pg_logicalinspect: Fix possible crash when passing a directory path.

Previously, pg_logicalinspect functions were too trusting of their
input and blindly passed it to SnapBuildRestoreSnapshot(). If the
input pointed to a directory, the server could a PANIC error while
attempting to fsync_fname() with isdir=false on a directory.

This commit adds validation checks for input filenames and passes the
LSN extracted from the filename to SnapBuildRestoreSnapshot() instead
of the filename itself. It also adds regression tests for various
input patterns and permission checks.

Bug: #18828
Reported-by: Robins Tharakan <tharakan@gmail.com>
Co-authored-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Co-authored-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/18828-0f4701c635064211@postgresql.org

diff --git a/contrib/pg_logicalinspect/Makefile b/contrib/pg_logicalinspect/Makefile
index 55124514d4239b1b721e8a87318b40ccd04fb965..17cee50d5c882712405d8671e31d37415a8ce974 100644 (file)
--- a/contrib/pg_logicalinspect/Makefile
+++ b/contrib/pg_logicalinspect/Makefile
@@ -11,6 +11,7 @@ DATA = pg_logicalinspect--1.0.sql
 
 EXTRA_INSTALL = contrib/test_decoding
 
+REGRESS = pg_logicalinspect
 ISOLATION = logical_inspect
 
 ISOLATION_OPTS = --temp-config $(top_srcdir)/contrib/pg_logicalinspect/logicalinspect.conf

diff --git a/contrib/pg_logicalinspect/expected/pg_logicalinspect.out b/contrib/pg_logicalinspect/expected/pg_logicalinspect.out
new file mode 100644 (file)
index 0000000..f6c9b62
--- /dev/null
+++ b/contrib/pg_logicalinspect/expected/pg_logicalinspect.out
@@ -0,0 +1,81 @@
+CREATE EXTENSION pg_logicalinspect;
+-- ===================================================================
+-- Tests for input validation
+-- ===================================================================
+SELECT pg_get_logical_snapshot_info('0-40796E18.foo');
+ERROR:  invalid snapshot file name "0-40796E18.foo"
+SELECT pg_get_logical_snapshot_info('0--40796E18.snap');
+ERROR:  invalid snapshot file name "0--40796E18.snap"
+SELECT pg_get_logical_snapshot_info('-1--40796E18.snap');
+ERROR:  invalid snapshot file name "-1--40796E18.snap"
+SELECT pg_get_logical_snapshot_info('0/40796E18.foo.snap');
+ERROR:  invalid snapshot file name "0/40796E18.foo.snap"
+SELECT pg_get_logical_snapshot_info('0/40796E18.snap');
+ERROR:  invalid snapshot file name "0/40796E18.snap"
+SELECT pg_get_logical_snapshot_info('');
+ERROR:  invalid snapshot file name ""
+SELECT pg_get_logical_snapshot_info(NULL);
+ pg_get_logical_snapshot_info 
+------------------------------
+ 
+(1 row)
+
+SELECT pg_get_logical_snapshot_info('../snapshots');
+ERROR:  invalid snapshot file name "../snapshots"
+SELECT pg_get_logical_snapshot_info('../snapshots/0-40796E18.snap');
+ERROR:  invalid snapshot file name "../snapshots/0-40796E18.snap"
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo');
+ERROR:  invalid snapshot file name "0-40796E18.foo"
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo.snap');
+ERROR:  invalid snapshot file name "0-40796E18.foo.snap"
+SELECT pg_get_logical_snapshot_meta('0/40796E18.snap');
+ERROR:  invalid snapshot file name "0/40796E18.snap"
+SELECT pg_get_logical_snapshot_meta('');
+ERROR:  invalid snapshot file name ""
+SELECT pg_get_logical_snapshot_meta(NULL);
+ pg_get_logical_snapshot_meta 
+------------------------------
+ 
+(1 row)
+
+SELECT pg_get_logical_snapshot_meta('../snapshots');
+ERROR:  invalid snapshot file name "../snapshots"
+-- ===================================================================
+-- Tests for permissions
+-- ===================================================================
+CREATE ROLE regress_pg_logicalinspect;
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- no
+ has_function_privilege 
+------------------------
+ f
+(1 row)
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- no
+ has_function_privilege 
+------------------------
+ f
+(1 row)
+
+-- Functions accessible by users with role pg_read_server_files.
+GRANT pg_read_server_files TO regress_pg_logicalinspect;
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- yes
+ has_function_privilege 
+------------------------
+ t
+(1 row)
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- yes
+ has_function_privilege 
+------------------------
+ t
+(1 row)
+
+-- ===================================================================
+-- Clean up
+-- ===================================================================
+DROP ROLE regress_pg_logicalinspect;
+DROP EXTENSION pg_logicalinspect;

