Fix pam

go.mod

@@ -3,8 +3,9 @@ module shell2
 go 1.25.4
 
 require (
+	github.com/GehirnInc/crypt v0.0.0-20230320061759-8cc1b52080c5
 	github.com/lib/pq v1.10.9
-	github.com/msteinert/pam/v2 v2.1.0
+	github.com/openwall/yescrypt-go v1.0.0
 	github.com/xtaci/kcp-go/v5 v5.6.61
 	github.com/xtaci/smux v1.5.50
 	golang.org/x/crypto v0.45.0

go.sum

@@ -1,10 +1,12 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/GehirnInc/crypt v0.0.0-20230320061759-8cc1b52080c5 h1:IEjq88XO4PuBDcvmjQJcQGg+w+UaafSy8G5Kcb5tBhI=
+github.com/GehirnInc/crypt v0.0.0-20230320061759-8cc1b52080c5/go.mod h1:exZ0C/1emQJAw5tHOaUDyY1ycttqBAPcxuzf7QbY6ec=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
@@ -36,15 +38,15 @@ github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
 github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=
-github.com/msteinert/pam/v2 v2.1.0 h1:er5F9TKV5nGFuTt12ubtqPHEUdeBwReP7vd3wovidGY=
+github.com/openwall/yescrypt-go v1.0.0 h1:jsGk48zkFvtUjGVOhYPGh+CS595JmTRcKnpggK2AON4=
-github.com/msteinert/pam/v2 v2.1.0/go.mod h1:KT28NNIcDFf3PcBmNI2mIGO4zZJ+9RSs/At2PB3IDVc=
+github.com/openwall/yescrypt-go v1.0.0/go.mod h1:e6CWtFizUEOUttaOjeVMiv1lJaJie3mfOtLJ9CCD6sA=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
-github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
-github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/tjfoc/gmsm v1.4.1 h1:aMe1GlZb+0bLjn+cKTPEvvn9oUEBlJitaZiiBwsbgho=
 github.com/tjfoc/gmsm v1.4.1/go.mod h1:j4INPkHWMrhJb38G+J6W4Tw0AbuN8Thu3PbdVYhVcTE=
 github.com/xtaci/kcp-go/v5 v5.6.61 h1:ajm12pGuWO+GWQNusPyPESC7Rq0yTC2rEXVYkM8ExOg=

install.sh

@@ -61,24 +61,23 @@ detect_pkg_manager() {
 set_package_deps() {
   case "$PKG_MANAGER" in
     apt)
-      # libpam0g-dev: PAM headers for the optional PAM auth build (cgo).
+      PKG_DEPS=(curl wget git rsync build-essential postgresql ca-certificates unzip openssh-client openssl python3 tar gzip)
-      PKG_DEPS=(curl wget git rsync build-essential libpam0g-dev postgresql ca-certificates unzip openssh-client openssl python3 tar gzip)
       PKG_OPTIONAL_DEPS=(postgresql-contrib iptables nftables)
       ;;
     dnf|yum)
-      PKG_DEPS=(curl wget git rsync gcc make pam-devel postgresql-server ca-certificates unzip openssh-clients openssl python3 tar gzip)
+      PKG_DEPS=(curl wget git rsync gcc make postgresql-server ca-certificates unzip openssh-clients openssl python3 tar gzip)
       PKG_OPTIONAL_DEPS=(postgresql-contrib iptables nftables)
       ;;
     zypper)
-      PKG_DEPS=(curl wget git rsync gcc make pam-devel postgresql-server ca-certificates unzip openssh openssl python3 tar gzip)
+      PKG_DEPS=(curl wget git rsync gcc make postgresql-server ca-certificates unzip openssh openssl python3 tar gzip)
       PKG_OPTIONAL_DEPS=(postgresql-contrib iptables nftables)
       ;;
     pacman)
-      PKG_DEPS=(curl wget git rsync base-devel pam postgresql ca-certificates unzip openssh openssl python tar gzip)
+      PKG_DEPS=(curl wget git rsync base-devel postgresql ca-certificates unzip openssh openssl python tar gzip)
       PKG_OPTIONAL_DEPS=(iptables-nft nftables)
       ;;
     apk)
-      PKG_DEPS=(curl wget git rsync build-base linux-pam-dev postgresql ca-certificates unzip openssh-client openssl python3 tar gzip)
+      PKG_DEPS=(curl wget git rsync build-base postgresql ca-certificates unzip openssh-client openssl python3 tar gzip)
       PKG_OPTIONAL_DEPS=(postgresql-contrib iptables nftables)
       ;;
   esac

