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RDKEMW-28267: Buffer bounds - ClearKey subsample validation, subtec map/memmove, cdmidecryptor unmap - #333
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jaihere4u wants to merge 1 commit into
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RDKEMW-28267: Buffer bounds - ClearKey subsample validation, subtec map/memmove, cdmidecryptor unmap#333jaihere4u wants to merge 1 commit into
jaihere4u wants to merge 1 commit into
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ClearKeyDrmSession: bound-check each subsample's clear/encrypted ranges against the mapped buffer size and the pbData scratch before every memcpy — a corrupt subsample table could otherwise drive OOB reads of the GstBuffer and OOB writes past the malloc'd scratch. gstsubtecmp4transform: check gst_buffer_map result before using the map (uninitialized GstMapInfo on failure), and use memmove for the mdat-shift copy which overlaps within the same buffer. gstcdmidecryptor: only gst_buffer_unmap the subsamples buffer when the preceding gst_buffer_map succeeded — previously the free_resources path unmapped a never-mapped buffer with an uninitialized GstMapInfo.
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🟡 Changes recommended
Unresolved critical bounds errors permit an eight-byte overread during MP4 payload copying and an out-of-bounds DRM scratch-buffer write caused by 32-bit counter overflow.
2 open issues
What changed in this PR
This PR hardens buffer handling in the middleware player’s DRM and subtitle paths as part of the memory and reliability audit.
Changes:
- Adds bounds checks when gathering and copying back ClearKey subsample data.
- Checks subtitle buffer mapping and replaces an overlapping
memcpywithmemmove. - Tracks successful subsample mapping to guard decryptor cleanup.
| File | Description |
|---|---|
gst-plugins/gst_subtec/gstsubtecmp4transform.cpp |
Handles mapping failure and uses overlap-safe copying. |
gst-plugins/drm/gst/gstcdmidecryptor.cpp |
Unmaps subsample data only after a successful map. |
drm/ClearKeyDrmSession.cpp |
Adds bounds validation around subsample copies. |
Review effort: Balanced
Comment on lines
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| // Skip the clear byte range from source buffer. | ||
| iCurrSource += nBytesClear; | ||
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| // Bounds-check the subsample ranges against the mapped buffer | ||
| // and the pbData scratch (sized to bufferMap.size). A corrupt | ||
| // subsample table must not read/write out of bounds. | ||
| if ((uint64_t)iCurrSource + nBytesEncrypted > bufferMap.size | ||
| || (uint64_t)cbData + nBytesEncrypted > bufferMap.size) | ||
| { | ||
| MW_LOG_ERR("ClearKeySession: ERROR : subsample range exceeds buffer size %zu", bufferMap.size); | ||
| cbData = 0; | ||
| break; | ||
| } |
| { | ||
| GST_DEBUG_OBJECT (subtecmp4transform, "offset %zu length %zu", offset, length); | ||
| memcpy(map.data, map.data + offset, length); | ||
| memmove(map.data, map.data + offset, length); |
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Jira: RDKEMW-28267 - Middleware PI memory & reliability audit.
Findings covered: BUF-01/02/03 (see ticket + attached MPI_Memory_Audit.html for file:line evidence).
Static-analysis findings; no runtime metrics yet - unit tests + sanitizer runs required before merge.