public_key:pem_decode/1 and public_key:verify/4

[Joakim G.]

Hi all,
It seems that public_key:pem_decode/1 can't decode public
keys.

I wanted use public_key:verify/4 to verify a digital signature
and for that I used public_key:pem_decode/1 to extract the
public key.

26> {ok, Bin} = file:read_file("key.pub").
{ok,<<"-----BEGIN RSA PUBLIC
KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5C9TfRVJDUuxz"...>>}
27> rp(Bin).
<<"-----BEGIN RSA PUBLIC
KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
RSA PUBLIC KEY-----\n">>
ok
28> public_key:pem_decode(Bin).
[]

That was a surprise.

Cheers
/Jocke

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[曹煦]

Maybe the asn1 type of your key file is not supported by public_key.  You can check it and use openssl to convert the key format.

在 2011-1-19，下午5:23， Joakim G. 写道：

> Hi all,
> It seems that public_key:pem_decode/1 can't decode public
> keys.
>
> I wanted use public_key:verify/4 to verify a digital signature
> and for that I used public_key:pem_decode/1 to extract the
> public key.
>
> 26> {ok, Bin} = file:read_file("key.pub").
> {ok,<<"-----BEGIN RSA PUBLIC
> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5C9TfRVJDUuxz"...>>}
> 27> rp(Bin).
> <<"-----BEGIN RSA PUBLIC
> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
> RSA PUBLIC KEY-----\n">>
> ok
> 28> public_key:pem_decode(Bin).
> []
>
> That was a surprise.
>
> Cheers
> /Jocke
>
> ________________________________________________________________
> erlang-questions (at) erlang.org mailing list.
> See http://www.erlang.org/faq.html
> To unsubscribe; mailto:[hidden email]
>

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[Ingela Andin-2]

Hi!

All possible PEM-types are not supported by public_key, the currently
supported types are mainly a result of what we need
for the ssl-application. More types may of course be added if there is
a need. You are welcome to contribute PEM-types that may be of common
use.

If you want the public part of your own rsa-key it is included in the
private-key and you can  decode that file with public_key and
pick out the public part.

Regards Ingela Erlang/OTP team - Ericsson AB


2011/1/19 caox <[hidden email]>:

> Maybe the asn1 type of your key file is not supported by public_key.  You can check it and use openssl to convert the key format.
>
> 在 2011-1-19，下午5:23， Joakim G. 写道：
>
>> Hi all,
>> It seems that public_key:pem_decode/1 can't decode public
>> keys.
>>
>> I wanted use public_key:verify/4 to verify a digital signature
>> and for that I used public_key:pem_decode/1 to extract the
>> public key.
>>
>> 26> {ok, Bin} = file:read_file("key.pub").
>> {ok,<<"-----BEGIN RSA PUBLIC
>> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5C9TfRVJDUuxz"...>>}
>> 27> rp(Bin).
>> <<"-----BEGIN RSA PUBLIC
>> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
>> RSA PUBLIC KEY-----\n">>
>> ok
>> 28> public_key:pem_decode(Bin).
>> []
>>
>> That was a surprise.
>>
>> Cheers
>> /Jocke
>>
>> ________________________________________________________________
>> erlang-questions (at) erlang.org mailing list.
>> See http://www.erlang.org/faq.html
>> To unsubscribe; mailto:[hidden email]
>>
>
>
> ________________________________________________________________
> erlang-questions (at) erlang.org mailing list.
> See http://www.erlang.org/faq.html
> To unsubscribe; mailto:[hidden email]
>
>

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[Joakim G.]

Thanks, I see.

I'm using keys as defined in:
https://gitweb.torproject.org/tor.git?a=blob_plain;hb=HEAD;f=doc/spec/tor-spec.txt

That is:

"For a public-key cipher, we use RSA with 1024-bit keys and a fixed
exponent of 65537.  We use OAEP-MGF1 padding, with SHA-1 as its digest
function.  We leave the optional "Label" parameter unset. (For OAEP
padding, see ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.pdf)"

I only have the public keys to work with. Not a surprise. :-)

I will see if I can find more info on this.

Cheers
/Jocke

On 2011-01-19 14:21, Ingela Andin wrote:

