DKIM: Enforce any "h" field present in the DNS publickey record. This can be set...

hash types, eg sha256, in signatues.  There is an IETF draft in discussion which deprecates sha1 so this
feature may start to be used.

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 0b4076c20dfaef1be45c8bc2db8c707a1cab33ee..ecb6b33a975abc406307de166970943a8e0b6b5b 100644 (file)
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -138,6 +138,9 @@ JH/21 Bug 2151: Avoid using SIZE on the MAIL for a callout verify, on any but
 JH/22 Retire historical build files to an "unsupported" subdir.  These are
       defined as "ones for which we have no current evidence of testing".
 
+JH/23 DKIM: enforce the DNS pubkey record "h" permitted-hashes optional field,
+      if present.  Previously it was ignored.
+
 
 Exim version 4.89
 -----------------

diff --git a/src/src/pdkim/pdkim.c b/src/src/pdkim/pdkim.c
index d41b60f1361b510a9ddc6ecd8a13a8424cb67821..d289ec7a336e60e9e8322778c34f60f046bf8031 100644 (file)
--- a/src/src/pdkim/pdkim.c
+++ b/src/src/pdkim/pdkim.c
@@ -132,6 +132,7 @@ switch(ext_status)
   {
   case PDKIM_VERIFY_FAIL_BODY: return "PDKIM_VERIFY_FAIL_BODY";
   case PDKIM_VERIFY_FAIL_MESSAGE: return "PDKIM_VERIFY_FAIL_MESSAGE";
+  case PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH: return "PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH";
   case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: return "PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE";
   case PDKIM_VERIFY_INVALID_BUFFER_SIZE: return "PDKIM_VERIFY_INVALID_BUFFER_SIZE";
   case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: return "PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD";
@@ -644,12 +645,8 @@ for (p = raw_record; ; p++)
              case 'v':
                pub->version = string_copy(cur_val); break;
              case 'h':
+               pub->hashes = string_copy(cur_val); break;
              case 'k':
-/* This field appears to never be used. Also, unclear why
-a 'k' (key-type_ would go in this field name.  There is a field
-"keytype", also never used.
-               pub->hashes = string_copy(cur_val);
-*/
                break;
              case 'g':
                pub->granularity = string_copy(cur_val); break;
@@ -682,7 +679,11 @@ a 'k' (key-type_ would go in this field name.  There is a field
 
 /* Set fallback defaults */
 if (!pub->version    ) pub->version     = string_copy(PDKIM_PUB_RECORD_VERSION);
-else if (Ustrcmp(pub->version, PDKIM_PUB_RECORD_VERSION) != 0) return NULL;
+else if (Ustrcmp(pub->version, PDKIM_PUB_RECORD_VERSION) != 0)
+  {
+  DEBUG(D_acl) debug_printf(" Bad v= field\n");
+  return NULL;
+  }
 
 if (!pub->granularity) pub->granularity = string_copy(US"*");
 /*
@@ -694,6 +695,7 @@ if (!pub->srvtype    ) pub->srvtype     = string_copy(US"*");
 if (pub->key.data)
   return pub;
 
+DEBUG(D_acl) debug_printf(" Missing p= field\n");
 return NULL;
 }
 
@@ -1631,6 +1633,25 @@ while (sig)
     if (!(sig->pubkey = pdkim_key_from_dns(ctx, sig, &vctx, err)))
       goto NEXT_VERIFY;
 
+    /* If the pubkey limits to a list of specific hashes, ignore sigs that
+    do not have the hash part of the sig algorithm matching */
+
+    if (sig->pubkey->hashes)
+      {
+      const uschar * list = sig->pubkey->hashes, * ele;
+      int sep = ':';
+      while ((ele = string_nextinlist(&list, &sep, NULL, 0)))
+       if (Ustrcmp(ele, pdkim_algos[sig->algo] + 4) == 0) break;
+      if (!ele)
+       {
+       DEBUG(D_acl) debug_printf("pubkey h=%s vs sig a=%s\n",
+                               sig->pubkey->hashes, pdkim_algos[sig->algo]);
+       sig->verify_status =      PDKIM_VERIFY_FAIL;
+       sig->verify_ext_status =  PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH;
+       goto NEXT_VERIFY;
+       }
+      }
+
     /* Check the signature */
     if ((*err = exim_rsa_verify(&vctx, is_sha1, &hhash, &sig->sighash)))
       {

diff --git a/src/src/pdkim/pdkim.h b/src/src/pdkim/pdkim.h
index 78e3c3c8b148f11b84e6e5e5ac70e4a1c33f39cc..9899356d572ca05ad954791af96e34d7480d907c 100644 (file)
--- a/src/src/pdkim/pdkim.h
+++ b/src/src/pdkim/pdkim.h
@@ -51,12 +51,13 @@
 
