[PATCH] SecureSocket: use fallback function if bit_length is not available in Python

[Jan Tluka]

Recently added SecureSocket feature brought dependency on Python 2.7
namely bit_length() method. Since we need to keep compatibility with
Python 2.6 that's on RHEL6 I added a fallback if bit_length is not
available. I compared the DH_GROUP and SRP_GROUP dicts both on Python2.6
and 2.7 and they had the same content (bit length), so this patch should
be safe.

Fixes issue 166.

Signed-off-by: Jan Tluka 
---
 lnst/Common/SecureSocket.py | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/lnst/Common/SecureSocket.py b/lnst/Common/SecureSocket.py
index b4ee8af..734d448 100644
--- a/lnst/Common/SecureSocket.py
+++ b/lnst/Common/SecureSocket.py
@@ -34,12 +34,23 @@ DH_GROUP = {"p": int("0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1"\
                      "15728E5A8AACAA68FFFFFFFFFFFFFFFF", 16),
             "g": 2}

+# to support both Python2.6 and 2.7, use following workaround to count
+# the bit length of a number; note that the workaround does not work for
+# value 0 but we don't use it for such value
+def bit_length(i):
+    try:
+        int(1).bit_length()
+    except AttributeError:
+        return len(bin(i)) - 2
+
+    return i.bit_length()
+
 DH_GROUP["q"] = (DH_GROUP["p"]-1)/2
-DH_GROUP["q_size"] = DH_GROUP["q"].bit_length()/8
-if DH_GROUP["q"].bit_length()%8:
+DH_GROUP["q_size"] = bit_length(DH_GROUP["q"])/8
+if bit_length(DH_GROUP["q"])%8:
     DH_GROUP["q_size"] += 1
-DH_GROUP["p_size"] = DH_GROUP["p"].bit_length()/8
-if DH_GROUP["p"].bit_length()%8:
+DH_GROUP["p_size"] = bit_length(DH_GROUP["p"])/8
+if bit_length(DH_GROUP["p"])%8:
     DH_GROUP["p_size"] += 1

SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
@@ -55,11 +66,11 @@ SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
              "g": 2}

SRP_GROUP["q"] = (SRP_GROUP["p"]-1)/2
-SRP_GROUP["q_size"] = SRP_GROUP["q"].bit_length()/8
-if SRP_GROUP["q"].bit_length()%8:
+SRP_GROUP["q_size"] = bit_length(SRP_GROUP["q"])/8
+if bit_length(SRP_GROUP["q"])%8:
     SRP_GROUP["q_size"] += 1
-SRP_GROUP["p_size"] = SRP_GROUP["p"].bit_length()/8
-if SRP_GROUP["p"].bit_length()%8:
+SRP_GROUP["p_size"] = bit_length(SRP_GROUP["p"])/8
+if bit_length(SRP_GROUP["p"])%8:
     SRP_GROUP["p_size"] += 1

class SecSocketException(Exception):

[Ondrej Lichtner]

On Wed, Mar 16, 2016 at 03:16:43PM +0100, Jan Tluka wrote:
> Recently added SecureSocket feature brought dependency on Python 2.7
> namely bit_length() method. Since we need to keep compatibility with
> Python 2.6 that's on RHEL6 I added a fallback if bit_length is not
> available. I compared the DH_GROUP and SRP_GROUP dicts both on Python2.6
> and 2.7 and they had the same content (bit length), so this patch should
> be safe.
>
> Fixes issue 166.
> Signed-off-by: Jan Tluka
>
> lnst/Common/SecureSocket.py | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/lnst/Common/SecureSocket.py b/lnst/Common/SecureSocket.py
> index b4ee8af..734d448 100644
> --- a/lnst/Common/SecureSocket.py
> +++ b/lnst/Common/SecureSocket.py
> @@ -34,12 +34,23 @@ DH_GROUP = {"p": int("0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1"\
>                       "15728E5A8AACAA68FFFFFFFFFFFFFFFF", 16),
>              "g": 2}
>
> +# to support both Python2.6 and 2.7, use following workaround to count
> +# the bit length of a number; note that the workaround does not work for
> +# value 0 but we don't use it for such value

What do you mean it doesn't work for 0? when I try it i get bit length 1
which seems fine to me.
> +def bit_length(i):
> try:
>    int(1).bit_length()
> except AttributeError:
>    return len(bin(i)) - 2
> return i.bit_length()

Why not:
try:
    return i.bit_length()
except:
    return len(bin(i)) - 2
> DH_GROUP["q"] = (DH_GROUP["p"]-1)/2
> -DH_GROUP["q_size"] = DH_GROUP["q"].bit_length()/8
> -if DH_GROUP["q"].bit_length()%8:
> +DH_GROUP["q_size"] = bit_length(DH_GROUP["q"])/8
> +if bit_length(DH_GROUP["q"])%8:
>      DH_GROUP["q_size"] += 1
> -DH_GROUP["p_size"] = DH_GROUP["p"].bit_length()/8
> -if DH_GROUP["p"].bit_length()%8:
> +DH_GROUP["p_size"] = bit_length(DH_GROUP["p"])/8
> +if bit_length(DH_GROUP["p"])%8:
>      DH_GROUP["p_size"] += 1
>
> SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
> @@ -55,11 +66,11 @@ SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
>               "g": 2}
>
> SRP_GROUP["q"] = (SRP_GROUP["p"]-1)/2
> -SRP_GROUP["q_size"] = SRP_GROUP["q"].bit_length()/8
> -if SRP_GROUP["q"].bit_length()%8:
> +SRP_GROUP["q_size"] = bit_length(SRP_GROUP["q"])/8
> +if bit_length(SRP_GROUP["q"])%8:
>      SRP_GROUP["q_size"] += 1
> -SRP_GROUP["p_size"] = SRP_GROUP["p"].bit_length()/8
> -if SRP_GROUP["p"].bit_length()%8:
> +SRP_GROUP["p_size"] = bit_length(SRP_GROUP["p"])/8
> +if bit_length(SRP_GROUP["p"])%8:
>      SRP_GROUP["p_size"] += 1
> class SecSocketException(Exception):
>
> 2.4.3
> _______________________________________________
> LNST-developers mailing list
> [e-mail]
> https://lists.fedorahosted.org/admin/lists/[e-mail]...