> Hi!
>
> All possible PEM-types are not supported by public_key, the currently
> supported types are mainly a result of what we need
> for the ssl-application. More types may of course be added if there is
> a need. You are welcome to contribute PEM-types that may be of common
> use.
>
> If you want the public part of your own rsa-key it is included in the
> private-key and you can  decode that file with public_key and
> pick out the public part.
>
> Regards Ingela Erlang/OTP team - Ericsson AB
>
>
> 2011/1/19 caox <[hidden email]>:
>> Maybe the asn1 type of your key file is not supported by public_key.  You can check it and use openssl to convert the key format.
>>
>> 在 2011-1-19，下午5:23， Joakim G. 写道：
>>
>>> Hi all,
>>> It seems that public_key:pem_decode/1 can't decode public
>>> keys.
>>>
>>> I wanted use public_key:verify/4 to verify a digital signature
>>> and for that I used public_key:pem_decode/1 to extract the
>>> public key.
>>>
>>> 26> {ok, Bin} = file:read_file("key.pub").
>>> {ok,<<"-----BEGIN RSA PUBLIC
>>> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5C9TfRVJDUuxz"...>>}
>>> 27> rp(Bin).
>>> <<"-----BEGIN RSA PUBLIC
>>> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
>>> RSA PUBLIC KEY-----\n">>
>>> ok
>>> 28> public_key:pem_decode(Bin).
>>> []
>>>
>>> That was a surprise.
>>>
>>> Cheers
>>> /Jocke
>>>
>>> ________________________________________________________________
>>> erlang-questions (at) erlang.org mailing list.
>>> See http://www.erlang.org/faq.html
>>> To unsubscribe; mailto:[hidden email]
>>>
>>
>>
>> ________________________________________________________________
>> erlang-questions (at) erlang.org mailing list.
>> See http://www.erlang.org/faq.html
>> To unsubscribe; mailto:[hidden email]
>>
>>
>
> ________________________________________________________________
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> See http://www.erlang.org/faq.html
> To unsubscribe; mailto:[hidden email]
>

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[Ingela Andin-2]

Hi again,

The PKCS-1 asn-1 spec is part of public key. PEM-files are mainly
base64-encoded  asn1 DER data.
Pem files looks something like this:

        <text>
        -----BEGIN SOMETHING-----<CR><LF>
        <Base64 encoding line><CR><LF>
        <Base64 encoding line><CR><LF>
        ...
        -----END SOMETHING-----<CR><LF>
        <text>

Adding support for the something = RSA PUBLIC KEY should be fairly
simple as the ASN1- spec is alredy in place.

2011/1/19 Joakim G. <[hidden email]>:

> Thanks, I see.
>
> I'm using keys as defined in:
> https://gitweb.torproject.org/tor.git?a=blob_plain;hb=HEAD;f=doc/spec/tor-spec.txt
>
> That is:
>
> "For a public-key cipher, we use RSA with 1024-bit keys and a fixed
> exponent of 65537.  We use OAEP-MGF1 padding, with SHA-1 as its digest
> function.  We leave the optional "Label" parameter unset. (For OAEP
> padding, see ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.pdf)"
>
> I only have the public keys to work with. Not a surprise. :-)

No not really, but you never know, with time I learnt not to take
anything for granted  ;)

>
> I will see if I can find more info on this.

[...]

I will put it on the wish-list, but we have got a lot of other things
on our table so a contribution
will proably speed things up.

Regards Ingela Erlang/OTP team - Ericsson AB

________________________________________________________________
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See http://www.erlang.org/faq.html
To unsubscribe; mailto:[hidden email]

[Joakim G.]

I updated pubkey_pem.html a tiny little bit and it seems to
work:

jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
pubkey_pem.erl.orig pubkey_pem.erl
157a158,159
> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
Entry) ->
>     {lists:reverse(Entry), Lines};
212a215,216
> pem_start('RSAPublicKey') ->
>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
221a226,227
> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>     <<"-----END RSA PUBLIC KEY-----">>;
232a239,240
> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>     'RSAPublicKey';

Thanks
/Jocke

On 2011-01-20 10:37, Ingela Andin wrote:

> Hi again,
>
> The PKCS-1 asn-1 spec is part of public key. PEM-files are mainly
> base64-encoded  asn1 DER data.
> Pem files looks something like this:
>
> <text>
> -----BEGIN SOMETHING-----<CR><LF>
> <Base64 encoding line><CR><LF>
> <Base64 encoding line><CR><LF>
> ...
> -----END SOMETHING-----<CR><LF>
> <text>
>
> Adding support for the something = RSA PUBLIC KEY should be fairly
> simple as the ASN1- spec is alredy in place.
>
> 2011/1/19 Joakim G. <[hidden email]>:
>> Thanks, I see.
>>
>> I'm using keys as defined in:
>> https://gitweb.torproject.org/tor.git?a=blob_plain;hb=HEAD;f=doc/spec/tor-spec.txt
>>
>> That is:
>>
>> "For a public-key cipher, we use RSA with 1024-bit keys and a fixed
>> exponent of 65537.  We use OAEP-MGF1 padding, with SHA-1 as its digest
>> function.  We leave the optional "Label" parameter unset. (For OAEP
>> padding, see ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.pdf)"
>>
>> I only have the public keys to work with. Not a surprise. :-)
>
> No not really, but you never know, with time I learnt not to take
> anything for granted  ;)
>
>>
>> I will see if I can find more info on this.
>
> [...]
>
> I will put it on the wish-list, but we have got a lot of other things
> on our table so a contribution
> will proably speed things up.
>
> Regards Ingela Erlang/OTP team - Ericsson AB
>
> ________________________________________________________________
> erlang-questions (at) erlang.org mailing list.
> See http://www.erlang.org/faq.html
> To unsubscribe; mailto:[hidden email]
>

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[Joakim G.]

lol. pubkey_pem.erl

/Jocke

On 2011-01-20 23:40, Joakim G. wrote:

