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Passphrase-based API of Secure Cell #577

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merged 16 commits into from
Feb 12, 2020
Merged

Passphrase-based API of Secure Cell #577

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9740893
Define passphrase API
ilammy Jan 20, 2020
f84a0f7
Tests for passphrase API
ilammy Jan 20, 2020
107cf81
Define authentication token format
ilammy Jan 21, 2020
ce273c0
Prepend authentication token in Seal mode
ilammy Jan 21, 2020
ba8645b
Secure Cell encryption
ilammy Jan 23, 2020
863c14e
Secure Cell decryption
ilammy Jan 23, 2020
afc4195
Note new arrivals in CHANGELOG
ilammy Jan 24, 2020
34e2470
Avoid incorrect terminology
ilammy Jan 28, 2020
e8e8c39
fixup! Avoid incorrect terminology
ilammy Jan 28, 2020
782b446
Improve naming of new parsing utilities
ilammy Feb 5, 2020
f409539
Relax restrictions on context buffer values
ilammy Feb 5, 2020
32ddb96
Simplify auth tag length output
ilammy Feb 5, 2020
a0ead0a
Generalize KDF handling in decryption path
ilammy Feb 5, 2020
77e3830
Generalize KDF handling in encryption path
ilammy Feb 10, 2020
212bd4b
Merge branch 'master' into kdf/core
ilammy Feb 10, 2020
f9db138
fixup! Simplify auth tag length output
ilammy Feb 11, 2020
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12 changes: 11 additions & 1 deletion CHANGELOG.md
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Expand Up @@ -5,7 +5,8 @@
Changes that are currently in development and have not been released yet.

**TL;DR:**
- Added API for generating symmetric keys for use with Secure Cell;
- Added API for generating symmetric keys for use with Secure Cell
- Added API for Secure Cell encryption with human-readable passphrases

_Code:_

Expand All @@ -19,6 +20,15 @@ _Code:_

- New function `themis_gen_sym_key()` can be used to securely generate symmetric keys for Secure Cell ([#560](https://github.com/cossacklabs/themis/pull/560)).

- **Secure Cell**

- New functions:

- `themis_secure_cell_encrypt_seal_with_passphrase()`
- `themis_secure_cell_decrypt_seal_with_passphrase()`

provide Seal mode API that is safe to use with passphrases ([#577](https://github.com/cossacklabs/themis/pull/577)).

