On Monday, 9 January 2017 15:16:46 CET Peter Krempa wrote:
When connecting as root, the "hostsfile" variable would be NULL due to the code leading to this point. This would result into a crash when attempting to set the known hosts file path.
Almost: the issue happens generally when known_hosts does not exist. Considering the following code in src/rpc/virnetclient.c (both virNetClientNewLibSSH2 and virNetClientNewLibssh have it): if (confdir) { if (!knownHostsPath) { if (virFileExists(confdir)) { virBufferAsprintf(&buf, "%s/known_hosts", confdir); if (!(knownhosts = virBufferContentAndReset(&buf))) goto no_memory; } } else { if (VIR_STRDUP(knownhosts, knownHostsPath) < 0) goto cleanup; } } knownHostsPath is left NULL if known_hosts is not passed as parameter, and either one of: a) confdir is NULL: reading virGetUserConfigDirectory (actually, virGetXDGDirectory) this happens only when XDG_CONFIG_HOME is not set, and neither is HOME b) confdir is not NULL, but it does not exist Regarding (a), there is no other "fix" doable within virNetClient itself, since all the ways to determine the user home failed (and thus no path can be determined). Regarding (b), IMHO virNetClient could drop the virFileExists check, letting the libssh and libssh2 drivers to handle: - libssh seems to handle a non-existing file fine, creating its directories and the file itself on its own when saving - the libssh2 already checks whether the file exists, using it only in that case
To avoid deviating from the approach taken in the libssh2 driver set the file to /dev/null so that all entries are discarded unless explicitly specified.
While this works (ssh_write_knownhost should handle /dev as existing already), IMHO it's better to make the libssh driver behave more close to the libssh2, i.e. setting knownHostsFile only when considered valid. What about the attached patch instead? -- Pino Toscano