> I updated pubkey_pem.html a tiny little bit and it seems to
> work:
>
> jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
> pubkey_pem.erl.orig pubkey_pem.erl
> 157a158,159
>> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
> Entry) ->
>>     {lists:reverse(Entry), Lines};
> 212a215,216
>> pem_start('RSAPublicKey') ->
>>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
> 221a226,227
>> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>     <<"-----END RSA PUBLIC KEY-----">>;
> 232a239,240
>> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>     'RSAPublicKey';
>
> Thanks
> /Jocke
>
> On 2011-01-20 10:37, Ingela Andin wrote:
>> Hi again,
>>
>> The PKCS-1 asn-1 spec is part of public key. PEM-files are mainly
>> base64-encoded  asn1 DER data.
>> Pem files looks something like this:
>>
>> <text>
>> -----BEGIN SOMETHING-----<CR><LF>
>> <Base64 encoding line><CR><LF>
>> <Base64 encoding line><CR><LF>
>> ...
>> -----END SOMETHING-----<CR><LF>
>> <text>
>>
>> Adding support for the something = RSA PUBLIC KEY should be fairly
>> simple as the ASN1- spec is alredy in place.
>>
>> 2011/1/19 Joakim G. <[hidden email]>:
>>> Thanks, I see.
>>>
>>> I'm using keys as defined in:
>>> https://gitweb.torproject.org/tor.git?a=blob_plain;hb=HEAD;f=doc/spec/tor-spec.txt
>>>
>>> That is:
>>>
>>> "For a public-key cipher, we use RSA with 1024-bit keys and a fixed
>>> exponent of 65537.  We use OAEP-MGF1 padding, with SHA-1 as its digest
>>> function.  We leave the optional "Label" parameter unset. (For OAEP
>>> padding, see ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.pdf)"
>>>
>>> I only have the public keys to work with. Not a surprise. :-)
>>
>> No not really, but you never know, with time I learnt not to take
>> anything for granted  ;)
>>
>>>
>>> I will see if I can find more info on this.
>>
>> [...]
>>
>> I will put it on the wish-list, but we have got a lot of other things
>> on our table so a contribution
>> will proably speed things up.
>>
>> Regards Ingela Erlang/OTP team - Ericsson AB
>>
>> ________________________________________________________________
>> erlang-questions (at) erlang.org mailing list.
>> See http://www.erlang.org/faq.html
>> To unsubscribe; mailto:[hidden email]
>>
>
> ________________________________________________________________
> erlang-questions (at) erlang.org mailing list.
> See http://www.erlang.org/faq.html
> To unsubscribe; mailto:[hidden email]
>

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[Seth Falcon-3]

Hi there,

I'm very interested in adding support for RSA public key decoding to
the public_key module.  My use case is similar in that I need to be
able to verify/decrypt when all I have is the RSA public key in PEM
format.

2011/1/20 Ingela Andin <[hidden email]>:
> The PKCS-1 asn-1 spec is part of public key. PEM-files are mainly
> base64-encoded  asn1 DER data.
[snip]
> Adding support for the something = RSA PUBLIC KEY should be fairly
> simple as the ASN1- spec is alredy in place.

I started working on such a patch and you are right that the changes
to read in the pem data are fairly simple.

However, once I have the DER format, I'm getting stuck with an error
coming out of public_key:der_decode.  Not sure if I'm doing it wrong
or if there is something wrong with the asn1 definition for RSA public
keys.

Here's what I'm trying (skipping the pem conversion for now):

shell:

  openssl genrsa > mykey.private
  openssl rsa -in mykey.private -outform der -pubout > mykey.public.der

erl:

  {ok, PubDer} = file:read_file("mykey.public.der").
  public_key:der_decode('RSAPublicKey', PubDer)

** exception error: no match of right hand side value {error,
                                                       {asn1,
                                                        {function_clause,

[{'OTP-PUB-KEY',decode_integer,

[{error,{asn1,{wrong_tag,{16,2}}}}]},

{'OTP-PUB-KEY',decode_integer,3},

{'OTP-PUB-KEY',dec_RSAPublicKey,2},

{'OTP-PUB-KEY',decode,2},

{public_key,der_decode,2},
                                                          {erl_eval,do_apply,5},
                                                          {shell,exprs,7},

{shell,eval_exprs,7}]}}}
     in function  public_key:der_decode/2



Aside: when I use openssl to extract the public key, the output I get
looks like:

-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBALyPPyTS+HyTV3oLf2z6W+H1NOKLos3K
ztRytqJoIdvbzNFYsnJqFhabzhQx2DdPvTiHLZM1QHQ1Ma5yw5hjaQcCAwEAAQ==
-----END PUBLIC KEY-----

Note that it only says "PUBLIC KEY", not "RSA PUBLIC KEY".  You will
get identical header values when extracting a DSA public key.
So I'm unsure about how one can detect what type of public key one
has.  Anyone know the details of how that's supposed to work?  This
throws a wrinkle in pem_decode/1.  It may be that one needs to have
pem_decode/2 for public keys where the user specifies what type of key
is expected.


