Ok, let me explain how I am debugging this, maybe someone finds it interesting.
At https://mbihj-yyaaa-aaaae-qaata-cai.ic0.app/1900kb.png it indeed says “Body does not pass verification”, while https://mbihj-yyaaa-aaaae-qaata-cai.ic0.app/1800kb.png goes through. Good, let’s focus on 1900kb.
Next I fetch that resource, using the raw URL, and get its SHA256:
~ $ curl -s https://mbihj-yyaaa-aaaae-qaata-cai.raw.ic0.app/1900kb.png|wc -c
1945600
~ $ curl -s https://mbihj-yyaaa-aaaae-qaata-cai.raw.ic0.app/1900kb.png|sha256sum -
f883650c320109b0d9b5df9df42e4727a96dc90597434bc658dbe06a9f3c1bb9 -
Now, I get the IC-Certification header, which is the thing that the service worker validates:
~ $ curl -i -s https://mbihj-yyaaa-aaaae-qaata-cai.raw.ic0.app/1900kb.png|grep -a -i ic-cert
ic-certificate: certificate=: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:, tree=:2dn3gwJLaHR0cF9hc3NldHODAYIEWCBpPd7hwyvGPRD+L+gQPssOg9oh5oXIvfhivneQtIX2qoMBggRYIKzZbIVGcXjtCTDU6L5twtnYx1ApB6rxeuJMR8yhFJ4SgwGCBFgg+r/H88YaYxgLygTHVhS1POtkfWWqQADrBYSuMHWdP3qDAYIEWCBYzw+ki8tOCR/BB3t6/BssPmPILgqxkzhd8nMZvPmBb4MBggRYIFM23wo1Y/VKvCk9NRSFvQduWNF3HzECLZKMZQoJbePjgwJLLzE5MDBrYi5wbmeCA1gg+INlDDIBCbDZtd+d9C5HJ6ltyQWXQ0vGWNvgap88G7k=:
There are two fields here, the tree and the certificate. The tree comes from the canister. I’ll copy the tree and convert it from Base64 to Hex using Base64 to Hex | Base64 Decode | Base64 Converter | Base64. This gives me
d9d9f783024b687474705f617373657473830182045820693ddee1c32bc63d10fe2fe8103ecb0e83da21e685c8bdf862be7790b485f6aa830182045820acd96c85467178ed0930d4e8be6dc2d9d8c7502907aaf17ae24c47cca1149e12830182045820fabfc7f3c61a63180bca04c75614b53ceb647d65aa4000eb0584ae30759d3f7a83018204582058cf0fa48bcb4e091fc1077b7afc1b2c3e63c82e0ab193385df27319bcf9816f8301820458205336df0a3563f54abc293d351485bd076e58d1771f31022d928c650a096de3e383024b2f313930306b622e706e6782035820f883650c320109b0d9b5df9df42e4727a96dc90597434bc658dbe06a9f3c1bb9
This is a CBOR value, and we can decode it with cbor.me, yielding an annotated value of
D9 D9F7 # tag(55799)
83 # array(3)
02 # unsigned(2)
4B # bytes(11)
687474705F617373657473 # "http_assets"
83 # array(3)
01 # unsigned(1)
82 # array(2)
04 # unsigned(4)
58 20 # bytes(32)
693DDEE1C32BC63D10FE2FE8103ECB0E83DA21E685C8BDF862BE7790B485F6AA # "i=\xDE\xE1\xC3+\xC6=\x10\xFE/\xE8\x10>\xCB\x0E\x83\xDA!\xE6\x85\xC8\xBD\xF8b\xBEw\x90\xB4\x85\xF6\xAA"
83 # array(3)
01 # unsigned(1)
82 # array(2)
04 # unsigned(4)
58 20 # bytes(32)
ACD96C85467178ED0930D4E8BE6DC2D9D8C7502907AAF17AE24C47CCA1149E12 # "\xAC\xD9l\x85Fqx\xED\t0\xD4\xE8\xBEm\xC2\xD9\xD8\xC7P)\a\xAA\xF1z\xE2LG\xCC\xA1\x14\x9E\x12"
83 # array(3)
01 # unsigned(1)
82 # array(2)
04 # unsigned(4)
58 20 # bytes(32)
FABFC7F3C61A63180BCA04C75614B53CEB647D65AA4000EB0584AE30759D3F7A # "\xFA\xBF\xC7\xF3\xC6\x1Ac\x18\v\xCA\x04\xC7V\x14\xB5<\xEBd}e\xAA@\x00\xEB\x05\x84\xAE0u\x9D?z"
83 # array(3)
01 # unsigned(1)
82 # array(2)
04 # unsigned(4)
58 20 # bytes(32)
58CF0FA48BCB4E091FC1077B7AFC1B2C3E63C82E0AB193385DF27319BCF9816F # "X\xCF\x0F\xA4\x8B\xCBN\t\x1F\xC1\a{z\xFC\e,>c\xC8.\n\xB1\x938]\xF2s\x19\xBC\xF9\x81o"
83 # array(3)
01 # unsigned(1)
82 # array(2)
04 # unsigned(4)
58 20 # bytes(32)
5336DF0A3563F54ABC293D351485BD076E58D1771F31022D928C650A096DE3E3 # "S6\xDF\n5c\xF5J\xBC)=5\x14\x85\xBD\anX\xD1w\x1F1\x02-\x92\x8Ce\n\tm\xE3\xE3"
83 # array(3)
02 # unsigned(2)
4B # bytes(11)
2F313930306B622E706E67 # "/1900kb.png"
82 # array(2)
03 # unsigned(3)
58 20 # bytes(32)
F883650C320109B0D9B5DF9DF42E4727A96DC90597434BC658DBE06A9F3C1BB9 # "\xF8\x83e\f2\x01\t\xB0\xD9\xB5\xDF\x9D\xF4.G'\xA9m\xC9\x05\x97CK\xC6X\xDB\xE0j\x9F<\e\xB9"
The details of this CBOR values are documented in the Interface Spec; the relevant pieces is what follows the "/1900kb.png" label; there we have a hash of F883650C320109B0D9B5DF9DF42E4727A96DC90597434BC658DBE06A9F3C1BB9. This matches the SHA256 above!
So the SHA256 matches. Since other resources do validate, it is unlikely that something else related to certification is broken (e.g. wrong certificate). So I predict the bug is in the service worker, and not in the canister.
My assumption is that the service worker doesn’t implement the streaming protocol for responses larger than 2MB correctly, but looking at the code I notice that the code isn’t buggy … it’s simply not there:
Well, the service worker was quite a last minute project, and then I heard there was significant churn in that team, so maybe that is excusable. Although it would be nice if at least we’d get a better error message here…