Merge branch 'yubikey' of git://github.com/Calrama/nixpkgs

2 files changed, 146 insertions, 113 deletions

diff --git a/nixos/modules/system/boot/luksroot.nix b/nixos/modules/system/boot/luksroot.nix
index 8547682284f7..117c526fcd38 100644
--- a/nixos/modules/system/boot/luksroot.nix
+++ b/nixos/modules/system/boot/luksroot.nix
@@ -39,153 +39,123 @@ let
     ${optionalString (luks.yubikeySupport && (yubikey != null)) ''
 
     rbtohex() {
-        od -An -vtx1 | tr -d ' \n'
+        ( od -An -vtx1 | tr -d ' \n' )
     }
 
     hextorb() {
-        tr '[:lower:]' '[:upper:]' | sed -e 's|\([0-9A-F]\{2\}\)|\\\\\\x\1|gI' | xargs printf
-    }
-
-    take() {
-        local c="$1"
-        shift
-        head -c $c "$@"
-    }
-
-    drop() {
-        local c="$1"
-        shift
-        if [ -e "$1" ]; then
-            cat "$1" | ( dd of=/dev/null bs="$c" count=1 2>/dev/null ; dd 2>/dev/null )
-        else
-            ( dd of=/dev/null bs="$c" count=1 2>/dev/null ; dd 2>/dev/null )
-        fi
+        ( tr '[:lower:]' '[:upper:]' | sed -e 's/\([0-9A-F]\{2\}\)/\\\\\\x\1/gI' | xargs printf )
     }
 
     open_yubikey() {
 
+        # Make all of these local to this function
+        # to prevent their values being leaked
+        local salt
+        local iterations
+        local k_user
+        local challenge
+        local response
+        local k_luks
+        local opened
+        local new_salt
+        local new_iterations
+        local new_challenge
+        local new_response
+        local new_k_luks
+
         mkdir -p ${yubikey.storage.mountPoint}
         mount -t ${yubikey.storage.fsType} ${toString yubikey.storage.device} ${yubikey.storage.mountPoint}
 
-        local uuid_r
-        local k_user
-        local challenge
-        local k_blob
-        local aes_blob_decrypted
-        local checksum_correct
-        local checksum
-        local uuid_luks
-        local user_record
-
-        uuid_luks="$(cryptsetup luksUUID ${device} | take 36 | tr -d '-')"
-
-        ${optionalString (!yubikey.multiUser) ''
-        user_record="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path})"
-        uuid_r="$(echo -n $user_record | take 32)"
-        ''}
+        salt="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path} | sed -n 1p | tr -d '\n')"
+        iterations="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path} | sed -n 2p | tr -d '\n')"
+        challenge="$(echo -n $salt | openssl-wrap dgst -binary -sha512 | rbtohex)"
+        response="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
 
         for try in $(seq 3); do
 
-            ${optionalString yubikey.multiUser ''
-            local user_id
-            echo -n "Enter user id: "
-            read -s user_id
-            echo
-            ''}
-
             ${optionalString yubikey.twoFactor ''
             echo -n "Enter two-factor passphrase: "
             read -s k_user
             echo
             ''}
 
-            ${optionalString yubikey.multiUser ''
-            local user_id_hash
-            user_id_hash="$(echo -n $user_id | openssl-wrap dgst -binary -sha512 | rbtohex)"
-
-            user_record="$(sed -n -e /^$user_id_hash[^$]*$/p ${yubikey.storage.mountPoint}${yubikey.storage.path} | tr -d '\n')"
-
-            if [ ! -z "$user_record" ]; then
-                user_record="$(echo -n $user_record | drop 128)"
-                uuid_r="$(echo -n $user_record | take 32)"
-            ''}
-
-                challenge="$(echo -n $k_user$uuid_r$uuid_luks | openssl-wrap dgst -binary -sha1 | rbtohex)"
-
-                k_blob="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
-
-                aes_blob_decrypted="$(echo -n $user_record | drop 32 | hextorb | openssl-wrap enc -d -aes-256-ctr -K $k_blob -iv $uuid_r | rbtohex)"
+            if [ ! -z "$k_user" ]; then
+                k_luks="$(echo -n $k_user | pbkdf2-sha512 ${toString yubikey.keyLength} $iterations $response | rbtohex)"
+            else
+                k_luks="$(echo | pbkdf2-sha512 ${toString yubikey.keyLength} $iterations $response | rbtohex)"
+            fi
 
-                checksum="$(echo -n $aes_blob_decrypted | drop 168)"
-                if [ "$(echo -n $aes_blob_decrypted | hextorb | take 84 | openssl-wrap dgst -binary -sha512 | rbtohex)" == "$checksum" ]; then
-                    checksum_correct=1
-                    break
-                else
-                    checksum_correct=0
-                    echo "Authentication failed!"
-                fi
+            echo -n "$k_luks" | hextorb | cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} --key-file=-
 
