public_key: ssh host key fingerprint generator added

3 files changed, 126 insertions, 1 deletions

diff --git a/lib/public_key/doc/src/public_key.xml b/lib/public_key/doc/src/public_key.xml
index 385604677c..edebfe0f84 100644
--- a/lib/public_key/doc/src/public_key.xml
+++ b/lib/public_key/doc/src/public_key.xml
@@ -822,6 +822,36 @@ fun(#'DistributionPoint'{}, #'CertificateList'{},
   </func>
 
   <func>
+    <name>ssh_hostkey_fingerprint(HostKey) -> string()</name>
+    <name>ssh_hostkey_fingerprint(DigestType, HostKey) -> string()</name>
+    <fsummary>Calculates a ssh fingerprint for a hostkey.</fsummary>
+    <type>
+      <v>Key = public_key()</v>
+      <v>DigestType = digest_type()</v>
+    </type>
+  <desc>
+    <p>Calculates a ssh fingerprint from a public host key as openssh does.</p>
+    <p>The algorithm in <c>ssh_hostkey_fingerprint/1</c> is md5 to be compatible with older
+    ssh-keygen commands. The string from the second variant is prepended by the algorithm name
+    in uppercase as in newer ssh-keygen commands.</p>
+    <p>Examples:</p>
+    <code>
+ 2> public_key:ssh_hostkey_fingerprint(Key).    
+ "f5:64:a6:c1:5a:cb:9f:0a:10:46:a2:5c:3e:2f:57:84"
+
+ 3> public_key:ssh_hostkey_fingerprint(md5,Key).
+ "MD5:f5:64:a6:c1:5a:cb:9f:0a:10:46:a2:5c:3e:2f:57:84"
+
+ 4> public_key:ssh_hostkey_fingerprint(sha,Key).
+ "SHA1:bSLY/C4QXLDL/Iwmhyg0PGW9UbY"
+
+ 5> public_key:ssh_hostkey_fingerprint(sha256,Key).
+ "SHA256:aZGXhabfbf4oxglxltItWeHU7ub3Dc31NcNw2cMJePQ"
+    </code>
+  </desc>
+  </func>
+
+  <func>
     <name>verify(Msg, DigestType, Signature, Key) -> boolean()</name>
     <fsummary>Verifies a digital signature.</fsummary>
     <type>
diff --git a/lib/public_key/src/public_key.erl b/lib/public_key/src/public_key.erl
index d23abfe256..418a824ab7 100644
--- a/lib/public_key/src/public_key.erl
+++ b/lib/public_key/src/public_key.erl
@@ -49,6 +49,7 @@
 	 pkix_normalize_name/1,
 	 pkix_path_validation/3,
 	 ssh_decode/2, ssh_encode/2,
+	 ssh_hostkey_fingerprint/1, ssh_hostkey_fingerprint/2,
 	 ssh_curvename2oid/1, oid2ssh_curvename/1,
 	 pkix_crls_validate/3,
 	 pkix_dist_point/1,
@@ -819,6 +820,41 @@ oid2ssh_curvename(?'secp384r1') -> <<"nistp384">>;
 oid2ssh_curvename(?'secp521r1') -> <<"nistp521">>.
 
 %%--------------------------------------------------------------------
+-spec ssh_hostkey_fingerprint(public_key()) -> string().
+-spec ssh_hostkey_fingerprint(md5, public_key()) -> string().
+
+ssh_hostkey_fingerprint(Key) ->
+    sshfp_string(md5, Key).
+
+ssh_hostkey_fingerprint(HashAlg, Key) ->
+    lists:concat([sshfp_alg_name(HashAlg),
+		  [$: | sshfp_string(HashAlg, Key)]
+		 ]).
+
+sshfp_string(HashAlg, Key) ->
+    %% Other HashAlgs than md5 will be printed with
+    %% other formats than hextstr by
+    %%    ssh-keygen -E <alg> -lf <file>
+    fp_fmt(sshfp_fmt(HashAlg), crypto:hash(HashAlg, public_key:ssh_encode(Key,ssh2_pubkey))).
+
+sshfp_alg_name(sha) -> "SHA1";
+sshfp_alg_name(Alg) -> string:to_upper(atom_to_list(Alg)).
+
+sshfp_fmt(md5) -> hexstr;
+sshfp_fmt(_) -> b64.
+
+fp_fmt(hexstr, Bin) ->
+    lists:flatten(string:join([io_lib:format("~2.16.0b",[C1]) || <<C1>> <= Bin], ":"));
+fp_fmt(b64, Bin) ->
+    %% This function clause *seems* to be
+    %%    [C || C<-base64:encode_to_string(Bin), C =/= $=]
+    %% but I am not sure. Must be checked.
+    B64Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
+    BitsInLast = 8*size(Bin) rem 6,
+    Padding = (6-BitsInLast) rem 6, % Want BitsInLast = [1:5] to map to padding [5:1] and 0 -> 0
+    [lists:nth(C+1,B64Chars) || <<C:6>> <= <<Bin/binary,0:Padding>> ].
+
+%%--------------------------------------------------------------------
 -spec short_name_hash({rdnSequence, [#'AttributeTypeAndValue'{}]}) ->
 			     string().
 
