CWE-593: Authentication Bypass: OpenSSL CTX Object Modified after SSL Objects are Created
Authentication Bypass: OpenSSL CTX Object Modified after SSL Objects are Created
Weakness ID: 593 (Weakness Variant)
Status: Draft
Description
Description Summary
The software modifies the SSL context after connection creation
has begun.
Extended Description
If the program modifies the SSL_CTX object after creating SSL objects from
it, there is the possibility that older SSL objects created from the
original context could all be affected by that change.
Time of Introduction
Architecture and Design
Implementation
Common Consequences
Scope
Effect
Authentication
No authentication takes place in this process, bypassing an assumed
protection of encryption.
Confidentiality
The encrypted communication between a user and a trusted host may be
subject to a "man in the middle" sniffing attack.
Demonstrative Examples
Example 1
(Bad Code)
C
#define CERT "secret.pem"
#define CERT2 "secret2.pem"
int main(){
SSL_CTX *ctx;
SSL *ssl;
init_OpenSSL();
seed_prng();
ctx = SSL_CTX_new(SSLv23_method());
if (SSL_CTX_use_certificate_chain_file(ctx, CERT) != 1)
int_error("Error loading certificate from file");
if (SSL_CTX_use_PrivateKey_file(ctx, CERT, SSL_FILETYPE_PEM)
!= 1)
int_error("Error loading private key from file");
if (!(ssl = SSL_new(ctx)))
int_error("Error creating an SSL context");
if ( SSL_CTX_set_default_passwd_cb(ctx, "new default password"
!= 1))
int_error("Doing something which is dangerous to do
anyways");
if (!(ssl2 = SSL_new(ctx)))
int_error("Error creating an SSL context");
}
Potential Mitigations
Phase
Description
Architecture and Design
Use a language which provides a cryptography framework at a higher
level of abstraction.
Implementation
Most SSL_CTX functions have SSL counterparts that act on SSL-type
objects.
Implementation
Applications should set up an SSL_CTX completely, before creating SSL
objects from it.
Description
