Support Python 3 in the crda build system (Take 2)

Support Python 3 in the crda build system (Take 2)

[ahmed.taahir]

Updated Intro:

This patchset takes into account helpful comments by Stefan.  The user
can now set the make variable BUILD_PYTHON to select which interpreter
runs key2pub.py.

key2pub.py is further simplified as well.

Original Intro:

crda's build system is one of the last packages with a hard dep on
python-2.7 on my Gentoo system.  This patchset adapts the utility
script 'key2pub.py' so that it will run under either Python 2.7 or
Python 3.x.  The main change is a switch from using M2Crypto to
PyCrypto, specifically for Python 3.x support.

In addition, Gentoo had a small collection of bugfix patches that were
applied every time someone installed crda.  I've included those that
seemed to have general applicability, as described in Patch 2.

[PATCH 1/2] Support python 3 in utils/key2pub.py.

[ahmed.taahir]

From: Taahir Ahmed <ahmed.taahir@gmail.com>

utils/key2pub.py can now be run under either python 2.7 or python 3.x.
This required some minor syntactical changes as well as switching from
M2Crypto to pycrypto, since M2Crypto doesn't support python 3.x.

The generate source files have been renamed to keys-*.h, to prevent a
pattern rule from attempting to build the generated file.

In addition, some errors in the generated source file keys-ssl.h are
fixed:

  * The correct OpenSSL header for BN_ULONG is included.

  * The generated constants are given the 'ull' suffix to prevent
    warnings about constants that are too large.
---
 Makefile         |  14 ++--
 reglib.c         |   4 +-
 utils/key2pub.py | 195 +++++++++++++++++++++++++++----------------------------
 3 files changed, 106 insertions(+), 107 deletions(-)
 mode change 100755 => 100644 utils/key2pub.py

diff --git a/Makefile b/Makefile
index a3ead30..4ce900c 100644
--- a/Makefile
+++ b/Makefile
@@ -25,6 +25,10 @@ UDEV_RULE_DIR?=/lib/udev/rules.d/
 PUBKEY_DIR?=pubkeys
 RUNTIME_PUBKEY_DIR?=/etc/wireless-regdb/pubkeys
 
+# Handle for the user to change the python interpreter that runs
+# utils/key2pub.py.  Python 2.7 and 3.x are supported.
+BUILDTIME_PYTHON ?= python
+
 CFLAGS += -O2 -fpic
 CFLAGS += -std=gnu99 -Wall -Werror -pedantic
 CFLAGS += -Wall -g
@@ -42,13 +46,13 @@ ifeq ($(USE_OPENSSL),1)
 CFLAGS += -DUSE_OPENSSL -DPUBKEY_DIR=\"$(RUNTIME_PUBKEY_DIR)\" `pkg-config --cflags openssl`
 LDLIBS += `pkg-config --libs openssl`
 
-$(LIBREG): keys-ssl.c
+$(LIBREG): keys-ssl.h
 
 else
 CFLAGS += -DUSE_GCRYPT
 LDLIBS += -lgcrypt
 
-$(LIBREG): keys-gcrypt.c
+$(LIBREG): keys-gcrypt.h
 
 endif
 MKDIR ?= mkdir -p
@@ -109,10 +113,10 @@ $(REG_BIN):
 	$(NQ)
 	$(Q) exit 1
 
-keys-%.c: utils/key2pub.py $(wildcard $(PUBKEY_DIR)/*.pem)
+keys-%.h: utils/key2pub.py $(wildcard $(PUBKEY_DIR)/*.pem)
 	$(NQ) '  GEN ' $@
 	$(NQ) '  Trusted pubkeys:' $(wildcard $(PUBKEY_DIR)/*.pem)
-	$(Q)./utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
+	$(Q) $(BUILDTIME_PYTHON) utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
 
 $(LIBREG): regdb.h reglib.h reglib.c
 	$(NQ) '  CC  ' $@
@@ -187,5 +191,5 @@ install: install-libreg install-libreg-headers crda crda.8.gz regdbdump.8.gz
 
 clean:
 	$(Q)rm -f $(LIBREG) crda regdbdump intersect db2rd optimize \
-		*.o *~ *.pyc keys-*.c *.gz \
+		*.o *~ *.pyc keys-*.h *.gz \
 	udev/$(UDEV_LEVEL)regulatory.rules udev/regulatory.rules.parsed
diff --git a/reglib.c b/reglib.c
index e00e9b8..aecff96 100644
--- a/reglib.c
+++ b/reglib.c
@@ -31,11 +31,11 @@
 #include "reglib.h"
 