diff --git a/contrib/pg_logicalinspect/pg_logicalinspect.c b/contrib/pg_logicalinspect/pg_logicalinspect.c
index cd575c6bd3639aebaea5878f93a370b665a7c2e1..3b64d8ad880f0b7a6de342a3c91fc9ea40811030 100644 (file)
--- a/contrib/pg_logicalinspect/pg_logicalinspect.c
+++ b/contrib/pg_logicalinspect/pg_logicalinspect.c
@@ -48,6 +48,45 @@ get_snapbuild_state_desc(SnapBuildState state)
    return stateDesc;
 }
 
+/*
+ * Extract the LSN from the given serialized snapshot file name.
+ */
+static XLogRecPtr
+parse_snapshot_filename(const char *filename)
+{
+   uint32      hi;
+   uint32      lo;
+   XLogRecPtr  lsn;
+   char        tmpfname[MAXPGPATH];
+
+   /*
+    * Extract the values to build the LSN.
+    *
+    * Note: Including ".snap" doesn't mean that sscanf() also does the format
+    * check including the suffix. The subsequent check validates if the given
+    * filename has the expected suffix.
+    */
+   if (sscanf(filename, "%X-%X.snap", &hi, &lo) != 2)
+       goto parse_error;
+
+   /*
+    * Bring back the extracted LSN to the snapshot file format and compare it
+    * to the given filename. This check strictly checks if the given filename
+    * follows the format of the snapshot filename.
+    */
+   sprintf(tmpfname, "%X-%X.snap", hi, lo);
+   if (strcmp(tmpfname, filename) != 0)
+       goto parse_error;
+
+   lsn = ((uint64) hi) << 32 | lo;
+
+   return lsn;
+
+parse_error:
+   ereport(ERROR,
+           errmsg("invalid snapshot file name \"%s\"", filename));
+}
+
 /*
  * Retrieve the logical snapshot file metadata.
  */
@@ -60,7 +99,7 @@ pg_get_logical_snapshot_meta(PG_FUNCTION_ARGS)
    Datum       values[PG_GET_LOGICAL_SNAPSHOT_META_COLS] = {0};
    bool        nulls[PG_GET_LOGICAL_SNAPSHOT_META_COLS] = {0};
    TupleDesc   tupdesc;
-   char        path[MAXPGPATH];
+   XLogRecPtr  lsn;
    int         i = 0;
    text       *filename_t = PG_GETARG_TEXT_PP(0);
 
@@ -68,12 +107,10 @@ pg_get_logical_snapshot_meta(PG_FUNCTION_ARGS)
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");
 
-   sprintf(path, "%s/%s",
-           PG_LOGICAL_SNAPSHOTS_DIR,
-           text_to_cstring(filename_t));
+   lsn = parse_snapshot_filename(text_to_cstring(filename_t));
 
    /* Validate and restore the snapshot to 'ondisk' */
-   SnapBuildRestoreSnapshot(&ondisk, path, CurrentMemoryContext, false);
+   SnapBuildRestoreSnapshot(&ondisk, lsn, CurrentMemoryContext, false);
 
    values[i++] = UInt32GetDatum(ondisk.magic);
    values[i++] = Int64GetDatum((int64) ondisk.checksum);
@@ -97,7 +134,7 @@ pg_get_logical_snapshot_info(PG_FUNCTION_ARGS)
    Datum       values[PG_GET_LOGICAL_SNAPSHOT_INFO_COLS] = {0};
    bool        nulls[PG_GET_LOGICAL_SNAPSHOT_INFO_COLS] = {0};
    TupleDesc   tupdesc;
-   char        path[MAXPGPATH];
+   XLogRecPtr  lsn;
    int         i = 0;
    text       *filename_t = PG_GETARG_TEXT_PP(0);
 
@@ -105,12 +142,10 @@ pg_get_logical_snapshot_info(PG_FUNCTION_ARGS)
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");
 
-   sprintf(path, "%s/%s",
-           PG_LOGICAL_SNAPSHOTS_DIR,
-           text_to_cstring(filename_t));
+   lsn = parse_snapshot_filename(text_to_cstring(filename_t));
 
