[Libguestfs] [PATCH nbdkit v2 2/6] main: Tighten up characters permitted in config keys.

[Richard W.M. Jones]

On Sat, Sep 08, 2018 at 04:05:45PM -0500, Eric Blake wrote:
> On 09/08/2018 03:15 AM, Richard W.M. Jones wrote:
> >Previously key=value on the command line allowed the key to be pretty
> >much anything that didn't contain an '=' character.  Even empty
> >strings were permitted.
> >
> >This tightens up the permitted keys so they must contain only ASCII
> >alphanumeric, period, underscore or dash characters, and must not be
> >an empty string.
> 
> Do we want to further restrict things to start with a letter or
> underscore (and not a dot, digit, or dash)?
> 
> >---
> >  docs/nbdkit-plugin.pod | 18 ++++++++++--------
> >  src/main.c             | 32 +++++++++++++++++++++++++++++++-
> >  2 files changed, 41 insertions(+), 9 deletions(-)
> >
> 
> >+static int
> >+is_config_key (const char *key, size_t len)
> >+{
> >+  const char allowed[] =
> >+    "abcdefghijklmnopqrstuvwxyz"
> >+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
> >+    "0123456789"
> >+    "._-";
> >+  size_t i;
> >+
> >+  if (key[0] == '\0')

Also this bit is wrong :-(

> >+    return 0;
> >+
> >+  for (i = 0; i < len; ++i) {
> >+    if (strchr (allowed, key[i]) == NULL)
> 
> Why not use strspn and checking against the length, instead of
> rolling an O(n^2) algorithm yourself?  The libc version might have
> optimizations to run faster, although the speed of this loop is
> probably in the noise.

Will post v3 in a moment.

Rich.

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