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Rewrite some tests using switch statements.

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Add a note for the reason I do this in the HACKING file.
This commit is contained in:
Romain Tartiere 2010-12-18 02:07:56 +00:00
parent 1d3c3f5dfd
commit 373cb4f0ef
3 changed files with 39 additions and 7 deletions
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12
HACKING
View file

@ -70,3 +70,15 @@ infrastructure ready for hacking the new card support:
knows...
- <tag>_tag_free() SHALL free all resources allocated for the tag
(surprising, isn't it?)
Various guidelines
------------------
- If a given card has different cryptographic modes, you SHOULD use
switch/cases to handle specific branches of code, even when applicable to
only one cypher. The idea is that if you don't provide support for all
cryptographic schemes, or if an evolution of the card provides more
cryptographic possibilities, when adding support for a new cypher, the
compiler can warn the developer about unhandled values in switch
statements. Please refer to the Mifare DESFire code for an example.

20
libfreefare/mifare_desfire.c
View file

@ -395,8 +395,14 @@ authenticate (MifareTag tag, uint8_t cmd, uint8_t key_no, MifareDESFireKey key)
MIFARE_DESFIRE (tag)->session_key = mifare_desfire_session_key_new (PCD_RndA, PICC_RndB, key);
memset (MIFARE_DESFIRE (tag)->ivect, 0, MAX_CRYPTO_BLOCK_SIZE);
if (MIFARE_DESFIRE (tag)->session_key->type == T_AES)
switch (MIFARE_DESFIRE (tag)->session_key->type) {
case T_DES:
case T_3DES:
break;
case T_AES:
cmac_generate_subkeys (MIFARE_DESFIRE (tag)->session_key);
break;
}
return 0;
}
@ -1196,10 +1202,16 @@ read_data (MifareTag tag, uint8_t command, uint8_t file_no, off_t offset, size_t
BUFFER_APPEND_LE (cmd, offset, 3, sizeof (off_t));
BUFFER_APPEND_LE (cmd, length, 3, sizeof (size_t));
// FIXME This is somewhat done in mifare_cryto_preprocess_data (or should be!!)
uint8_t ocs = cs;
if ((MIFARE_DESFIRE (tag)->session_key) && (MIFARE_DESFIRE (tag)->session_key->type == T_AES) && (cs | MDCM_MACED)) {
cs = MDCM_PLAIN;
if ((MIFARE_DESFIRE (tag)->session_key) && (cs | MDCM_MACED)) {
switch (MIFARE_DESFIRE (tag)->session_key->type) {
case T_DES:
case T_3DES:
break;
case T_AES:
cs = MDCM_PLAIN;
break;
}
}
uint8_t *p = mifare_cryto_preprocess_data (tag, cmd, &__cmd_n, 8, cs | CMAC_COMMAND);
cs = ocs;

14
libfreefare/mifare_desfire_authenticate.c
View file

@ -403,12 +403,20 @@ mifare_cryto_preprocess_data (MifareTag tag, void *data, size_t *nbytes, off_t o
memcpy (res, data, *nbytes);
if (!(communication_settings & NO_CRC)) {
// ... CRC ...
switch (key->type) {
case T_DES:
case T_3DES:
iso14443a_crc_append ((uint8_t *)res + offset, *nbytes - offset);
} else {
bzero ((uint8_t *) res + *nbytes, 2);
*nbytes += 2;
break;
case T_AES:
// Never reached.
abort ();
break;
}
}
// ... and 0 padding
memset ((uint8_t *)(res) + *nbytes + 2, 0, edl - *nbytes - 2);
memset ((uint8_t *)(res) + *nbytes, 0, edl - *nbytes);
*nbytes = edl;