    /* Validate and restore the snapshot to 'ondisk' */
-   SnapBuildRestoreSnapshot(&ondisk, path, CurrentMemoryContext, false);
+   SnapBuildRestoreSnapshot(&ondisk, lsn, CurrentMemoryContext, false);
 
    values[i++] = CStringGetTextDatum(get_snapbuild_state_desc(ondisk.builder.state));
    values[i++] = TransactionIdGetDatum(ondisk.builder.xmin);

diff --git a/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql b/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql
new file mode 100644 (file)
index 0000000..143cf45
--- /dev/null
+++ b/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql
@@ -0,0 +1,48 @@
+CREATE EXTENSION pg_logicalinspect;
+
+-- ===================================================================
+-- Tests for input validation
+-- ===================================================================
+
+SELECT pg_get_logical_snapshot_info('0-40796E18.foo');
+SELECT pg_get_logical_snapshot_info('0--40796E18.snap');
+SELECT pg_get_logical_snapshot_info('-1--40796E18.snap');
+SELECT pg_get_logical_snapshot_info('0/40796E18.foo.snap');
+SELECT pg_get_logical_snapshot_info('0/40796E18.snap');
+SELECT pg_get_logical_snapshot_info('');
+SELECT pg_get_logical_snapshot_info(NULL);
+SELECT pg_get_logical_snapshot_info('../snapshots');
+SELECT pg_get_logical_snapshot_info('../snapshots/0-40796E18.snap');
+
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo');
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo.snap');
+SELECT pg_get_logical_snapshot_meta('0/40796E18.snap');
+SELECT pg_get_logical_snapshot_meta('');
+SELECT pg_get_logical_snapshot_meta(NULL);
+SELECT pg_get_logical_snapshot_meta('../snapshots');
+
+-- ===================================================================
+-- Tests for permissions
+-- ===================================================================
+CREATE ROLE regress_pg_logicalinspect;
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- no
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- no
+
+-- Functions accessible by users with role pg_read_server_files.
+GRANT pg_read_server_files TO regress_pg_logicalinspect;
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- yes
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- yes
+
+-- ===================================================================
+-- Clean up
+-- ===================================================================
+
+DROP ROLE regress_pg_logicalinspect;
+
+DROP EXTENSION pg_logicalinspect;

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index bd0680dcbe558c4cce42d87a45315d3c4beb1d56..b64e53de017b924dd51fc88d0d41f08c6d14b906 100644 (file)
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1691,12 +1691,17 @@ out:
  * If 'missing_ok' is true, will not throw an error if the file is not found.
  */
 bool
-SnapBuildRestoreSnapshot(SnapBuildOnDisk *ondisk, const char *path,
+SnapBuildRestoreSnapshot(SnapBuildOnDisk *ondisk, XLogRecPtr lsn,
                         MemoryContext context, bool missing_ok)
 {
    int         fd;
    pg_crc32c   checksum;
    Size        sz;
+   char        path[MAXPGPATH];
+
+   sprintf(path, "%s/%X-%X.snap",
+           PG_LOGICAL_SNAPSHOTS_DIR,
+           LSN_FORMAT_ARGS(lsn));
 
    fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 
@@ -1788,18 +1793,13 @@ static bool
 SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 {
    SnapBuildOnDisk ondisk;
-   char        path[MAXPGPATH];
 
    /* no point in loading a snapshot if we're already there */
    if (builder->state == SNAPBUILD_CONSISTENT)
        return false;
 
-   sprintf(path, "%s/%X-%X.snap",
-           PG_LOGICAL_SNAPSHOTS_DIR,
-           LSN_FORMAT_ARGS(lsn));
-
    /* validate and restore the snapshot to 'ondisk' */
-   if (!SnapBuildRestoreSnapshot(&ondisk, path, builder->context, true))
+   if (!SnapBuildRestoreSnapshot(&ondisk, lsn, builder->context, true))
        return false;
 
    /*

diff --git a/src/include/replication/snapbuild_internal.h b/src/include/replication/snapbuild_internal.h
index 081b01b890ac686cca33e12b24eb4a829771396b..3b915dc8793b8b5af3cdf1e046c5ad52e605bab8 100644 (file)
--- a/src/include/replication/snapbuild_internal.h
+++ b/src/include/replication/snapbuild_internal.h
@@ -193,7 +193,7 @@ typedef struct SnapBuildOnDisk
    /* variable amount of TransactionIds follows */
 } SnapBuildOnDisk;
 
-extern bool SnapBuildRestoreSnapshot(SnapBuildOnDisk *ondisk, const char *path,
+extern bool SnapBuildRestoreSnapshot(SnapBuildOnDisk *ondisk, XLogRecPtr lsn,
                                     MemoryContext context, bool missing_ok);
 
 #endif                         /* SNAPBUILD_INTERNAL_H */