemd maintainer (Lennart Poettering) responded to the report that the behavior reported was actually the intent. At the time, it was used to spawn new servicesin correct execution order. However, they had not considered the possibility that incorrectly specifying services names and overloading the unit list would result in a DOS. This was an error in two parts. The first was in the design of the command. By allowing non-existant services, they were planning for this behavior. Second, the complete lack of input handling allows attackers to spam the command with garbage/fake service names and crash the system. The fix for this bug was to implement proper garbage collection of unused services. This is done on unit (service) load. The fix removes bad/fake services at runtime in order to prevent DOS.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
CVE: CVE-2012-1101
CWE: 184
ipc:
  note: "When the OS command is called with an unknown (fake) service, that fake service
    name is appended the \nsystemctl service list. \n"
  answer: true
  question: |
    Did the feature that this vulnerability affected use inter-process
    communication? IPC includes OS signals, pipes, stdin/stdout, message
    passing, and clipboard. Writing to files that another program in this
    software system reads is another form of IPC.

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
bugs:
- https://bugzilla.redhat.com/show_bug.cgi?id=680122
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=662029
- https://bugzilla.redhat.com/show_bug.cgi?id=799902
i18n:
  note: "There was a loss of integrity of services in systemctl since fake services
    could\nspawned resulting in a lack of clarity of which services are legitiimate.
    This \nvulnerability also resulted in a lack of availability due to denial of
    service.\nThere was no impact in any internationalization features.\n"
  answer: false
  question: |
    Was the feature impacted by this vulnerability about internationalization
    (i18n)?

    An internationalization feature is one that enables people from all
    over the world to use the system. This includes translations, locales,
    typography, unicode, or various other features.

    Answer should be true or false
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
vccs:
- note: Automatically found by archeogit
  commit: 9a46fc3b9014de1bf0ed1f3004a536b08a19ebb3
- note: 
  commit: 
fixes:
- note: Mentioned in NVD
  commit: 9a46fc3b9014de1bf0ed1f3004a536b08a19ebb3
vouch:
  note: There are no discussions or posts available about conversation related to
    the bug fix.
  answer: false
  question: "Was there any part of the fix that involved one person vouching for \nanother's
    work?\n\nThis can include:\n  * signing off on a commit message\n  * mentioning
    a discussion with a colleague checking the work\n  * upvoting a solution on a
    pull request\n\nAnswer must be true or false.\nWrite a note about how you came
    to the conclusions you did, regardless of what your answer was.\n"
bounty:
  amt: 
  url: 
  announced: 
lessons:
  yagni:
    note: 
    applies: 
  question: |
    Are there any common lessons we have learned from class that apply to this
    vulnerability? In other words, could this vulnerability serve as an example
    of one of those lessons?

    Leave "applies" blank or put false if you did not see that lesson (you do
    not need to put a reason). Put "true" if you feel the lesson applies and put
    a quick explanation of how it applies.

    Don't feel the need to claim that ALL of these apply, but it's pretty likely
    that one or two of them apply.