If I can get a bit further I will put together a patch.

Thanks,

 + seth

--
Seth Falcon | @sfalcon | http://userprimary.net/

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[Seth Falcon-3]

2011/1/20 Joakim G. <[hidden email]>:

> I updated pubkey_pem.html a tiny little bit and it seems to
> work:
>
> jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
> pubkey_pem.erl.orig pubkey_pem.erl
> 157a158,159
>> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
> Entry) ->
>>     {lists:reverse(Entry), Lines};
> 212a215,216
>> pem_start('RSAPublicKey') ->
>>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
> 221a226,227
>> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>     <<"-----END RSA PUBLIC KEY-----">>;
> 232a239,240
>> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>     'RSAPublicKey';
>
> Thanks

Our mails crossed.  When you say "this seems to work", were you able
to actually use the public key for verification/decryption?

________________________________________________________________
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[Ingela Andin]

Hi!

Well PEM-files that only BEGIN PUBLIC KEY and not BEGIN RSA PUBLIC KEY are
using another ASN1 spec and can contain both RSA and DSA keys. It
seems that it is the
ASN1-spec SubjectPublicKeyInfo from PKIXExplicit88.asn1 also part of public_key.

Regards Ingela Erlang/OTP team - Ericsson AB

P.S

Some time ago someone asked for  PKCS-8
http://tools.ietf.org/html/rfc5208  support,
which ASN1 specs are not currently part of the public_key application
and therefore needs to be added,
in order to support them. I do not know if this is intrests you it is
only so you know.


2011/1/20 Seth Falcon <[hidden email]>:

> Hi there,
>
> I'm very interested in adding support for RSA public key decoding to
> the public_key module.  My use case is similar in that I need to be
> able to verify/decrypt when all I have is the RSA public key in PEM
> format.
>
> 2011/1/20 Ingela Andin <[hidden email]>:
>> The PKCS-1 asn-1 spec is part of public key. PEM-files are mainly
>> base64-encoded  asn1 DER data.
> [snip]
>> Adding support for the something = RSA PUBLIC KEY should be fairly
>> simple as the ASN1- spec is alredy in place.
>
> I started working on such a patch and you are right that the changes
> to read in the pem data are fairly simple.
>
> However, once I have the DER format, I'm getting stuck with an error
> coming out of public_key:der_decode.  Not sure if I'm doing it wrong
> or if there is something wrong with the asn1 definition for RSA public
> keys.
>
> Here's what I'm trying (skipping the pem conversion for now):
>
> shell:
>
>  openssl genrsa > mykey.private
>  openssl rsa -in mykey.private -outform der -pubout > mykey.public.der
>
> erl:
>
>  {ok, PubDer} = file:read_file("mykey.public.der").
>  public_key:der_decode('RSAPublicKey', PubDer)
>
> ** exception error: no match of right hand side value {error,
>                                                       {asn1,
>                                                        {function_clause,
>
> [{'OTP-PUB-KEY',decode_integer,
>
> [{error,{asn1,{wrong_tag,{16,2}}}}]},
>
> {'OTP-PUB-KEY',decode_integer,3},
>
> {'OTP-PUB-KEY',dec_RSAPublicKey,2},
>
> {'OTP-PUB-KEY',decode,2},
>
> {public_key,der_decode,2},
>                                                          {erl_eval,do_apply,5},
>                                                          {shell,exprs,7},
>
> {shell,eval_exprs,7}]}}}
>     in function  public_key:der_decode/2
>
>
>
> Aside: when I use openssl to extract the public key, the output I get
> looks like:
>
> -----BEGIN PUBLIC KEY-----
> MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBALyPPyTS+HyTV3oLf2z6W+H1NOKLos3K
> ztRytqJoIdvbzNFYsnJqFhabzhQx2DdPvTiHLZM1QHQ1Ma5yw5hjaQcCAwEAAQ==
> -----END PUBLIC KEY-----
>
> Note that it only says "PUBLIC KEY", not "RSA PUBLIC KEY".  You will
> get identical header values when extracting a DSA public key.
> So I'm unsure about how one can detect what type of public key one
> has.  Anyone know the details of how that's supposed to work?  This
> throws a wrinkle in pem_decode/1.  It may be that one needs to have
> pem_decode/2 for public keys where the user specifies what type of key
> is expected.
>
>
> If I can get a bit further I will put together a patch.
>
> Thanks,
>
>  + seth
>
> --
> Seth Falcon | @sfalcon | http://userprimary.net/
>
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[Joakim G.]

With this patch public_key:pem_decode/1 returns a RSAPublicKey
record as defined in public_key.hrl (instead of just []).

I haven't used the output yet though. :-)

I will experiment with public_key:verify/4 over the weekend.