diff --git a/lib/public_key/test/public_key_SUITE.erl b/lib/public_key/test/public_key_SUITE.erl
index b22b69a0f2..f4ae8042d0 100644
--- a/lib/public_key/test/public_key_SUITE.erl
+++ b/lib/public_key/test/public_key_SUITE.erl
@@ -45,7 +45,14 @@ all() ->
      {group, sign_verify},
      pkix, pkix_countryname, pkix_emailaddress, pkix_path_validation,
      pkix_iso_rsa_oid, pkix_iso_dsa_oid, pkix_crl, general_name,
-     short_cert_issuer_hash, short_crl_issuer_hash].
+     short_cert_issuer_hash, short_crl_issuer_hash,
+     ssh_hostkey_fingerprint_md5_implicit,
+     ssh_hostkey_fingerprint_md5,
+     ssh_hostkey_fingerprint_sha,
+     ssh_hostkey_fingerprint_sha256,
+     ssh_hostkey_fingerprint_sha384,
+     ssh_hostkey_fingerprint_sha512
+    ].
 
 groups() -> 
     [{pem_decode_encode, [], [dsa_pem, rsa_pem, ec_pem, encrypted_pem,
@@ -529,6 +536,48 @@ ssh_openssh_public_key_long_header(Config) when is_list(Config) ->
     Decoded = public_key:ssh_decode(Encoded, rfc4716_public_key).
 
 %%--------------------------------------------------------------------
+%% Check of different host keys left to later
+ssh_hostkey_fingerprint_md5_implicit(_Config) ->
+    Expected = "4b:0b:63:de:0f:a7:3a:ab:2c:cc:2d:d1:21:37:1d:3a",
+    Expected = public_key:ssh_hostkey_fingerprint(ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
+%% Check of different host keys left to later
+ssh_hostkey_fingerprint_md5(_Config) ->
+    Expected = "MD5:4b:0b:63:de:0f:a7:3a:ab:2c:cc:2d:d1:21:37:1d:3a",
+    Expected = public_key:ssh_hostkey_fingerprint(md5, ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
+%% Since this kind of fingerprint is not available yet on standard
+%% distros, we do like this instead. The Expected is generated with:
+%%       $ openssh-7.3p1/ssh-keygen -E sha1 -lf <file>
+%%       2048 SHA1:Soammnaqg06jrm2jivMSnzQGlmk none@example.org (RSA)
+ssh_hostkey_fingerprint_sha(_Config) ->
+    Expected = "SHA1:Soammnaqg06jrm2jivMSnzQGlmk",
+    Expected = public_key:ssh_hostkey_fingerprint(sha, ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
+%% Since this kind of fingerprint is not available yet on standard
+%% distros, we do like this instead.
+ssh_hostkey_fingerprint_sha256(_Config) ->
+    Expected = "SHA256:T7F1BahkJWR7iJO8+rpzWOPbp7LZP4MlNrDExdNYOvY",
+    Expected = public_key:ssh_hostkey_fingerprint(sha256, ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
+%% Since this kind of fingerprint is not available yet on standard
+%% distros, we do like this instead.
+ssh_hostkey_fingerprint_sha384(_Config) ->
+    Expected = "SHA384:QhkLoGNI4KXdPvC//HxxSCP3uTQVADqxdajbgm+Gkx9zqz8N94HyP1JmH8C4/aEl",
+    Expected = public_key:ssh_hostkey_fingerprint(sha384, ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
+%% Since this kind of fingerprint is not available yet on standard
+%% distros, we do like this instead.
+ssh_hostkey_fingerprint_sha512(_Config) ->
+    Expected = "SHA512:ezUismvm3ADQQb6Nm0c1DwQ6ydInlJNfsnSQejFkXNmABg1Aenk9oi45CXeBOoTnlfTsGG8nFDm0smP10PBEeA",
+    Expected = public_key:ssh_hostkey_fingerprint(sha512, ssh_hostkey(rsa)).
+
+%%--------------------------------------------------------------------
 encrypt_decrypt() ->
     [{doc, "Test public_key:encrypt_private and public_key:decrypt_public"}].
 encrypt_decrypt(Config) when is_list(Config) -> 
@@ -929,3 +978,13 @@ incorrect_countryname_pkix_cert() ->
 
