Azure / Azure/azure-functions-python-worker
[Bug] Python Azure Function worker incorrectly URL encodes cookie value
- Dominant language
- Python
- Stars
- 357
- Forks
- 116
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- Merged PRs (30d)
- 1
Description
### Expected Behavior
Azure Function worker using Python FastAPI should not URL encode cookie values
Expected behavior on HTTP Response Headers:
`set-cookie: test="hello//world"; Path=/; SameSite=lax`
e.g. when using Python FastAPI without Azure Functions, it correctly does not URL encode.
````
import uvicorn
from fastapi import FastAPI
from fastapi.responses import PlainTextResponse
app = FastAPI()
@app.get("/")
def http_trigger():
response = PlainTextResponse("", status_code=200)
response.set_cookie(key='test', value='hello//world')
return response
if __name__ == "__main__":
uvicorn.run(app, host="127.0.0.1", port=7071)
````
Run `curl -v http://localhost:7071/` and response is correct as `set-cookie: test="hello//world"; Path=/; SameSite=lax`
### Actual Behavior
Actual incorrect behavior on HTTP Response Headers, cookie value is incorrect and unexpectedly URL encoded
`Set-Cookie: test=hello%2F%2Fworld; domain=; path=/; samesite=lax`
Tested bug with
* Python 3.12 with FastAPI
* Azure Functions Core tools 4.3.0 locally
* Deployed to production Azure Function
### Steps to Reproduce
1. Run `func start` or deploy to Azure using sample code provided below
2. Send a test HTTP request e.g. `curl -v http://localhost:7071/`
3. Azure Functions worker incorrectly URL encodes the response cookie value in the `Set-Cookie` header
### Relevant code being tried
```shell
import azure.functions as func
from fastapi import FastAPI
from fastapi.responses import PlainTextResponse
app = FastAPI()
func_app = func.AsgiFunctionApp(app=app, http_auth_level=func.AuthLevel.ANONYMOUS)
@app.get("/")
def http_trigger():
response = PlainTextResponse("", status_code=200)
response.set_cookie(key='test', value='hello//world')
return response
```
### Relevant log output
```shell
N/A
```
### requirements.txt file
```shell
azure-functions
fastapi
```
### Where are you facing this problem?
Production Environment (explain below)
### Function app name
Private
### Additional Information
_No response_
Contributor guide
Research direction
Begin with the ASGI adapter path created by func.AsgiFunctionApp and compare its response-header handling with FastAPI's PlainTextResponse.set_cookie output. Reproduce with func start and curl -v using the value hello//world; done means the Set-Cookie header preserves the expected cookie value and a regression check covers it.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- azure, fastapi, python
- Domain
- api, backend
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 45/100