 #ifdef USE_OPENSSL
-#include "keys-ssl.c"
+#include "keys-ssl.h"
 #endif
 
 #ifdef USE_GCRYPT
-#include "keys-gcrypt.c"
+#include "keys-gcrypt.h"
 #endif
 
 int debug = 0;
diff --git a/utils/key2pub.py b/utils/key2pub.py
old mode 100755
new mode 100644
index 3e84cd2..d6adefe
--- a/utils/key2pub.py
+++ b/utils/key2pub.py
@@ -1,126 +1,118 @@
 #!/usr/bin/env python
 
+import io
 import sys
 try:
-       from M2Crypto import RSA
-except ImportError, e:
-       sys.stderr.write('ERROR: Failed to import the "M2Crypto" module: %s\n' % e.message)
-       sys.stderr.write('Please install the "M2Crypto" Python module.\n')
-       sys.stderr.write('On Debian GNU/Linux the package is called "python-m2crypto".\n')
-       sys.exit(1)
-
-def print_ssl_64(output, name, val):
-    while val[0] == '\0':
-        val = val[1:]
-    while len(val) % 8:
-        val = '\0' + val
-    vnew = []
-    while len(val):
-        vnew.append((val[0], val[1], val[2], val[3], val[4], val[5], val[6], val[7]))
-        val = val[8:]
-    vnew.reverse()
-    output.write('static BN_ULONG %s[%d] = {\n' % (name, len(vnew)))
-    idx = 0
-    for v1, v2, v3, v4, v5, v6, v7, v8 in vnew:
-        if not idx:
-            output.write('\t')
-        output.write('0x%.2x%.2x%.2x%.2x%.2x%.2x%.2x%.2x, ' % (ord(v1), ord(v2), ord(v3), ord(v4), ord(v5), ord(v6), ord(v7), ord(v8)))
-        idx += 1
-        if idx == 2:
-            idx = 0
-            output.write('\n')
-    if idx:
-        output.write('\n')
-    output.write('};\n\n')
-
-def print_ssl_32(output, name, val):
-    while val[0] == '\0':
-        val = val[1:]
-    while len(val) % 4:
-        val = '\0' + val
-    vnew = []
-    while len(val):
-        vnew.append((val[0], val[1], val[2], val[3], ))
-        val = val[4:]
-    vnew.reverse()
-    output.write('static BN_ULONG %s[%d] = {\n' % (name, len(vnew)))
-    idx = 0
-    for v1, v2, v3, v4 in vnew:
-        if not idx:
-            output.write('\t')
-        output.write('0x%.2x%.2x%.2x%.2x, ' % (ord(v1), ord(v2), ord(v3), ord(v4)))
-        idx += 1
-        if idx == 4:
-            idx = 0
-            output.write('\n')
-    if idx:
-        output.write('\n')
-    output.write('};\n\n')
+    from Crypto.PublicKey import RSA
+except ImportError as e:
+    sys.stderr.write('ERROR: Failed to import the "Crypto.PublicKey" module: %s\n' % e.message)
+    sys.stderr.write('Please install the "Crypto.PublicKey" Python module.\n')
+    sys.stderr.write('On Debian GNU/Linux the package is called "python-crypto".\n')
+    sys.exit(1)
+
+def bitwise_collect(value, radix_bits):
+    words = []
+    radix_mask = (1 << radix_bits) - 1
+    while value != 0:
+        words.append(value & radix_mask)
+        value >>= radix_bits
+    return words
+
+def print_c_table(words, bits_per_word):
+    # 4 bits per hex char.
+    chars_per_word = bits_per_word // 4
+
+    # If the word size is not a multiple of four (surely impossible) round up.
+    if bits_per_word % 4:
+        chars_per_word += 1
+
+    # 2 chars for the 0x, 2 chars for the 'ul'
+    chars_per_literal = chars_per_word + 4
+
+    # 2 chars for the trailing ', '
+    chars_per_field = chars_per_literal + 2
+
+    # How many fields fit on an 80 char line (with leading tab).
+    fields_per_line = (80 - 8) // chars_per_field
+
+    for i in range(len(words)):
+
+        if i % fields_per_line == 0:
+            if i != 0:
+                output.write(u', ')
+            output.write(u'\n\t')
+        else:
+            output.write(u', ')
+
+        output.write(u'0x{0:0{1}x}ul'.format(words[i], chars_per_word))
+
+    output.write(u'\n')
 
