Fix potential buffer overruns in proto.c.

Prevent potential buffer overruns when using strcpy to gid buffer. This
has been introduced by commit a8fd13c.

Reported-by: Tom Lane as per coverity
Author: Peter Smith
Reviewed-by: Amit Kapila
Discussion: https://www.postgresql.org/message-id/161029.1626639923%40sss.pgh.pa.us

Author: Amit Kapila

src/backend/replication/logical/proto.c

@@ -141,7 +141,7 @@ logicalrep_read_begin_prepare(StringInfo in, LogicalRepPreparedTxnData *begin_da
 	begin_data->xid = pq_getmsgint(in, 4);
 
 	/* read gid (copy it into a pre-allocated buffer) */
-	strcpy(begin_data->gid, pq_getmsgstring(in));
+	strlcpy(begin_data->gid, pq_getmsgstring(in), sizeof(begin_data->gid));
 }
 
 /*
@@ -198,7 +198,7 @@ logicalrep_read_prepare(StringInfo in, LogicalRepPreparedTxnData *prepare_data)
 	prepare_data->xid = pq_getmsgint(in, 4);
 
 	/* read gid (copy it into a pre-allocated buffer) */
-	strcpy(prepare_data->gid, pq_getmsgstring(in));
+	strlcpy(prepare_data->gid, pq_getmsgstring(in), sizeof(prepare_data->gid));
 }
 
 /*
@@ -254,7 +254,7 @@ logicalrep_read_commit_prepared(StringInfo in, LogicalRepCommitPreparedTxnData *
 	prepare_data->xid = pq_getmsgint(in, 4);
 
 	/* read gid (copy it into a pre-allocated buffer) */
-	strcpy(prepare_data->gid, pq_getmsgstring(in));
+	strlcpy(prepare_data->gid, pq_getmsgstring(in), sizeof(prepare_data->gid));
 }
 
 /*
@@ -314,7 +314,7 @@ logicalrep_read_rollback_prepared(StringInfo in,
 	rollback_data->xid = pq_getmsgint(in, 4);
 
 	/* read gid (copy it into a pre-allocated buffer) */
-	strcpy(rollback_data->gid, pq_getmsgstring(in));
+	strlcpy(rollback_data->gid, pq_getmsgstring(in), sizeof(rollback_data->gid));
 }
 
 /*