Cheers
/Jocke

On 2011-01-21 00:03, Seth Falcon wrote:

> 2011/1/20 Joakim G. <[hidden email]>:
>> I updated pubkey_pem.html a tiny little bit and it seems to
>> work:
>>
>> jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
>> pubkey_pem.erl.orig pubkey_pem.erl
>> 157a158,159
>>> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
>> Entry) ->
>>>     {lists:reverse(Entry), Lines};
>> 212a215,216
>>> pem_start('RSAPublicKey') ->
>>>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
>> 221a226,227
>>> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>     <<"-----END RSA PUBLIC KEY-----">>;
>> 232a239,240
>>> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>     'RSAPublicKey';
>>
>> Thanks
>
> Our mails crossed.  When you say "this seems to work", were you able
> to actually use the public key for verification/decryption?
>
> ________________________________________________________________
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> See http://www.erlang.org/faq.html
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[Seth Falcon-3]

Hi,

On Fri, Jan 21, 2011 at 12:48 AM, Ingela Andin <[hidden email]> wrote:
> Well PEM-files that only BEGIN PUBLIC KEY and not BEGIN RSA PUBLIC
> KEY are using another ASN1 spec and can contain both RSA and DSA
> keys. It seems that it is the ASN1-spec SubjectPublicKeyInfo from
> PKIXExplicit88.asn1 also part of public_key.

Thanks, that was a very useful hint :-)

I can now read RSA public key PEM files as generated by openssl.
Here's the recipe (assuming stock public_key module):

    read_rsa_public_key(Key) ->
        Bin = erlang:iolist_to_binary(public_key_lines(re:split(Key,
"\n"), [])),
        Spki = public_key:der_decode('SubjectPublicKeyInfo',
base64:mime_decode(Bin)),
        {_, _, {0, KeyDer}} = Spki,
        public_key:der_decode('RSAPublicKey', KeyDer).

    public_key_lines([<<"-----BEGIN PUBLIC KEY-----">>|Rest], Acc) ->
        public_key_lines(Rest, Acc);
    public_key_lines([<<"-----END PUBLIC KEY-----">>|Rest], Acc) ->
        lists:reverse(Acc);
    public_key_lines([Line|Rest], Acc) ->
        public_key_lines(Rest, [Line|Acc]).

I have a patch to the public_key module that makes this easier by
introducing three new functions: public_key_type/1,
pem_decode_public_key/1, and der_decode_public_key/1.

public_key_type takes either a SubjectPublicKeyInfo record (as
returned by der_decode/2 when given type 'SubjectPublicKeyInfo') or
the algorithm id tuple that is a part of the 'SubjectPublicKeyInfo'
record.  It is a wrapper for
pubkey_cert_records:supportedPublicKeyAlgorithms/1.


pem_decode_public_key

    takes a PEM binary and in the case that pem_decode(PEM) returns
    'SubjectPublicKeyInfo', it determines the public key type and does
    der_decode so that the return value is the public key in a form
    usable by functions like public_key:decrypt_public/2.  If the PEM
    does not contain 'SubjectPublicKeyInfo', then it is passed through
    unchanged.  I think this would be useful for Joakim's use case.

der_decode_public_key

    behaves similarly, but is given the DER encoded version of the
    public key to start with.  Here, as I understand it, the problem
    is a bit stickier because you can't know what type it is.  So it
    tries each of ['SubjectPublicKeyInfo', 'RSAPublicKey',
    'DSAPublicKey'] and returns similar to pem_decode_public_key.

I've put the work-in-progress on a branch here:

    https://github.com/seth/otp/tree/sf/rsa_pub_key

I'm not sure if this is going in the right direction, so wrote this up
(sorry for the length) to get some feedback.  I'm willing to make
adjustments and spend time polishing a patch if there is some
agreement on general direction.

Best,

+ seth


--
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[Joakim G.]

On 2011-01-21 12:47, Joakim G. wrote:
> With this patch public_key:pem_decode/1 returns a RSAPublicKey
> record as defined in public_key.hrl (instead of just []).
>
> I haven't used the output yet though. :-)
>
> I will experiment with public_key:verify/4 over the weekend.

To verify: my naive fix did what is was supposed to do, i.e. this
works with the patch applied:

    [PemEntry] = public_key:pem_decode(<<"-----BEGIN RSA PUBLIC
KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
RSA PUBLIC KEY-----">>),
    RSAPublicKey = public_key:pem_entry_decode(PemEntry),

I could then call:

==

verify(PlainText, Signature,
       #'RSAPublicKey'{modulus = Mod, publicExponent = Exp}) ->
    PlainText ==
        crypto:rsa_public_decrypt(Signature,
                                  [crypto:mpint(Exp), crypto:mpint(Mod)],
                                  rsa_pkcs1_padding).

==

to verify a signature.

AFAICS public_key:verify/4 is broken.

I'm happpy now. The work can continue. :-)

/Jocke

> Cheers
> /Jocke
>
> On 2011-01-21 00:03, Seth Falcon wrote:
>> 2011/1/20 Joakim G. <[hidden email]>:
>>> I updated pubkey_pem.html a tiny little bit and it seems to
>>> work:
>>>
>>> jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
>>> pubkey_pem.erl.orig pubkey_pem.erl
>>> 157a158,159
>>>> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
>>> Entry) ->
>>>>     {lists:reverse(Entry), Lines};
>>> 212a215,216
>>>> pem_start('RSAPublicKey') ->
>>>>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
>>> 221a226,227
>>>> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>>     <<"-----END RSA PUBLIC KEY-----">>;
>>> 232a239,240
>>>> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>>     'RSAPublicKey';
>>>
>>> Thanks
>>
>> Our mails crossed.  When you say "this seems to work", were you able
>> to actually use the public key for verification/decryption?
>>
>> ________________________________________________________________
>> erlang-questions (at) erlang.org mailing list.
>> See http://www.erlang.org/faq.html
>> To unsubscribe; mailto:[hidden email]
>>
>
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[Joakim G.]