 def print_ssl(output, name, val):
+    output.write(u'#include <stdint.h>\n')
+    output.write(u'#include <openssl/bn.h>\n')
+
     import struct
-    output.write('#include <stdint.h>\n')
     if len(struct.pack('@L', 0)) == 8:
-        return print_ssl_64(output, name, val)
+        bits_per_word = 64
     else:
-        return print_ssl_32(output, name, val)
+        bits_per_word = 32
+
+    # OpenSSL expects 'wordbit'-bit words given least-significant-word first.
+    vwords = bitwise_collect(val, bits_per_word)
+
+    output.write(u'static BN_ULONG {}[] = {{'.format(name))
+    print_c_table(vwords, bits_per_word)
+    output.write(u'};\n\n')
 
 def print_ssl_keys(output, n):
-    output.write(r'''
+    output.write(u'''
 struct pubkey {
-	struct bignum_st e, n;
+        struct bignum_st e, n;
 };
 
-#define KEY(data) {				\
-	.d = data,				\
-	.top = sizeof(data)/sizeof(data[0]),	\
+#define KEY(data) {                          \\
+        .d = data,                           \\
+        .top = sizeof(data)/sizeof(data[0]), \\
 }
 
-#define KEYS(e,n)	{ KEY(e), KEY(n), }
+#define KEYS(e,n)    { KEY(e), KEY(n), }
 
 static struct pubkey keys[] = {
 ''')
-    for n in xrange(n + 1):
-        output.write('	KEYS(e_%d, n_%d),\n' % (n, n))
-    output.write('};\n')
+    for n in range(n + 1):
+        output.write(u'	KEYS(e_{0}, n_{0}),\n'.format(n))
+    output.write(u'};\n')
     pass
 
 def print_gcrypt(output, name, val):
-    output.write('#include <stdint.h>\n')
-    while val[0] == '\0':
-        val = val[1:]
-    output.write('static const uint8_t %s[%d] = {\n' % (name, len(val)))
-    idx = 0
-    for v in val:
-        if not idx:
-            output.write('\t')
-        output.write('0x%.2x, ' % ord(v))
-        idx += 1
-        if idx == 8:
-            idx = 0
-            output.write('\n')
-    if idx:
-        output.write('\n')
-    output.write('};\n\n')
+    # gcrypt expects 8-bit words most-significant-word first
+    vwords = bitwise_collect(val, 8)
+    vwords.reverse()
+
+    output.write(u'#include <stdint.h>\n')
+    output.write(u'static const uint8_t {}[] = {{'.format(name))
+    print_c_table(vwords, 8)
+    output.write(u'};\n\n')
 
 def print_gcrypt_keys(output, n):
-    output.write(r'''
+    output.write(u'''
 struct key_params {
-	const uint8_t *e, *n;
-	uint32_t len_e, len_n;
+        const uint8_t *e, *n;
+        uint32_t len_e, len_n;
 };
 
-#define KEYS(_e, _n) {			\
-	.e = _e, .len_e = sizeof(_e),	\
-	.n = _n, .len_n = sizeof(_n),	\
+#define KEYS(_e, _n) {                \\
+        .e = _e, .len_e = sizeof(_e), \\
+        .n = _n, .len_n = sizeof(_n), \\
 }
 
 static const struct key_params keys[] = {
 ''')
-    for n in xrange(n + 1):
-        output.write('	KEYS(e_%d, n_%d),\n' % (n, n))
-    output.write('};\n')
-    
+    for n in range(n + 1):
+        output.write(u'	KEYS(e_{0}, n_{0}),\n'.format(n))
+    output.write(u'};\n')
+
 
 modes = {
     '--ssl': (print_ssl, print_ssl_keys),
@@ -135,21 +127,24 @@ except IndexError:
     mode = None
 
 if not mode in modes:
-    print 'Usage: %s [%s] input-file... output-file' % (sys.argv[0], '|'.join(modes.keys()))
+    print('Usage: {} [{}] input-file... output-file'.format(sys.argv[0], '|'.join(modes.keys())))
     sys.exit(2)
 
