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Fix encrypted PDF files with P values >2^31-1.

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Michael R Sweet 2025-04-20 17:34:38 -04:00
parent 29eea131b9
commit d7f3c64f63
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GPG Key ID: BE67C75EC81F3244
3 changed files with 25 additions and 12 deletions
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1
CHANGES.md
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@ -7,6 +7,7 @@ v1.5.3 - YYYY-MM-DD
- Fixed decryption of PDF files "protected" by 40-bit RC4 (Issue #42)
- Fixed decryption of UTF-16 strings (Issue #42)
- Fixed decryption of PDF files with large permission values.
v1.5.2 - 2025-04-12

12
pdfio-crypto.c
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@ -582,6 +582,7 @@ _pdfioCryptoUnlock(
file_idlen; // Length of file ID
_pdfio_md5_t md5; // MD5 context
uint8_t file_digest[16]; // MD5 digest of file ID and pad
double p; // Permissions value as a double
// See if we support the type of encryption specified by the Encrypt object
@ -689,8 +690,13 @@ _pdfioCryptoUnlock(
// Grab the remaining values we need to unlock the PDF...
pdf->file_keylen = (size_t)(length / 8);
pdf->permissions = (pdfio_permission_t)pdfioDictGetNumber(encrypt_dict, "P");
p = pdfioDictGetNumber(encrypt_dict, "P");
PDFIO_DEBUG("_pdfioCryptoUnlock: P=%.0f\n", p);
if (p < 0x7fffffff) // Handle integers > 2^31-1
pdf->permissions = (pdfio_permission_t)p;
else
pdf->permissions = (pdfio_permission_t)(p - 4294967296.0);
PDFIO_DEBUG("_pdfioCryptoUnlock: permissions=%d\n", pdf->permissions);
owner_key = pdfioDictGetBinary(encrypt_dict, "O", &owner_keylen);
@ -993,9 +999,11 @@ make_owner_key(
// Encrypt 20 times...
uint8_t encrypt_key[16]; // RC4 encryption key
for (i = 0; i < 20; i ++)
for (i = 20; i > 0;)
{
// XOR each byte in the digest with the loop counter to make a key...
i --;
for (j = 0; j < sizeof(encrypt_key); j ++)
encrypt_key[j] = (uint8_t)(digest[j] ^ i);

24
pdfio-value.c
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@ -397,18 +397,22 @@ _pdfioValueRead(pdfio_file_t *pdf, // I - PDF file
ret = v;
}
else if ((timeval = get_date_time(token + 1)) != 0)
{
v->type = PDFIO_VALTYPE_DATE;
v->value.date = timeval;
ret = v;
}
else if (token[0] == '(')
{
// String
v->type = PDFIO_VALTYPE_STRING;
v->value.string = pdfioStringCreate(pdf, token + 1);
ret = v;
if ((timeval = get_date_time(token + 1)) != 0)
{
// Date
v->type = PDFIO_VALTYPE_DATE;
v->value.date = timeval;
ret = v;
}
else
{
// String
v->type = PDFIO_VALTYPE_STRING;
v->value.string = pdfioStringCreate(pdf, token + 1);
ret = v;
}
}
else if (token[0] == '/')
{