Thanks. A nice addition to the public_key module.

/Jocke

On 2011-01-24 06:14, Seth Falcon wrote:

> Hi,
>
> On Fri, Jan 21, 2011 at 12:48 AM, Ingela Andin <[hidden email]> wrote:
>> Well PEM-files that only BEGIN PUBLIC KEY and not BEGIN RSA PUBLIC
>> KEY are using another ASN1 spec and can contain both RSA and DSA
>> keys. It seems that it is the ASN1-spec SubjectPublicKeyInfo from
>> PKIXExplicit88.asn1 also part of public_key.
>
> Thanks, that was a very useful hint :-)
>
> I can now read RSA public key PEM files as generated by openssl.
> Here's the recipe (assuming stock public_key module):
>
>     read_rsa_public_key(Key) ->
>         Bin = erlang:iolist_to_binary(public_key_lines(re:split(Key,
> "\n"), [])),
>         Spki = public_key:der_decode('SubjectPublicKeyInfo',
> base64:mime_decode(Bin)),
>         {_, _, {0, KeyDer}} = Spki,
>         public_key:der_decode('RSAPublicKey', KeyDer).
>
>     public_key_lines([<<"-----BEGIN PUBLIC KEY-----">>|Rest], Acc) ->
>         public_key_lines(Rest, Acc);
>     public_key_lines([<<"-----END PUBLIC KEY-----">>|Rest], Acc) ->
>         lists:reverse(Acc);
>     public_key_lines([Line|Rest], Acc) ->
>         public_key_lines(Rest, [Line|Acc]).

<trunc/>

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[Ingela Andin-2]

Hi!

public_key:verify/4 is not broken, it is just that verifies signatures
created by the
algorithm implemented by  public_key:sign/3 and not the ones created by
the algorithm implemented by public_key:encrypt_private/2 as yours seems to be.
You should try public_key:decrypt_public/3 instead.

Regards Ingela Erlang/OTP team - Ericsson AB


2011/1/24 Joakim G. <[hidden email]>:

> On 2011-01-21 12:47, Joakim G. wrote:
>> With this patch public_key:pem_decode/1 returns a RSAPublicKey
>> record as defined in public_key.hrl (instead of just []).
>>
>> I haven't used the output yet though. :-)
>>
>> I will experiment with public_key:verify/4 over the weekend.
>
> To verify: my naive fix did what is was supposed to do, i.e. this
> works with the patch applied:
>
>    [PemEntry] = public_key:pem_decode(<<"-----BEGIN RSA PUBLIC
> KEY-----\nMIGJAoGBAKhhZ8RrKaA0RWhjXJlSpTHd7/h6Luww9qeyUkEqBQyiCooZZGCYNle5\nC9TfRVJDUuxzigvXuTh0tlba+9AyIe2hxAztjs43pSKy5VnnJlSjMBVDay8XmNjh\nlUxid/ZV2hDkKlwHDCnZjdZpeXqdtGbZ7o3N7wOBzJSRQ7kqzQHXAgMBAAE=\n-----END
> RSA PUBLIC KEY-----">>),
>    RSAPublicKey = public_key:pem_entry_decode(PemEntry),
>
> I could then call:
>
> ==
>
> verify(PlainText, Signature,
>       #'RSAPublicKey'{modulus = Mod, publicExponent = Exp}) ->
>    PlainText ==
>        crypto:rsa_public_decrypt(Signature,
>                                  [crypto:mpint(Exp), crypto:mpint(Mod)],
>                                  rsa_pkcs1_padding).
>
> ==
>
> to verify a signature.
>
> AFAICS public_key:verify/4 is broken.
>
> I'm happpy now. The work can continue. :-)
>
> /Jocke
>
>> Cheers
>> /Jocke
>>
>> On 2011-01-21 00:03, Seth Falcon wrote:
>>> 2011/1/20 Joakim G. <[hidden email]>:
>>>> I updated pubkey_pem.html a tiny little bit and it seems to
>>>> work:
>>>>
>>>> jocke@xev:~/installs/otp_src_R14B01/lib/public_key/src$ diff -bwt
>>>> pubkey_pem.erl.orig pubkey_pem.erl
>>>> 157a158,159
>>>>> join_entry([<<"-----END RSA PUBLIC KEY-----", _/binary>>| Lines],
>>>> Entry) ->
>>>>>     {lists:reverse(Entry), Lines};
>>>> 212a215,216
>>>>> pem_start('RSAPublicKey') ->
>>>>>     <<"-----BEGIN RSA PUBLIC KEY-----">>;
>>>> 221a226,227
>>>>> pem_end(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>>>     <<"-----END RSA PUBLIC KEY-----">>;
>>>> 232a239,240
>>>>> asn1_type(<<"-----BEGIN RSA PUBLIC KEY-----">>) ->
>>>>>     'RSAPublicKey';
>>>>
>>>> Thanks
>>>
>>> Our mails crossed.  When you say "this seems to work", were you able
>>> to actually use the public key for verification/decryption?
>>>
>>> ________________________________________________________________
>>> erlang-questions (at) erlang.org mailing list.
>>> See http://www.erlang.org/faq.html
>>> To unsubscribe; mailto:[hidden email]
>>>
>>
>> ________________________________________________________________
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>> See http://www.erlang.org/faq.html
>> To unsubscribe; mailto:[hidden email]
>>
>
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[Ingela Andin]