-output = open(outfile, 'w')
+output = io.open(outfile, 'w')
+output.write(u'/* This file was generated by utils/key2pub.py. */\n\n')
 
 # load key
 idx = 0
 for f in files:
-    try:
-        key = RSA.load_pub_key(f)
-    except RSA.RSAError:
-        key = RSA.load_key(f)
 
-    modes[mode][0](output, 'e_%d' % idx, key.e[4:])
-    modes[mode][0](output, 'n_%d' % idx, key.n[4:])
+    key_contents = io.open(f, 'rb').read()
+    key = RSA.importKey(key_contents)
+
+    modes[mode][0](output, 'e_{}'.format(idx), key.e)
+    modes[mode][0](output, 'n_{}'.format(idx), key.n)
+
     idx += 1
 
 modes[mode][1](output, idx - 1)
+
+output.write(u'\n/* End output of utils/key2pub.py. */\n')
-- 
2.3.6

[PATCH 2/2] Small build system improvements.

[ahmed.taahir]

From: Taahir Ahmed <ahmed.taahir@gmail.com>

Phony targets are properly declared.

User's CFLAGS are not clobbered with '-O2 -g' unless the user has set no
cflags.
---
 Makefile | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 4ce900c..b5aa8e3 100644
--- a/Makefile
+++ b/Makefile
@@ -29,17 +29,19 @@ RUNTIME_PUBKEY_DIR?=/etc/wireless-regdb/pubkeys
 # utils/key2pub.py.  Python 2.7 and 3.x are supported.
 BUILDTIME_PYTHON ?= python
 
-CFLAGS += -O2 -fpic
+CFLAGS ?= -O2 -g
+CFLAGS += -fPIC
 CFLAGS += -std=gnu99 -Wall -Werror -pedantic
-CFLAGS += -Wall -g
 LDLIBREG += -lreg
 LDLIBS += $(LDLIBREG)
 LDLIBS += -lm
 LIBREG += libreg.so
 LDFLAGS += -L ./
 
+.PHONY: all
 all: all_noverify verify
 
+.PHONY: all_noverify
 all_noverify: $(LIBREG) crda intersect regdbdump db2rd optimize
 
 ifeq ($(USE_OPENSSL),1)
@@ -122,11 +124,13 @@ $(LIBREG): regdb.h reglib.h reglib.c
 	$(NQ) '  CC  ' $@
 	$(Q)$(CC) $(CFLAGS) $(CPPFLAGS) -o $@ -shared -Wl,-soname,$(LIBREG) $^
 
+.PHONY: install-libreg-headers
 install-libreg-headers:
 	$(NQ) '  INSTALL  libreg-headers'
 	$(Q)mkdir -p $(DESTDIR)/$(INCLUDE_DIR)
 	$(Q)cp *.h $(DESTDIR)/$(INCLUDE_DIR)/
 
+.PHONY: install-libreg
 install-libreg:
 	$(NQ) '  INSTALL  libreg'
 	$(Q)mkdir -p $(DESTDIR)/$(LIBDIR)
@@ -167,6 +171,7 @@ verify: $(REG_BIN) regdbdump
 	@$(NQ) ' GZIP' $<
 	$(Q)gzip < $< > $@
 
+.PHONY: install
 install: install-libreg install-libreg-headers crda crda.8.gz regdbdump.8.gz
 	$(NQ) '  INSTALL  crda'
 	$(Q)$(MKDIR) $(DESTDIR)/$(SBINDIR)
@@ -189,6 +194,7 @@ install: install-libreg install-libreg-headers crda crda.8.gz regdbdump.8.gz
 	$(NQ) '  INSTALL  regdbdump.8.gz'
 	$(Q)$(INSTALL) -m 644 -t $(DESTDIR)/$(MANDIR)/man8/ regdbdump.8.gz
 
+.PHONY: clean
 clean:
 	$(Q)rm -f $(LIBREG) crda regdbdump intersect db2rd optimize \
 		*.o *~ *.pyc keys-*.h *.gz \
-- 
2.3.6

Re: [PATCH 1/2] Support python 3 in utils/key2pub.py.

