Bug 1934

Summary: mac_init() calls HMAC_Init() without previously having called HMAC_CTX_init().
Product: Portable OpenSSH Reporter: Robert Dugal <rdugal>
Component: MiscellaneousAssignee: Assigned to nobody <unassigned-bugs>
Status: CLOSED FIXED    
Severity: normal CC: djm
Priority: P2    
Version: 5.8p1   
Hardware: All   
OS: All   
Bug Depends on:    
Bug Blocks: 1930    
Attachments:
Description Flags
macinit.diff dtucker: ok+

Description Robert Dugal 2011-09-08 00:00:50 AEST 
I have been doing some work with OpenSSH 5.8p1, attempting to use an alternative engine for crypto. In mac.c, the function mac_init() calls HMAC_Init() without previously having called HMAC_CTX_init(). However, OpenSSL documentation states that HMAC_CTX_init() is mandatory.

See http://www.openssl.org/docs/crypto/hmac.html

HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_init() must have been called before the first use of an HMAC_CTX in this function. N.B. HMAC_Init() had this undocumented  behaviour in previous versions of OpenSSL - failure to switch to  HMAC_Init_ex() in programs that expect it will cause them to stop working.

While this appears to currently cause no issues with OpenSSH 5.8p1 using OpenSSL 1.0.0d and the default crypto engine, it may cause problems (such as segfaults in my case) when attempting to use an alternative engine.
Comment 1 Damien Miller 2011-12-02 11:27:12 AEDT 
Created attachment 2110 [details]
macinit.diff

insert HMAC_CTX_init
Comment 2 Damien Miller 2011-12-02 11:44:15 AEDT 
patch applied - will be in openssh-6.0. Thanks!
Comment 3 Damien Miller 2015-08-11 23:02:20 AEST 
Set all RESOLVED bugs to CLOSED with release of OpenSSH 7.1