 #define PDKIM_VERIFY_FAIL_BODY                    1
 #define PDKIM_VERIFY_FAIL_MESSAGE                 2
-#define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   3
-#define PDKIM_VERIFY_INVALID_BUFFER_SIZE          4
-#define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     5
-#define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        6
-#define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      7
-#define PDKIM_VERIFY_INVALID_DKIM_VERSION         8
+#define PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH      3
+#define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   4
+#define PDKIM_VERIFY_INVALID_BUFFER_SIZE          5
+#define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     6
+#define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        7
+#define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      8
+#define PDKIM_VERIFY_INVALID_DKIM_VERSION         9
 
 /* -------------------------------------------------------------------------- */
 /* Some parameter values */
@@ -100,8 +101,8 @@ typedef struct pdkim_pubkey {
   uschar *version;                /* v=  */
   uschar *granularity;            /* g=  */
 
-#ifdef notdef
   uschar *hashes;                 /* h=  */
+#ifdef notdef
   uschar *keytype;                /* k=  */
 #endif
   uschar *srvtype;                /* s=  */

diff --git a/test/dnszones-src/db.test.ex b/test/dnszones-src/db.test.ex
index f7c9e313bbf7589913dc804b3f44a297f846e256..73db57f9ce60cf8d0649d7e5174a21c1bdfc7301 100644 (file)
--- a/test/dnszones-src/db.test.ex
+++ b/test/dnszones-src/db.test.ex
@@ -491,13 +491,19 @@ DELAY=1500 delay1500 A HOSTIPV4
 ;  openssl rsa -in aux-fixed/dkim/dkim.private -out /dev/stdout -pubout -outform PEM
 ;
 ; Deliberate bad version, having extra backslashes
+; sha256-hash-only version.... appears to be too long, gets truncated
 ;
 ; Another, 512-bit (with a Notes field)
+; 512 requiring sha1 hash
+; 512 requiring sha256 hash
 ;
 sel._domainkey TXT "v=DKIM1; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXRFf+VhT+lCgFhhSkinZKcFNeRzjYdW8vT29Rbb3NadvTFwAd+cVLPFwZL8H5tUD/7JbUPqNTCPxmpgIL+V5T4tEZMorHatvvUM2qfcpQ45IfsZ+YdhbIiAslHCpy4xNxIR3zylgqRUF4+Dtsaqy3a5LhwMiKCLrnzhXk1F1hxwIDAQAB"
 sel_bad._domainkey TXT "v=DKIM1\; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXRFf+VhT+lCgFhhSkinZKcFNeRzjYdW8vT29Rbb3NadvTFwAd+cVLPFwZL8H5tUD/7JbUPqNTCPxmpgIL+V5T4tEZMorHatvvUM2qfcpQ45IfsZ+YdhbIiAslHCpy4xNxIR3zylgqRUF4+Dtsaqy3a5LhwMiKCLrnzhXk1F1hxwIDAQAB"
+sel_sha256._domainkey TXT "v=DKIM1; h=sha256; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXRFf+VhT+lCgFhhSkinZKcFNeRzjYdW8vT29Rbb3NadvTFwAd+cVLPFwZL8H5tUD/7JbUPqNTCPxmpgIL+V5T4tEZMorHatvvUM2qfcpQ45IfsZ+YdhbIiAslHCpy4xNxIR3zylgqRUF4+Dtsaqy3a5LhwMiKCLrnzhXk1F1hxwIDAQAB"
 
 ses._domainkey TXT "v=DKIM1; n=halfkilo; p=MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAL6eAQxd9didJ0/+05iDwJOqT6ly826Vi8aGPecsBiYK5/tAT97fxXk+dPWMZp9kQxtknEzYjYjAydzf+HQ2yJMCAwEAAQ=="
+ses_sha1._domainkey TXT "v=DKIM1; h=sha1; p=MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAL6eAQxd9didJ0/+05iDwJOqT6ly826Vi8aGPecsBiYK5/tAT97fxXk+dPWMZp9kQxtknEzYjYjAydzf+HQ2yJMCAwEAAQ=="
+ses_sha256._domainkey TXT "v=DKIM1; h=sha256; p=MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAL6eAQxd9didJ0/+05iDwJOqT6ly826Vi8aGPecsBiYK5/tAT97fxXk+dPWMZp9kQxtknEzYjYjAydzf+HQ2yJMCAwEAAQ=="
 
