Re: [Qemu-devel] [PATCH 06/18] block/ssh: Propagate errors through check_host_key()

["Richard W.M. Jones" <rjones@redhat.com>]

On Tue, May 13, 2014 at 06:02:40PM +0200, Markus Armbruster wrote:
> Cc: "Richard W.M. Jones" <rjones@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

>  block/ssh.c | 68 ++++++++++++++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 49 insertions(+), 19 deletions(-)
> 
> diff --git a/block/ssh.c b/block/ssh.c
> index e38d232..1df1946 100644
> --- a/block/ssh.c
> +++ b/block/ssh.c
> @@ -106,6 +106,31 @@ static void ssh_state_free(BDRVSSHState *s)
>      }
>  }
>  
> +static void GCC_FMT_ATTR(3, 4)
> +session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
> +{
> +    va_list args;
> +    char *msg;
> +
> +    va_start(args, fs);
> +    msg = g_strdup_vprintf(fs, args);
> +    va_end(args);
> +
> +    if (s->session) {
> +        char *ssh_err;
> +        int ssh_err_code;
> +
> +        /* This is not an errno.  See <libssh2.h>. */
> +        ssh_err_code = libssh2_session_last_error(s->session,
> +                                                  &ssh_err, NULL, 0);
> +        error_setg(errp, "%s: %s (libssh2 error code: %d)",
> +                   msg, ssh_err, ssh_err_code);
> +    } else {
> +        error_setg(errp, "%s", msg);
> +    }
> +    g_free(msg);
> +}
> +
>  /* Wrappers around error_report which make sure to dump as much
>   * information from libssh2 as possible.
>   */
> @@ -242,7 +267,7 @@ static void ssh_parse_filename(const char *filename, QDict *options,
>  }
>  
>  static int check_host_key_knownhosts(BDRVSSHState *s,
> -                                     const char *host, int port)
> +                                     const char *host, int port, Error **errp)
>  {
>      const char *home;
>      char *knh_file = NULL;
> @@ -256,14 +281,15 @@ static int check_host_key_knownhosts(BDRVSSHState *s,
>      hostkey = libssh2_session_hostkey(s->session, &len, &type);
>      if (!hostkey) {
>          ret = -EINVAL;
> -        session_error_report(s, "failed to read remote host key");
> +        session_error_setg(errp, s, "failed to read remote host key");
>          goto out;
>      }
>  
>      knh = libssh2_knownhost_init(s->session);
>      if (!knh) {
>          ret = -EINVAL;
> -        session_error_report(s, "failed to initialize known hosts support");
> +        session_error_setg(errp, s,
> +                           "failed to initialize known hosts support");
>          goto out;
>      }
>  
> @@ -288,21 +314,23 @@ static int check_host_key_knownhosts(BDRVSSHState *s,
>          break;
>      case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
>          ret = -EINVAL;
> -        session_error_report(s, "host key does not match the one in known_hosts (found key %s)",
> -                             found->key);
> +        session_error_setg(errp, s,
> +                      "host key does not match the one in known_hosts"
> +                      " (found key %s)", found->key);
>          goto out;
>      case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
>          ret = -EINVAL;
> -        session_error_report(s, "no host key was found in known_hosts");
> +        session_error_setg(errp, s, "no host key was found in known_hosts");
>          goto out;
>      case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
>          ret = -EINVAL;
> -        session_error_report(s, "failure matching the host key with known_hosts");
> +        session_error_setg(errp, s,
> +                      "failure matching the host key with known_hosts");
>          goto out;
>      default:
>          ret = -EINVAL;
> -        session_error_report(s, "unknown error matching the host key with known_hosts (%d)",
> -                             r);
> +        session_error_setg(errp, s, "unknown error matching the host key"
> +                      " with known_hosts (%d)", r);
>          goto out;
>      }
>  
> @@ -357,20 +385,20 @@ static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
>  
>  static int
>  check_host_key_hash(BDRVSSHState *s, const char *hash,
> -                    int hash_type, size_t fingerprint_len)
> +                    int hash_type, size_t fingerprint_len, Error **errp)
>  {
>      const char *fingerprint;
>  
>      fingerprint = libssh2_hostkey_hash(s->session, hash_type);
>      if (!fingerprint) {
> -        session_error_report(s, "failed to read remote host key");
> +        session_error_setg(errp, s, "failed to read remote host key");
>          return -EINVAL;
>      }
>  
>      if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
>                             hash) != 0) {
> -        error_report("remote host key does not match host_key_check '%s'",
> -                     hash);
> +        error_setg(errp, "remote host key does not match host_key_check '%s'",
> +                   hash);
>          return -EPERM;
>      }
>  
> @@ -378,7 +406,7 @@ check_host_key_hash(BDRVSSHState *s, const char *hash,
>  }
>  
>  static int check_host_key(BDRVSSHState *s, const char *host, int port,
> -                          const char *host_key_check)
> +                          const char *host_key_check, Error **errp)
>  {
>      /* host_key_check=no */
>      if (strcmp(host_key_check, "no") == 0) {
> @@ -388,21 +416,21 @@ static int check_host_key(BDRVSSHState *s, const char *host, int port,
>      /* host_key_check=md5:xx:yy:zz:... */
>      if (strncmp(host_key_check, "md5:", 4) == 0) {
>          return check_host_key_hash(s, &host_key_check[4],
> -                                   LIBSSH2_HOSTKEY_HASH_MD5, 16);
> +                                   LIBSSH2_HOSTKEY_HASH_MD5, 16, errp);
>      }
>  
>      /* host_key_check=sha1:xx:yy:zz:... */
>      if (strncmp(host_key_check, "sha1:", 5) == 0) {
>          return check_host_key_hash(s, &host_key_check[5],
> -                                   LIBSSH2_HOSTKEY_HASH_SHA1, 20);
> +                                   LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp);
>      }
>  
>      /* host_key_check=yes */
>      if (strcmp(host_key_check, "yes") == 0) {
> -        return check_host_key_knownhosts(s, host, port);
> +        return check_host_key_knownhosts(s, host, port, errp);
>      }
>  
> -    error_report("unknown host_key_check setting (%s)", host_key_check);
> +    error_setg(errp, "unknown host_key_check setting (%s)", host_key_check);
>      return -EINVAL;
>  }
>  
> @@ -541,8 +569,10 @@ static int connect_to_ssh(BDRVSSHState *s, QDict *options,
>      }
>  
>      /* Check the remote host's key against known_hosts. */
> -    ret = check_host_key(s, host, port, host_key_check);
> +    ret = check_host_key(s, host, port, host_key_check, &err);
>      if (ret < 0) {
> +        qerror_report_err(err);
> +        error_free(err);
>          goto err;
>      }
>  
> -- 
> 1.8.1.4

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/