[PATCH 07/18] crypto: new decryption policy "auto"
Daniel Kahn Gillmor
dkg at fifthhorseman.net
Tue Oct 24 23:51:52 PDT 2017
This new automatic decryption policy should make it possible to
decrypt messages that we have stashed session keys for, without
incurring a call to the user's asymmetric keys.
---
doc/man1/notmuch-config.rst | 11 ++++++++---
lib/index.cc | 3 ++-
lib/indexopts.c | 13 ++++++++-----
lib/notmuch.h | 1 +
mime-node.c | 7 ++++---
notmuch-client.h | 4 +++-
notmuch.c | 3 ++-
test/T357-index-decryption.sh | 12 +++++++++++-
util/crypto.c | 8 +++++++-
util/crypto.h | 3 ++-
10 files changed, 48 insertions(+), 17 deletions(-)
diff --git a/doc/man1/notmuch-config.rst b/doc/man1/notmuch-config.rst
index 6961737f..14642062 100644
--- a/doc/man1/notmuch-config.rst
+++ b/doc/man1/notmuch-config.rst
@@ -142,9 +142,14 @@ The available configuration items are described below.
**[STORED IN DATABASE]**
When indexing an encrypted e-mail message, if this variable is
- set to true, notmuch will try to decrypt the message and index
- the cleartext. Be aware that the index is likely sufficient
- to reconstruct the cleartext of the message itself, so please
+ set to ``true``, notmuch will try to decrypt the message and
+ index the cleartext. If ``auto``, it will try to index the
+ cleartext if a stashed session key is already known for the message,
+ but will not try to access your secret keys. Use ``false`` to
+ avoid decrypting even when a session key is already known.
+
+ Be aware that the notmuch index is likely sufficient to
+ reconstruct the cleartext of the message itself, so please
ensure that the notmuch message index is adequately protected.
DO NOT USE ``index.try_decrypt=true`` without considering the
security of your index.
diff --git a/lib/index.cc b/lib/index.cc
index 483fe31d..d9a0018c 100644
--- a/lib/index.cc
+++ b/lib/index.cc
@@ -548,7 +548,8 @@ _index_encrypted_mime_part (notmuch_message_t *message,
}
}
#endif
- clear = _notmuch_crypto_decrypt (message, crypto_ctx, encrypted_data, NULL, &err);
+ clear = _notmuch_crypto_decrypt (notmuch_indexopts_get_try_decrypt (indexopts),
+ message, crypto_ctx, encrypted_data, NULL, &err);
if (err) {
_notmuch_database_log (notmuch, "Failed to decrypt during indexing. (%d:%d) [%s]\n",
err->domain, err->code, err->message);
diff --git a/lib/indexopts.c b/lib/indexopts.c
index 23557143..93a2c9eb 100644
--- a/lib/indexopts.c
+++ b/lib/indexopts.c
@@ -33,11 +33,14 @@ notmuch_database_get_default_indexopts (notmuch_database_t *db)
if (err)
return ret;
- if (try_decrypt &&
- ((!(strcasecmp(try_decrypt, "true"))) ||
- (!(strcasecmp(try_decrypt, "yes"))) ||
- (!(strcasecmp(try_decrypt, "1")))))
- notmuch_indexopts_set_try_decrypt (ret, NOTMUCH_DECRYPT_TRUE);
+ if (try_decrypt) {
+ if ((!(strcasecmp(try_decrypt, "true"))) ||
