Version: Next

hmac-auth

Description#

The hmac-auth plugin supports HMAC (Hash-based Message Authentication Code) authentication as a mechanism to ensure the integrity of requests, preventing them from being modified during transmissions. To use the plugin, you would configure HMAC secret keys on Consumers and enable the plugin on Routes or Services.

Once enabled, the plugin verifies the HMAC signature in the request's Authorization header and check that incoming requests are from trusted sources. Specifically, when APISIX receives an HMAC-signed request, the key ID is extracted from the Authorization header. APISIX then retrieves the corresponding consumer configuration, including the secret key. If the key ID is valid and exists, APISIX generates an HMAC signature using the request's Date header and the secret key. If this generated signature matches the signature provided in the Authorization header, the request is authenticated and forwarded to upstream services.

The plugin implementation is based on draft-cavage-http-signatures.

Attributes#

The following attributes are available for configurations on Consumers or Credentials.

Name	Type	Required	Default	Valid values	Description
key_id	string	True			Unique identifier for the consumer, which identifies the associated configurations such as the secret key.
secret_key	string	True			Secret key used to generate an HMAC. This field supports saving the value in Secret Manager using the APISIX Secret resource.

The following attributes are available for configurations on Routes or Services.

Name	Type	Required	Default	Valid values	Description
allowed_algorithms	array[string]	False	["hmac-sha1", "hmac-sha256", "hmac-sha512"]	combination of "hmac-sha1", "hmac-sha256", and "hmac-sha512"	The list of HMAC algorithms allowed.
clock_skew	integer	False	300	>=1	Maximum allowable time difference in seconds between the client request's timestamp and APISIX server's current time. This helps account for discrepancies in time synchronization between the client’s and server’s clocks and protect against replay attacks. The timestamp in the Date header (must be in GMT format) will be used for the calculation.
signed_headers	array[string]	False			The list of HMAC-signed headers that should be included in the client request's HMAC signature.
validate_request_body	boolean	False	false		If true, validate the integrity of the request body to ensure it has not been tampered with during transmission. Specifically, the plugin creates a SHA-256 base64-encoded digest and compare it to the `Digest` header. If the Digest` header is missing or if the digests do not match, the validation fails.
hide_credentials	boolean	False	false		If true, do not pass the authorization request header to upstream services.

NOTE: encrypt_fields = {"secret_key"} is also defined in the schema, which means that the field will be stored encrypted in etcd. See encrypted storage fields.

Examples#

note

You can fetch the admin_key from config.yaml and save to an environment variable with the following command:

admin_key=$(yq '.deployment.admin.admin_key[0].key' conf/config.yaml | sed 's/"//g')

Before proceeding, create a sample consumer and configure its credential, which will be used for all examples below.

Create a consumer john:

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "john"
    }
  }'

Create hmac-auth credential for john:

curl "http://127.0.0.1:9180/apisix/admin/consumers/john/credentials" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "cred-john-hmac-auth",
    "plugins": {
      "hmac-auth": {
        "key_id": "john-key",
        "secret_key": "john-secret-key"
      }
    }
  }'

Implement HMAC Authentication on a Route#

The following example shows how to implement HMAC authentications on a route using the most minimal configurations.

Create a route with the hmac-auth plugin using its default configurations:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "hmac-auth-route",
    "uri": "/get",
    "methods": ["GET"],
    "plugins": {
      "hmac-auth": {}
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Generate a signature. You can use the below Python snippet or other stack of your choice:

hmac-sig-header-gen.py

import hmac
import hashlib
import base64
from datetime import datetime, timezone

key_id = "john-key"                # key id
secret_key = b"john-secret-key"    # secret key
request_method = "GET"             # HTTP method
request_path = "/get"              # route URI
algorithm= "hmac-sha256"           # can use other algorithms in allowed_algorithms

# get current datetime in GMT
# note: the signature will become invalid after the clock skew (default 300s)
# you can regenerate the signature after it becomes invalid, or increase the clock
# skew to prolong the validity within the advised security boundary
gmt_time = datetime.now(timezone.utc).strftime('%a, %d %b %Y %H:%M:%S GMT')

# construct the signing string (ordered)
# the date and any subsequent custom headers should be lowercased and separated by a
# single space character, i.e. `<key>:<space><value>`
# https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12#section-2.1.6
signing_string = (
  f"{key_id}\n"
  f"{request_method} {request_path}\n"
  f"date: {gmt_time}\n"
)

