diff --git a/.github/workflows/pullrequest.yml b/.github/workflows/pullrequest.yml
index 2dfdf09..957c5c5 100644
--- a/.github/workflows/pullrequest.yml
+++ b/.github/workflows/pullrequest.yml
@@ -46,7 +46,7 @@ jobs:
       - name: Install some build requirements
         id: dnf
         run: |
-          dnf install -y efivar-devel nss-devel openssl-devel
+          dnf install -y efivar-devel nss-devel openssl-devel nss-tools
       - name: Run tests on ${{ matrix.distro }} for ${{ matrix.arch }}
         id: test
         run: |
diff --git a/Makefile b/Makefile
index a2e41f8..112ce1e 100644
--- a/Makefile
+++ b/Makefile
@@ -31,7 +31,11 @@ deps all :
 $(SUBDIRS) :
 	$(MAKE) -C $@ all
 
-.PHONY: $(SUBDIRS)
+test : all
+	@echo "Running functional tests..."
+	@cd $(TOPDIR) && tests/run-tests.sh
+
+.PHONY: $(SUBDIRS) test
 
 GITTAG = $(VERSION)
 
diff --git a/src/efikeygen.c b/src/efikeygen.c
index e9070e3..1c97d83 100644
--- a/src/efikeygen.c
+++ b/src/efikeygen.c
@@ -1313,7 +1313,8 @@ int main(int argc, char *argv[])
 	memcpy(&ias.issuer, &cert->issuer, sizeof(ias.issuer));
 	memcpy(&ias.serialNumber, &cert->serialNumber, sizeof(ias.serialNumber));
 
-	add_trust(cms, &ias, is_ca ? ",,CTu" : ",,u");
+	if (add_trust(cms, &ias, is_ca ? ",,CTu" : ",,u") < 0)
+		nsserr(1, "could not set trust for certificate");
 
 	SECITEM_FreeItem(&sigder, PR_FALSE);
 	SECITEM_FreeItem(&signature, PR_FALSE);
diff --git a/src/file_kmod.c b/src/file_kmod.c
index 6880cda..cf68336 100644
--- a/src/file_kmod.c
+++ b/src/file_kmod.c
@@ -10,6 +10,7 @@
 #include <stdint.h>
 
 #include "pesign.h"
+#include "signed_data.h"
 
 #include <prerror.h>
 
@@ -35,67 +36,32 @@ kmod_generate_digest(cms_context *cms, unsigned char *addr, size_t len)
 	return 0;
 }
 
-struct write_sig_info {
-	int outfd;
-	int rc;
-	size_t sig_len;
-};
-
-static void
-kmod_signature_out(void *arg, const char *buf, unsigned long len)
-{
-	struct write_sig_info *info = (struct write_sig_info *) arg;
-	int rc;
-
-	rc = write_file(info->outfd, buf, len);
-	if (rc < 0) {
-		info->rc = rc;
-		return;
-	}
-
-	info->sig_len += len;
-}
-
 ssize_t
 kmod_write_signature(cms_context *cms, int outfd)
 {
-	SEC_PKCS7ContentInfo *cinfo;
-	SECItem *digest = cms->digests[cms->selected_digest].pe_digest;
-	SECStatus rv;
-	struct write_sig_info info = {
-		.outfd = outfd,
-	};
+	SECItem sd_der;
 	ssize_t rc = -1;
 
-	cinfo = SEC_PKCS7CreateSignedData(cms->cert,
-					  certUsageObjectSigner, NULL,
-					  digest_get_digest_oid(cms),
-					  digest, NULL, NULL);
-	if (!cinfo) {
+	memset(&sd_der, '\0', sizeof(sd_der));
+
+	/* Use generate_spc_signed_data() instead of SEC_PKCS7CreateSignedData()
+	 * to avoid strict certificate chain validation that fails for self-signed
+	 * certificates even when trust flags are properly set. */
+	rc = generate_spc_signed_data(cms, &sd_der);
+	if (rc < 0) {
 		cms->log(cms, LOG_ERR, "failed to create signed data: %s (%s)",
 			 PORT_ErrorToString(PORT_GetError()),
 			 PORT_ErrorToName(PORT_GetError()));
 		return -1;
 	}
 
