Searching for Cryptography materials

Searching expanded keys

radare2 is capable of finding expanded keys with /ca command for AES and SM4 block ciphers. It searches from current seek position up to the search.distance limit, or until end of file is reached. You can interrupt current search by pressing Ctrl-C. For example, to look for AES keys in a memory dump:

0x00000000]> /ca aes
Searching 40 bytes in [0x0-0x1ab]
hits: 1
0x000000fb hit0_0 6920e299a5202a6d656e636869746f2a

For AES, the output length gives you the size of the AES key used: 128, 192 or 256 bits. If you are simply looking for plaintext AES keys in your binary, /ca will not find them they must have been expanded by the key expansion algorithm.

Searching private keys and certificates

/cr command implements the search of private keys (RSA and ECC). /cd command implements a similar feature to search certificates.

[0x00000000]> /cr
Searching 11 bytes in [0x0-0x15a]
hits: 2
0x000000fa hit1_0 302e020100300506032b657004220420fb3d588296fed5694ff7049eafb74490bf4bc6467ee11a08...

Entropy analysis

p=e might give some hints if high entropy sections are found trying to cover up a hardcoded secret.

There is the possibility to delimit entropy sections for later use with \s command:

[0x00000000]> b
[0x00000000]> b 4096
[0x00000000]> /s
0x00100000 - 0x00101000 ~ 5.556094
0x014e2c88 - 0x014e3c88 ~ 0.000000
0x01434374 - 0x01435374 ~ 6.332087
0x01435374 - 0x0144c374 ~ 3.664636
0x0144c374 - 0x0144d374 ~ 1.664368
0x0144d374 - 0x0144f374 ~ 4.229199
0x0144f374 - 0x01451374 ~ 2.000000
[0x00000000]> /s*
f entropy_section_0 0x00001000 0x00100000
f entropy_section_1 0x00001000 0x014e2c88
f entropy_section_2 0x00001000 0x01434374
f entropy_section_3 0x00017000 0x01435374
f entropy_section_4 0x00001000 0x0144c374
f entropy_section_5 0x00002000 0x0144d374
f entropy_section_6 0x00002000 0x0144f374

The blocksize is increased to 4096 bytes from the default 100 bytes so that the entropy search /s can work on reasonably sized chunks for entropy analysis. The sections flags can be applied with the dot operator, ./s* and then looped through px 32 @@ entropy*.

Searching data matching hash digest

Sometimes it is useful to search if some data blocks in a binary match a given digest. The command /h implement such feature. For example running the following command:

[0x00000000]> /h sha256 83264abaf298b9238ca63cb2fd9ff0f41a7a1520ee2a17c56df459fc806de1d6 512
INFO: Searching sha256 for 512 byte length
INFO: Search in range 0x00000000 and 0x00000284
INFO: Carving 132 blocks:
INFO: Found at 0x64
f hash.sha256.83264abaf298b9238ca63cb2fd9ff0f41a7a1520ee2a17c56df459fc806de1d6 = 0x64

Launches a search of 512-bytes blocks of data in the binary which SHA256 hash would results in the digest 83264abaf298b9238ca63cb2fd9ff0f41a7a1520ee2a17c56df459fc806de1d6. If a digest is found, the offset of its location is printed.