Hi Seth!

Thank you very much for working on this.  I have looked at your branch
and my thoughts are the following.

I think that the decoding of  'SubjectPublicKeyInfo',  from
pem_decode_public_key, should rather be handled in the
function pem_entry_decode. As I think the normal thing is that you
want the actual key and not a 'SubjectPublicKeyInfo', that would
mean just a little more decoding is done by pem_entry_decode. (You can
match on the 'SubjectPublicKeyInfo' in the function head to
create a clause for this.)
It will not then be a 100 % symmetric with pem_entry_encode but I
think  that is ok, it could be mentioned in the documentation.
Another reason that this is a good idea is that it will not then be
sensitive to that the public_key is the only entry in the file.
PEM files may contain several entries which is not handled by your function.

When it comes to the function der_decode_publick_key I am not sure it
is needed as I think it
is uncommon that you end up with a "DER-blob" that you do not know how
it is encoded.

Regards Ingela Erlang/OTP team - Ericssson AB

2011/1/24 Seth Falcon <[hidden email]>:

> Hi,
>
> On Fri, Jan 21, 2011 at 12:48 AM, Ingela Andin <[hidden email]> wrote:
>> Well PEM-files that only BEGIN PUBLIC KEY and not BEGIN RSA PUBLIC
>> KEY are using another ASN1 spec and can contain both RSA and DSA
>> keys. It seems that it is the ASN1-spec SubjectPublicKeyInfo from
>> PKIXExplicit88.asn1 also part of public_key.
>
> Thanks, that was a very useful hint :-)
>
> I can now read RSA public key PEM files as generated by openssl.
> Here's the recipe (assuming stock public_key module):
>
>    read_rsa_public_key(Key) ->
>        Bin = erlang:iolist_to_binary(public_key_lines(re:split(Key,
> "\n"), [])),
>        Spki = public_key:der_decode('SubjectPublicKeyInfo',
> base64:mime_decode(Bin)),
>        {_, _, {0, KeyDer}} = Spki,
>        public_key:der_decode('RSAPublicKey', KeyDer).
>
>    public_key_lines([<<"-----BEGIN PUBLIC KEY-----">>|Rest], Acc) ->
>        public_key_lines(Rest, Acc);
>    public_key_lines([<<"-----END PUBLIC KEY-----">>|Rest], Acc) ->
>        lists:reverse(Acc);
>    public_key_lines([Line|Rest], Acc) ->
>        public_key_lines(Rest, [Line|Acc]).
>
> I have a patch to the public_key module that makes this easier by
> introducing three new functions: public_key_type/1,
> pem_decode_public_key/1, and der_decode_public_key/1.
>
> public_key_type takes either a SubjectPublicKeyInfo record (as
> returned by der_decode/2 when given type 'SubjectPublicKeyInfo') or
> the algorithm id tuple that is a part of the 'SubjectPublicKeyInfo'
> record.  It is a wrapper for
> pubkey_cert_records:supportedPublicKeyAlgorithms/1.
>
>
> pem_decode_public_key
>
>    takes a PEM binary and in the case that pem_decode(PEM) returns
>    'SubjectPublicKeyInfo', it determines the public key type and does
>    der_decode so that the return value is the public key in a form
>    usable by functions like public_key:decrypt_public/2.  If the PEM
>    does not contain 'SubjectPublicKeyInfo', then it is passed through
>    unchanged.  I think this would be useful for Joakim's use case.
>
> der_decode_public_key
>
>    behaves similarly, but is given the DER encoded version of the
>    public key to start with.  Here, as I understand it, the problem
>    is a bit stickier because you can't know what type it is.  So it
>    tries each of ['SubjectPublicKeyInfo', 'RSAPublicKey',
>    'DSAPublicKey'] and returns similar to pem_decode_public_key.
>
> I've put the work-in-progress on a branch here:
>
>    https://github.com/seth/otp/tree/sf/rsa_pub_key
>
> I'm not sure if this is going in the right direction, so wrote this up
> (sorry for the length) to get some feedback.  I'm willing to make
> adjustments and spend time polishing a patch if there is some
> agreement on general direction.
>
> Best,
>
> + seth
>
>
> --
> Seth Falcon | @sfalcon | http://userprimary.net/
>

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[Seth Falcon-3]

On Mon, Jan 24, 2011 at 2:51 AM, Ingela Andin <[hidden email]> wrote:
> I think that the decoding of  'SubjectPublicKeyInfo',  from
> pem_decode_public_key, should rather be handled in the
> function pem_entry_decode. As I think the normal thing is that you
> want the actual key and not a 'SubjectPublicKeyInfo', that would
> mean just a little more decoding is done by pem_entry_decode. (You can
> match on the 'SubjectPublicKeyInfo' in the function head to
> create a clause for this.)