[jtojnar]

On Wed, 2015-07-22 at 00:21 -0500, ahmed.taahir@gmail.com wrote:
> From: Taahir Ahmed <ahmed.taahir@gmail.com>
> 
> utils/key2pub.py can now be run under either python 2.7 or python
> 3.x.
> This required some minor syntactical changes as well as switching
> from
> M2Crypto to pycrypto, since M2Crypto doesn't support python 3.x.
[...]
>  CFLAGS += -O2 -fpic
>  CFLAGS += -std=gnu99 -Wall -Werror -pedantic
>  CFLAGS += -Wall -g
> @@ -42,13 +46,13 @@ ifeq ($(USE_OPENSSL),1)
>  CFLAGS += -DUSE_OPENSSL -DPUBKEY_DIR=\"$(RUNTIME_PUBKEY_DIR)\" `pkg-
> config --cflags openssl`
>  LDLIBS += `pkg-config --libs openssl`
>  
> -$(LIBREG): keys-ssl.c
> +$(LIBREG): keys-ssl.h
>  
>  else
>  CFLAGS += -DUSE_GCRYPT
>  LDLIBS += -lgcrypt
>  
> -$(LIBREG): keys-gcrypt.c
> +$(LIBREG): keys-gcrypt.h

Changing the file names to headers appears to install them. We probably
do not want to do that either.

[...]
> -    modes[mode][0](output, 'e_%d' % idx, key.e[4:])
> -    modes[mode][0](output, 'n_%d' % idx, key.n[4:])
> +    key_contents = io.open(f, 'rb').read()
> +    key = RSA.importKey(key_contents)

It is a good practice to close opened files. It would be even better to
use context manager (i.e. `with io.open(f, 'rb') as key_file:`) since
it will close the file automatically.

Other than this the patches look good, crda builds with both Python 2
and Python 3 with the patch and produce the same keys-gcrypt.h files.
Comparing to the keys-gcrypt.c, apart from the trivial formatting
changes, the ul suffixes for numbers are the only difference.

I was not able to build crda with USE_OPENSSL=1 with or without this
patch due to a large number of compilation errors. However, the
differences between keys-ssl.c and keys-ssl.h are equivalent to the
grypt ones. Also the addition of ul suffixes fixed the overflow errors, so definitely an improvement in this case as well.

Re: [PATCH 1/2] Support python 3 in utils/key2pub.py.

[Stefan Lippers-Hollmann]

Hi

On 2015-07-21, Taahir Ahmed wrote:
> On Wednesday 22 July 2015 04:50:45 Stefan Lippers-Hollmann wrote:
> > You omit $(pwd) from ./utils/key2pub.py, while /utils/key2pub.py
> > won't exist.
> 
> Wow, that's a really bad mistake on my part.  It should indeed probably
> be './utils/key2pub.py'.  I made this change after my general testing,
> simply because emacs was undoing the execute bit every time I saved
> key2pub.py.
> 
> It's not really a material change, so I'll probably just put it back the
> way it was.
> 
> The rest of the patch is tested, I pinky-swear :)
>  
> > As little as I know about python packaging policies in Debian
> > (and probably Fedora), /usr/bin/python is never supposed to point
> > to python3 - afaik the interpreter should always be called python3
> > there, so I don't really see how that's going to work there.
> 
> I'm not assuming that the system interpreter is any particular version:
> key2pub.py has been modified so it runs under either 2.7 or 3.x.
> 
> Some more simplification might be possible if 2.7 support is dropped,
> but not much, and I didn't want to rock the boat.

The problem, as I understand it, is that the python3 interpreter will
never be available as (/usr/bin/)python on Debian (or Fedora; even if
python2.x is not installed on the system), but always be called python3. 
So your new python3 compatibility is never actually used, neither on a 
python3-only system.

Therefore I'd suggest this approach instead, either make the python
interpreter user configurable, e.g.:

PYTHON ?= python

so the user can specify the interpreter when invoking make (as in
make PYTHON=python3), xor trying to auto-detect it (untested):

ifeq ($(shell which python3),)
  PYTHON = python
else
  PYTHON = python3
endif

and then using 

$(Q) $(PYTHON) ./utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@

wherever python is needed.

