Removing OpenSSL dependency for plugins.

Compiling a plugin required having access to OpenSSL headers because
they were pulled in by Bro headers that the plugin had to include.
Removinng then OpenSSL dependency from those Bro headers.

I'm also reverting a4e5591e. This is a different fix for the same
problem, and reverting that commit gives us a test case. :-)

src/ChunkedIO.cc

@@ -5,7 +5,9 @@
 #include <sys/time.h>
 #include <netinet/in.h>
 #include <assert.h>
+
 #include <openssl/ssl.h>
+#include <openssl/err.h>
 
 #include <algorithm>
 

src/ChunkedIO.h

@@ -14,9 +14,6 @@
 # include <krb5.h>
 #endif
 
-#include <openssl/ssl.h>
-#include <openssl/err.h>
-
 class CompressedChunkedIO;
 
 // #define DEBUG_COMMUNICATION 10
@@ -244,6 +241,11 @@ private:
 	bro::Flare read_flare;
 };
 
+// From OpenSSL. We forward-declare these here to avoid introducing a
+// dependency on OpenSSL headers just for this header file.
+typedef struct ssl_ctx_st SSL_CTX;
+typedef struct ssl_st SSL;
+
 // Chunked I/O using an SSL connection.
 class ChunkedIOSSL : public ChunkedIO {
 public:

src/File.cc

@@ -18,6 +18,10 @@
 #include <errno.h>
 #include <unistd.h>
 
+#include <openssl/evp.h>
+#include <openssl/pem.h>
+#include <openssl/err.h>
+
 #include <algorithm>
 
 #include "File.h"

src/File.h

@@ -11,11 +11,11 @@
 # ifdef NEED_KRB5_H
 #  include <krb5.h>
 # endif // NEED_KRB5_H
-extern "C" {
-# include "openssl/evp.h"
-# include "openssl/pem.h"
-# include "openssl/err.h"
-}
+
+// From OpenSSL. We forward-declare these here to avoid introducing a
+// dependency on OpenSSL headers just for this header file.
+typedef struct evp_pkey_st EVP_PKEY;
+typedef struct evp_cipher_ctx_st EVP_CIPHER_CTX;
 
 class BroType;
 class RotateTimer;

src/file_analysis/analyzer/x509/X509.cc

@@ -14,6 +14,7 @@
 #include <openssl/x509v3.h>
 #include <openssl/asn1.h>
 #include <openssl/opensslconf.h>
+#include <openssl/err.h>
 
 using namespace file_analysis;
 

src/file_analysis/analyzer/x509/functions.bif

@@ -6,6 +6,8 @@
 #include <openssl/asn1.h>
 #include <openssl/x509_vfy.h>
 #include <openssl/ocsp.h>
+#include <openssl/pem.h>
+#include <openssl/err.h>
 
 // This is the indexed map of X509 certificate stores.
 static map<Val*, X509_STORE*> x509_stores;

src/main.cc

@@ -18,7 +18,8 @@ extern "C" {
 }
 #endif
 
-#include <openssl/md5.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
 
 extern "C" void OPENSSL_add_all_algorithms_conf(void);