this opensource application (in windows) does meet your requirements: http://www.codeproject.com/KB/cpp/VerifyIntegrity.aspx On Sat, May 28, 2011 at 10:22 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > On Sat, May 28, 2011 at 6:03 AM, Arvid Brodin <arvid.brodin@xxxxxxxx> wrote: >> Peter Teoh wrote: >>> On Tue, May 24, 2011 at 6:43 AM, Arvid Brodin <arvid.brodin@xxxxxxxx> wrote: >>>> Hi, >>>> >>>> I want to perform an md5 checksum on a process' text segment (I create a file >>>> /proc/<pid>/text_checksum that, when read, should give the md5sum). >>>> >>>> The crypto api documentation (Documentation/crypto/api-intro.txt) seems to be >>>> quite lacking. The only example is: >>>> >>>> tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC); >>>> if (IS_ERR(tfm)) >>>> fail(); >>>> >>>> /* ... set up the scatterlists ... */ >>>> >>>> desc.tfm = tfm; >>>> desc.flags = 0; >>>> >>>> if (crypto_hash_digest(&desc, sg, 2, result)) >>>> fail(); >>>> >>>> crypto_free_hash(tfm); >>>> >>>> Looking at some existing code, I see usage of crypto_hash_init(), >>>> crypto_hash_final(), desc.flag set to CRYPTO_TFM_REQ_MAY_SLEEP, >>>> ... (e.g. in fs/ecryptfs/crypto.c). Does anybody know what they do? Do I need >>> >>> http://www.redhat.com/archives/dm-devel/2005-August/msg00058.html >> >> Thanks, that explains the CRYPTO_TFM_REQ_MAY_SLEEP flag! >> >> >>>> to, or should I, use them? The functions are are declared in include/linux/crypto.h >>>> as some kind of wrapper functions, but lack documentation. Also, Google has not >>>> been my friend here. >>> >>> http://www.linuxjournal.com/article/6451?page=0,0 >> >> >> This link is one I've found before, and it really does not explain anything >> about the usage of crypto_hash_{digest,init,update,final}() as far as I can >> see. So I'm still looking for help on this! >> >> >> Thanks, >> Arvid Brodin >> Enea Services Stockholm AB >> > > As these function are just wrapper over the real crypto API, they have > nothing to do with md5. > > It is not explained....I guess it is because they are self-explanatory > (eg "crypto_hash_digest()" is calculating digest from the hash etc). > I guess reading more crypto concept will help. > > look into the crypto/tcrypt.c:do_test() - where usage of different > crypto scheme is shown (md5, sha1 etc). > > read wiki: > > http://en.wikipedia.org/wiki/MD5 > > and u know that the input is 16 bytes, which is what the > crypto/md5.c:md5_transform() is calculating: > > static void md5_transform(u32 *hash, u32 const *in) > > and understanding the above will finally help u to understand > md5_update(): which is calling md5_transform() repeatedly for each > block. This also help to explain crypto_hash_update(). > > In its complete usage: > > for (start = jiffies, end = start + sec * HZ, bcount = 0; > time_before(jiffies, end); bcount++) { > ret = crypto_hash_init(desc); > if (ret) > return ret; > for (pcount = 0; pcount < blen; pcount += plen) { > ret = crypto_hash_update(desc, sg, plen); > if (ret) > return ret; > } > /* we assume there is enough space in 'out' for the result */ > ret = crypto_hash_final(desc, out); > if (ret) > return ret; > } > > plen will correspond to the page by page of your text segment. (not > including the descriptor allocation part) > > and another complete example of using all the API is in > test_hash_speed(): hash is allocated, calculated and finally freed. > > I think more important is the method of the idea - not all the pages > of the text segment are loaded into the memory, and if u attempt to > access it in userspace, u will trigger a pagefault to load the text > segment into memory. but if u attempt to access it in kernel mode > while it is not available.....hmmmmm......more info will be available > after debugging.... > > See page 24 of the following document: > > EXECUTABLE WHITELISTS AND PROCESS AUTHENTICATION FOR PROTECTION > > http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.129.5235&rep=rep1&type=pdf > > -- > Regards, > Peter Teoh > -- Regards, Peter Teoh _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
