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<a href="https://gitlab.com/ltx2018">lutianxiong</a>
commented:
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<p dir="auto">i found heap-memory address stored in session->key.proto.tls12 was overwrite by read_server_hello(handshake.c,line 1947)</p>
<pre class="code highlight js-syntax-highlight plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext"> if (!vers->tls13_sem) {</span>
<span id="LC2" class="line" lang="plaintext"> gnutls_memset(&session->key.proto.tls13, 0,</span>
<span id="LC3" class="line" lang="plaintext"> sizeof(session->key.proto.tls13));</span>
<span id="LC4" class="line" lang="plaintext"> reset_binders(session);</span>
<span id="LC5" class="line" lang="plaintext"> }</span>
<span id="LC6" class="line" lang="plaintext"></span></code></pre>
<p dir="auto">following is debuginfo:</p>
<pre class="code highlight js-syntax-highlight plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext">1947 if (!vers->tls13_sem) {</span>
<span id="LC2" class="line" lang="plaintext">(gdb) p session->key.proto.tls12.dh</span>
<span id="LC3" class="line" lang="plaintext">$7 = {params = {params = {0x602000004d10, 0x0, 0x602000004cd0, 0x0 <repeats 13 times>}, params_nr = 3, pkflags = 0, qbits = 0, curve = GNUTLS_ECC_CURVE_INVALID, dh_group = GNUTLS_GROUP_INVALID, gost_params = GNUTLS_GOST_PARAMSET_UNKNOWN, raw_pub = {data = 0x0,</span>
<span id="LC4" class="line" lang="plaintext"> size = 0}, raw_priv = {data = 0x0, size = 0}, seed_size = 0, seed = '\000' <repeats 255 times>, palgo = GNUTLS_DIG_UNKNOWN, spki = {pk = GNUTLS_PK_UNKNOWN, rsa_pss_dig = GNUTLS_DIG_UNKNOWN, salt_size = 0, legacy = 0, dsa_dig = GNUTLS_DIG_UNKNOWN, flags = 0},</span>
<span id="LC5" class="line" lang="plaintext"> algo = GNUTLS_PK_DH}, client_Y = 0x602000004cb0}</span>
<span id="LC6" class="line" lang="plaintext">(gdb) n</span>
<span id="LC7" class="line" lang="plaintext">1948 gnutls_memset(&session->key.proto.tls13, 0,</span>
<span id="LC8" class="line" lang="plaintext">(gdb) n</span>
<span id="LC9" class="line" lang="plaintext">1950 reset_binders(session);</span>
<span id="LC10" class="line" lang="plaintext">(gdb) n</span>
<span id="LC11" class="line" lang="plaintext">1956 if (!vers->tls13_sem &&</span>
<span id="LC12" class="line" lang="plaintext">(gdb) p session->key.proto.tls12.dh</span>
<span id="LC13" class="line" lang="plaintext">$8 = {params = {params = {0x602000000000, 0x0, 0x602000004cd0, 0x0 <repeats 13 times>}, params_nr = 3, pkflags = 0, qbits = 0, curve = GNUTLS_ECC_CURVE_INVALID, dh_group = GNUTLS_GROUP_INVALID, gost_params = GNUTLS_GOST_PARAMSET_UNKNOWN, raw_pub = {data = 0x0,</span>
<span id="LC14" class="line" lang="plaintext"> size = 0}, raw_priv = {data = 0x0, size = 0}, seed_size = 0, seed = '\000' <repeats 255 times>, palgo = GNUTLS_DIG_UNKNOWN, spki = {pk = GNUTLS_PK_UNKNOWN, rsa_pss_dig = GNUTLS_DIG_UNKNOWN, salt_size = 0, legacy = 0, dsa_dig = GNUTLS_DIG_UNKNOWN, flags = 0},</span>
<span id="LC15" class="line" lang="plaintext"> algo = GNUTLS_PK_DH}, client_Y = 0x602000004cb0}</span>
<span id="LC16" class="line" lang="plaintext">(gdb)</span></code></pre>
<p dir="auto">later, while gnutls_deinit the session:
gnutls_pk_params_release(&session->key.proto.tls12.dh.params) trigger the read-heap-buffer-overflow</p>
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