一、問題
在Qt中使用https，執行時報錯：

qt.network.ssl: QSslSocket: cannot resolve SSLv2_client_method
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二、原因分析
SSLv2由於某些漏洞導致的不安全原因， 在某些linux發行版裡的openssl庫禁用掉了SSLv2

三、解決辦法
重新編譯openssl

1、下載openssl
git clone https://github.com/openssl/openssl.git
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2、編譯
./config enable-shared
make -j4
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3、部署
將ssl和crypto庫拷貝到Qt目錄lib下：

cp libssl.so* libcrypto.so* ~/Qt5.6.3/5.6.3/gcc_64/lib/ -a
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4、新的錯誤
重新執行時，報錯
qt.network.ssl: QSslSocket: cannot call unresolved function *

qt.network.ssl: QSslSocket: cannot resolve CRYPTO_num_locks
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_id_callback
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_locking_callback
qt.network.ssl: QSslSocket: cannot resolve ERR_free_strings
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_cleanup
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_init
qt.network.ssl: QSslSocket: cannot resolve sk_new_null
qt.network.ssl: QSslSocket: cannot resolve sk_push
qt.network.ssl: QSslSocket: cannot resolve sk_free
qt.network.ssl: QSslSocket: cannot resolve sk_num
qt.network.ssl: QSslSocket: cannot resolve sk_pop_free
qt.network.ssl: QSslSocket: cannot resolve sk_value
qt.network.ssl: QSslSocket: cannot resolve SSL_library_init
qt.network.ssl: QSslSocket: cannot resolve SSL_load_error_strings
qt.network.ssl: QSslSocket: cannot resolve SSL_get_ex_new_index
qt.network.ssl: QSslSocket: cannot resolve SSLv2_client_method
qt.network.ssl: QSslSocket: cannot resolve SSLv3_client_method
qt.network.ssl: QSslSocket: cannot resolve SSLv23_client_method
qt.network.ssl: QSslSocket: cannot resolve SSLv2_server_method
qt.network.ssl: QSslSocket: cannot resolve SSLv3_server_method
qt.network.ssl: QSslSocket: cannot resolve SSLv23_server_method
qt.network.ssl: QSslSocket: cannot resolve X509_STORE_CTX_get_chain
qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_noconf
qt.network.ssl: QSslSocket: cannot resolve OPENSSL_add_all_algorithms_conf
qt.network.ssl: QSslSocket: cannot resolve SSLeay
qt.network.ssl: QSslSocket: cannot resolve SSLeay_version
qt.network.ssl: QSslSocket: cannot call unresolved function CRYPTO_num_locks
qt.network.ssl: QSslSocket: cannot call unresolved function CRYPTO_set_id_callback
qt.network.ssl: QSslSocket: cannot call unresolved function CRYPTO_set_locking_callback
qt.network.ssl: QSslSocket: cannot call unresolved function SSL_library_init
qt.network.ssl: QSslSocket: cannot call unresolved function SSLv23_client_method
qt.network.ssl: QSslSocket: cannot call unresolved function sk_num
qt.network.ssl: QSslSocket: cannot call unresolved function SSLeay
qt.network.ssl: QSslSocket: cannot call unresolved function SSLeay
qt.network.ssl: QSslSocket: cannot call unresolved function SSLeay
qt.network.ssl: QSslSocket: cannot call unresolved function SSLeay
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四、解決新錯誤
參考部落格：https://www.cnblogs.com/btian/p/6130560.html
Qt5.6對openssl版本的要求1.0，而從git上下載的最新版本是1.1的；
其它Qt的版本對openssl的要求未測試。

1、檢視版本資訊
git branch -r
origin/HEAD -> origin/master
origin/OpenSSL-engine-0_9_6-stable
origin/OpenSSL-fips-0_9_7-stable
origin/OpenSSL-fips-0_9_8-stable
origin/OpenSSL-fips-1_2-stable
origin/OpenSSL-fips-2_0-dev
origin/OpenSSL-fips-2_0-stable
origin/OpenSSL-fips2-0_9_7-stable
origin/OpenSSL_0_9_6-stable
origin/OpenSSL_0_9_7-stable
origin/OpenSSL_0_9_8-stable
origin/OpenSSL_0_9_8fg-stable
origin/OpenSSL_1_0_0-stable
origin/OpenSSL_1_0_1-stable
origin/OpenSSL_1_0_2-stable
origin/OpenSSL_1_1_0-stable
origin/OpenSSL_1_1_1-stable
origin/SSLeay
origin/master
origin/tls1.3-draft-18
origin/tls1.3-draft-19

2、匯出1.0.2版本
git checkout -b openssl-1.0.2 origin/OpenSSL_1_0_2-stable

3、編譯
./config enable-shared
make -j4

4、部署
cp libssl.so* libcrypto.so* ~/Qt5.6.3/5.6.3/gcc_64/lib/ -a

重新執行不再報錯
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原文連結：https://blog.csdn.net/u010168781/article/details/85632637