-	rv = SEC_PKCS7Encode(cinfo, kmod_signature_out, &info, NULL, NULL,
-			     NULL);
-	if (rv != SECSuccess) {
-		cms->log(cms, LOG_ERR, "failed to encode signed data: %d", rv);
-		goto out;
-	}
-
-	if (info.rc != 0) {
-		cms->log(cms, LOG_ERR, "Signed data encode error %d", info.rc);
-		rc = info.rc;
-		goto out;
+	rc = write_file(outfd, sd_der.data, sd_der.len);
+	if (rc < 0) {
+		cms->log(cms, LOG_ERR, "failed to write signature: %m");
+		return -1;
 	}
 
-	rc = info.sig_len;
-
-out:
-	SEC_PKCS7DestroyContentInfo(cinfo);
-	return rc;
+	return sd_der.len;
 }
 
 static const char magic_number[] = "~Module signature appended~\n";
diff --git a/tests/run-tests.sh b/tests/run-tests.sh
new file mode 100755
index 0000000..2c41575
--- /dev/null
+++ b/tests/run-tests.sh
@@ -0,0 +1,63 @@
+#!/bin/bash
+# Main test runner for pesign functional tests
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+FAILED_TESTS=()
+PASSED_TESTS=()
+
+echo "======================================"
+echo "Running pesign functional tests"
+echo "======================================"
+echo
+
+run_test() {
+    local test_script="$1"
+    local test_name=$(basename "$test_script" .sh)
+
+    echo -e "${YELLOW}Running: ${test_name}${NC}"
+
+    if bash "$test_script"; then
+        echo -e "${GREEN}✓ PASSED: ${test_name}${NC}"
+        PASSED_TESTS+=("$test_name")
+    else
+        echo -e "${RED}✗ FAILED: ${test_name}${NC}"
+        FAILED_TESTS+=("$test_name")
+    fi
+    echo
+}
+
+# Run all test scripts
+for test in "$SCRIPT_DIR"/test-*.sh; do
+    if [ -f "$test" ]; then
+        run_test "$test"
+    fi
+done
+
+# Summary
+echo "======================================"
+echo "Test Summary"
+echo "======================================"
+echo -e "${GREEN}Passed: ${#PASSED_TESTS[@]}${NC}"
+echo -e "${RED}Failed: ${#FAILED_TESTS[@]}${NC}"
+
+if [ ${#FAILED_TESTS[@]} -gt 0 ]; then
+    echo
+    echo "Failed tests:"
+    for test in "${FAILED_TESTS[@]}"; do
+        echo -e "  ${RED}✗${NC} $test"
+    done
+    exit 1
+fi
+
+echo
+echo -e "${GREEN}All tests passed!${NC}"
+exit 0
diff --git a/tests/test-ca-signed.sh b/tests/test-ca-signed.sh
new file mode 100755
index 0000000..307d25d
--- /dev/null
+++ b/tests/test-ca-signed.sh
@@ -0,0 +1,117 @@
+#!/bin/bash
+# Test CA and signing certificate setup
+# Based on AlmaLinux documentation
+
+set -e
+
+TEST_NAME="ca-signed"
+WORK_DIR=$(mktemp -d)
+trap "rm -rf $WORK_DIR" EXIT
+
+echo "  Setting up CA and signing certificates..."
+
+# Create certificate database
+mkdir -m 0700 -p "$WORK_DIR/ca"
+echo "" | certutil -d "$WORK_DIR/ca" -N --empty-password
+
+# Generate CA certificate
+./src/efikeygen -d "$WORK_DIR/ca" \
+    --ca --self-sign \
+    --not-valid-after=$(date +%s --date='+10 years') \
+    --nickname='Test Secure Boot CA' \
+    --common-name='CN=Test Secure Boot CA,O=Test Organization,E=test@example.com'
+
+# Verify CA was created
+if ! certutil -d "$WORK_DIR/ca" -L -n 'Test Secure Boot CA' > /dev/null 2>&1; then
+    echo "  ERROR: CA certificate not created"
+    exit 1
+fi
+
+# Generate signing certificate signed by CA (marked as --kernel)