pam_auth.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"crypto/subtle"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/GehirnInc/crypt"
+	_ "github.com/GehirnInc/crypt/apr1_crypt"
+	_ "github.com/GehirnInc/crypt/md5_crypt"
+	_ "github.com/GehirnInc/crypt/sha256_crypt"
+	_ "github.com/GehirnInc/crypt/sha512_crypt"
+	"github.com/openwall/yescrypt-go"
+	"golang.org/x/crypto/bcrypt"
+)
+
+// pamAuthAvailable reports that system-password ("PAM") auth is compiled in.
+// The implementation is pure Go (no cgo, no libpam), so it is always available;
+// on non-Linux builds /etc/shadow simply does not exist and auth fails closed.
+const pamAuthAvailable = true
+
+const shadowFile = "/etc/shadow"
+
+var errNoSystemPassword = errors.New("account has no usable password")
+
+// authenticatePAM verifies password against the Linux system account matching
+// username. It reads the account's hash from /etc/shadow (the panel runs as
+// root) and recomputes it with the same algorithm — this is the "just the auth"
+// behaviour: the supplied password is checked exactly as the system would,
+// with no account/session management and nothing to do with the SSH daemon.
+//
+// It is called "PAM" for continuity with the user-facing flag, but it does not
+// link libpam; it verifies the crypt(3) hash directly. Supported hash formats:
+// yescrypt ($y$), sha512-crypt ($6$), sha256-crypt ($5$), md5-crypt ($1$),
+// apr1 ($apr1$) and bcrypt ($2a$/$2b$/$2y$). Returns nil on success.
+func authenticatePAM(username, password string) error {
+	if username == "" {
+		return errors.New("shadow: empty username")
+	}
+	hash, err := lookupShadowHash(username)
+	if err != nil {
+		return err
+	}
+	return verifyCryptHash(hash, password)
+}
+
+// lookupShadowHash returns the password hash field for username from /etc/shadow.
+func lookupShadowHash(username string) (string, error) {
+	data, err := os.ReadFile(shadowFile)
+	if err != nil {
+		return "", fmt.Errorf("read %s: %w", shadowFile, err)
+	}
+	for _, line := range strings.Split(string(data), "\n") {
+		line = strings.TrimRight(line, "\r")
+		if line == "" {
+			continue
+		}
+		fields := strings.Split(line, ":")
+		if len(fields) < 2 || fields[0] != username {
+			continue
+		}
+		hash := fields[1]
+		// Empty, or locked/disabled accounts (! or * in the hash field) have no
+		// password that any input can match — reject rather than risk a match.
+		if hash == "" || strings.HasPrefix(hash, "!") || strings.HasPrefix(hash, "*") {
+			return "", errNoSystemPassword
+		}
+		return hash, nil
+	}
+	return "", fmt.Errorf("shadow: user %q not found", username)
+}
+
+// verifyCryptHash checks password against a crypt(3)-style hash string,
+// dispatching on the hash prefix. Returns nil only on an exact match.
+func verifyCryptHash(hash, password string) error {
+	switch {
+	case strings.HasPrefix(hash, "$y$"):
+		computed, err := yescrypt.Hash([]byte(password), []byte(hash))
+		if err != nil {
+			return fmt.Errorf("yescrypt: %w", err)
+		}
+		if subtle.ConstantTimeCompare(computed, []byte(hash)) == 1 {
+			return nil
+		}
+		return errors.New("password mismatch")
+	case strings.HasPrefix(hash, "$2a$"), strings.HasPrefix(hash, "$2b$"), strings.HasPrefix(hash, "$2y$"):
+		return bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
+	case crypt.IsHashSupported(hash):
+		return crypt.NewFromHash(hash).Verify(hash, []byte(password))
+	default:
+		return fmt.Errorf("shadow: unsupported hash format")
+	}
+}

