ONBUILD cannot trigger FROM or MAINTAINER

Docs > Datadog Security > Code Security > Infrastructure as Code (IaC) Security > IaC Security Rules > ONBUILD cannot trigger FROM or MAINTAINER

Metadata

Id: 408460f2-2a0f-21ab-ab37-4fb86ac3b5ce

Cloud Provider: Dockerfile

Platform: Dockerfile

Severity: Medium

Category: Best Practices

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Provider Reference

Description

ONBUILD instructions must not trigger FROM, MAINTAINER, or another ONBUILD, because these directives can change the base image or persisted metadata in downstream builds. This can create recursive or unexpected build behavior that undermines build integrity and supply-chain security.

This rule inspects dockerfile_container resources for Dockerfile ONBUILD instructions and verifies that the triggered subcommand is not FROM, MAINTAINER, or ONBUILD.

Resources where ONBUILD triggers FROM, MAINTAINER, or ONBUILD are flagged and should be refactored to invoke safer build actions (for example, RUN or COPY).

Secure ONBUILD example:

ONBUILD RUN apt-get update && apt-get install -y curl

Compliant Code Examples

FROM maven:3-jdk-8

LABEL maintainer="java-platform@example.com"
LABEL description="Maven base image for Java applications"
LABEL version="1.0.0"

# Set Maven environment variables
ENV MAVEN_CONFIG=/root/.m2 \
    MAVEN_OPTS="-XX:+TieredCompilation -XX:TieredStopAtLevel=1"

# Install additional build tools
RUN apt-get update && apt-get install -y --no-install-recommends \
    git \
    openssh-client \
    && rm -rf /var/lib/apt/lists/*

# Configure Maven settings
RUN mkdir -p /root/.m2 && \
    echo '<settings><localRepository>/root/.m2/repository</localRepository></settings>' > /root/.m2/settings.xml

# Create application directory
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

# Negative case 1: ONBUILD ADD is allowed (correct)
ONBUILD ADD . /usr/src/app

# Copy Maven wrapper if present
ONBUILD COPY mvnw* ./
ONBUILD COPY .mvn .mvn

# Download dependencies (will be cached)
ONBUILD COPY pom.xml ./
ONBUILD RUN mvn dependency:go-offline

# Copy source and build
ONBUILD COPY src ./src

# Negative case 2: ONBUILD RUN is allowed (correct)
ONBUILD RUN mvn install

# Package the application
ONBUILD RUN mvn clean package -DskipTests

# Set default command
CMD ["mvn", "--version"]

Non-Compliant Code Examples

FROM debian:bullseye-slim

LABEL maintainer="base-images@example.com"
LABEL description="Base image with incorrect ONBUILD usage"

# Install common dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
    curl \
    ca-certificates \
    git \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /app

# Positive case 1: ONBUILD FROM is not allowed (incorrect)
ONBUILD FROM debian

# Set up common build patterns
ONBUILD RUN mkdir -p /app/logs

# Positive case 2: ONBUILD MAINTAINER is not allowed (incorrect)
ONBUILD MAINTAINER Ron Weasley

# Configure build-time dependencies
ONBUILD RUN apt-get update && apt-get install -y build-essential

# Set environment variables
ENV APP_ENV=production \
    LOG_LEVEL=info

# Create application user
RUN groupadd -r appuser && \
    useradd -r -g appuser appuser

# Expose default port
EXPOSE 8080

USER appuser

CMD ["/bin/bash"]