From 9b584953e7bf91e342af87ef44606acd6206cd1c Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Mon, 14 Dec 2020 12:38:13 +0900
Subject: [PATCH] Improve some code around cryptohash functions

This adjusts some code related to recent changes for cryptohash
functions:
- Add a variable in md5.h to track down the size of a computed result,
moved from pgcrypto.  Note that pg_md5_hash() assumed a result of this
size already.
- Call explicit_bzero() on the hashed data when freeing the context for
fallback implementations.  For MD5, particularly, it would be annoying
to leave some non-zeroed data around.
- Clean up some code related to recent changes of uuid-ossp.  .gitignore
still included md5.c and a comment was incorrect.

Discussion: https://postgr.es/m/X9HXKTgrvJvYO7Oh@paquier.xyz
---
 contrib/pgcrypto/internal.c   |  4 ----
 contrib/uuid-ossp/.gitignore  |  1 -
 contrib/uuid-ossp/uuid-ossp.c |  4 ++--
 src/common/cryptohash.c       | 20 ++++++++++++++++++++
 src/common/md5_common.c       |  2 +-
 src/include/common/md5.h      |  4 ++++
 6 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/contrib/pgcrypto/internal.c b/contrib/pgcrypto/internal.c
index e6d90c56567..ea377bdf83a 100644
--- a/contrib/pgcrypto/internal.c
+++ b/contrib/pgcrypto/internal.c
@@ -41,10 +41,6 @@
 #include "common/cryptohash.h"
 #include "common/md5.h"
 
-#ifndef MD5_DIGEST_LENGTH
-#define MD5_DIGEST_LENGTH 16
-#endif
-
 #ifndef SHA1_DIGEST_LENGTH
 #ifdef SHA1_RESULTLEN
 #define SHA1_DIGEST_LENGTH SHA1_RESULTLEN
diff --git a/contrib/uuid-ossp/.gitignore b/contrib/uuid-ossp/.gitignore
index 6c989c78729..d7260edc610 100644
--- a/contrib/uuid-ossp/.gitignore
+++ b/contrib/uuid-ossp/.gitignore
@@ -1,4 +1,3 @@
-/md5.c
 /sha1.c
 # Generated subdirectories
 /log/
diff --git a/contrib/uuid-ossp/uuid-ossp.c b/contrib/uuid-ossp/uuid-ossp.c
index 8f81c94e725..2ff7d9448bc 100644
--- a/contrib/uuid-ossp/uuid-ossp.c
+++ b/contrib/uuid-ossp/uuid-ossp.c
@@ -41,8 +41,8 @@
 #undef uuid_hash
 
 /*
- * Some BSD variants offer md5 and sha1 implementations but Linux does not,
- * so we use a copy of the ones from pgcrypto.  Not needed with OSSP, though.
+ * Some BSD variants offer sha1 implementation but Linux does not, so we use
+ * a copy from pgcrypto.  Not needed with OSSP, though.
  */
 #ifndef HAVE_UUID_OSSP
 #include "sha1.h"
diff --git a/src/common/cryptohash.c b/src/common/cryptohash.c
index 5cc2572eb6e..cf4588bad72 100644
--- a/src/common/cryptohash.c
+++ b/src/common/cryptohash.c
@@ -197,6 +197,26 @@ pg_cryptohash_free(pg_cryptohash_ctx *ctx)
 {
 	if (ctx == NULL)
 		return;
+
+	switch (ctx->type)
+	{
+		case PG_MD5:
+			explicit_bzero(ctx->data, sizeof(pg_md5_ctx));
+			break;
+		case PG_SHA224:
+			explicit_bzero(ctx->data, sizeof(pg_sha224_ctx));
+			break;
+		case PG_SHA256:
+			explicit_bzero(ctx->data, sizeof(pg_sha256_ctx));
+			break;
+		case PG_SHA384:
+			explicit_bzero(ctx->data, sizeof(pg_sha384_ctx));
+			break;
+		case PG_SHA512:
+			explicit_bzero(ctx->data, sizeof(pg_sha512_ctx));
+			break;
+	}
+
 	FREE(ctx->data);
 	explicit_bzero(ctx, sizeof(pg_cryptohash_ctx));
 	FREE(ctx);
diff --git a/src/common/md5_common.c b/src/common/md5_common.c
index 74c274175fe..abf79e5918f 100644
--- a/src/common/md5_common.c
+++ b/src/common/md5_common.c
@@ -69,7 +69,7 @@ bytesToHex(uint8 b[16], char *s)
 bool
 pg_md5_hash(const void *buff, size_t len, char *hexsum)
 {
-	uint8		sum[16];
+	uint8		sum[MD5_DIGEST_LENGTH];
 	pg_cryptohash_ctx *ctx;
 
 	ctx = pg_cryptohash_create(PG_MD5);
diff --git a/src/include/common/md5.h b/src/include/common/md5.h
index 53036d2d17e..5dac70cbc50 100644
--- a/src/include/common/md5.h
+++ b/src/include/common/md5.h
@@ -16,6 +16,10 @@
 #ifndef PG_MD5_H
 #define PG_MD5_H
 
+/* Size of result generated by MD5 computation */
+#define MD5_DIGEST_LENGTH 16
+
+/* password-related data */
 #define MD5_PASSWD_CHARSET	"0123456789abcdef"
 #define MD5_PASSWD_LEN	35