binary classifier: detect elixir release-candidate versions (#4851)

The elixir-binary and elixir-library classifiers' regexes only matched
the bare semver triplet (and a single sub-segment for the library), so
release-candidate elixir images were either missed entirely or had
their version truncated:

  $ syft -q elixir:1.12.0-rc | grep elixir   # nothing
  $ syft -q elixir:1.13.0-rc.0 | grep elixir
  elixir   1.13.0   binary                   # truncated, "-rc.0" lost

Extend the version capture group to optionally include
"-<a-z0-9>+(\\.<digits>)?" so "1.12.0-rc.1", "1.13.0-rc.0", etc. match
exactly as the elixir.app and the binary's ELIXIR_VERSION line have
them.

Add a logical fixture under testdata/classifiers/snippets/elixir/
1.12.0-rc.1/linux-amd64 (cloned from the existing 1.19.1 fixture with
just the version strings changed) and register it in
Test_Cataloger_PositiveCases.

Closes #4819

Signed-off-by: Chris (ChrisJr404) <11917633+ChrisJr404@users.noreply.github.com>
Co-authored-by: Chris (ChrisJr404) <11917633+ChrisJr404@users.noreply.github.com>

syft/pkg/cataloger/binary/classifier_cataloger_test.go

@@ -1754,6 +1754,25 @@ func Test_Cataloger_PositiveCases(t *testing.T) {
 				},
 			},
 		},
+		{
+			// release-candidate elixir image — pre-fix the matchers stripped the
+			// "-rc.1" suffix from the elixir-library result and missed the
+			// elixir-binary entirely (#4819).
+			logicalFixture: "elixir/1.12.0-rc.1/linux-amd64",
+			expected: pkg.Package{
+				Name:      "elixir",
+				Version:   "1.12.0-rc.1",
+				Type:      "binary",
+				PURL:      "pkg:generic/elixir@1.12.0-rc.1",
+				Locations: locations("elixir", "lib/elixir/ebin/elixir.app"),
+				Metadata: pkg.BinarySignature{
+					Matches: []pkg.ClassifierMatch{
+						match("elixir-binary", "elixir"),
+						match("elixir-library", "lib/elixir/ebin/elixir.app"),
+					},
+				},
+			},
+		},
 		{
 			logicalFixture: "istio_pilot-discovery/1.29.0-alpha.0/linux-amd64",
 			expected: pkg.Package{

syft/pkg/cataloger/binary/classifiers.go

@@ -768,7 +768,9 @@ func DefaultClassifiers() []binutils.Classifier {
 			Class:    "elixir-binary",
 			FileGlob: "**/elixir",
 			EvidenceMatcher: m.FileContentsVersionMatcher(
-				`(?m)ELIXIR_VERSION=(?P<version>[0-9]+\.[0-9]+\.[0-9]+)`),
+				// Capture optional pre-release suffix (-rc.1, -alpha.0, -beta.2,
+				// etc.) so release-candidate elixir images (#4819) match.
+				`(?m)ELIXIR_VERSION=(?P<version>[0-9]+\.[0-9]+\.[0-9]+(?:-[a-z0-9]+(?:\.[0-9]+)?)?)`),
 			Package: "elixir",
 			PURL:    mustPURL("pkg:generic/elixir@version"),
 			CPEs: []cpe.CPE{
@@ -779,7 +781,8 @@ func DefaultClassifiers() []binutils.Classifier {
 			Class:    "elixir-library",
 			FileGlob: "**/elixir/ebin/elixir.app",
 			EvidenceMatcher: m.FileContentsVersionMatcher(
-				`(?m)\{vsn,"(?P<version>[0-9]+\.[0-9]+\.[0-9]+(-[a-z0-9]+)?)"\}`),
+				// Same pre-release extension as elixir-binary above.
+				`(?m)\{vsn,"(?P<version>[0-9]+\.[0-9]+\.[0-9]+(?:-[a-z0-9]+(?:\.[0-9]+)?)?)"\}`),
 			Package: "elixir",
 			PURL:    mustPURL("pkg:generic/elixir@version"),
 			CPEs:    singleCPE("cpe:2.3:a:elixir-lang:elixir:*:*:*:*:*:*:*:*", cpe.NVDDictionaryLookupSource),

syft/pkg/cataloger/binary/testdata/classifiers/snippets/elixir/1.12.0-rc.1/linux-amd64/elixir

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: 2021 The Elixir Team
+# SPDX-FileCopyrightText: 2012 Plataformatec
+
+set -e
+
+ELIXIR_VERSION=1.12.0-rc.1
+
+if [ $# -eq 0 ] || { [ $# -eq 1 ] && { [ "$1" = "--help" ] || [ "$1" = "-h" ]; }; }; then
+  cat <<USAGE >&2
+Usage: $(basename "$0") [options] [.exs file] [data]
+
+## General options
+
+  -e "COMMAND"                 Evaluates the given command (*)
+  -h, --help                   Prints this message (standalone)
+  -r "FILE"                    Requires the given files/patterns (*)
+  -S SCRIPT                    Finds and executes the given script in \$PATH

syft/pkg/cataloger/binary/testdata/classifiers/snippets/elixir/1.12.0-rc.1/linux-amd64/lib/elixir/ebin/elixir.app

@@ -0,0 +1,19 @@
+{application,elixir,
+    [{description,"elixir"},
+     {vsn,"1.12.0-rc.1"},
+     {modules,
+         ['Elixir.Access','Elixir.Agent.Server','Elixir.Agent',
+          'Elixir.Application','Elixir.ArgumentError',
+          elixir_overridable,elixir_parser,elixir_quote,elixir_rewrite,
+          elixir_sup,elixir_tokenizer,elixir_utils,iex]},
+     {registered,[elixir_sup,elixir_config,elixir_code_server]},
+     {applications,[kernel,stdlib,compiler]},
+     {mod,{elixir,[]}},
+     {env,
+         [{ansi_syntax_colors,
+              [{atom,cyan},
+               {binary,default_color},
+               {operator,default_color}]},
+          {check_endianness,true},
+          {dbg_callback,{'Elixir.Macro',dbg,[]}},
+          {time_zone_database,'Elixir.Calendar.UTCOnlyTimeZoneDatabase'}]}]}.