[3.9] gh-107077: Raise SSLCertVerificationError even if the error is set via SSL_ERROR_SYSCALL (GH-107586) (#107590)

(cherry picked from commit 77e0919)

Co-authored-by: Pablo Galindo Salgado <[email protected]>
Co-authored-by: T. Wouters <[email protected]>
Co-authored-by: Łukasz Langa <[email protected]>
Co-authored-by: Serhiy Storchaka <[email protected]>

Author: 5 people

Misc/NEWS.d/next/Library/2023-08-03-12-52-19.gh-issue-107077.-pzHD6.rst

@@ -0,0 +1,6 @@
+Seems that in some conditions, OpenSSL will return ``SSL_ERROR_SYSCALL``
+instead of ``SSL_ERROR_SSL`` when a certification verification has failed,
+but the error parameters will still contain ``ERR_LIB_SSL`` and
+``SSL_R_CERTIFICATE_VERIFY_FAILED``. We are now detecting this situation and
+raising the appropiate ``ssl.SSLCertVerificationError``. Patch by Pablo
+Galindo

Modules/_ssl.c

@@ -817,6 +817,10 @@ PySSL_SetError(PySSLSocket *sslsock, int ret, const char *filename, int lineno)
                     errstr = "Some I/O error occurred";
                 }
             } else {
+                if (ERR_GET_LIB(e) == ERR_LIB_SSL &&
+                        ERR_GET_REASON(e) == SSL_R_CERTIFICATE_VERIFY_FAILED) {
+                    type = PySSLCertVerificationErrorObject;
+                }
                 p = PY_SSL_ERROR_SYSCALL;
             }
             break;