Sure.  I agree that the common case is that you want the public key in
a form that can be used for encrypt/decrypt as easily as possible.
I'll try reworking things so that this happens inside pem_entry_decode
-- and then remove the pem_decode_public_key function.

Can you point me at docs on how to run the tests for the public_key
module?

> It will not then be a 100 % symmetric with pem_entry_encode but I
> think  that is ok, it could be mentioned in the documentation.
> Another reason that this is a good idea is that it will not then be
> sensitive to that the public_key is the only entry in the file.
> PEM files may contain several entries which is not handled by your
> function.

Do you think it should be possible to reproduce the
SubjectPublicKeyInfo-style PEM file given an 'RSAPublicKey' record
type?  I think this has some value, aside from symmetry, because it is
the default output of openssl.

I admit that I haven't yet worked through the encoding cases in any
detail, so perhaps I'm not clear on how this is supposed to work.

> When it comes to the function der_decode_publick_key I am not sure it
> is needed as I think it
> is uncommon that you end up with a "DER-blob" that you do not know how
> it is encoded.

ok, will remove.

+ seth

--
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[Ingela Andin]

Hi Seth,

2011/1/24 Seth Falcon <[hidden email]>:
> On Mon, Jan 24, 2011 at 2:51 AM, Ingela Andin <[hidden email]> wrote:
>> I think that the decoding of  'SubjectPublicKeyInfo',  from
>> pem_decode_public_key, should rather be handled in the
>> function pem_entry_decode. As I think the normal thing is that you
>> want the actual key and not a 'SubjectPublicKeyInfo', that would
>> mean just a little more decoding is done by pem_entry_decode. (You can
>> match on the 'SubjectPublicKeyInfo' in the function head to
>> create a clause for this.)


> Sure.  I agree that the common case is that you want the public key in
> a form that can be used for encrypt/decrypt as easily as possible.
> I'll try reworking things so that this happens inside pem_entry_decode
> -- and then remove the pem_decode_public_key function.
>
> Can you point me at docs on how to run the tests for the public_key
> module?

https://github.com/erlang/otp/wiki/Running-tests

I think this should still work, but we are in the process of  migrating from one
testfrontend to another. So maybe Lucas can point you eleswhere if needed.

>> It will not then be a 100 % symmetric with pem_entry_encode but I
>> think  that is ok, it could be mentioned in the documentation.
>> Another reason that this is a good idea is that it will not then be
>> sensitive to that the public_key is the only entry in the file.
>> PEM files may contain several entries which is not handled by your
>> function.
>
> Do you think it should be possible to reproduce the
> SubjectPublicKeyInfo-style PEM file given an 'RSAPublicKey' record
> type?  I think this has some value, aside from symmetry, because it is
> the default output of openssl.
>
> I admit that I haven't yet worked through the encoding cases in any
> detail, so perhaps I'm not clear on how this is supposed to work.
>

I thought some more about this and I feel the right way to go is have
several clauses in pem_entry_encode for the asn1-type  'SubjectPublicKeyInfo'
some thing along the lines

pem_entry_decode( 'SubjectPublicKeyInfo',  #'RSAPublicKey'{}) ->

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[Ingela Andin-2]

Ah, sorry accidently hit send before finished ...

[...]

> I thought some more about this and I feel the right way to go is have
> several clauses in pem_entry_encode for the asn1-type  'SubjectPublicKeyInfo'
> some thing along the lines
>
> pem_entry_decode(,  #'RSAPublicKey'{} = Key) ->
        SubjectPublicKeyInfo =
create_subject_public_key_info_from_rsa_public_key(Key),
        pem_entry_decode( 'SubjectPublicKeyInfo', Key).

Regards Ingela Erlang/OTP team - Ericsson AB

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[Seth Falcon-3]

On Mon, Jan 24, 2011 at 2:05 PM, Ingela Andin <[hidden email]> wrote:

> Ah, sorry accidently hit send before finished ...
>
> [...]
>
>> I thought some more about this and I feel the right way to go is have
>> several clauses in pem_entry_encode for the asn1-type  'SubjectPublicKeyInfo'
>> some thing along the lines
>>
>> pem_entry_decode(,  #'RSAPublicKey'{} = Key) ->
>        SubjectPublicKeyInfo =
> create_subject_public_key_info_from_rsa_public_key(Key),
>        pem_entry_decode( 'SubjectPublicKeyInfo', Key).
>

If you meant pem_entry_encode in the lines above, then I think I
follow you.  Otherwise, I'm confused about whether we are talking
about encode or decode :-)

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