    If you think of another lesson we covered in class that applies here, feel
    free to give it a small name and add one in the same format as these.
  serial_killer:
    note: 
    applies: 
  complex_inputs:
    note: 
    applies: 
  distrust_input:
    note: |
      In this case, the OS command was built under the impression that the user would also enter the correct
      service name. If it was taken into account to handle for incorrect or unknown services, this vulnerability wouldn't
      have occured.
    applies: true
  least_privilege:
    note: 
    applies: 
  native_wrappers:
    note: 
    applies: 
  defense_in_depth:
    note: 
    applies: 
  secure_by_default:
    note: 
    applies: 
  environment_variables:
    note: 
    applies: 
  security_by_obscurity:
    note: 
    applies: 
  frameworks_are_optional:
    note: 
    applies: 
reviews: []
sandbox:
  note: |
    An un-authorized and unprivileged user can abuse the vulnerability to increase the services list with
    fake services. This isn't even allowed by the root user - therefore getting around all access control.
  answer: true
  question: "Did this vulnerability violate a sandboxing feature that the system\nprovides?
    \n\nA sandboxing feature is one that allows files, users, or other features \nlimited
    access. Vulnerabilities that violate sandboxes are usually based on \naccess control,
    checking privileges incorrectly, path traversal, and the \nlike.\n\nAnswer should
    be true or false\nWrite a note about how you came to the conclusions you did,
    regardless of\nwhat your answer was.\n"
upvotes: 7
CWE_note: 
mistakes:
  answer: "In the original bug report from 2011, the systemd maintainer (Lennart Poettering)
    \nresponded to the report that the behavior reported was actually the intent.
    \nAt the time, it was used to spawn new servicesin correct execution order. However,
    \nthey had not considered the possibility that incorrectly specifying services
    names\nand overloading the unit list would result in a DOS. This was an error
    in two parts. \nThe first was in the design of the command. By allowing non-existant
    services, they \nwere planning for this behavior. Second, the complete lack of
    input handling allows \nattackers to spam the command with garbage/fake service
    names and crash the system. \nThe fix for this bug was to implement proper garbage
    collection of unused services. \nThis is done on unit (service) load. The fix
    removes bad/fake services at runtime\nin order to prevent DOS.\n"
  question: "In your opinion, after all of this research, what mistakes were made
    that\nled to this vulnerability? Coding mistakes? Design mistakes?\nMaintainability?
    Requirements? Miscommunications?\n\nThere can, and usually are, many mistakes
    behind a vulnerability.\n\nRemember that mistakes can come in many forms:\n* slip:
    failing to complete a properly planned step due to inattention\n          e.g.
    wrong key in the ignition\n          e.g. using < instead of <=\n* lapse: failing
    to complete a properly planned step due to memory failure\n          e.g. forgetting
    to put car in reverse before backing up\n          e.g. forgetting to check null\n*
    planning error: error that occurs when the plan is inadequate\n          e.g.
    getting stuck in traffic because you didn’t consider the \n               impact
    of the bridge closing\n          e.g. calling the wrong method\n          e.g.
    using a poor design\n\nThese are grey areas, of course. But do your best to analyze
    the mistakes \naccording to this framework.\n\nLook at the CWE entry for this
    vulnerability and examine the mitigations\nthey have written there. Are they doing
    those? Does the fix look proper?\n\nWrite a thoughtful entry here that people
    in the software engineering\nindustry would find interesting.\n"
nickname: Systemd Service Overload
subsystem:
  name: systemctl
  note: 
  question: "What subsystems was the mistake in? These are subsystems WITHIN systemd\n\nTwo
    areas to look:\n  - Bug labels\n  - Directory names\n\nLook at the path of the
    source code files code that were fixed to get\ndirectory names. Look at comments
    in the code. Look at the bug reports how\nthe bug report was tagged. \n\nExample
    systemd subsystems are:\n  * fsck\n  * apparmor\n  * fstab\n  * sd-daemon\n\nName
    should be:\n  * all lowercase English letters\n  * NOT a specific file\n  * can
    have digits, and _-@/\n\nCan be multiple subsystems involved, in which case you
    can make it an array\ne.g.\n    name: [\"subsystemA\", \"subsystemB\"] # ok\n
    \   name: subsystemA # also ok\n"
discovered:
  answer: "The vulnerability was originally reported as a bug in https://bugzilla.redhat.com/show_bug.cgi?id=680122#c0.
    \nIt was found when a developer accidentally typed in an incorrect service name
    into systemctl and noticed that instead of\ngiving an error message, it actually
    spawned a new service with the incorrect name. The same bug was then re-reported
    in\n2012 as a vulnerability, but at that time the bug had already been fixed.\n"
  contest: false
  question: |
    How was this vulnerability discovered?

    Go to the bug report and read the conversation to find out how this was
    originally found. Answer in longform below in "answer", fill in the date in
    YYYY-MM-DD, and then determine if the vulnerability was found by a Google
    employee (you can tell from their email address). If it's clear that the
    vulenrability was discovered by a contest, fill in the name there.

    The automated, contest, and developer flags can be true, false, or nil.