Regards
	Stefan Lippers-Hollmann

Re: [PATCH 1/2] Support python 3 in utils/key2pub.py.

[Taahir Ahmed]

[-- Attachment #1: Type: text/plain, Size: 1073 bytes --]

On Wednesday 22 July 2015 04:50:45 Stefan Lippers-Hollmann wrote:
> You omit $(pwd) from ./utils/key2pub.py, while /utils/key2pub.py
> won't exist.

Wow, that's a really bad mistake on my part.  It should indeed probably
be './utils/key2pub.py'.  I made this change after my general testing,
simply because emacs was undoing the execute bit every time I saved
key2pub.py.

It's not really a material change, so I'll probably just put it back the
way it was.

The rest of the patch is tested, I pinky-swear :)
 
> As little as I know about python packaging policies in Debian
> (and probably Fedora), /usr/bin/python is never supposed to point
> to python3 - afaik the interpreter should always be called python3
> there, so I don't really see how that's going to work there.

I'm not assuming that the system interpreter is any particular version:
key2pub.py has been modified so it runs under either 2.7 or 3.x.

Some more simplification might be possible if 2.7 support is dropped,
but not much, and I didn't want to rock the boat.

Thanks for the prompt review!

Taahir

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 473 bytes --]

Re: [PATCH 1/2] Support python 3 in utils/key2pub.py.

[Stefan Lippers-Hollmann]

Hi

On 2015-07-21, ahmed.taahir@gmail.com wrote:
> From: Taahir Ahmed <ahmed.taahir@gmail.com>
> 
> utils/key2pub.py can now be run under either python 2.7 or python 3.x.
> This required some minor syntactical changes as well as switching from
> M2Crypto to pycrypto, since M2Crypto doesn't support python 3.x.
[...]
> diff --git a/Makefile b/Makefile
> index a3ead30..65fc780 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -112,7 +112,7 @@ $(REG_BIN):
>  keys-%.c: utils/key2pub.py $(wildcard $(PUBKEY_DIR)/*.pem)
>  	$(NQ) '  GEN ' $@
>  	$(NQ) '  Trusted pubkeys:' $(wildcard $(PUBKEY_DIR)/*.pem)
> -	$(Q)./utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
> +	$(Q) python /utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
[...]

Without having tested it, nor being that familiar with python coding,
but this hunk seems to be problematic on two accords.

You omit $(pwd) from ./utils/key2pub.py, while /utils/key2pub.py
won't exist.

As little as I know about python packaging policies in Debian
(and probably Fedora), /usr/bin/python is never supposed to point
to python3 - afaik the interpreter should always be called python3
there, so I don't really see how that's going to work there.

Sorry if I missed anything obvious, but these things just caught
my attention without having looked any deeper.

Regards
	Stefan Lippers-Hollmann

[PATCH 1/2] Support python 3 in utils/key2pub.py.

[ahmed.taahir]

From: Taahir Ahmed <ahmed.taahir@gmail.com>

utils/key2pub.py can now be run under either python 2.7 or python 3.x.
This required some minor syntactical changes as well as switching from
M2Crypto to pycrypto, since M2Crypto doesn't support python 3.x.

In addition, some errors in the generated source file keys-ssl.h are
fixed:

  * The correct OpenSSL header for BN_ULONG is included.

  * The generated constants are given the 'ull' suffix to prevent
    warnings about constants that are too large.
---
 Makefile         |   2 +-
 utils/key2pub.py | 146 ++++++++++++++++++++++++++++---------------------------
 2 files changed, 75 insertions(+), 73 deletions(-)

diff --git a/Makefile b/Makefile
index a3ead30..65fc780 100644
--- a/Makefile
+++ b/Makefile
@@ -112,7 +112,7 @@ $(REG_BIN):
 keys-%.c: utils/key2pub.py $(wildcard $(PUBKEY_DIR)/*.pem)
 	$(NQ) '  GEN ' $@
 	$(NQ) '  Trusted pubkeys:' $(wildcard $(PUBKEY_DIR)/*.pem)
-	$(Q)./utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
+	$(Q) python /utils/key2pub.py --$* $(wildcard $(PUBKEY_DIR)/*.pem) $@
 
