OpenSSL hash memory leak

[Jordan Brown]

The most obvious question is "how are you allocating your message_data
buffer?".  You don't show that.

On 2/22/2019 2:27 AM, prithiraj das wrote:
>
> Hi All,
>
> Using OpenSSL 1.0.2g, I have written a code to generate the hash of a
> file in an embeddded device having linux OS and low memory capacity
> and the files are generally of size 44 MB or more. The first time or
> even the second time on some occasions, the hash of any file is
> successfully generated. On the 3rd or 4th time (possibly due to lack
> of memory/memory leak), the system reboots before the hash can be
> generated.  After restart, the same thing happens when the previous
> steps are repeated.
> The stats below shows the memory usage before and after computing the
> hash. 
>
> *root at at91sam9m10g45ek:~# free*
> *                      total        used          free         shared 
>   buff/cache   available*
> *Mem:         252180       13272      223048         280         
> 15860          230924*
> *Swap:                0           0               0*
> *
> *
> *After computing hash :-*
> *root at at91sam9m10g45ek:~# free*
> *                      total        used          free       shared   
> buff/cache   available*
> *Mem:         252180       13308      179308        280       59564   
>        230868*
> *Swap:             0                0              0*
>
> Buff/cache increases by almost 44MB (same as file size) everytime I
> generate the hash and free decreases. I believe the file is being
> loaded into buffer and not being freed. 
>
> I am using the below code to compute the message digest. This code is
> part of a function ComputeHash and the file pointer here is fph.
>
>   * EVP_add_digest(EVP_sha256());*
> * md = EVP_get_digestbyname("sha256");*
> * *
> * if(!md) {*
> *        printf("Unknown message digest \n");*
> *        exit(1);*
> * }*
> * printf("Message digest algorithm successfully loaded\n");*
> * mdctx = EVP_MD_CTX_create();*
> * EVP_DigestInit_ex(mdctx, md, NULL);*
> *
> *
> * // Reading data to array of unsigned chars*
> * long long int bytes_read = 0;*
> *
> *
> * printf("FILE size of the file to be hashed is %ld",filesize);*
> *
> *
> * //reading image file in chunks below and fph is the file pointer to
> the 44MB file*
> * while ((bytes_read = fread (message_data, 1, BUFFER_SIZE, fph)) != 0)*
> * EVP_DigestUpdate(mdctx, message_data, bytes_read);*
> * EVP_DigestFinal_ex(mdctx, hash_data.md_value, &hash_data.md_len);*
> * printf("\n%d\n",EVP_MD_CTX_size(mdctx));*
> * printf("\n%d\n",EVP_MD_CTX_type(mdctx));*
> * hash_data.md_type=EVP_MD_CTX_type(mdctx);*
> * EVP_MD_CTX_destroy(mdctx);*
> * //fclose(fp);*
> * printf("Generated Digest is:\n ");*
> * for(i = 0; i < hash_data.md_len; i++)*
> *        printf("%02x", hash_data.md_value[i]);*
> * printf("\n");*
> * EVP_cleanup();*
> *         return hash_data;*
> *
> *
> In the the code below, I have done fclose(fp)
> *verify_hash=ComputeHash(fp,size1);*
> *fclose(fp);*
> *
> *
> I believe that instead of loading the entire file all at once I am
> reading the 44MB file in chunks and computing the hash using the piece
> of code below: (fph is the file pointer)
> *while ((bytes_read = fread (message_data, 1, BUFFER_SIZE, fph)) != 0)*
> * EVP_DigestUpdate(mdctx, message_data, bytes_read);*
> *
> *
> Where I am going wrong? How can I free the buff/cache after
> computation of message digest?  Please suggest ways to tackle this.
>
>
> Thanks and Regards,
> Prithiraj
>

-- 
Jordan Brown, Oracle ZFS Storage Appliance, Oracle Solaris

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