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From 2699fc035a75d0774c1f013e9320882287f78adb Mon Sep 17 00:00:00 2001
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From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
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Date: Mon, 5 Feb 2024 11:01:23 +0200
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Subject: [PATCH] Run REFRESH MATERIALIZED VIEW CONCURRENTLY in right security
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context
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The internal commands in REFRESH MATERIALIZED VIEW CONCURRENTLY are
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correctly executed in SECURITY_RESTRICTED_OPERATION mode, except for
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creating the temporary "diff" table, because you cannot create
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temporary tables in SRO mode. But creating the temporary "diff" table
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is a pretty complex CTAS command that selects from another temporary
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table created earlier in the command. If you can cajole that CTAS
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command to execute code defined by the table owner, the table owner
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can run code with the privileges of the user running the REFRESH
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command.
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The proof-of-concept reported to the security team relied on CREATE
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RULE to convert the internally-built temp table to a view. That's not
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possible since commit b23cd185fd, and I was not able to find a
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different way to turn the SELECT on the temp table into code
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execution, so as far as I know this is only exploitable in v15 and
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below. That's a fiddly assumption though, so apply this patch to
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master and all stable versions.
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Thanks to Pedro Gallegos for the report.
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Security: CVE-2023-5869
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Reviewed-by: Noah Misch
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---
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src/backend/commands/matview.c | 33 ++++++++++++++++++++++++++-------
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1 file changed, 26 insertions(+), 7 deletions(-)
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diff --git a/src/backend/commands/matview.c b/src/backend/commands/matview.c
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index e485661fa1..e87bdac285 100644
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--- a/src/backend/commands/matview.c
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+++ b/src/backend/commands/matview.c
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@@ -646,14 +646,35 @@
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errdetail("Row: %s",
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SPI_getvalue(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1))));
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}
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-
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+ /*
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+ * Create the temporary "diff" table.
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+ *
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+ * Temporarily switch out of the SECURITY_RESTRICTED_OPERATION context,
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+ * because you cannot create temp tables in SRO context. For extra
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+ * paranoia, add the composite type column only after switching back to
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+ * SRO context.
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+ */
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SetUserIdAndSecContext(relowner,
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save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
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+ resetStringInfo(&querybuf);
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+ appendStringInfo(&querybuf,
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+ "CREATE TEMP TABLE %s (tid pg_catalog.tid)",
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+ diffname);
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+ if (SPI_exec(querybuf.data, 0) != SPI_OK_UTILITY)
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+ elog(ERROR, "SPI_exec failed: %s", querybuf.data);
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+ SetUserIdAndSecContext(relowner,
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+ save_sec_context | SECURITY_RESTRICTED_OPERATION);
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+ resetStringInfo(&querybuf);
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+ appendStringInfo(&querybuf,
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+ "ALTER TABLE %s ADD COLUMN newdata %s",
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+ diffname, tempname);
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+ if (SPI_exec(querybuf.data, 0) != SPI_OK_UTILITY)
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+ elog(ERROR, "SPI_exec failed: %s", querybuf.data);
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/* Start building the query for creating the diff table. */
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resetStringInfo(&querybuf);
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appendStringInfo(&querybuf,
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- "CREATE TEMP TABLE %s AS "
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+ "INSERT INTO %s "
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"SELECT mv.ctid AS tid, newdata.*::%s AS newdata "
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"FROM %s mv FULL JOIN %s newdata ON (",
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diffname, tempname, matviewname, tempname);
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@@ -783,11 +804,9 @@
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"ORDER BY tid");
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/* Create the temporary "diff" table. */
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- if (SPI_exec(querybuf.data, 0) != SPI_OK_UTILITY)
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+ if (SPI_exec(querybuf.data, 0) != SPI_OK_INSERT)
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elog(ERROR, "SPI_exec failed: %s", querybuf.data);
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- SetUserIdAndSecContext(relowner,
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- save_sec_context | SECURITY_RESTRICTED_OPERATION);
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/*
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* We have no further use for data from the "full-data" temp table, but we
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eabdullin