 $(LIBREG): regdb.h reglib.h reglib.c
 	$(NQ) '  CC  ' $@
diff --git a/utils/key2pub.py b/utils/key2pub.py
index 3e84cd2..ff92748 100755
--- a/utils/key2pub.py
+++ b/utils/key2pub.py
@@ -1,126 +1,128 @@
 #!/usr/bin/env python
 
+import io
 import sys
 try:
-       from M2Crypto import RSA
-except ImportError, e:
-       sys.stderr.write('ERROR: Failed to import the "M2Crypto" module: %s\n' % e.message)
-       sys.stderr.write('Please install the "M2Crypto" Python module.\n')
-       sys.stderr.write('On Debian GNU/Linux the package is called "python-m2crypto".\n')
-       sys.exit(1)
+    from Crypto.PublicKey import RSA
+except ImportError as e:
+    sys.stderr.write('ERROR: Failed to import the "Crypto.PublicKey" module: %s\n' % e.message)
+    sys.stderr.write('Please install the "Crypto.PublicKey" Python module.\n')
+    sys.stderr.write('On Debian GNU/Linux the package is called "python-crypto".\n')
+    sys.exit(1)
+
+def bitwise_collect(value, radix_bits):
+    words = []
+    radix_mask = (1 << radix_bits) - 1
+    while value != 0:
+        words.append(value & radix_mask)
+        value >>= radix_bits
+    return words
 
 def print_ssl_64(output, name, val):
-    while val[0] == '\0':
-        val = val[1:]
-    while len(val) % 8:
-        val = '\0' + val
-    vnew = []
-    while len(val):
-        vnew.append((val[0], val[1], val[2], val[3], val[4], val[5], val[6], val[7]))
-        val = val[8:]
-    vnew.reverse()
-    output.write('static BN_ULONG %s[%d] = {\n' % (name, len(vnew)))
+    # OpenSSL expects 64-bit words given least-significant-word first.
+    vwords = bitwise_collect(val, 64)
+
+    output.write(u'static BN_ULONG {}[] = {{\n'.format(name))
     idx = 0
-    for v1, v2, v3, v4, v5, v6, v7, v8 in vnew:
+    for vword in vwords:
         if not idx:
-            output.write('\t')
-        output.write('0x%.2x%.2x%.2x%.2x%.2x%.2x%.2x%.2x, ' % (ord(v1), ord(v2), ord(v3), ord(v4), ord(v5), ord(v6), ord(v7), ord(v8)))
+            output.write(u'\t')
+        output.write(u'0x{:016x}ULL, '.format(vword))
         idx += 1
         if idx == 2:
             idx = 0
-            output.write('\n')
+            output.write(u'\n')
     if idx:
-        output.write('\n')
-    output.write('};\n\n')
+        output.write(u'\n')
+    output.write(u'};\n\n')
 
 def print_ssl_32(output, name, val):
-    while val[0] == '\0':
-        val = val[1:]
-    while len(val) % 4:
-        val = '\0' + val
-    vnew = []
-    while len(val):
-        vnew.append((val[0], val[1], val[2], val[3], ))
-        val = val[4:]
-    vnew.reverse()
-    output.write('static BN_ULONG %s[%d] = {\n' % (name, len(vnew)))
+    # OpenSSL expects 32-bit words given least-significant-word first.
+    vwords = bitwise_collect(val, 32)
+
+    output.write(u'static BN_ULONG {}[] = {{\n'.format(name))
     idx = 0
-    for v1, v2, v3, v4 in vnew:
+    for vword in vwords:
         if not idx:
-            output.write('\t')
-        output.write('0x%.2x%.2x%.2x%.2x, ' % (ord(v1), ord(v2), ord(v3), ord(v4)))
+            output.write(u'\t')
+        output.write(u'0x{:08x}, '.format(vword))
         idx += 1
         if idx == 4:
             idx = 0
-            output.write('\n')
+            output.write(u'\n')
     if idx:
-        output.write('\n')
-    output.write('};\n\n')
+        output.write(u'\n')
+    output.write(u'};\n\n')
 
 def print_ssl(output, name, val):
+
+    output.write(u'#include <stdint.h>\n')
+    output.write(u'#include <openssl/bn.h>\n')
+
     import struct
-    output.write('#include <stdint.h>\n')
     if len(struct.pack('@L', 0)) == 8:
         return print_ssl_64(output, name, val)
     else:
         return print_ssl_32(output, name, val)
 
 def print_ssl_keys(output, n):
-    output.write(r'''
+    output.write(u'''
 struct pubkey {
 	struct bignum_st e, n;
 };
 