- **C++**

- New function `themispp::gen_sym_key()` can be used to generate symmetric keys for Secure Cell ([#561](https://github.com/cossacklabs/themis/pull/561)).
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8 changes: 8 additions & 0 deletions Themis.xcodeproj/project.pbxproj
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Expand Up @@ -198,6 +198,8 @@
9F4A2620223ABEF2005CB63A /* secure_session_utils.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F4A242E223A74AF005CB63A /* secure_session_utils.c */; };
9F4A2621223ABEF2005CB63A /* secure_session.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F4A2438223A74AF005CB63A /* secure_session.c */; };
9F4A2622223ABEF2005CB63A /* sym_enc_message.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F4A2431223A74AF005CB63A /* sym_enc_message.c */; };
9F6B385523D9D11600EA5D1B /* secure_cell_seal_passphrase.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F6B385423D9D11600EA5D1B /* secure_cell_seal_passphrase.c */; };
9F6B385623D9D11600EA5D1B /* secure_cell_seal_passphrase.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F6B385423D9D11600EA5D1B /* secure_cell_seal_passphrase.c */; };
9F874AB322CCB0D100E8DECA /* soter_ec_key.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F874AB122CCB0D100E8DECA /* soter_ec_key.c */; };
9F874AB422CCB0D100E8DECA /* soter_ec_key.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F874AB122CCB0D100E8DECA /* soter_ec_key.c */; };
9F874AB522CCB0D100E8DECA /* soter_rsa_key.c in Sources */ = {isa = PBXBuildFile; fileRef = 9F874AB222CCB0D100E8DECA /* soter_rsa_key.c */; };
Expand Down Expand Up @@ -256,6 +258,7 @@
9F00E8D7223C197900EC1EF3 /* themis.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = themis.framework; sourceTree = BUILT_PRODUCTS_DIR; };
9F00E940223C1AFA00EC1EF3 /* openssl.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = openssl.framework; path = Carthage/Build/Mac/openssl.framework; sourceTree = "<group>"; };
9F33485723B38D9B00368291 /* soter_kdf.c */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.c; name = soter_kdf.c; path = src/soter/openssl/soter_kdf.c; sourceTree = "<group>"; };
9F34EA3023D9CA0A0079A1D7 /* secure_cell_seal_passphrase.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; name = secure_cell_seal_passphrase.h; path = src/themis/secure_cell_seal_passphrase.h; sourceTree = "<group>"; };
9F4A2342223A73B0005CB63A /* soter_hash.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = soter_hash.h; path = src/soter/soter_hash.h; sourceTree = "<group>"; };
9F4A2343223A73B0005CB63A /* soter_asym_cipher.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = soter_asym_cipher.h; path = src/soter/soter_asym_cipher.h; sourceTree = "<group>"; };
9F4A2344223A73B0005CB63A /* soter_sign_rsa.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = soter_sign_rsa.h; path = src/soter/soter_sign_rsa.h; sourceTree = "<group>"; };
Expand Down Expand Up @@ -405,6 +408,7 @@
9F4A24C1223A8FA8005CB63A /* skeygen.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = skeygen.h; path = "src/wrappers/themis/Obj-C/objcthemis/skeygen.h"; sourceTree = "<group>"; };
9F4A24C2223A8FA8005CB63A /* smessage.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = smessage.h; path = "src/wrappers/themis/Obj-C/objcthemis/smessage.h"; sourceTree = "<group>"; };
9F4A24C3223A8FA8005CB63A /* scell_token.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = scell_token.h; path = "src/wrappers/themis/Obj-C/objcthemis/scell_token.h"; sourceTree = "<group>"; };
9F6B385423D9D11600EA5D1B /* secure_cell_seal_passphrase.c */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.c; name = secure_cell_seal_passphrase.c; path = src/themis/secure_cell_seal_passphrase.c; sourceTree = "<group>"; };
9F874AB122CCB0D100E8DECA /* soter_ec_key.c */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.c; name = soter_ec_key.c; path = src/soter/soter_ec_key.c; sourceTree = "<group>"; };
9F874AB222CCB0D100E8DECA /* soter_rsa_key.c */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.c; name = soter_rsa_key.c; path = src/soter/soter_rsa_key.c; sourceTree = "<group>"; };
9F98F32422CCEA5D008E14E6 /* soter_wipe.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = soter_wipe.h; path = src/soter/soter_wipe.h; sourceTree = "<group>"; };
Expand Down Expand Up @@ -591,6 +595,8 @@
9F4A2430223A74AF005CB63A /* secure_cell_alg.h */,
9F4A241E223A74AE005CB63A /* secure_cell.c */,
9F4A242C223A74AF005CB63A /* secure_cell.h */,
9F6B385423D9D11600EA5D1B /* secure_cell_seal_passphrase.c */,
9F34EA3023D9CA0A0079A1D7 /* secure_cell_seal_passphrase.h */,
9F4A241F223A74AE005CB63A /* secure_comparator_t.h */,
9F4A2432223A74AF005CB63A /* secure_comparator.c */,
9F4A2434223A74AF005CB63A /* secure_comparator.h */,
Expand Down Expand Up @@ -808,6 +814,7 @@
9F00E925223C1AC000EC1EF3 /* soter_hash.c in Sources */,
9F00E926223C1AC000EC1EF3 /* soter_rand.c in Sources */,
9F874AB422CCB0D100E8DECA /* soter_ec_key.c in Sources */,
9F6B385623D9D11600EA5D1B /* secure_cell_seal_passphrase.c in Sources */,
9F00E927223C1AC000EC1EF3 /* soter_rsa_common.c in Sources */,
9F00E928223C1AC000EC1EF3 /* soter_rsa_key_pair_gen.c in Sources */,
9F00E929223C1AC000EC1EF3 /* soter_rsa_key.c in Sources */,
Expand Down Expand Up @@ -901,6 +908,7 @@
9F4A2608223ABECC005CB63A /* soter_hash.c in Sources */,
9F4A2609223ABECC005CB63A /* soter_rand.c in Sources */,
9F874AB322CCB0D100E8DECA /* soter_ec_key.c in Sources */,
9F6B385523D9D11600EA5D1B /* secure_cell_seal_passphrase.c in Sources */,
9F4A260A223ABECC005CB63A /* soter_rsa_common.c in Sources */,
9F4A260B223ABECC005CB63A /* soter_rsa_key_pair_gen.c in Sources */,
9F4A260C223ABECC005CB63A /* soter_rsa_key.c in Sources */,
Expand Down
116 changes: 116 additions & 0 deletions src/themis/secure_cell.c
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Expand Up @@ -16,6 +16,7 @@