 
 ; End

diff --git a/test/log/4500 b/test/log/4500
index 0e0f8400d30afb51e83ebaec385b284ca7e41a88..ec8ef088e148cbd81b72a93b30e226635d773ad4 100644 (file)
--- a/test/log/4500
+++ b/test/log/4500
@@ -10,3 +10,6 @@
 1999-03-02 09:44:33 10HmaZ-0005vi-00 DKIM: d=test.ex s=sel c=simple/simple a=rsa-sha256 b=1024 [verification succeeded]
 1999-03-02 09:44:33 10HmaZ-0005vi-00 signer: test.ex bits: 1024
 1999-03-02 09:44:33 10HmaZ-0005vi-00 <= CALLER@bloggs.com H=(xxx) [127.0.0.1] P=smtp S=sss id=qwerty1234@disco-zombie.net
+1999-03-02 09:44:33 10HmbA-0005vi-00 DKIM: d=test.ex s=ses_sha1 c=simple/simple a=rsa-sha1 b=512 [verification succeeded]
+1999-03-02 09:44:33 10HmbA-0005vi-00 signer: test.ex bits: 512
+1999-03-02 09:44:33 10HmbA-0005vi-00 <= CALLER@bloggs.com H=(xxx) [127.0.0.1] P=smtp S=sss id=qwerty1234@disco-zombie.net

diff --git a/test/log/4506 b/test/log/4506
index fb0f2256784fa7d304b5039d00ac583686fbc84c..027169df06fc3294bf0b51590b8d8c6d1eb41d6a 100644 (file)
--- a/test/log/4506
+++ b/test/log/4506
@@ -13,3 +13,6 @@
 1999-03-02 09:44:33 10HmbA-0005vi-00 DKIM: validation error: RSA_LONG_LINE
 1999-03-02 09:44:33 10HmbA-0005vi-00 DKIM: Error during validation, disabling signature verification: RSA_LONG_LINE
 1999-03-02 09:44:33 10HmbA-0005vi-00 <= CALLER@bloggs.com H=(xxx) [127.0.0.1] P=smtp S=sss id=qwerty1234@disco-zombie.net
+1999-03-02 09:44:33 10HmbB-0005vi-00 DKIM: d=test.ex s=ses_sha256 c=simple/simple a=rsa-sha1 b=512 [verification failed - unspecified reason]
+1999-03-02 09:44:33 10HmbB-0005vi-00 signer: test.ex bits: 512
+1999-03-02 09:44:33 10HmbB-0005vi-00 <= CALLER@bloggs.com H=(xxx) [127.0.0.1] P=smtp S=sss id=qwerty1234@disco-zombie.net

diff --git a/test/scripts/4500-DKIM/4500 b/test/scripts/4500-DKIM/4500
index 6728b141d3056137c6c5608b870daf5e5dac001c..6b3ff5fcf3409527824e0161f37a20cfa1df932e 100644 (file)
--- a/test/scripts/4500-DKIM/4500
+++ b/test/scripts/4500-DKIM/4500
@@ -93,6 +93,40 @@ Date: Thu, 19 Nov 2015 17:00:07 -0700
 Message-ID: <qwerty1234@disco-zombie.net>
 Subject: simple test
 
