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--></style></head><body lang=EN-US link=blue vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Maybe this should have been run in a virtual enviroment</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Sent from <a href="https://go.microsoft.com/fwlink/?LinkId=550986">Mail</a> for Windows 10</p><p class=MsoNormal><o:p> </o:p></p><div style='mso-element:para-border-div;border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='border:none;padding:0in'><b>From: </b><a href="mailto:uri@ll.mit.edu">Blumenthal, Uri - 0553 - MITLL</a><br><b>Sent: </b>Friday, April 28, 2017 4:33 PM<br><b>To: </b><a href="mailto:openssl-users@openssl.org">openssl-users@openssl.org</a><br><b>Subject: </b>[openssl-users] EVP_MD_CTX and EVP_PKEY_CTX? How to init? How tofree?</p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I’m playing with RSA-PSS signatures, and stumbled upon a few problems. I tried the OpenSSL manual pages, but still coming short of complete understanding. :-)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This is how I initialize the contexts (error handlers removed for brevity):<o:p></o:p></p><p class=p1><span class=apple-tab-span><o:p> </o:p></span></p><p class=p1><span class=apple-tab-span> </span>ctx = <span class=s1>EVP_PKEY_CTX_new</span>(privkey, NULL);</p><p class=p4><span class=apple-tab-span> </span><span class=s3>md_ctx = </span>EVP_MD_CTX_create<span class=s3>();</span></p><p class=p1><span class=apple-tab-span> </span><span class=s2>const</span> <span class=s5>EVP_MD</span> *md = <span class=s1>EVP_sha256</span>();</p><p class=p1><span class=apple-tab-span> </span>rv = <span class=s1>EVP_DigestInit_ex</span>(md_ctx, md, NULL);</p><p class=p1><span class=apple-tab-span> </span>rv = <span class=s1>EVP_DigestSignInit</span>(md_ctx, &ctx, md, NULL, privkey);</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>First question: do I need <span style='font-family:Monaco'>EVP_DigestInit_ex()</span> there?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Second question: do I have to specify hash-function (<span style='font-family:Monaco'>EVP_MD*</span>) twice? First when initializing <span style='font-family:Monaco'>EVP_MD_CTX</span>, and second for <span style='font-family:Monaco'>EVP_DigestSignInit()</span>?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>At the end I need to dispose of both <span style='font-family:Monaco'>ctx</span> and <span style='font-family:Monaco'>md_ctx</span>. That leads to my third question/problem. The code I tried (based on what the man page says: to avoid memory leak, I need to do <span style='font-family:Monaco'>EVP_MD_CTX_destroy(md_ctx)</span> crashes with SIGV:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Monaco;color:black'> </span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'>EVP_MD_CTX_destroy</span><span style='font-size:10.5pt;font-family:Monaco;color:black'>(md_ctx); // this succeeds</span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Monaco;color:black'> </span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'>EVP_PKEY_CTX_free</span><span style='font-size:10.5pt;font-family:Monaco;color:black'>(ctx); // but here the code crashes</span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Same happens when I reverse the above order:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Monaco;color:black'> </span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'>EVP_PKEY_CTX_free</span><span style='font-size:10.5pt;font-family:Monaco;color:black'>(ctx); // this succeeds</span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Monaco;color:black'> </span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'>EVP_MD_CTX_destroy</span><span style='font-size:10.5pt;font-family:Monaco;color:black'>(md_ctx); // but then this one causes crash</span><span style='font-size:10.5pt;font-family:Monaco;color:#793D93'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So what’s the correct way of freeing both of them? Or is it that because they’re sort of “bound together” by <span class=s1>EVP_DigestSignInit</span>(md_ctx, &ctx, md, NULL, privkey); freeing one frees the other?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks!<o:p></o:p></p><p class=MsoNormal><span style='font-size:10.5pt;color:black'>— <o:p></o:p></span></p><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Regards,<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Uri<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>