mbedtls: fix memory leak when destroying SSL connection data

[raporrass]

Using cURL 7.46 with mbedTLS 2.2.1 I've come across some memory leak according to Valgrind:

==93== 8,940 (1,080 direct, 7,860 indirect) bytes in 10 blocks are definitely lost in loss record 6 of 7
==93==    at 0x402B1E5: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
[...]
==93==    by 0x80C7856: rsa_alloc_wrap (pk_wrap.c:136)
==93==    by 0x80C7233: mbedtls_pk_setup (pk.c:106)
==93==    by 0x80C8CA6: mbedtls_pk_parse_key (pkparse.c:1087)
==93==    by 0x80C8F8D: mbedtls_pk_parse_keyfile (pkparse.c:134)
==93==    by 0x808AF31: mbedtls_connect_common
==93==    by 0x8089D0E: Curl_ssl_connect_nonblocking
==93==    by 0x808E16E: Curl_http_connect

To fix this, I've added some missing mbedtls_xxx_free to Curl_mbedtls_close. I've also substituted some memcpy with the proper mbedtls_xxx_init function when available.

[mention-bot]

By analyzing the blame information on this pull request, we identified @sasq64, @jay and @bagder to be potential reviewers

[bagder]

Does curl even work with mbedtls atm without this patch? I wanted to try this patch but I get a segmentation fault using git master and mbedtls 2.1.2! Seems to be related to alpn...

$ ./src/curl https://curl.haxx.se/
Segmentation fault
$ gdb --args ./src/curl https://curl.haxx.se/
[snip]
(gdb) run
Program received signal SIGSEGV, Segmentation fault.
strlen () at ../sysdeps/x86_64/strlen.S:106
106     ../sysdeps/x86_64/strlen.S: No such file or directory.
(gdb) bt
#0  strlen () at ../sysdeps/x86_64/strlen.S:106
#1  0x000000000049c144 in ssl_write_alpn_ext ()
#2  0x000000000049ce1a in ssl_write_client_hello ()
#3  0x00000000004a1848 in mbedtls_ssl_handshake_client_step ()
#4  0x000000000049837e in mbedtls_ssl_handshake_step ()
#5  0x000000000049840b in mbedtls_ssl_handshake ()
#6  0x0000000000438ae8 in mbedtls_connect_step2 (conn=0x7c6848, sockindex=0)
    at vtls/mbedtls.c:432
#7  0x00000000004396c2 in mbedtls_connect_common (conn=0x7c6848, sockindex=0, 
    nonblocking=true, done=0x7fffffffd81c) at vtls/mbedtls.c:776

[jay]

Does curl even work with mbedtls atm without this patch?

It works with mbedTLS, at least it does in Windows. I don't know about that version though. I'm using 2.2.1 because versions before that had some problems like Mbed-TLS/mbedtls#380. I've been using mbedTLS as my curl SSL backend for about 3 weeks now on my personal computers just to see how it fared. I can connect to https://curl.haxx.se/ without a problem.

curl 7.47.0-DEV (i686-w64-mingw32) libcurl/7.47.0-DEV mbedTLS/2.2.1 zlib/1.2.8 libidn/1.32 libssh2/1.6.0 nghttp2/1.6.0
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp scp sftp smtp smtps telnet tftp
Features: AsynchDNS Debug TrackMemory IDN IPv6 Largefile SSPI Kerberos SPNEGO NTLM SSL libz HTTP2

Do you get a crash on other sites?

[bagder]

Do you get a crash on other sites?

I do. But I should get an updated version and work out this problem separately since it isn't really related to this PR. I'll file a separate issue if it remains.

[bagder]

thanks!