[Pkg-gnupg-commit] [gnupg2] 07/34: gpg, sm: Error out on compliance mismatch while decrypting.

[Daniel Kahn Gillmor]

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dkg pushed a commit to branch upstream
in repository gnupg2.

commit 4e117f206beb38287ddcd3251fb7baabadfbddbb
Author: Werner Koch <wk at gnupg.org>
Date:   Tue Aug 1 08:41:47 2017 +0200

    gpg,sm: Error out on compliance mismatch while decrypting.
    
    * g10/pubkey-enc.c (get_session_key): Bail out if the algo is not
    allowed in the current compliance mode.
    * sm/decrypt.c (gpgsm_decrypt): Ditto.
    --
    
    The idea here is that the owner of the key created a non-compliant key
    and later receives a mail encrypted to that key.  The sender should
    have checked this key too but we can't guarantee that.  By hard
    failing here the owner of the key will notice that he had created a
    non-compliant key and thus has a chance to generate a new compliant
    key.  In case the compliant criteria changes and the owner wants to
    decrypt an old message he can still switch gpg to another compliant
    mode.
    
    Fixes-commit: a0d0cbee7654ad7582400efaa92d493cd8e669e9
    GnuPG-bug-id: 3308
    Signed-off-by: Werner Koch <wk at gnupg.org>
---
 g10/pubkey-enc.c | 42 ++++++++++++++++++++++++------------------
 sm/decrypt.c     | 19 ++++++++++++-------
 2 files changed, 36 insertions(+), 25 deletions(-)

diff --git a/g10/pubkey-enc.c b/g10/pubkey-enc.c
index 272562b..d7ba953 100644
--- a/g10/pubkey-enc.c
+++ b/g10/pubkey-enc.c
@@ -90,16 +90,19 @@ get_session_key (ctrl_t ctrl, PKT_pubkey_enc * k, DEK * dek)
       sk->pubkey_algo = k->pubkey_algo; /* We want a pubkey with this algo.  */
       if (!(rc = get_seckey (ctrl, sk, k->keyid)))
         {
-          /* Print compliance warning.  */
-          if (!gnupg_pk_is_compliant (opt.compliance,
-                                      sk->pubkey_algo,
-                                      sk->pkey, nbits_from_pk (sk), NULL))
-            log_info (_("Note: key %s is not suitable for encryption"
-                        " in %s mode\n"),
-                      keystr_from_pk (sk),
-                      gnupg_compliance_option_string (opt.compliance));
-
-          rc = get_it (ctrl, k, dek, sk, k->keyid);
+          /* Check compliance.  */
+          if (! gnupg_pk_is_allowed (opt.compliance, PK_USE_DECRYPTION,
+                                     sk->pubkey_algo,
+                                     sk->pkey, nbits_from_pk (sk), NULL))
+            {
+              log_info (_("key %s is not suitable for decryption"
+                          " in %s mode\n"),
+                        keystr_from_pk (sk),
+                        gnupg_compliance_option_string (opt.compliance));
+              rc = gpg_error (GPG_ERR_PUBKEY_ALGO);
+            }
+          else
+            rc = get_it (ctrl, k, dek, sk, k->keyid);
         }
     }
   else if (opt.skip_hidden_recipients)
@@ -128,14 +131,17 @@ get_session_key (ctrl_t ctrl, PKT_pubkey_enc * k, DEK * dek)
             log_info (_("anonymous recipient; trying secret key %s ...\n"),
                       keystr (keyid));
 
-          /* Print compliance warning.  */
-          if (!gnupg_pk_is_compliant (opt.compliance,
-                                      sk->pubkey_algo,
-                                      sk->pkey, nbits_from_pk (sk), NULL))
-            log_info (_("Note: key %s is not suitable for encryption"
-                        " in %s mode\n"),
-                      keystr_from_pk (sk),
-                      gnupg_compliance_option_string (opt.compliance));
+          /* Check compliance.  */
+          if (! gnupg_pk_is_allowed (opt.compliance, PK_USE_DECRYPTION,
+                                     sk->pubkey_algo,
+                                     sk->pkey, nbits_from_pk (sk), NULL))
+            {
+              log_info (_("key %s is not suitable for decryption"
+                          " in %s mode\n"),
+                          keystr_from_pk (sk),
+                          gnupg_compliance_option_string (opt.compliance));
+              continue;
+            }
 
           rc = get_it (ctrl, k, dek, sk, keyid);
           if (!rc)
diff --git a/sm/decrypt.c b/sm/decrypt.c
index cdce1d4..60ed14a 100644
--- a/sm/decrypt.c
+++ b/sm/decrypt.c
@@ -480,19 +480,22 @@ gpgsm_decrypt (ctrl_t ctrl, int in_fd, estream_t out_fp)
                     unsigned int nbits;
                     int pk_algo = gpgsm_get_key_algo_info (cert, &nbits);
 
-                    /* Print compliance warning.  */
-                    if (! gnupg_pk_is_compliant (opt.compliance,
-                                                 pk_algo, NULL, nbits, NULL))
+                    /* Check compliance.  */
+                    if (!gnupg_pk_is_allowed (opt.compliance,
+                                              PK_USE_DECRYPTION,
+                                              pk_algo, NULL, nbits, NULL))
                       {
                         char  kidstr[10+1];
 
                         snprintf (kidstr, sizeof kidstr, "0x%08lX",
                                   gpgsm_get_short_fingerprint (cert, NULL));
                         log_info
-                          (_("Note: key %s is not suitable for encryption"
+                          (_("key %s is not suitable for decryption"
                              " in %s mode\n"),
                            kidstr,
                            gnupg_compliance_option_string (opt.compliance));
+                        rc = gpg_error (GPG_ERR_PUBKEY_ALGO);
+                        goto oops;
                       }
 
                     /* Check that all certs are compliant with CO_DE_VS.  */
@@ -504,9 +507,11 @@ gpgsm_decrypt (ctrl_t ctrl, int in_fd, estream_t out_fp)
 
                 oops:
                   if (rc)
-                    /* We cannot check compliance of certs that we
-                     * don't have.  */
-                    is_de_vs = 0;
+                    {
+                      /* We cannot check compliance of certs that we
+                       * don't have.  */
+                      is_de_vs = 0;
+                    }
                   xfree (issuer);
                   xfree (serial);
                   ksba_cert_release (cert);

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