Bug 235647

Summary: pam_verror & pam_vinfo may cause segmentation fault
Product: Base System Reporter: hoomanfazaeli
Component: miscAssignee: freebsd-bugs (Nobody) <bugs>
Status: New ---    
Severity: Affects Many People CC: des
Priority: ---    
Version: CURRENT   
Hardware: Any   
OS: Any   

Description hoomanfazaeli 2019-02-10 17:59:51 UTC
The pam_verror may cause segmentation fault.

Consider the following scenario:

1. A service module (for instance, pam_unix) calls PAM_VERBOSE_ERROR.
   That macro expands to _pam_verbose_error call.

2. _pam_verbose_error calls pam_verror if the PAM_SILENT flag is not 
  set on the PAM handle and no_warn option is not set for the service 

3. pam_verror allocates 'char *rsp' on stack w/o initializing it to NULL,
   (a dangling pointer), and makes 
   pam_vprompt(pamh, PAM_ERROR_MSG, &rsp, fmt, ap) call. 

4. Now if the the PAM conversation is NULL, pam_vprompt soon returns 
   w/ PAM_SYSTEM_ERR and __does not__ set *rsp. 

5. pam_verror then does FREE(rsp) and if rsp happens to be anything other 
   than NULL, a segmentation fault happens.
Comment 1 hoomanfazaeli 2019-02-10 18:03:37 UTC
The very same bug exists in pam_vinfo.