+./src/efikeygen -d "$WORK_DIR/ca" \
+    --kernel \
+    --not-valid-after=$(date +%s --date='+10 years') \
+    --signer='Test Secure Boot CA' \
+    --nickname='Test Secure Boot Signing' \
+    --common-name='CN=Test Secure Boot Signing,O=Test Organization,E=test@example.com'
+
+# Verify signing certificate was created
+if ! certutil -d "$WORK_DIR/ca" -L -n 'Test Secure Boot Signing' > /dev/null 2>&1; then
+    echo "  ERROR: Signing certificate not created"
+    exit 1
+fi
+
+# Export certificates
+certutil -d "$WORK_DIR/ca" -L -n "Test Secure Boot CA" -r > "$WORK_DIR/test-secureboot-ca.cer"
+certutil -d "$WORK_DIR/ca" -L -n "Test Secure Boot Signing" -r > "$WORK_DIR/test-secureboot.cer"
+
+# Verify certificate files exist and are not empty
+if [ ! -s "$WORK_DIR/test-secureboot-ca.cer" ]; then
+    echo "  ERROR: CA certificate export failed"
+    exit 1
+fi
+
+if [ ! -s "$WORK_DIR/test-secureboot.cer" ]; then
+    echo "  ERROR: Signing certificate export failed"
+    exit 1
+fi
+
+echo "  ✓ CA and signing certificates created successfully"
+
+# Verify CA trust flags (CA cert should have CA trust)
+CA_TRUST=$(certutil -d "$WORK_DIR/ca" -L | grep "Test Secure Boot CA" | awk '{print $NF}')
+if echo "$CA_TRUST" | grep -q "C\|T"; then
+    echo "  ✓ CA trust flags: $CA_TRUST"
+else
+    echo "  ✗ CA trust flags missing CA trust: $CA_TRUST"
+    exit 1
+fi
+
+# Verify signing cert trust flags
+SIGN_TRUST=$(certutil -d "$WORK_DIR/ca" -L | grep "Test Secure Boot Signing" | awk '{print $NF}')
+if [ -z "$SIGN_TRUST" ]; then
+    echo "  ✗ No trust flags found for signing cert"
+    exit 1
+else
+    echo "  ✓ Signing cert trust flags: $SIGN_TRUST"
+fi
+
+# Get test data directory
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+TEST_DATA="$SCRIPT_DIR/data"
+
+# Use real kernel and module files
+KERNEL="$TEST_DATA/vmlinuz-6.19.10-200.fc43.x86_64"
+MODULE="$TEST_DATA/vfat.ko"
+
+# Test signing a kernel (should work - cert was created with --kernel)
+echo "  Testing kernel signing with CA-signed certificate..."
+if ./src/pesign --certdir "$WORK_DIR/ca" \
+        --certificate 'Test Secure Boot Signing' \
+        --in "$KERNEL" \
+        --sign \
+        --out "$WORK_DIR/kernel-signed" 2>"$WORK_DIR/kernel-error.log"; then
+    echo "  ✓ CA-signed cert signed kernel (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/kernel-signed" 2>/dev/null | head -5
+else
+    echo "  ✗ CA-signed cert failed to sign kernel (exit $?)"
+    [ -s "$WORK_DIR/kernel-error.log" ] && cat "$WORK_DIR/kernel-error.log"
+    exit 1
+fi
+
+# Test signing a module (kernel certs can sign modules)
+echo "  Testing module signing with CA-signed certificate..."
+if ./src/pesign --certdir "$WORK_DIR/ca" \
+        --certificate 'Test Secure Boot Signing' \
+        --in "$MODULE" \
+        --sign \
+        --out "$WORK_DIR/module-signed.ko" 2>"$WORK_DIR/module-error.log"; then
+    echo "  ✓ CA-signed cert signed module (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/module-signed.ko" 2>/dev/null | head -5
+else
+    echo "  ✗ CA-signed cert failed to sign module (exit $?)"