-            ${optionalString yubikey.multiUser ''
+            if [ $? == "0" ]; then
+                opened=true
+                break
             else
-                checksum_correct=0
+                opened=false
                 echo "Authentication failed!"
             fi
-            ''}
         done
 
-        if [ "$checksum_correct" != "1" ]; then
+        if [ "$opened" == false ]; then
             umount ${yubikey.storage.mountPoint}
             echo "Maximum authentication errors reached"
             exit 1
         fi
 
-        local k_yubi
-        k_yubi="$(echo -n $aes_blob_decrypted | take 40)"
+        echo -n "Gathering entropy for new salt (please enter random keys to generate entropy if this blocks for long)..."
+        for i in $(seq ${toString yubikey.saltLength}); do
+            byte="$(dd if=/dev/random bs=1 count=1 2>/dev/null | rbtohex)";
+            new_salt="$new_salt$byte";
+            echo -n .
+        done;
+        echo "ok"
 
-        local k_luks
-        k_luks="$(echo -n $aes_blob_decrypted | drop 40 | take 128)"
+        new_iterations="$iterations"
+        ${optionalString (yubikey.iterationStep > 0) ''
+        new_iterations="$(($new_iterations + ${toString yubikey.iterationStep}))"
+        ''}
 
-        echo -n "$k_luks" | hextorb | cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} --key-file=-
+        new_challenge="$(echo -n $new_salt | openssl-wrap dgst -binary -sha512 | rbtohex)"
 
-        update_failed=false
+        new_response="$(ykchalresp -${toString yubikey.slot} -x $new_challenge 2>/dev/null)"
 
-        local new_uuid_r
-        new_uuid_r="$(uuidgen)"
-        if [ $? != "0" ]; then
-            for try in $(seq 10); do
-                sleep 1
-                new_uuid_r="$(uuidgen)"
-                if [ $? == "0" ]; then break; fi
-                if [ $try -eq 10 ]; then update_failed=true; fi
-            done
+        if [ ! -z "$k_user" ]; then
+            new_k_luks="$(echo -n $k_user | pbkdf2-sha512 ${toString yubikey.keyLength} $new_iterations $new_response | rbtohex)"
+        else
+            new_k_luks="$(echo | pbkdf2-sha512 ${toString yubikey.keyLength} $new_iterations $new_response | rbtohex)"
         fi
 
-        if [ "$update_failed" == false ]; then
-            new_uuid_r="$(echo -n $new_uuid_r | take 36 | tr -d '-')"
-
-            local new_challenge
-            new_challenge="$(echo -n $k_user$new_uuid_r$uuid_luks | openssl-wrap dgst -binary -sha1 | rbtohex)"
-
-            local new_k_blob
-            new_k_blob="$(echo -n $new_challenge | hextorb | openssl-wrap dgst -binary -sha1 -mac HMAC -macopt hexkey:$k_yubi | rbtohex)"
+        mkdir -p ${yubikey.ramfsMountPoint}
+        # A ramfs is used here to ensure that the file used to update
+        # the key slot with cryptsetup will never get swapped out.
+        # Warning: Do NOT replace with tmpfs!
+        mount -t ramfs none ${yubikey.ramfsMountPoint}
 
-            local new_aes_blob
-            new_aes_blob=$(echo -n "$k_yubi$k_luks$checksum" | hextorb | openssl-wrap enc -e -aes-256-ctr -K "$new_k_blob" -iv "$new_uuid_r" | rbtohex)
+        echo -n "$new_k_luks" | hextorb > ${yubikey.ramfsMountPoint}/new_key
+        echo -n "$k_luks" | hextorb | cryptsetup luksChangeKey ${device} --key-file=- ${yubikey.ramfsMountPoint}/new_key
 
-            ${optionalString yubikey.multiUser ''
-            sed -i -e "s|^$user_id_hash$user_record|$user_id_hash$new_uuid_r$new_aes_blob|1"
-            ''}
-
-            ${optionalString (!yubikey.multiUser) ''
-            echo -n "$new_uuid_r$new_aes_blob" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
-            ''}
+        if [ $? == "0" ]; then
+            echo -ne "$new_salt\n$new_iterations" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
         else
-            echo "Warning: Could not obtain new UUID, current challenge persists!"
+            echo "Warning: Could not update LUKS key, current challenge persists!"
         fi
 
+        rm -f ${yubikey.ramfsMountPoint}/new_key
+        umount ${yubikey.ramfsMountPoint}
+        rm -rf ${yubikey.ramfsMountPoint}
+
         umount ${yubikey.storage.mountPoint}
     }
 
+    ${optionalString (yubikey.gracePeriod > 0) ''
+    echo -n "Waiting ${toString yubikey.gracePeriod} seconds as grace..."
+    for i in $(seq ${toString yubikey.gracePeriod}); do
+        sleep 1
+        echo -n .
+    done
+    echo "ok"
+    ''}
+
     yubikey_missing=true
     ykinfo -v 1>/dev/null 2>&1
     if [ $? != "0" ]; then
@@ -336,21 +306,45 @@ in
               description = "Whether to use a passphrase and a Yubikey (true), or only a Yubikey (false)";
             };
 
