pspDecryptPRX() tried types 0, 1, 2, 5 and 6. flash0:/vsh/etc/index_XXg.dat -
the index of what the XMB shows, fetched through sceResmgr_9DC14891 - needs
type 9, so it failed and the shell had no menu to build.
Type 9 is type 6 with three differences, all following from a type 9 file
carrying a real ECDSA signature at 0x104..0x12C where a type 6 file has nothing:
- The "must be empty" header check stops at 0x104 instead of 0x10C. The index's
signature starts there, so 8 of its bytes were failing type 6's check - the
original failure.
- The signature is left out of the hashed header rather than fed into it. JPCSP
zeroes buf2[0x34..0x5C), which is that same range once its header
rearrangement is undone, so PRXType9 just leaves the field zero.
- ecdsa_hash in the KIRK CMD1 header stays 0. Type 6/7 set it, but the branch
type 9 takes writes only the mode word, and setting it made KIRK reject the
block.
Tried last in the chain: its header check is a subset of type 6's, so a genuine
type 6 PRX would pass it and then fail on the hash, and trying it earlier would
shadow the real answer. False positives are not really possible either way - the
SHA1 check inside has to match before anything is decrypted.
Verified end to end: 496 bytes in, 159 out (the comp_size in the header),
starting "release:". sceResmgr checks that prefix and says so in its log line,
since a wrong-but-plausible decrypt would otherwise look like success here and
fail much later as an unreadable index.
The VSH now draws something different - the per-frame display list settles at 24
stall points rather than 38 - but what it shows is not visually confirmed;
framebuffer readback doesn't work under headless on either backend.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZq8ZtJmFY7bkX5FVkr3P9
Found the cause of the red error screen the VSH ends on. Every resource load in
the boot succeeds - fonts, all the plugin RCOs, topmenu_icon.rco - and then:
sceIoOpen(flash0:/vsh/etc/index_02g.dat) -> fd 8
sceIoRead(8, 092a2d40, 496)
sceIoClose(8)
unresolved import sceResmgr/9dc14891, called from 'vsh_module'
sceKernelExitDeleteThread(1)
index_02g.dat is the index of what the XMB displays, and it is encrypted (it
starts "PSPsysGP"). sceResmgr_9DC14891 decrypts it. There was no sceResmgr module
at all, so the call trapped, the index stayed encrypted, and the ScePafJob thread
building the top menu exited - a shell with everything loaded and nothing to show.
This adds the module and the three tags it needs (0x0B2B90F0/91F0/92F0, keys and
code 0x5C) to PrxDecrypter.
It is not the whole fix yet: pspDecryptPRX() tries decryption types 0, 1, 2, 5
and 6, and this needs type 9, which JPCSP passes explicitly. So the call is now
reached and fails cleanly with a logged error instead of trapping, but does not
yet decrypt. Type 9 is a variant of type 2 and is the next job; the notes in
docs/VSHBootInvestigation.md say where it is in JPCSP and how to check a port
(159 bytes out, starting "release:").
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZq8ZtJmFY7bkX5FVkr3P9
Henrik Rydgård