+    [ -s "$WORK_DIR/module-error.log" ] && cat "$WORK_DIR/module-error.log"
+    exit 1
+fi
+
+exit 0
diff --git a/tests/test-self-signed-kernel.sh b/tests/test-self-signed-kernel.sh
new file mode 100755
index 0000000..f2b43d3
--- /dev/null
+++ b/tests/test-self-signed-kernel.sh
@@ -0,0 +1,91 @@
+#!/bin/bash
+# Test self-signed kernel signing certificate setup
+# Based on Red Hat documentation
+
+set -e
+
+TEST_NAME="self-signed-kernel"
+WORK_DIR=$(mktemp -d)
+trap "rm -rf $WORK_DIR" EXIT
+
+echo "  Setting up self-signed kernel signing certificate..."
+
+# Create certificate database
+mkdir -m 0700 -p "$WORK_DIR/certdb"
+echo "" | certutil -d "$WORK_DIR/certdb" -N --empty-password
+
+# Generate self-signed kernel certificate
+./src/efikeygen --dbdir "$WORK_DIR/certdb" \
+    --self-sign \
+    --kernel \
+    --common-name 'CN=Test Kernel Signing Key' \
+    --nickname 'Test Kernel Key'
+
+# Verify certificate was created
+if ! certutil -d "$WORK_DIR/certdb" -L -n 'Test Kernel Key' > /dev/null 2>&1; then
+    echo "  ERROR: Certificate not created"
+    exit 1
+fi
+
+# Export certificate
+certutil -d "$WORK_DIR/certdb" \
+    -n 'Test Kernel Key' \
+    -Lr \
+    > "$WORK_DIR/kernel_cert.cer"
+
+# Verify certificate file exists and is not empty
+if [ ! -s "$WORK_DIR/kernel_cert.cer" ]; then
+    echo "  ERROR: Certificate export failed"
+    exit 1
+fi
+
+echo "  ✓ Self-signed kernel certificate created successfully"
+
+# Verify trust flags are set (should be u,u,u for user cert)
+TRUST=$(certutil -d "$WORK_DIR/certdb" -L | grep "Test Kernel Key" | awk '{print $NF}')
+if [ -z "$TRUST" ]; then
+    echo "  ✗ No trust flags found"
+    exit 1
+else
+    echo "  ✓ Trust flags: $TRUST"
+fi
+
+# Get test data directory
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+TEST_DATA="$SCRIPT_DIR/data"
+
+# Use real kernel and module files
+KERNEL="$TEST_DATA/vmlinuz-6.19.10-200.fc43.x86_64"
+MODULE="$TEST_DATA/vfat.ko"
+
+# Test signing a kernel (should work)
+echo "  Testing kernel signing with kernel certificate..."
+if ./src/pesign --certdir "$WORK_DIR/certdb" \
+        --certificate 'Test Kernel Key' \
+        --in "$KERNEL" \
+        --sign \
+        --out "$WORK_DIR/kernel-signed" 2>"$WORK_DIR/kernel-error.log"; then
+    echo "  ✓ Kernel cert signed kernel (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/kernel-signed" 2>/dev/null | head -5
+else
+    echo "  ✗ Kernel cert failed to sign kernel (exit $?)"
+    [ -s "$WORK_DIR/kernel-error.log" ] && cat "$WORK_DIR/kernel-error.log"
+    exit 1
+fi
+
+# Test signing a module (kernel certs can sign modules)
+echo "  Testing module signing with kernel certificate..."
+if ./src/pesign --certdir "$WORK_DIR/certdb" \
+        --certificate 'Test Kernel Key' \
+        --in "$MODULE" \
+        --sign \
+        --out "$WORK_DIR/module-signed.ko" 2>"$WORK_DIR/module-error.log"; then
+    echo "  ✓ Kernel cert signed module (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/module-signed.ko" 2>/dev/null | head -5
+else
+    echo "  ✗ Kernel cert failed to sign module (exit $?)"
+    [ -s "$WORK_DIR/module-error.log" ] && cat "$WORK_DIR/module-error.log"
