Why gets is unsafe

The platform is listed along with how frequently the given weakness appears for that instance. Languages C Undetermined Prevalence.

Common Consequences. This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list.

For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact. Likelihood Of Exploit.

Demonstrative Examples. Example 1 The code below calls gets to read information into a buffer. Example Language: C. Potential Mitigations. Phases: Implementation; Requirements Ban the use of dangerous functions.

Use their safe equivalent. Weakness Ordinalities. Ordinality Description Primary. This information is often useful in understanding where a weakness fits within the context of external information sources. Taxonomy Mappings. Thomas Owens Thomas Owens k 94 94 gold badges silver badges bronze badges. It's actually not gcc which warns, it's the glibc which contains a pragma or attribute on gets that causes the compiler to emit a warning when used.

Why is gets dangerous The first internet worm the Morris Internet Worm escaped about 30 years ago , and it used gets and a buffer overflow as one of its methods of propagating from system to system. You should forget you ever heard that gets existed. Alternatives to gets fgets As everyone else said, the canonical alternative to gets is fgets specifying stdin as the file stream. Recommended practice 6 The fgets function allows properly-written programs to safely process input lines too long to store in the result array.

Jonathan Leffler Jonathan Leffler k gold badges silver badges bronze badges. In many cases, you will want to read-and-discard these characters. I wonder why they didn't add an fgets alternative that allows one to use its functionality without having to make a silly strlen call. For example, an fgets variant which returned the number of bytes read into the string would make it easy for code to see if the last byte read was a newline. If the behavior of passing a null pointer for the buffer was defined as "read and discard up to n-1 bytes until the next newline", that would allow code to easily discard the tail of over-length lines.

The nearest approach to that is probably POSIX getline and its relative getdelim , which do return the length of the 'line' read by the commands, allocating space as required to be able to store the whole line. Even that can cause problems if you end up with a single-line JSON file that is multiple gigabytes in size; can you afford all that memory? And while we're at it, can we have strcpy and strcat variants that return a pointer to the null byte at the end?

Are you hacking stackoverflow to get upvotes? Show 10 more comments. The function is unsafe because it assumes consistent input. Jack Jack k 27 27 gold badges silver badges bronze badges. I've no clue about the fgets part though.

In that case, if hardware is incapable of submitting lines over bytes long it might be justifiable to gets into a byte buffer, though I would think the advantages of being able to specify a shorter buffer when expecting smaller input would more than justify the cost. Such a pattern would make it possible for code to pass an arbitrary substring not just the tail of another string without having to copy anything, and would allow methods like gets and strcat to safely accept as much as will fit.

Show 4 more comments. But this also has its problems such as: extra characters entered by the user will be picked up the next time around. Actually, the original C99 standard did not explicitly deprecate gets either in section 7. There isn't even a footnote on it being dangerous. But C11 did remove it from the standard — and not before time!

Thiago Silveira Thiago Silveira 4, 4 4 gold badges 25 25 silver badges 29 29 bronze badges. This is the reason that one reference gives: Reading a line that overflows the array pointed to by s results in undefined behavior. Gerd Klima Gerd Klima 1, 10 10 silver badges 14 14 bronze badges. WOOHOO You'll be happy to know that the committee just voted unanimously, as it turns out to remove gets from the draft as well.

It is excellent that it is being removed from the standard. However, most implementations will provide it as a 'now non-standard extension' for at least the next 20 years, because of backwards compatibility. I just made up the -std parameter — pmg. Yu Hao Yu Hao k 42 42 gold badges silver badges bronze badges. This is a nuisance of course because when you want to write some shitty code you generally also want to do it as quickly as possible and with minimal brainpower usage.

I hope the implementations will stop at just the warnings. Aradhana Mohanty Aradhana Mohanty 69 1 1 silver badge 4 4 bronze badges. Note that the real danger is not in being able to crash your program, but in being able to make it run arbitrary code.

In general, exploiting undefined behavior. Thank you. Steve Summit Steve Summit This is still a nuisance of course because when you want to write some shitty code you generally also want to do it as quickly as possible and with minimal brainpower usage.

The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? This script is used to scan the survival host in the network, which is usually used automatically in the CMDB.

The principle of judging whether it is the Linux host is like this Since the Linux Article main: Dismissal, Site, Web, List, Item, File level, do not throw an exception when you use the "object name" that does not exist. Expressed as follows: spwebservice. Programmer All technical sharing website that all programmers love.