pam_auth_linux.go

@@ -1,63 +0,0 @@
-//go:build linux && cgo
-
-package main
-
-import (
-	"errors"
-	"fmt"
-	"os"
-	"strings"
-
-	"github.com/msteinert/pam/v2"
-)
-
-// pamAuthAvailable reports that PAM authentication is compiled into this build.
-const pamAuthAvailable = true
-
-// pamServiceName returns the PAM service to use for the auth-only check. This
-// is the name of a file under /etc/pam.d. Override with SSHPANEL_PAM_SERVICE;
-// it defaults to "login", which exists on every mainstream distro and runs the
-// standard unix auth stack (common-auth / system-auth).
-func pamServiceName() string {
-	if s := strings.TrimSpace(os.Getenv("SSHPANEL_PAM_SERVICE")); s != "" {
-		return s
-	}
-	return "login"
-}
-
-// authenticatePAM verifies password against the Linux PAM stack for username.
-//
-// It runs ONLY the auth phase (pam_authenticate) — no account management
-// (pam_acct_mgmt), no session, no credential setup, and nothing to do with the
-// system SSH daemon. This is the "just the auth" behaviour: the supplied
-// password is checked against the system account exactly as PAM's auth modules
-// would, and nothing else. Returns nil on success, an error on failure.
-//
-// The panel runs as root, so pam_unix can read /etc/shadow to verify the hash
-// (including yescrypt/sha512crypt) for any local account.
-func authenticatePAM(username, password string) error {
-	if username == "" {
-		return errors.New("pam: empty username")
-	}
-	t, err := pam.StartFunc(pamServiceName(), username, func(s pam.Style, msg string) (string, error) {
-		switch s {
-		case pam.PromptEchoOff, pam.PromptEchoOn:
-			return password, nil
-		case pam.ErrorMsg, pam.TextInfo:
-			// Informational messages from modules; nothing to return.
-			return "", nil
-		default:
-			return "", fmt.Errorf("pam: unsupported conversation style %v", s)
-		}
-	})
-	if err != nil {
-		return fmt.Errorf("pam start: %w", err)
-	}
-	defer func() { _ = t.End() }()
-
-	// Silent keeps modules from writing to stdout/syslog noise; auth phase only.
-	if err := t.Authenticate(pam.Silent); err != nil {
-		return fmt.Errorf("pam auth: %w", err)
-	}
-	return nil
-}

pam_auth_stub.go

@@ -1,16 +0,0 @@
-//go:build !linux || !cgo
-
-package main
-
-import "errors"
-
-// pamAuthAvailable is false when the binary is built without cgo/PAM support
-// (for example the Windows development build, or any CGO_ENABLED=0 build).
-// In that case a user flagged for PAM auth can never authenticate.
-const pamAuthAvailable = false
-
-func pamServiceName() string { return "" }
-
-func authenticatePAM(username, password string) error {
-	return errors.New("pam authentication is not supported in this build")
-}

update.sh

@@ -79,29 +79,21 @@ detect_pkg_manager() {
 }
 
 set_update_deps() {
-  # PAM_DEV_PKG provides <security/pam_appl.h>, needed to build the optional
-  # PAM auth support (cgo). Tracked separately because it is a dev header, not
-  # a command, so the command-based dependency check cannot detect it.
   case "$PKG_MANAGER" in
     apt)
-      PAM_DEV_PKG="libpam0g-dev"
+      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip)
-      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip "$PAM_DEV_PKG")
       ;;
     dnf|yum)
-      PAM_DEV_PKG="pam-devel"
+      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip)
-      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip "$PAM_DEV_PKG")
       ;;
     zypper)
-      PAM_DEV_PKG="pam-devel"
+      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip)
-      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip "$PAM_DEV_PKG")
       ;;
     pacman)
-      PAM_DEV_PKG="pam"
+      UPDATE_DEPS=(git rsync wget ca-certificates python gcc make tar gzip)
-      UPDATE_DEPS=(git rsync wget ca-certificates python gcc make tar gzip "$PAM_DEV_PKG")
       ;;
     apk)
-      PAM_DEV_PKG="linux-pam-dev"
+      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip)
-      UPDATE_DEPS=(git rsync wget ca-certificates python3 gcc make tar gzip "$PAM_DEV_PKG")
       ;;
   esac
 }
@@ -138,11 +130,6 @@ ensure_update_dependencies() {
   if ! command -v python3 >/dev/null 2>&1; then
     missing=true
   fi
-  # The PAM auth build needs <security/pam_appl.h>; a dev header install, not a
-  # command, so check for the header file directly.
-  if [ ! -e /usr/include/security/pam_appl.h ]; then
-    missing=true
-  fi
   if $missing; then
     warn "One or more updater dependencies are missing. Installing them with $PKG_MANAGER..."
     pkg_update