# create signature
signature = hmac.new(secret_key, signing_string.encode('utf-8'), hashlib.sha256).digest()
signature_base64 = base64.b64encode(signature).decode('utf-8')

# construct the request headers
headers = {
  "Date": gmt_time,
  "Authorization": (
    f'Signature keyId="{key_id}",algorithm="{algorithm}",'
    f'headers="@request-target date",'
    f'signature="{signature_base64}"'
  )
}

# print headers
print(headers)

Run the script:

python3 hmac-sig-header-gen.py

You should see the request headers printed:

{'Date': 'Fri, 06 Sep 2024 06:41:29 GMT', 'Authorization': 'Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="wWfKQvPDr0wHQ4IHdluB4IzeNZcj0bGJs2wvoCOT5rM="'}

Using the headers generated, send a request to the route:

curl -X GET "http://127.0.0.1:9080/get" \
  -H "Date: Fri, 06 Sep 2024 06:41:29 GMT" \
  -H 'Authorization: Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="wWfKQvPDr0wHQ4IHdluB4IzeNZcj0bGJs2wvoCOT5rM="'

You should see an HTTP/1.1 200 OK response similar to the following:

{
  "args": {},
  "headers": {
    "Accept": "*/*",
    "Authorization": "Signature keyId=\"john-key\",algorithm=\"hmac-sha256\",headers=\"@request-target date\",signature=\"wWfKQvPDr0wHQ4IHdluB4IzeNZcj0bGJs2wvoCOT5rM=\"",
    "Date": "Fri, 06 Sep 2024 06:41:29 GMT",
    "Host": "127.0.0.1",
    "User-Agent": "curl/8.6.0",
    "X-Amzn-Trace-Id": "Root=1-66d96513-2e52d4f35c9b6a2772d667ea",
    "X-Consumer-Username": "john",
    "X-Credential-Identifier": "cred-john-hmac-auth",
    "X-Forwarded-Host": "127.0.0.1"
  },
  "origin": "192.168.65.1, 34.0.34.160",
  "url": "http://127.0.0.1/get"
}

Hide Authorization Information From Upstream#

As seen the in the last example, the Authorization header passed to the upstream includes the signature and all other details. This could potentially introduce security risks.

The following example shows how to prevent these information from being sent to the upstream service.

Update the plugin configuration to set hide_credentials to true:

curl "http://127.0.0.1:9180/apisix/admin/routes/hmac-auth-route" -X PATCH \
-H "X-API-KEY: ${admin_key}" \
-d '{
  "plugins": {
    "hmac-auth": {
      "hide_credentials": true
    }
  }
}'

Send a request to the route:

curl -X GET "http://127.0.0.1:9080/get" \
  -H "Date: Fri, 06 Sep 2024 06:41:29 GMT" \
  -H 'Authorization: Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="wWfKQvPDr0wHQ4IHdluB4IzeNZcj0bGJs2wvoCOT5rM="'

You should see an HTTP/1.1 200 OK response and notice the Authorization header is entirely removed:

{
  "args": {},
  "headers": {
    "Accept": "*/*",
    "Host": "127.0.0.1",
    "User-Agent": "curl/8.6.0",
    "X-Amzn-Trace-Id": "Root=1-66d96513-2e52d4f35c9b6a2772d667ea",
    "X-Consumer-Username": "john",
    "X-Credential-Identifier": "cred-john-hmac-auth",
    "X-Forwarded-Host": "127.0.0.1"
  },
  "origin": "192.168.65.1, 34.0.34.160",
  "url": "http://127.0.0.1/get"
}

Enable Body Validation#

The following example shows how to enable body validation to ensure the integrity of the request body.

Create a route with the hmac-auth plugin as such:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "hmac-auth-route",
    "uri": "/post",
    "methods": ["POST"],
    "plugins": {
      "hmac-auth": {
        "validate_request_body": true
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Generate a signature. You can use the below Python snippet or other stack of your choice:

hmac-sig-digest-header-gen.py

import hmac
import hashlib
import base64
from datetime import datetime, timezone

key_id = "john-key"                # key id
secret_key = b"john-secret-key"    # secret key
request_method = "POST"             # HTTP method
request_path = "/post"              # route URI
algorithm= "hmac-sha256"            # can use other algorithms in allowed_algorithms
body = '{"name": "world"}'          # example request body