[Ondrej Lichtner]

On Mon, Mar 21, 2016 at 11:11:51AM +0100, Ondrej Lichtner wrote:
> On Wed, Mar 16, 2016 at 03:16:43PM +0100, Jan Tluka wrote:
> > Recently added SecureSocket feature brought dependency on Python 2.7
> > namely bit_length() method. Since we need to keep compatibility with
> > Python 2.6 that's on RHEL6 I added a fallback if bit_length is not
> > available. I compared the DH_GROUP and SRP_GROUP dicts both on Python2.6
> > and 2.7 and they had the same content (bit length), so this patch should
> > be safe.
> >
> > Fixes issue 166.
> > Signed-off-by: Jan Tluka
> >
> > lnst/Common/SecureSocket.py | 27 +++++++++++++++++++--------
> >  1 file changed, 19 insertions(+), 8 deletions(-)
> >
> > diff --git a/lnst/Common/SecureSocket.py b/lnst/Common/SecureSocket.py
> > index b4ee8af..734d448 100644
> > --- a/lnst/Common/SecureSocket.py
> > +++ b/lnst/Common/SecureSocket.py
> > @@ -34,12 +34,23 @@ DH_GROUP = {"p": int("0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1"\
> >                       "15728E5A8AACAA68FFFFFFFFFFFFFFFF", 16),
> >              "g": 2}
> >
> > +# to support both Python2.6 and 2.7, use following workaround to count
> > +# the bit length of a number; note that the workaround does not work for
> > +# value 0 but we don't use it for such value
>
> What do you mean it doesn't work for 0? when I try it i get bit length 1
> which seems fine to me.

Ah, never mind, the bit_length() method returns 0 for 0... so the
branches return different lengths for 0...
Ok, keep the comment, you're right... we won't be using this for 0
> > +def bit_length(i):
> > try:
> >    int(1).bit_length()
> > except AttributeError:
> >    return len(bin(i)) - 2
> > return i.bit_length()
>
> Why not:
> try:
>     return i.bit_length()
> except:
>     return len(bin(i)) - 2
> > DH_GROUP["q"] = (DH_GROUP["p"]-1)/2
> > -DH_GROUP["q_size"] = DH_GROUP["q"].bit_length()/8
> > -if DH_GROUP["q"].bit_length()%8:
> > +DH_GROUP["q_size"] = bit_length(DH_GROUP["q"])/8
> > +if bit_length(DH_GROUP["q"])%8:
> >      DH_GROUP["q_size"] += 1
> > -DH_GROUP["p_size"] = DH_GROUP["p"].bit_length()/8
> > -if DH_GROUP["p"].bit_length()%8:
> > +DH_GROUP["p_size"] = bit_length(DH_GROUP["p"])/8
> > +if bit_length(DH_GROUP["p"])%8:
> >      DH_GROUP["p_size"] += 1
> >
> > SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
> > @@ -55,11 +66,11 @@ SRP_GROUP = {"p": int("0xAC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC"
> >               "g": 2}
> >
> > SRP_GROUP["q"] = (SRP_GROUP["p"]-1)/2
> > -SRP_GROUP["q_size"] = SRP_GROUP["q"].bit_length()/8
> > -if SRP_GROUP["q"].bit_length()%8:
> > +SRP_GROUP["q_size"] = bit_length(SRP_GROUP["q"])/8
> > +if bit_length(SRP_GROUP["q"])%8:
> >      SRP_GROUP["q_size"] += 1
> > -SRP_GROUP["p_size"] = SRP_GROUP["p"].bit_length()/8
> > -if SRP_GROUP["p"].bit_length()%8:
> > +SRP_GROUP["p_size"] = bit_length(SRP_GROUP["p"])/8
> > +if bit_length(SRP_GROUP["p"])%8:
> >      SRP_GROUP["p_size"] += 1
> > class SecSocketException(Exception):
> >
> > 2.4.3
> > _______________________________________________
> > LNST-developers mailing list
> > [e-mail]
> > https://lists.fedorahosted.org/admin/lists/[e-mail]...
>
> LNST-developers mailing list
> [e-mail]
> https://lists.fedorahosted.org/admin/lists/[e-mail]...

[Jan Tluka]

Mon, Mar 21, 2016 at 11:11:51AM CET, [e-mail] wrote:
> On Wed, Mar 16, 2016 at 03:16:43PM +0100, Jan Tluka wrote:
> > Recently added SecureSocket feature brought dependency on Python 2.7
> > namely bit_length() method. Since we need to keep compatibility with
> > Python 2.6 that's on RHEL6 I added a fallback if bit_length is not
> > available. I compared the DH_GROUP and SRP_GROUP dicts both on Python2.6
> > and 2.7 and they had the same content (bit length), so this patch should
> > be safe.
> >
> > Fixes issue 166.
> > Signed-off-by: Jan Tluka
> >
> > +def bit_length(i):
> > try:
> >    int(1).bit_length()
> > except AttributeError:
> >    return len(bin(i)) - 2
> > return i.bit_length()
>
> Why not:
> try:
>    return i.bit_length()
> except:
>    return len(bin(i)) - 2

Ok, will resend with this fix.

-Jan