+    exit 1
+fi
+
+exit 0
diff --git a/tests/test-self-signed-module.sh b/tests/test-self-signed-module.sh
new file mode 100755
index 0000000..e12bf4d
--- /dev/null
+++ b/tests/test-self-signed-module.sh
@@ -0,0 +1,90 @@
+#!/bin/bash
+# Test self-signed module-only signing certificate setup
+# Based on Red Hat documentation
+
+set -e
+
+TEST_NAME="self-signed-module"
+WORK_DIR=$(mktemp -d)
+trap "rm -rf $WORK_DIR" EXIT
+
+echo "  Setting up self-signed module-only certificate..."
+
+# Create certificate database
+mkdir -m 0700 -p "$WORK_DIR/certdb"
+echo "" | certutil -d "$WORK_DIR/certdb" -N --empty-password
+
+# Generate self-signed module certificate
+./src/efikeygen --dbdir "$WORK_DIR/certdb" \
+    --self-sign \
+    --module \
+    --common-name 'CN=Test Module Signing Key' \
+    --nickname 'Test Module Key'
+
+# Verify certificate was created
+if ! certutil -d "$WORK_DIR/certdb" -L -n 'Test Module Key' > /dev/null 2>&1; then
+    echo "  ERROR: Certificate not created"
+    exit 1
+fi
+
+# Export certificate
+certutil -d "$WORK_DIR/certdb" \
+    -n 'Test Module Key' \
+    -Lr \
+    > "$WORK_DIR/module_cert.cer"
+
+# Verify certificate file exists and is not empty
+if [ ! -s "$WORK_DIR/module_cert.cer" ]; then
+    echo "  ERROR: Certificate export failed"
+    exit 1
+fi
+
+echo "  ✓ Self-signed module certificate created successfully"
+
+# Verify trust flags are set (should be u,u,u for user cert)
+TRUST=$(certutil -d "$WORK_DIR/certdb" -L | grep "Test Module Key" | awk '{print $NF}')
+if [ -z "$TRUST" ]; then
+    echo "  ✗ No trust flags found"
+    exit 1
+else
+    echo "  ✓ Trust flags: $TRUST"
+fi
+
+# Get test data directory
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+TEST_DATA="$SCRIPT_DIR/data"
+
+# Use real kernel and module files
+KERNEL="$TEST_DATA/vmlinuz-6.19.10-200.fc43.x86_64"
+MODULE="$TEST_DATA/vfat.ko"
+
+# Test signing a kernel (should this work with module cert?)
+echo "  Testing kernel signing with module certificate..."
+if ./src/pesign --certdir "$WORK_DIR/certdb" \
+        --certificate 'Test Module Key' \
+        --in "$KERNEL" \
+        --sign \
+        --out "$WORK_DIR/kernel-signed" 2>"$WORK_DIR/kernel-error.log"; then
+    echo "  ⚠ Module cert signed kernel (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/kernel-signed" 2>/dev/null | head -5
+else
+    echo "  ✓ Module cert rejected for kernel signing (exit $?)"
+    [ -s "$WORK_DIR/kernel-error.log" ] && cat "$WORK_DIR/kernel-error.log"
+fi
+
+# Test signing a module (should work)
+echo "  Testing module signing with module certificate..."
+if ./src/pesign --certdir "$WORK_DIR/certdb" \
+        --certificate 'Test Module Key' \
+        --in "$MODULE" \
+        --sign \
+        --out "$WORK_DIR/module-signed.ko" 2>"$WORK_DIR/module-error.log"; then
+    echo "  ✓ Module cert signed module (exit 0)"
+    ./src/pesign --show-signature --in "$WORK_DIR/module-signed.ko" 2>/dev/null | head -5
+else
+    echo "  ✗ Module cert failed to sign module (exit $?)"
+    [ -s "$WORK_DIR/module-error.log" ] && cat "$WORK_DIR/module-error.log"
+    exit 1
+fi
+
+exit 0