    If there is no evidence as to how this vulnerability was found, then please
    explain where you looked.
  automated: false
  developer: true
discussion:
  note: https://bugzilla.redhat.com/show_bug.cgi?id=680122#c1
  question: "Was there any discussion surrounding this?\n\nA discussion can include
    debates, disputes, or polite talk about how to \nresolve uncertainty.\n\nExample
    include:\n  * Is this out of our scope?\n  * Is this a security?\n  * How should
    we fix this?\n\nJust because you see multiple comments doesn't mean it's a discussion.
    \nFor example:\n  * \"Fix line 10\". \"Ok\" is not what we call a discussion\n
    \ * \"Ping\" (reminding people)\n\nCheck the bugs reports, pull requests, and
    mailing lists archives.\n\nThese answers should be boolean.\n  discussed_as_security:
    true or false\n  any_discussion: true or false\n\nPut any links to disagreements
    you found in the notes section, or any other\ncomment you want to make.\n"
  any_discussion: true
  discussed_as_security: false
stacktrace:
  note: |
    A small stack trace was included in a bug report comment. It included that the crash (resulting from the vulnerability)
    occured in the initilizer function for systemctl. The fix for the bug was included in a separate file (unit.c)
  question: "Are there any stacktraces in the bug reports? \n\nSecondly, if there
    is a stacktrace, is the fix in the same file that the \nstacktrace points to?
    \n\nIf there are no stacktraces, then both of these are false - but be sure to\nmention
    where you checked in the note.\n\nAnswer must be true or false.\nWrite a note
    about how you came to the conclusions you did, regardless of\nwhat your answer
    was.\n"
  any_stacktraces: true
  stacktrace_with_fix: false
description: "A vulnerability in the Debian OS allowed a user to abuse a command within
  \nsystemctl to create an arbitrary entry into the Linux systems service manager.
  By overloading the service list, \nthe manager would fail during the login/boot
  phase of Debian resulting in a denial of service.\n"
unit_tested:
  fix: false
  code: false
  question: |
    Were automated unit tests involved in this vulnerability?
    Was the original code unit tested, or not unit tested? Did the fix involve
    improving the automated tests?

    For code: and fix: - your answer should be boolean.

    For the code_answer below, look not only at the fix but the surrounding
    code near the fix in related directories and determine if and was there were
    unit tests involved for this subsystem.

    For the fix_answer below, check if the fix for the vulnerability involves
    adding or improving an automated test to ensure this doesn't happen again.
  fix_answer: No tests were updated along with the bug fix
  code_answer: No tests were done on the original functionality.
reported_date: '2011-02-24'
specification:
  note: There were no reported specification violations reported.
  answer: false
  instructions: |
    Is there mention of a violation of a specification? For example, the POSIX
    spec, an RFC spec, a network protocol spec, or some other requirements
    specification.

    Be sure to check the following artifacts for this:
      * bug reports
      * security advisories
      * commit message
      * pull request
      * mailing lists
      * anything else

    The answer field should be boolean. In answer_note, please explain
    why you come to that conclusion.
announced_date: '2012-03-05'
curation_level: 1
published_date: '2020-03-11'
forgotten_check:
  note: In this case, the developers forgot to check to ensure that the entered service
    actually existed.
  answer: true
  question: "Does the fix for the vulnerability involve adding a forgotten check?\n\nA
    \"forgotten check\" can mean many things. It often manifests as the fix \ninserting
    an entire if-statement or a conditional to an existing \nif-statement. Or a call
    to a method that checks something.\n\nExample of checks can include:\n  * null
    pointer checks\n  * check the current role, e.g. root\n  * boundary checks for
    a number\n  * consult file permissions\n  * check a return value\n\nAnswer must
    be true or false.\nWrite a note about how you came to the conclusions you did,
    regardless of\nwhat your answer was.\n"
CWE_instructions: |
  Please go to http://cwe.mitre.org and find the most specific, appropriate CWE
  entry that describes your vulnerability. We recommend going to
  https://cwe.mitre.org/data/definitions/699.html for the Software Development
  view of the vulnerabilities. We also recommend the tool
  http://www.cwevis.org/viz to help see how the classifications work.

  If you have anything to note about why you classified it this way, write
  something in CWE_note. This field is optional.

  Just the number here is fine. No need for name or CWE prefix. If more than one
  apply here, then place them in an array like this
    CWE: ["123", "456"] # this is ok
    CWE: [123, 456]     # also ok
    CWE: 123            # also ok
autodiscoverable:
  note: "This vulnerability behaves similar to that of buffer overflow. Simply by
    repetetively calling\nthe OS command which had the vulnerability, you could overflow
    the maximum memory of the services list\nand crash the system resulting in a DOS.
    No knowledge of the domain would have been required - just \npure brute forcing.\n"
  answer: true
  instructions: |
    Is it plausible that a fully automated tool could have discovered
    this? These are tools that require little knowledge of the domain,
     e.g. automatic static analysis, compiler warnings, fuzzers.

    Examples for true answers: SQL injection, XSS, buffer overflow

    In systemd, the actually use OZZ Fuzz. If there's a link to it, add it here.

    Examples for false: RFC violations, permissions issues, anything
    that requires the tool to be "aware" of the project's
    domain-specific requirements.

