For the CTR DRBG, the drbg_state->scratchpad temp buffer (i.e. the memory location immediately before the drbg_state->tfm variable is the buffer that the BCC function operates on. BCC operates blockwise. Making the temp buffer drbg_statelen(drbg) in size is sufficient when the DRBG state length is a multiple of the block size. For AES192 this is not the case and the length for temp is insufficient (yes, that also means for such ciphers, the final output of all BCC rounds are truncated before used to update the state of the DRBG!!). The patch enlarges the temp buffer from drbg_statelen to drbg_statelen + drbg_blocklen to have sufficient space. Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx> --- crypto/drbg.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/crypto/drbg.c b/crypto/drbg.c index 86d483f..c2f02b7 100644 --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -441,8 +441,16 @@ static int drbg_ctr_bcc(struct drbg_state *drbg, * length: drbg_blocklen(drbg) * temp * start: iv + drbg_blocklen(drbg) - * length: (drbg_keylen(drbg) + drbg_blocklen(drbg) == - * drbg_statelen(drbg)) + * length: drbg_satelen(drbg) + drbg_blocklen(drbg) + * note: temp is the buffer that the BCC function operates + * on. BCC operates blockwise. drbg_statelen(drbg) + * is sufficient when the DRBG state length is a multiple + * of the block size. For AES192 (and maybe other ciphers) + * this is not correct and the length for temp is + * insufficient (yes, that also means for such ciphers, + * the final output of all BCC rounds are truncated). + * Therefore, add drbg_blocklen(drbg) to cover all + * possibilities. */ /* Derivation Function for CTR DRBG as defined in 10.4.2 */ @@ -1214,7 +1222,7 @@ static inline int drbg_alloc_state(struct drbg_state *drbg) drbg_statelen(drbg) + /* df_data */ drbg_blocklen(drbg) + /* pad */ drbg_blocklen(drbg) + /* iv */ - drbg_statelen(drbg); /* temp */ + drbg_statelen(drbg) + drbg_blocklen(drbg); /* temp */ else sb_size = drbg_statelen(drbg) + drbg_blocklen(drbg); -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