# get current datetime in GMT
# note: the signature will become invalid after the clock skew (default 300s).
# you can regenerate the signature after it becomes invalid, or increase the clock
# skew to prolong the validity within the advised security boundary
gmt_time = datetime.now(timezone.utc).strftime('%a, %d %b %Y %H:%M:%S GMT')

# construct the signing string (ordered)
# the date and any subsequent custom headers should be lowercased and separated by a
# single space character, i.e. `<key>:<space><value>`
# https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12#section-2.1.6
signing_string = (
    f"{key_id}\n"
    f"{request_method} {request_path}\n"
    f"date: {gmt_time}\n"
)

# create signature
signature = hmac.new(secret_key, signing_string.encode('utf-8'), hashlib.sha256).digest()
signature_base64 = base64.b64encode(signature).decode('utf-8')

# create the SHA-256 digest of the request body and base64 encode it
body_digest = hashlib.sha256(body.encode('utf-8')).digest()
body_digest_base64 = base64.b64encode(body_digest).decode('utf-8')

# construct the request headers
headers = {
    "Date": gmt_time,
    "Digest": f"SHA-256={body_digest_base64}",
    "Authorization": (
        f'Signature keyId="{key_id}",algorithm="hmac-sha256",'
        f'headers="@request-target date",'
        f'signature="{signature_base64}"'
    )
}

# print headers
print(headers)

Run the script:

python3 hmac-sig-digest-header-gen.py

You should see the request headers printed:

{'Date': 'Fri, 06 Sep 2024 09:16:16 GMT', 'Digest': 'SHA-256=78qzJuLwSpZ8HacsTdFCQJWxzPMOf8bYctRk2ySLpS8=', 'Authorization': 'Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="rjS6NxOBKmzS8CZL05uLiAfE16hXdIpMD/L/HukOTYE="'}

Using the headers generated, send a request to the route:

curl "http://127.0.0.1:9080/post" -X POST \
  -H "Date: Fri, 06 Sep 2024 09:16:16 GMT" \
  -H "Digest: SHA-256=78qzJuLwSpZ8HacsTdFCQJWxzPMOf8bYctRk2ySLpS8=" \
  -H 'Authorization: Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="rjS6NxOBKmzS8CZL05uLiAfE16hXdIpMD/L/HukOTYE="' \
  -d '{"name": "world"}'

You should see an HTTP/1.1 200 OK response similar to the following:

{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "{\"name\": \"world\"}": ""
  },
  "headers": {
    "Accept": "*/*",
    "Authorization": "Signature keyId=\"john-key\",algorithm=\"hmac-sha256\",headers=\"@request-target date\",signature=\"rjS6NxOBKmzS8CZL05uLiAfE16hXdIpMD/L/HukOTYE=\"",
    "Content-Length": "17",
    "Content-Type": "application/x-www-form-urlencoded",
    "Date": "Fri, 06 Sep 2024 09:16:16 GMT",
    "Digest": "SHA-256=78qzJuLwSpZ8HacsTdFCQJWxzPMOf8bYctRk2ySLpS8=",
    "Host": "127.0.0.1",
    "User-Agent": "curl/8.6.0",
    "X-Amzn-Trace-Id": "Root=1-66d978c3-49f929ad5237da5340bbbeb4",
    "X-Consumer-Username": "john",
    "X-Credential-Identifier": "cred-john-hmac-auth",
    "X-Forwarded-Host": "127.0.0.1"
  },
  "json": null,
  "origin": "192.168.65.1, 34.0.34.160",
  "url": "http://127.0.0.1/post"
}

If you send a request without the digest or with an invalid digest:

curl "http://127.0.0.1:9080/post" -X POST \
  -H "Date: Fri, 06 Sep 2024 09:16:16 GMT" \
  -H "Digest: SHA-256=78qzJuLwSpZ8HacsTdFCQJWxzPMOf8bYctRk2ySLpS8=" \
  -H 'Authorization: Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date",signature="rjS6NxOBKmzS8CZL05uLiAfE16hXdIpMD/L/HukOTYE="' \
  -d '{"name": "world"}'

You should see an HTTP/1.1 401 Unauthorized response with the following message:

{"message":"client request can't be validated"}

Mandate Signed Headers#

The following example shows how you can mandate certain headers to be signed in the request's HMAC signature.