+ (!(strcasecmp(try_decrypt, "yes"))) ||
+ (!(strcasecmp(try_decrypt, "1"))))
+ notmuch_indexopts_set_try_decrypt (ret, NOTMUCH_DECRYPT_TRUE);
+ else if (!strcasecmp(try_decrypt, "auto"))
+ notmuch_indexopts_set_try_decrypt (ret, NOTMUCH_DECRYPT_AUTO);
+ }
free (try_decrypt);
return ret;
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 26fe8f81..7b1c61ad 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -2241,6 +2241,7 @@ notmuch_database_get_default_indexopts (notmuch_database_t *db);
typedef enum {
NOTMUCH_DECRYPT_FALSE,
NOTMUCH_DECRYPT_TRUE,
+ NOTMUCH_DECRYPT_AUTO,
} notmuch_decryption_policy_t;
/**
diff --git a/mime-node.c b/mime-node.c
index eb6a16c0..815c1787 100644
--- a/mime-node.c
+++ b/mime-node.c
@@ -205,7 +205,8 @@ node_decrypt_and_verify (mime_node_t *node, GMimeObject *part,
break;
node->decrypt_attempted = true;
- node->decrypted_child = _notmuch_crypto_decrypt (parent ? parent->envelope_file : NULL,
+ node->decrypted_child = _notmuch_crypto_decrypt (node->ctx->crypto->decrypt,
+ parent ? parent->envelope_file : NULL,
cryptoctx, encrypteddata, &decrypt_result, &err);
}
if (! node->decrypted_child) {
@@ -270,7 +271,7 @@ _mime_node_create (mime_node_t *parent, GMimeObject *part)
}
#if (GMIME_MAJOR_VERSION < 3)
- if ((GMIME_IS_MULTIPART_ENCRYPTED (part) && (node->ctx->crypto->decrypt == NOTMUCH_DECRYPT_TRUE))
+ if ((GMIME_IS_MULTIPART_ENCRYPTED (part) && (node->ctx->crypto->decrypt != NOTMUCH_DECRYPT_FALSE))
|| (GMIME_IS_MULTIPART_SIGNED (part) && node->ctx->crypto->verify)) {
GMimeContentType *content_type = g_mime_object_get_content_type (part);
const char *protocol = g_mime_content_type_get_parameter (content_type, "protocol");
@@ -286,7 +287,7 @@ _mime_node_create (mime_node_t *parent, GMimeObject *part)
#endif
/* Handle PGP/MIME parts */
- if (GMIME_IS_MULTIPART_ENCRYPTED (part) && (node->ctx->crypto->decrypt == NOTMUCH_DECRYPT_TRUE)) {
+ if (GMIME_IS_MULTIPART_ENCRYPTED (part) && (node->ctx->crypto->decrypt != NOTMUCH_DECRYPT_FALSE)) {
if (node->nchildren != 2) {
/* this violates RFC 3156 section 4, so we won't bother with it. */
fprintf (stderr, "Error: %d part(s) for a multipart/encrypted "
diff --git a/notmuch-client.h b/notmuch-client.h
index 79b826c1..6aec9974 100644
--- a/notmuch-client.h
+++ b/notmuch-client.h
@@ -415,7 +415,9 @@ struct mime_node {
/* Construct a new MIME node pointing to the root message part of
* message. If crypto->verify is true, signed child parts will be
* verified. If crypto->decrypt is NOTMUCH_DECRYPT_TRUE, encrypted
- * child parts will be decrypted. If the crypto contexts
+ * child parts will be decrypted using either stored session keys or
+ * asymmetric crypto. If crypto->decrypt is NOTMUCH_DECRYPT_AUTO,
+ * only session keys will be tried. If the crypto contexts
* (crypto->gpgctx or crypto->pkcs7) are NULL, they will be lazily
* initialized.
