CWE-697: Incorrect Comparison
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Edit Custom FilterThe product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses.
This Pillar covers several possibilities:
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.
This table shows the weaknesses and high level categories that are related to this
weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to
similar items that may exist at higher and lower levels of abstraction. In addition,
relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user
may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
The different Modes of Introduction provide information
about how and when this
weakness may be introduced. The Phase identifies a point in the life cycle at which
introduction
may occur, while the Note provides a typical scenario related to introduction during the
given
phase.
This listing shows possible areas for which the given
weakness could appear. These
may be for specific named Languages, Operating Systems, Architectures, Paradigms,
Technologies,
or a class of such platforms. The platform is listed along with how frequently the given
weakness appears for that instance.
Languages Class: Not Language-Specific (Undetermined Prevalence) Technologies Class: Not Technology-Specific (Undetermined Prevalence) Example 1 Consider an application in which Truck objects are defined to be the same if they have the same make, the same model, and were manufactured in the same year. (bad code)
Example Language: Java
public class Truck {
private String make;
private String model; private int year; public boolean equals(Object o) { if (o == null) return false;
if (o == this) return true; if (!(o instanceof Truck)) return false; Truck t = (Truck) o; return (this.make.equals(t.getMake()) && this.model.equals(t.getModel())); Here, the equals() method only checks the make and model of the Truck objects, but the year of manufacture is not included. Example 2 This example defines a fixed username and password. The AuthenticateUser() function is intended to accept a username and a password from an untrusted user, and check to ensure that it matches the username and password. If the username and password match, AuthenticateUser() is intended to indicate that authentication succeeded. (bad code)
Example Language: C
/* Ignore CWE-259 (hard-coded password) and CWE-309 (use of password system for authentication) for this example. */
char *username = "admin"; char *pass = "password"; int AuthenticateUser(char *inUser, char *inPass) { if (strncmp(username, inUser, strlen(inUser))) { }logEvent("Auth failure of username using strlen of inUser"); }return(AUTH_FAIL); if (! strncmp(pass, inPass, strlen(inPass))) { logEvent("Auth success of password using strlen of inUser"); }return(AUTH_SUCCESS); else { logEvent("Auth fail of password using sizeof"); }return(AUTH_FAIL); int main (int argc, char **argv) {
int authResult; }if (argc < 3) { ExitError("Usage: Provide a username and password"); }authResult = AuthenticateUser(argv[1], argv[2]); if (authResult == AUTH_SUCCESS) { DoAuthenticatedTask(argv[1]); }else { ExitError("Authentication failed"); }In AuthenticateUser(), the strncmp() call uses the string length of an attacker-provided inPass parameter in order to determine how many characters to check in the password. So, if the attacker only provides a password of length 1, the check will only examine the first byte of the application's password before determining success. As a result, this partial comparison leads to improper authentication (CWE-287). Any of these passwords would still cause authentication to succeed for the "admin" user: (attack code)
p
pa pas pass This significantly reduces the search space for an attacker, making brute force attacks more feasible. The same problem also applies to the username, so values such as "a" and "adm" will succeed for the username. While this demonstrative example may not seem realistic, see the Observed Examples for CVE entries that effectively reflect this same weakness.
This MemberOf Relationships table shows additional CWE Categories and Views that
reference this weakness as a member. This information is often useful in understanding where a
weakness fits within the context of external information sources.
Research Gap Weaknesses related to this Pillar appear to be under-studied, especially with respect to classification schemes. Input from academic and other communities could help identify and resolve gaps or organizational difficulties within CWE. Maintenance
This entry likely has some relationships with case sensitivity (CWE-178), but case sensitivity is a factor in other types of weaknesses besides comparison. Also, in cryptography, certain attacks are possible when certain comparison operations do not take place in constant time, causing a timing-related information leak (CWE-208).
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