Create a route with the hmac-auth plugin which requires three headers to be present in the HMAC signature:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "hmac-auth-route",
    "uri": "/get",
    "methods": ["GET"],
    "plugins": {
      "hmac-auth": {
        "signed_headers": ["date","x-custom-header-a", "x-custom-header-b"]
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Generate a signature. You can use the below Python snippet or other stack of your choice:

hmac-sig-req-header-gen.py

import hmac
import hashlib
import base64
from datetime import datetime, timezone

key_id = "john-key"                # key id
secret_key = b"john-secret-key"    # secret key
request_method = "GET"             # HTTP method
request_path = "/get"              # route URI
algorithm= "hmac-sha256"           # can use other algorithms in allowed_algorithms
custom_header_a = "hello123"       # required custom header
custom_header_b = "world456"       # required custom header

# get current datetime in GMT
# note: the signature will become invalid after the clock skew (default 300s)
# you can regenerate the signature after it becomes invalid, or increase the clock
# skew to prolong the validity within the advised security boundary
gmt_time = datetime.now(timezone.utc).strftime('%a, %d %b %Y %H:%M:%S GMT')

# construct the signing string (ordered)
# the date and any subsequent custom headers should be lowercased and separated by a
# single space character, i.e. `<key>:<space><value>`
# https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12#section-2.1.6
signing_string = (
    f"{key_id}\n"
    f"{request_method} {request_path}\n"
    f"date: {gmt_time}\n"
    f"x-custom-header-a: {custom_header_a}\n"
    f"x-custom-header-b: {custom_header_b}\n"
)

# create signature
signature = hmac.new(secret_key, signing_string.encode('utf-8'), hashlib.sha256).digest()
signature_base64 = base64.b64encode(signature).decode('utf-8')

# construct the request headers
headers = {
    "Date": gmt_time,
    "Authorization": (
        f'Signature keyId="{key_id}",algorithm="hmac-sha256",'
        f'headers="@request-target date x-custom-header-a x-custom-header-b",'
        f'signature="{signature_base64}"'
    ),
    "x-custom-header-a": custom_header_a,
    "x-custom-header-b": custom_header_b
}

# print headers
print(headers)

Run the script:

python3 hmac-sig-req-header-gen.py

You should see the request headers printed:

{'Date': 'Fri, 06 Sep 2024 09:58:49 GMT', 'Authorization': 'Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date x-custom-header-a x-custom-header-b",signature="MwJR8JOhhRLIyaHlJ3Snbrf5hv0XwdeeRiijvX3A3yE="', 'x-custom-header-a': 'hello123', 'x-custom-header-b': 'world456'}

Using the headers generated, send a request to the route:

curl -X GET "http://127.0.0.1:9080/get" \
     -H "Date: Fri, 06 Sep 2024 09:58:49 GMT" \
     -H 'Authorization: Signature keyId="john-key",algorithm="hmac-sha256",headers="@request-target date x-custom-header-a x-custom-header-b",signature="MwJR8JOhhRLIyaHlJ3Snbrf5hv0XwdeeRiijvX3A3yE="' \
     -H "x-custom-header-a: hello123" \
     -H "x-custom-header-b: world456"

You should see an HTTP/1.1 200 OK response similar to the following:

{
  "args": {},
  "headers": {
    "Accept": "*/*",
    "Authorization": "Signature keyId=\"john-key\",algorithm=\"hmac-sha256\",headers=\"@request-target date x-custom-header-a x-custom-header-b\",signature=\"MwJR8JOhhRLIyaHlJ3Snbrf5hv0XwdeeRiijvX3A3yE=\"",
    "Date": "Fri, 06 Sep 2024 09:58:49 GMT",
    "Host": "127.0.0.1",
    "User-Agent": "curl/8.6.0",
    "X-Amzn-Trace-Id": "Root=1-66d98196-64a58db25ece71c077999ecd",
    "X-Consumer-Username": "john",
    "X-Credential-Identifier": "cred-john-hmac-auth",
    "X-Custom-Header-A": "hello123",
    "X-Custom-Header-B": "world456",
    "X-Forwarded-Host": "127.0.0.1"
  },
  "origin": "192.168.65.1, 103.97.2.206",
  "url": "http://127.0.0.1/get"
}

Delete Plugin#

To remove the hmac-auth Plugin on the Route, you can delete the corresponding JSON configuration from the Plugin configuration. APISIX will automatically reload and you do not have to restart for this to take effect.

curl http://127.0.0.1:9180/apisix/admin/routes/1 -H "X-API-KEY: $admin_key" -X PUT -d '
{
    "uri": "/index.html",
    "plugins": {},
    "upstream": {
        "type": "roundrobin",
        "nodes": {
            "127.0.0.1:1980": 1
        }
    }
}'