*
diff --git a/notmuch.c b/notmuch.c
index 1abd8288..62706748 100644
--- a/notmuch.c
+++ b/notmuch.c
@@ -103,6 +103,7 @@ const notmuch_opt_desc_t notmuch_shared_indexing_options [] = {
.present = &indexing_cli_choices.try_decrypt_set, .keywords =
(notmuch_keyword_t []){ { "false", NOTMUCH_DECRYPT_FALSE },
{ "true", NOTMUCH_DECRYPT_TRUE },
+ { "auto", NOTMUCH_DECRYPT_AUTO },
{ 0, 0 } },
.name = "try-decrypt" },
{ }
@@ -128,7 +129,7 @@ notmuch_process_shared_indexing_options (notmuch_database_t *notmuch, g_mime_3_u
}
}
#if (GMIME_MAJOR_VERSION < 3)
- if (indexing_cli_choices.opts && notmuch_indexopts_get_try_decrypt (indexing_cli_choices.opts) == NOTMUCH_DECRYPT_TRUE) {
+ if (indexing_cli_choices.opts && notmuch_indexopts_get_try_decrypt (indexing_cli_choices.opts) != NOTMUCH_DECRYPT_FALSE) {
const char* gpg_path = notmuch_config_get_crypto_gpg_path (config);
if (gpg_path && strcmp(gpg_path, "gpg"))
fprintf (stderr, "Warning: deprecated crypto.gpg_path is set to '%s'\n"
diff --git a/test/T357-index-decryption.sh b/test/T357-index-decryption.sh
index 670d1ae9..d453d568 100755
--- a/test/T357-index-decryption.sh
+++ b/test/T357-index-decryption.sh
@@ -140,6 +140,16 @@ test_expect_equal \
"$output" \
"$expected"
+# ensure no session keys are present:
+test_begin_subtest 'reindex using only session keys'
+test_expect_success 'notmuch reindex --try-decrypt=auto tag:encrypted and property:index.decryption=success'
+test_begin_subtest "reindexed encrypted messages, decrypting only with session keys"
+output=$(notmuch search wumpus)
+expected=''
+test_expect_equal \
+ "$output" \
+ "$expected"
+
# and the same search, but by property ($expected is untouched):
test_begin_subtest "emacs search by property with both messages unindexed"
output=$(notmuch search property:index.decryption=success)
@@ -180,7 +190,7 @@ notmuch restore <<EOF
#notmuch-dump batch-tag:3 config,properties,tags
#= simple-encrypted at crypto.notmuchmail.org session-key=9%3AFC09987F5F927CC0CC0EE80A96E4C5BBF4A499818FB591207705DFDDD6112CF9
EOF
-notmuch reindex --try-decrypt=true id:simple-encrypted at crypto.notmuchmail.org
+notmuch reindex --try-decrypt=auto id:simple-encrypted at crypto.notmuchmail.org
output=$(notmuch search sekrit)
expected='thread:0000000000000001 2016-12-22 [1/1] Daniel Kahn Gillmor; encrypted message (encrypted inbox unread)'
test_expect_equal \
diff --git a/util/crypto.c b/util/crypto.c
index e014db5d..9789f203 100644
--- a/util/crypto.c
+++ b/util/crypto.c
@@ -140,13 +140,16 @@ void _notmuch_crypto_cleanup (unused(_notmuch_crypto_t *crypto))
#endif
GMimeObject *
-_notmuch_crypto_decrypt (notmuch_message_t *message,
+_notmuch_crypto_decrypt (notmuch_decryption_policy_t decrypt,
+ notmuch_message_t *message,
g_mime_3_unused(GMimeCryptoContext* crypto_ctx),
GMimeMultipartEncrypted *part,
GMimeDecryptResult **decrypt_result,
GError **err)
{
GMimeObject *ret = NULL;
+ if (decrypt == NOTMUCH_DECRYPT_FALSE)
+ return NULL;
/* the versions of notmuch that can support session key decryption */
#if (GMIME_MAJOR_VERSION >= 3 || (GMIME_MAJOR_VERSION == 2 && GMIME_MINOR_VERSION == 6 && GMIME_MICRO_VERSION >= 21))
@@ -176,6 +179,9 @@ _notmuch_crypto_decrypt (notmuch_message_t *message,
}
#endif
+ if (decrypt == NOTMUCH_DECRYPT_AUTO)
+ return ret;
+
#if (GMIME_MAJOR_VERSION < 3)
ret = g_mime_multipart_encrypted_decrypt(part, crypto_ctx,
decrypt_result, err);
diff --git a/util/crypto.h b/util/crypto.h
index b23ca747..dc95b4ca 100644
--- a/util/crypto.h
+++ b/util/crypto.h
@@ -16,7 +16,8 @@ typedef struct _notmuch_crypto {
} _notmuch_crypto_t;
GMimeObject *
-_notmuch_crypto_decrypt (notmuch_message_t *message,
+_notmuch_crypto_decrypt (notmuch_decryption_policy_t decrypt,
+ notmuch_message_t *message,
GMimeCryptoContext* crypto_ctx,
GMimeMultipartEncrypted *part,
GMimeDecryptResult **decrypt_result,
--
2.14.2
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