#include "themis/secure_cell.h"

#include "themis/secure_cell_seal_passphrase.h"
#include "themis/sym_enc_message.h"

themis_status_t themis_secure_cell_encrypt_seal(const uint8_t* master_key,
Expand Down Expand Up @@ -101,6 +102,121 @@ themis_status_t themis_secure_cell_decrypt_seal(const uint8_t* master_key,
plain_message_length);
}

themis_status_t themis_secure_cell_encrypt_seal_with_passphrase(const uint8_t* passphrase,
size_t passphrase_length,
const uint8_t* user_context,
size_t user_context_length,
const uint8_t* message,
size_t message_length,
uint8_t* encrypted_message,
size_t* encrypted_message_length)
{
themis_status_t res = THEMIS_FAIL;
size_t auth_token_length = 0;
size_t ciphertext_length = 0;
size_t total_length = 0;

THEMIS_CHECK_PARAM(encrypted_message_length != NULL);

/*
* Since Seal mode prepends authentication token to the message
* we need to get the size of this token at first.
*/
res = themis_auth_sym_encrypt_message_with_passphrase(passphrase,
passphrase_length,
message,
message_length,
user_context,
user_context_length,
NULL,
&auth_token_length,
NULL,
&ciphertext_length);
if (res != THEMIS_BUFFER_TOO_SMALL) {
return res;
}

total_length = auth_token_length + ciphertext_length;
if (!encrypted_message || *encrypted_message_length < total_length) {
*encrypted_message_length = total_length;
return THEMIS_BUFFER_TOO_SMALL;
}

res = themis_auth_sym_encrypt_message_with_passphrase(passphrase,
passphrase_length,
message,
message_length,
user_context,
user_context_length,
encrypted_message,
&auth_token_length,
encrypted_message + auth_token_length,
&ciphertext_length);
if (res == THEMIS_SUCCESS || res == THEMIS_BUFFER_TOO_SMALL) {
*encrypted_message_length = auth_token_length + ciphertext_length;
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Reuse total_length here?

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This is intentional because the themis_auth_sym_encrypt_message_with_passphrase() call might have modified those values. Of course, it does not modify them and accurately reports required lengths so we could reuse the value. But I'd leave that for future-proofing.

For all functions that return buffers, it's not strictly incorrect behavior to return slightly bigger required buffer size during measurement stage (BUFFER_TOO_SMALL) and then return accurate – and possibly smaller – actual size of the buffer used on SUCCESS. Currently we are able to accurately determine required length without actually processing the data, but it might not be the case in the future.

}
return res;
}

themis_status_t themis_secure_cell_decrypt_seal_with_passphrase(const uint8_t* passphrase,
size_t passphrase_length,
const uint8_t* user_context,
size_t user_context_length,
const uint8_t* encrypted_message,
size_t encrypted_message_length,
uint8_t* plain_message,
size_t* plain_message_length)
{
themis_status_t res = THEMIS_FAIL;
size_t auth_token_length = 0;
size_t message_length = 0;

THEMIS_CHECK_PARAM(plain_message_length != NULL);

/*
* Since Seal mode prepends authentication token to the message we need
* to get the size of this token at first. Token size is not available
* directly so we infer it from the size of encrypted message and
* plaintext message length embedded in the token.
*
* Note that this might fail if the encrypted message does not start with
* a valid token. It also might produce a false positive if the data looks
* like a token but does not contain valid measurements. This will lead to
* a decryption failure later.
*/
res = themis_auth_sym_decrypt_message_with_passphrase(passphrase,
passphrase_length,
user_context,
user_context_length,
encrypted_message,
encrypted_message_length,
NULL,
0,
NULL,
&message_length);
if (res != THEMIS_BUFFER_TOO_SMALL) {
return res;
}

/* We should not overflow here. If we do then the message is corrupted. */
if (encrypted_message_length < message_length) {
return THEMIS_FAIL;
}
auth_token_length = encrypted_message_length - message_length;

res = themis_auth_sym_decrypt_message_with_passphrase(passphrase,
passphrase_length,
user_context,
user_context_length,
encrypted_message,
auth_token_length,
encrypted_message + auth_token_length,
message_length,
plain_message,
plain_message_length);
return res;
}

themis_status_t themis_secure_cell_encrypt_token_protect(const uint8_t* master_key,
const size_t master_key_length,
const uint8_t* user_context,
Expand Down
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