-#define KEY(data) {				\
-	.d = data,				\
-	.top = sizeof(data)/sizeof(data[0]),	\
+#define KEY(data) {                          \\
+	.d = data,                           \\
+	.top = sizeof(data)/sizeof(data[0]), \\
 }
 
-#define KEYS(e,n)	{ KEY(e), KEY(n), }
+#define KEYS(e,n)    { KEY(e), KEY(n), }
 
 static struct pubkey keys[] = {
 ''')
     for n in xrange(n + 1):
-        output.write('	KEYS(e_%d, n_%d),\n' % (n, n))
-    output.write('};\n')
+        output.write(u'	KEYS(e_{0}, n_{0}),\n'.format(n))
+    output.write(u'};\n')
     pass
 
 def print_gcrypt(output, name, val):
-    output.write('#include <stdint.h>\n')
-    while val[0] == '\0':
-        val = val[1:]
-    output.write('static const uint8_t %s[%d] = {\n' % (name, len(val)))
+    # gcrypt expects 8-bit words most-significant-word first
+    vwords = bitwise_collect(val, 8)
+    vwords.reverse()
+    
+    output.write(u'#include <stdint.h>\n')
+    output.write(u'static const uint8_t %s[%d] = {\n' % (name, len(vwords)))
     idx = 0
-    for v in val:
+    for vword in vwords:
         if not idx:
-            output.write('\t')
-        output.write('0x%.2x, ' % ord(v))
+            output.write(u'\t')
+        output.write(u'0x{:02x}, '.format(vword))
         idx += 1
         if idx == 8:
             idx = 0
-            output.write('\n')
+            output.write(u'\n')
     if idx:
-        output.write('\n')
-    output.write('};\n\n')
+        output.write(u'\n')
+    output.write(u'};\n\n')
 
 def print_gcrypt_keys(output, n):
-    output.write(r'''
+    output.write(u'''
 struct key_params {
 	const uint8_t *e, *n;
 	uint32_t len_e, len_n;
 };
 
-#define KEYS(_e, _n) {			\
-	.e = _e, .len_e = sizeof(_e),	\
-	.n = _n, .len_n = sizeof(_n),	\
+#define KEYS(_e, _n) {                \\
+	.e = _e, .len_e = sizeof(_e), \\
+	.n = _n, .len_n = sizeof(_n), \\
 }
 
 static const struct key_params keys[] = {
 ''')
-    for n in xrange(n + 1):
-        output.write('	KEYS(e_%d, n_%d),\n' % (n, n))
-    output.write('};\n')
-    
+    for n in range(n + 1):
+        output.write(u'	KEYS(e_{0}, n_{0}),\n'.format(n))
+    output.write(u'};\n')
+
 
 modes = {
     '--ssl': (print_ssl, print_ssl_keys),
@@ -135,21 +137,21 @@ except IndexError:
     mode = None
 
 if not mode in modes:
-    print 'Usage: %s [%s] input-file... output-file' % (sys.argv[0], '|'.join(modes.keys()))
+    print('Usage: {} [{}] input-file... output-file'.format(sys.argv[0], '|'.join(modes.keys())))
     sys.exit(2)
 
-output = open(outfile, 'w')
+output = io.open(outfile, 'w')
 
 # load key
 idx = 0
 for f in files:
-    try:
-        key = RSA.load_pub_key(f)
-    except RSA.RSAError:
-        key = RSA.load_key(f)
 
-    modes[mode][0](output, 'e_%d' % idx, key.e[4:])
-    modes[mode][0](output, 'n_%d' % idx, key.n[4:])
+    key_contents = io.open(f, 'rb').read()
+    key = RSA.importKey(key_contents)
+
+    modes[mode][0](output, 'e_{}'.format(idx), key.e)
+    modes[mode][0](output, 'n_{}'.format(idx), key.n)
+
     idx += 1
 
 modes[mode][1](output, idx - 1)
-- 
2.3.6