+This is a simple test.
+.
+??? 250
+QUIT
+??? 221
+****
+#
+#
+# This should pass.  The pubkey dns decord has a additional sha1-only h= field
+#
+#  - sha1, 512b
+# Mail original in aux-fixed/4500.msg1.txt
+# Sig generated by: perl aux-fixed/dkim/sign.pl --keyfile=aux-fixed/dkim/dkim512.private \
+#                       --method=simple/simple --selector=ses_sha1 < aux-fixed/4500.msg1.txt
+client 127.0.0.1 PORT_D
+??? 220
+HELO xxx
+??? 250
+MAIL FROM:<CALLER@bloggs.com>
+??? 250
+RCPT TO:<a@test.ex>
+??? 250
+DATA
+??? 354
+DKIM-Signature: v=1; a=rsa-sha1; c=simple/simple; d=test.ex; h=from:to
+       :date:message-id:subject; s=ses_sha1; bh=OB9dZVu7+5/ufs3TH9leIcE
+       pXSo=; b=hG14R3Eb/f13Pw6J0LmovHAL01KHVmVrTZ7KJrqieYTQemUaseoU2pB
+       7/g8NUwG/AsYoaw3gaAK8PqxSk2lcIQ==
+From: mrgus@text.ex
+To: bakawolf@yahoo.com
+Date: Thu, 19 Nov 2015 17:00:07 -0700
+Message-ID: <qwerty1234@disco-zombie.net>
+Subject: simple test
+
 This is a simple test.
 .
 ??? 250

diff --git a/test/scripts/4500-DKIM/4506 b/test/scripts/4500-DKIM/4506
index 6eb81cc16ee1c805cbca918cf1d2ccaf98979972..e8d7c41f021fc82182cfc640b3caf432a42a4c32 100644 (file)
--- a/test/scripts/4500-DKIM/4506
+++ b/test/scripts/4500-DKIM/4506
@@ -134,6 +134,41 @@ QUIT
 ****
 #
 #
+# This should fail as the sig on the mail uses sha1 but the dns record requires sha256
+#
+#  - sha256, 512b
+# Mail original in aux-fixed/4500.msg1.txt
+# Sig generated by: perl aux-fixed/dkim/sign.pl --keyfile=aux-fixed/dkim/dkim512.private \
+#                       --method=simple/simple --selector=ses_sha1 < aux-fixed/4500.msg1.txt
+# and then modifying the s= manually
+client 127.0.0.1 PORT_D
+??? 220
+HELO xxx
+??? 250
+MAIL FROM:<CALLER@bloggs.com>
+??? 250
+RCPT TO:<a@test.ex>
+??? 250
+DATA
+??? 354
+DKIM-Signature: v=1; a=rsa-sha1; c=simple/simple; d=test.ex; h=from:to
+       :date:message-id:subject; s=ses_sha256; bh=OB9dZVu7+5/ufs3TH9leIcE
+       pXSo=; b=hG14R3Eb/f13Pw6J0LmovHAL01KHVmVrTZ7KJrqieYTQemUaseoU2pB
+       7/g8NUwG/AsYoaw3gaAK8PqxSk2lcIQ==
+From: mrgus@text.ex
+To: bakawolf@yahoo.com
+Date: Thu, 19 Nov 2015 17:00:07 -0700
+Message-ID: <qwerty1234@disco-zombie.net>
+Subject: simple test
+
+This is a simple test.
+.
+??? 250
+QUIT
+??? 221
+****
+#
+#
 killdaemon
 no_stdout_check
 no_msglog_check

diff --git a/test/stderr/4520 b/test/stderr/4520
index c1bafcdcc3d219dedeca0d5b7937f33f8abcc421..fc64a9e93cbb305d624931e17881b14f2b94f6b6 100644 (file)
--- a/test/stderr/4520
+++ b/test/stderr/4520
@@ -28,6 +28,7 @@ PDKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
  Raw record: v=DKIM1\;{SP}p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXRFf+VhT+lCgFhhSkinZKcFNeRzjYdW8vT29Rbb3NadvTFwAd+cVLPFwZL8H5tUD/7JbUPqNTCPxmpgIL+V5T4tEZMorHatvvUM2qfcpQ45IfsZ+YdhbIiAslHCpy4xNxIR3zylgqRUF4+Dtsaqy3a5LhwMiKCLrnzhXk1F1hxwIDAQAB
  v=DKIM1\
  p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXRFf+VhT+lCgFhhSkinZKcFNeRzjYdW8vT29Rbb3NadvTFwAd+cVLPFwZL8H5tUD/7JbUPqNTCPxmpgIL+V5T4tEZMorHatvvUM2qfcpQ45IfsZ+YdhbIiAslHCpy4xNxIR3zylgqRUF4+Dtsaqy3a5LhwMiKCLrnzhXk1F1hxwIDAQAB
+ Bad v= field
  Error while parsing public key record
 WARNING: bad dkim key in dns
 PDKIM (finished checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<