 incorrect_emailaddress_pkix_cert() ->
     <<48,130,3,74,48,130,2,50,2,9,0,133,49,203,25,198,156,252,230,48,13,6,9,42,134, 72,134,247,13,1,1,5,5,0,48,103,49,11,48,9,6,3,85,4,6,19,2,65,85,49,19,48,17, 6,3,85,4,8,12,10,83,111,109,101,45,83,116,97,116,101,49,33,48,31,6,3,85,4,10, 12,24,73,110,116,101,114,110,101,116,32,87,105,100,103,105,116,115,32,80,116, 121,32,76,116,100,49,32,48,30,6,9,42,134,72,134,247,13,1,9,1,12,17,105,110, 118,97,108,105,100,64,101,109,97,105,108,46,99,111,109,48,30,23,13,49,51,49, 49,48,55,50,48,53,54,49,56,90,23,13,49,52,49,49,48,55,50,48,53,54,49,56,90, 48,103,49,11,48,9,6,3,85,4,6,19,2,65,85,49,19,48,17,6,3,85,4,8,12,10,83,111, 109,101,45,83,116,97,116,101,49,33,48,31,6,3,85,4,10,12,24,73,110,116,101, 114,110,101,116,32,87,105,100,103,105,116,115,32,80,116,121,32,76,116,100,49, 32,48,30,6,9,42,134,72,134,247,13,1,9,1,12,17,105,110,118,97,108,105,100,64, 101,109,97,105,108,46,99,111,109,48,130,1,34,48,13,6,9,42,134,72,134,247,13, 1,1,1,5,0,3,130,1,15,0,48,130,1,10,2,130,1,1,0,190,243,49,213,219,60,232,105, 1,127,126,9,130,15,60,190,78,100,148,235,246,223,21,91,238,200,251,84,55,212, 78,32,120,61,85,172,0,144,248,5,165,29,143,79,64,178,51,153,203,76,115,238, 192,49,173,37,121,203,89,62,157,13,181,166,30,112,154,40,202,140,104,211,157, 73,244,9,78,236,70,153,195,158,233,141,42,238,2,143,160,225,249,27,30,140, 151,176,43,211,87,114,164,108,69,47,39,195,123,185,179,219,28,218,122,53,83, 77,48,81,184,14,91,243,12,62,146,86,210,248,228,171,146,225,87,51,146,155, 116,112,238,212,36,111,58,41,67,27,6,61,61,3,84,150,126,214,121,57,38,12,87, 121,67,244,37,45,145,234,131,115,134,58,194,5,36,166,52,59,229,32,47,152,80, 237,190,58,182,248,98,7,165,198,211,5,31,231,152,116,31,108,71,218,64,188, 178,143,27,167,79,15,112,196,103,116,212,65,197,94,37,4,132,103,91,217,73, 223,207,185,7,153,221,240,232,31,44,102,108,82,83,56,242,210,214,74,71,246, 177,217,148,227,220,230,4,176,226,74,194,37,2,3,1,0,1,48,13,6,9,42,134,72, 134,247,13,1,1,5,5,0,3,130,1,1,0,89,247,141,154,173,123,123,203,143,85,28,79, 73,37,164,6,17,89,171,224,149,22,134,17,198,146,158,192,241,41,253,58,230, 133,71,189,43,66,123,88,15,242,119,227,249,99,137,61,200,54,161,0,177,167, 169,114,80,148,90,22,97,78,162,181,75,93,209,116,245,46,81,232,64,157,93,136, 52,57,229,113,197,218,113,93,42,161,213,104,205,137,30,144,183,58,10,98,47, 227,177,96,40,233,98,150,209,217,68,22,221,133,27,161,152,237,46,36,179,59, 172,97,134,194,205,101,137,71,192,57,153,20,114,27,173,233,166,45,56,0,61, 205,45,202,139,7,132,103,248,193,157,184,123,43,62,172,236,110,49,62,209,78, 249,83,219,133,1,213,143,73,174,16,113,143,189,41,84,60,128,222,30,177,104, 134,220,52,239,171,76,59,176,36,113,176,214,118,16,44,235,21,167,199,216,200, 76,219,142,248,13,70,145,205,216,230,226,148,97,223,216,179,68,209,222,63, 140,137,24,164,192,149,194,79,119,247,75,159,49,116,70,241,70,116,11,40,119, 176,157,36,160,102,140,255,34,248,25,231,136,59>>.
+
+
+
+ssh_hostkey(rsa) ->
+    [{PKdecoded,_}] =
+	public_key:ssh_decode(
+	  <<"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDYXcYmsyJBstl4EfFYzfQJmSiUE162zvSGSoMYybShYOI6rnnyvvihfw8Aml+2gZ716F2tqG48FQ/yPZEGWNPMrCejPpJctaPWhpNdNMJ8KFXSEgr5bY2mEpa19DHmuDeXKzeJJ+X7s3fVdYc4FMk5731KIW6Huf019ZnTxbx0VKG6b1KAJBg3vpNsDxEMwQ4LFMB0JHVklOTzbxmpaeULuIxvl65A+eGeFVeo2Q+YI9UnwY1vSgmc9Azwy8Ie9Z0HpQBN5I7Uc5xnknT8V6xDhgNfXEfzsgsRdDfZLECt1WO/1gP9wkosvAGZWt5oG8pbNQWiQdFq536ck8WQD9WD none@example.org">>,
+	  public_key),
+    PKdecoded.
+