Use of getlogin() in Multithreaded Application
Weakness ID: 558 (Weakness Variant)Status: Draft
+ Description

Description Summary

The application uses the getlogin() function in a multithreaded context, potentially causing it to return incorrect values.

Extended Description

The getlogin() function returns a pointer to a string that contains the name of the user associated with the calling process. The function is not reentrant, meaning that if it is called from another process, the contents are not locked out and the value of the string can be changed by another process. This makes it very risky to use because the username can be changed by other processes, so the results of the function cannot be trusted.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Demonstrative Examples

Example 1

The following code relies on getlogin() to determine whether or not a user is trusted. It is easily subverted.

(Bad Code)
Example Language: C 
pwd = getpwnam(getlogin());
if (isTrustedGroup(pwd->pw_gid)) {
allow();
} else {
deny();
}
+ Potential Mitigations

Using names for security purposes is not advised. Names are easy to forge and can have overlapping user IDs, potentially causing confusion or impersonation.

Use getlogin_r() instead, which is reentrant, meaning that other processes are locked out from changing the username.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class227Failure to Fulfill API Contract ('API Abuse')
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory557Concurrency Issues
Development Concepts (primary)699
ChildOfWeakness BaseWeakness Base663Use of a Non-reentrant Function in an Unsynchronized Context
Research Concepts (primary)1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsOften Misused: Authentication
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
Anonymous Tool Vendor (under NDA)Externally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable Platforms, Description, Relationships, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative Examples, Taxonomy Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Misused Authentication: getlogin()
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