-            multiUser = mkOption {
-              default = false;
-              type = types.bool;
-              description = "Whether to allow multiple users to authenticate with a Yubikey";
-            };
-
             slot = mkOption {
               default = 2;
               type = types.int;
               description = "Which slot on the Yubikey to challenge";
             };
 
+            saltLength = mkOption {
+              default = 16;
+              type = types.int;
+              description = "Length of the new salt in byte (64 is the effective maximum)";
+            };
+
+            keyLength = mkOption {
+              default = 64;
+              type = types.int;
+              description = "Length of the LUKS slot key derived with PBKDF2 in byte";
+            };
+
+            iterationStep = mkOption {
+              default = 0;
+              type = types.int;
+              description = "How much the iteration count for PBKDF2 is increased at each successful authentication";
+            };
+
+            gracePeriod = mkOption {
+              default = 2;
+              type = types.int;
+              description = "Time in seconds to wait before attempting to find the Yubikey";
+            };
+
+            ramfsMountPoint = mkOption {
+              default = "/crypt-ramfs";
+              type = types.string;
+              description = "Path where the ramfs used to update the LUKS key will be mounted in stage-1";
+            };
+
             storage = mkOption {
               type = types.optionSet;
-              description = "Options related to the authentication record";
+              description = "Options related to the storing the salt";
 
               options = {
                 device = mkOption {
@@ -358,7 +352,7 @@ in
                   type = types.path;
                   description = ''
                     An unencrypted device that will temporarily be mounted in stage-1.
-                    Must contain the authentication record for this LUKS device.
+                    Must contain the current salt to create the challenge for this LUKS device.
                   '';
                 };
 
@@ -378,7 +372,7 @@ in
                   default = "/crypt-storage/default";
                   type = types.string;
                   description = ''
-                    Absolute path of the authentication record on the unencrypted device with
+                    Absolute path of the salt on the unencrypted device with
                     that device's root directory as "/".
                   '';
                 };
@@ -420,11 +414,13 @@ in
       cp -pdv ${pkgs.popt}/lib/libpopt*.so.* $out/lib
 
       ${optionalString luks.yubikeySupport ''
-      cp -pdv ${pkgs.utillinux}/bin/uuidgen $out/bin
       cp -pdv ${pkgs.ykpers}/bin/ykchalresp $out/bin
       cp -pdv ${pkgs.ykpers}/bin/ykinfo $out/bin
       cp -pdv ${pkgs.openssl}/bin/openssl $out/bin
 
+      cc -O3 -I${pkgs.openssl}/include -L${pkgs.openssl}/lib ${./pbkdf2-sha512.c} -o $out/bin/pbkdf2-sha512 -lcrypto
+      strip -s $out/bin/pbkdf2-sha512
+
       cp -pdv ${pkgs.libusb1}/lib/libusb*.so.* $out/lib
       cp -pdv ${pkgs.ykpers}/lib/libykpers*.so.* $out/lib
       cp -pdv ${pkgs.libyubikey}/lib/libyubikey*.so.* $out/lib
@@ -444,7 +440,6 @@ EOF
     boot.initrd.extraUtilsCommandsTest = ''
       $out/bin/cryptsetup --version
       ${optionalString luks.yubikeySupport ''
-        $out/bin/uuidgen --version
         $out/bin/ykchalresp -V
         $out/bin/ykinfo -V
         cat > $out/bin/openssl-wrap <<EOF
diff --git a/nixos/modules/system/boot/pbkdf2-sha512.c b/nixos/modules/system/boot/pbkdf2-sha512.c
new file mode 100644
index 000000000000..b40c383ac023
--- /dev/null
+++ b/nixos/modules/system/boot/pbkdf2-sha512.c
@@ -0,0 +1,38 @@
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+#include <openssl/evp.h>
+
+void hextorb(uint8_t* hex, uint8_t* rb)
+{
+	while(sscanf(hex, "%2x", rb) == 1)
+	{
+		hex += 2;
+		rb += 1;
+	}
+	*rb = '\0';
+}
+
+int main(int argc, char** argv)
+{
+	uint8_t k_user[2048];
+	uint8_t salt[2048];
+	uint8_t key[4096];
+
+	uint32_t key_length = atoi(argv[1]);
+	uint32_t iteration_count = atoi(argv[2]);
+
+	hextorb(argv[3], salt);
+	uint32_t salt_length = strlen(argv[3]) / 2;
+
+	fgets(k_user, 2048, stdin);
+	uint32_t k_user_length = strlen(k_user);
+	if(k_user[k_user_length - 1] == '\n') {
+			k_user[k_user_length - 1] = '\0';
+	}
+
+	PKCS5_PBKDF2_HMAC(k_user, k_user_length, salt, salt_length, iteration_count, EVP_sha512(), key_length, key);
+	fwrite(key, 1, key_length, stdout);
+
+	return 0;
+}
\ No newline at end of file