    The answer field should be boolean. In answer_note, please explain
    why you come to that conclusion.
vcc_instructions: "The vulnerability-contributing commits.\n\nThese are found by our
  tools by traversing the Git Blame history, where we \ndetermine which commit(s)
  introduced the functionality. \n\nLook up these VCC commits and verify that they
  are not simple refactorings, \nand that they are, in fact introducing the vulnerability
  into the system. \nOften, introducing the file or function is where the VCC is,
  but VCCs can be \nanything. \n\nPlace any notes you would like to make in the notes
  field.\n"
bugs_instructions: "What bugs and/or pull requests are involved in this vulnerability?
  \n\nFor systemd, this is typically their GitHub issues, but could also include \nbugs
  from other databases. Put a URL instead of a single number.\n"
yaml_instructions: |
  =================
  ===YAML Primer===
  =================
  This is a dictionary data structure, akin to JSON.
  Everything before a colon is a key, and the values here are usually strings
  For one-line strings, you can just use quotes after the colon
  For multi-line strings, as we do for our instructions, you put a | and then
  indent by two spaces

  For readability, we hard-wrap multi-line strings at 80 characters. This is
  not absolutely required, but appreciated.
fixes_instructions: "Please put the commit hash in \"commit\" below.\n\nThis must
  be a git commit hash from the systemd source repo, a  40-character \nhexademical
  string/\n\nPlace any notes you would like to make in the notes field.\n"
bounty_instructions: |
  If you came across any indications that a bounty was paid out for this
  vulnerability, fill it out here. Or correct it if the information already here
  was wrong. Otherwise, leave it blank.
interesting_commits:
  commits:
  - note: don't recheck conditions when a unit is already starting but unit_start()
      is invoked
    commit: a82e5507a6e03766957d43ca8818112ae9766288
  - note: fix unit when trying to load unit instances for uninstanciable types
    commit: 796ba5549416b8a2c037da1d40fa76cb1a53f5df
  question: |
    Are there any interesting commits between your VCC(s) and fix(es)?

    Use this to specify any commits you think are notable in some way, and
    explain why in the note.
order_of_operations:
  note: "The fix was completed by adding the loaded unit (service) to a garbage collector
    queue to \ncleanup unused or non-existent services.\n"
  answer: false
  question: "Does the fix for the vulnerability involve correcting an order of \noperations?\n\nThis
    means the fix involves moving code around or changing the order of \nhow things
    are done. \n\nAnswer must be true or false.\nWrite a note about how you came to
    the conclusions you did, regardless of\nwhat your answer was.\n"
curated_instructions: "If you are manually editing this file, then you are \"curating\"
  it. \n\nSet the version number that you were given in the instructions. \n \nThis
  will enable additional editorial checks on this file to make sure you \nfill everything
  out properly. If you are a student, we cannot accept your work\nas finished unless
  curated is properly updated. \n"
upvotes_instructions: |
  For the first round, ignore this upvotes number.

  For the second round of reviewing, you will be giving a certain amount of
  upvotes to each vulnerability you see. Your peers will tell you how
  interesting they think this vulnerability is, and you'll add that to the
  upvotes score on your branch.
nickname_instructions: |
  A catchy name for this vulnerability that would draw attention it.
  If the report mentions a nickname, use that.
  Must be under 30 characters. Optional.
reported_instructions: |
  What date was the vulnerability reported to the security team? Look at the
  security bulletins and bug reports. It is not necessarily the same day that
  the CVE was created.  Leave blank if no date is given.

  Please enter your date in YYYY-MM-DD format.
announced_instructions: |
  Was there a date that this vulnerability was announced to the world? You can
  find this in changelogs, blogs, bug reports, or perhaps the CVE date.

  This is not the same as published date in the NVD - that is below.

  Please enter your date in YYYY-MM-DD format.
published_instructions: |
  Is there a published fix or patch date for this vulnerability?
  Please enter your date in YYYY-MM-DD format.
description_instructions: |
  You can get an initial description from the CVE entry on cve.mitre.org. These
  descriptions are a fine start, but they can be kind of jargony.

  Rewrite this description IN YOUR OWN WORDS. Make it interesting and easy to
  read to anyone with some programming experience. We can always pull up the NVD
  description later to get more technical.

  Try to still be specific in your description, but remove project-specific
  stuff. Remove references to versions, specific filenames, and other jargon
  that outsiders to this project would not understand. Technology like "regular
  expressions" is fine, and security phrases like "invalid write" are fine to
  keep too.

  Your target audience is people just like you before you took any course in
  security

See a mistake? Is something missing from our story? We welcome contributions! All of our work is open-source and version-controlled on GitHub. You can curate using our Curation Wizard.

Use our Curation Wizard

Or go to GitHub

  • There are no articles here... yet

Timeline

Hover over an event to see its title.
Click on the event to learn more.
Filter by event type with the buttons below.

expand_less