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by rollcat 935 days ago
Oh, Purism. The guys who included a separate chip to deny the user the ability to upgrade the firmware, so that they could meet FSF's completely arbitrary requirements for a honorary badge of freedom (see the hypocrisy?), but neglected an IOMMU, so the baseband (or any other device on the bus) can wreak unlimited havoc (see the irony?). Great alternative indeed.
1 comments
fsflover 935 days ago
> separate chip to deny the user the ability to upgrade the firmware

This is false: https://news.ycombinator.com/item?id=26784382 and https://old.reddit.com/r/Purism/comments/pcos2x/would_it_be_...

> neglected an IOMMU, so the baseband (or any other device on the bus) can wreak unlimited havoc

The Librem 5 doesn't need an IOMMU, because it uses separated components, and it uses serial buses (USB 2.0/3.0, SDIO, I2C and I2S) that don't allow direct memory access, so there is absolute no chance of the WiFi/BT, cellular modem, GNSS and USB controller being able to access the RAM or the SoC's cache

From https://news.ycombinator.com/item?id=30769589

Do you think that all laptops are also totally insecure, since they use USB?

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lightedman 935 days ago
"No chance of DMA access"

The USB URB structure have a field named 'dma_addr_t transfer_dma', used for DMA access. I've abused that to chain vulnerabilities. To boot, it is possible to develop an I2C-B2C or SPI bus master which is capable of DMA toward the host memory. Linux 2.5 kernels and later, USB device drivers have additional control over how DMA may be used to perform I/O operations.

Do any of these guys actually read the hardware specs or do any real hardware hacking?

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