Use SASLprep to normalize passwords for SCRAM authentication.

An important step of SASLprep normalization, is to convert the string to
Unicode normalization form NFKC. Unicode normalization requires a fairly
large table of character decompositions, which is generated from data
published by the Unicode consortium. The script to generate the table is
put in src/common/unicode, as well test code for the normalization.
A pre-generated version of the tables is included in src/include/common,
so you don't need the code in src/common/unicode to build PostgreSQL, only
if you wish to modify the normalization tables.

The SASLprep implementation depends on the UTF-8 functions from
src/backend/utils/mb/wchar.c. So to use it, you must also compile and link
that. That doesn't change anything for the current users of these
functions, the backend and libpq, as they both already link with wchar.o.
It would be good to move those functions into a separate file in
src/commmon, but I'll leave that for another day.

No documentation changes included, because there is no details on the
SCRAM mechanism in the docs anyway. An overview on that in the protocol
specification would probably be good, even though SCRAM is documented in
detail in RFC5802. I'll write that as a separate patch. An important thing
to mention there is that we apply SASLprep even on invalid UTF-8 strings,
to support other encodings.

Patch by Michael Paquier and me.

Discussion: https://www.postgresql.org/message-id/CAB7nPqSByyEmAVLtEf1KxTRh=PWNKiWKEKQR=e1yGehz=wbymQ@mail.gmail.com

1 files changed, 30 insertions, 0 deletions

diff --git a/src/include/common/saslprep.h b/src/include/common/saslprep.h
new file mode 100644
index 00000000000..ec5c8ce361d
--- /dev/null
+++ b/src/include/common/saslprep.h
@@ -0,0 +1,30 @@
+/*-------------------------------------------------------------------------
+ *
+ * saslprep.h
+ *	  SASLprep normalization, for SCRAM authentication
+ *
+ * These definitions are used by both frontend and backend code.
+ *
+ * Copyright (c) 2017, PostgreSQL Global Development Group
+ *
+ * src/include/common/saslprep.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SASLPREP_H
+#define SASLPREP_H
+
+/*
+ * Return codes for pg_saslprep() function.
+ */
+typedef enum
+{
+	SASLPREP_SUCCESS = 0,
+	SASLPREP_OOM = -1,			/* out of memory (only in frontend) */
+	SASLPREP_INVALID_UTF8 = -2, /* input is not a valid UTF-8 string */
+	SASLPREP_PROHIBITED = -3	/* output would contain prohibited characters */
+} pg_saslprep_rc;
+
+extern pg_saslprep_rc pg_saslprep(const char *input, char **output);
+
+#endif   /* SASLPREP_H */