Fix asn.1 parser on big endian (#228)

Author: DmitriyMusatkin

.github/workflows/ci.yml

@@ -406,3 +406,31 @@ jobs:
       run: |
         aws s3 cp s3://aws-crt-test-stuff/ci/${{ env.BUILDER_VERSION }}/linux-container-ci.sh ./linux-container-ci.sh && chmod a+x ./linux-container-ci.sh
         ./linux-container-ci.sh ${{ env.BUILDER_VERSION }} aws-crt-${{ env.LINUX_BASE_IMAGE }} build -p ${{ env.PACKAGE_NAME }} --variant=no-tests --cmake-extra=-DBYO_CRYPTO=ON
+
+  s390x: # big-endian
+    runs-on: ubuntu-24.04
+    steps:
+    - uses: aws-actions/configure-aws-credentials@v4
+      with:
+        role-to-assume: ${{ env.CRT_CI_ROLE }}
+        aws-region: ${{ env.AWS_DEFAULT_REGION }}
+    - uses: actions/checkout@v4
+    - uses: uraimo/run-on-arch-action@v3
+      name: Run commands
+      id: runcmd
+      with:
+        arch: s390x
+        distro: ubuntu22.04
+        install: |
+          apt-get update -q -y
+          apt-get -y install sudo
+          apt-get -y install cmake
+          apt-get -y install make
+          apt-get -y install g++
+          apt-get -y install python3
+          apt-get -y install git
+        run: |
+          lscpu | grep Endian
+          python3 -c "from urllib.request import urlretrieve; urlretrieve('${{ env.BUILDER_HOST }}/${{ env.BUILDER_SOURCE }}/${{ env.BUILDER_VERSION }}/builder.pyz?run=${{ env.RUN }}', 'builder')"
+          chmod a+x builder
+          ./builder build -p ${{ env.PACKAGE_NAME }} --variant s390x --cmake-extra=-DENABLE_SANITIZERS=OFF

builder.json

@@ -145,6 +145,13 @@
             "!test_steps": [
                 "test"
             ]
+        },
+        "s390x": {
+            "hosts": {
+                "ubuntu": {
+                    "!pkg_setup": []
+                }
+            }
         }
     },
     "test_steps": [

source/der.c

@@ -80,16 +80,22 @@ static int s_der_read_tlv(struct aws_byte_cursor *cur, struct der_tlv *tlv) {
     if (len_bytes & 0x80) {
         len_bytes &= 0x7f;
         switch (len_bytes) {
-            case 1:
-                if (!aws_byte_cursor_read_u8(cur, (uint8_t *)&len)) {
+            case 1: {
+                uint8_t len_u8;
+                if (!aws_byte_cursor_read_u8(cur, &len_u8)) {
                     return aws_raise_error(AWS_ERROR_CAL_MALFORMED_ASN1_ENCOUNTERED);
                 }
+                len = len_u8;
                 break;
-            case 2:
-                if (!aws_byte_cursor_read_be16(cur, (uint16_t *)&len)) {
+            }
+            case 2: {
+                uint16_t len_u16;
+                if (!aws_byte_cursor_read_be16(cur, &len_u16)) {
                     return aws_raise_error(AWS_ERROR_CAL_MALFORMED_ASN1_ENCOUNTERED);
                 }
+                len = len_u16;
                 break;
+            }
             case 4:
                 if (!aws_byte_cursor_read_be32(cur, &len)) {
                     return aws_raise_error(AWS_ERROR_CAL_MALFORMED_ASN1_ENCOUNTERED);