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Defer object/value decryption to after the object is loaded (Issue #42)

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This commit is contained in:
Michael R Sweet
2023-12-14 16:02:26 -05:00
parent 5d760e7315
commit 7330cc35ba
5 changed files with 233 additions and 96 deletions
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271
pdfio-value.c
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@ -10,6 +10,13 @@
#include "pdfio-private.h"
//
// Local functions...
//
static time_t get_date_time(const char *s);
//
// '_pdfioValueCopy()' - Copy a value to a PDF file.
//
@ -105,6 +112,97 @@ _pdfioValueCopy(pdfio_file_t *pdfdst, // I - Destination PDF file
}
//
// '_pdfioValueDecrypt()' - Decrypt a value.
//
bool // O - `true` on success, `false` on error
_pdfioValueDecrypt(pdfio_file_t *pdf, // I - PDF file
pdfio_obj_t *obj, // I - Object
_pdfio_value_t *v, // I - Value
size_t depth)// I - Depth
{
_pdfio_crypto_ctx_t ctx; // Decryption context
_pdfio_crypto_cb_t cb; // Decryption callback
size_t ivlen; // Number of initialization vector bytes
uint8_t temp[32768]; // Temporary buffer for decryption
size_t templen; // Number of actual data bytes
time_t timeval; // Date/time value
if (depth > PDFIO_MAX_DEPTH)
{
_pdfioFileError(pdf, "Value too deep.");
return (false);
}
switch (v->type)
{
case PDFIO_VALTYPE_ARRAY :
return (_pdfioArrayDecrypt(pdf, obj, v->value.array, depth + 1));
break;
case PDFIO_VALTYPE_DICT :
return (_pdfioDictDecrypt(pdf, obj, v->value.dict, depth + 1));
break;
case PDFIO_VALTYPE_BINARY :
// Decrypt the binary string...
if (v->value.binary.datalen > (sizeof(temp) - 32))
{
_pdfioFileError(pdf, "Unable to read encrypted binary string - too long.");
return (false);
}
ivlen = v->value.binary.datalen;
if ((cb = _pdfioCryptoMakeReader(pdf, obj, &ctx, v->value.binary.data, &ivlen)) == NULL)
return (false);
templen = (cb)(&ctx, temp, v->value.binary.data + ivlen, v->value.binary.datalen - ivlen);
// Copy the decrypted string back to the value and adjust the length...
memcpy(v->value.binary.data, temp, templen);
if (pdf->encryption >= PDFIO_ENCRYPTION_AES_128)
v->value.binary.datalen = templen - temp[templen - 1];
else
v->value.binary.datalen = templen;
break;
case PDFIO_VALTYPE_STRING :
// Decrypt regular string...
templen = strlen(v->value.string);
if (templen > (sizeof(temp) - 33))
{
_pdfioFileError(pdf, "Unable to read encrypted string - too long.");
return (false);
}
ivlen = templen;
if ((cb = _pdfioCryptoMakeReader(pdf, obj, &ctx, (uint8_t *)v->value.string, &ivlen)) == NULL)
return (false);
templen = (cb)(&ctx, temp, (uint8_t *)v->value.string + ivlen, templen - ivlen);
temp[templen] = '\0';
if ((timeval = get_date_time((char *)temp)) != 0)
{
// Change the type to date...
v->type = PDFIO_VALTYPE_DATE;
v->value.date = timeval;
}
else
{
// Copy the decrypted string back to the value...
v->value.string = pdfioStringCreate(pdf, (char *)temp);
}
break;
}
return (true);
}
//
// '_pdfioValueDebug()' - Print the contents of a value.
//
@ -196,6 +294,7 @@ _pdfioValueRead(pdfio_file_t *pdf, // I - PDF file
size_t depth) // I - Depth of value
{
char token[32768]; // Token buffer
time_t timeval; // Date/time value
#ifdef DEBUG
static const char * const valtypes[] =
{
@ -245,73 +344,10 @@ _pdfioValueRead(pdfio_file_t *pdf, // I - PDF file
if ((v->value.dict = _pdfioDictRead(pdf, obj, tb, depth + 1)) == NULL)
return (NULL);
}
else if (!strncmp(token, "(D:", 3))
else if (!strncmp(token, "(D:", 3) && (timeval = get_date_time(token + 1)) != 0)
{
// Possible date value of the form:
//
// (D:YYYYMMDDhhmmssZ)
// (D:YYYYMMDDhhmmss+HH'mm)
// (D:YYYYMMDDhhmmss-HH'mm)
//
int i; // Looping var
struct tm dateval; // Date value
int offset; // Date offset
for (i = 3; i < 17; i ++)
{
if (!isdigit(token[i] & 255))
break;
}
if (i >= 17)
{
if (token[i] == 'Z')
{
i ++;
}
else if (token[i] == '-' || token[i] == '+')
{
if (isdigit(token[i + 1] & 255) && isdigit(token[i + 2] & 255) && token[i + 3] == '\'' && isdigit(token[i + 4] & 255) && isdigit(token[i + 5] & 255))
{
i += 6;
if (token[i] == '\'')
i ++;
}
}
}
if (token[i])
{
// Just a string...
v->type = PDFIO_VALTYPE_STRING;
v->value.string = pdfioStringCreate(pdf, token + 1);
}
else
{
// Date value...
memset(&dateval, 0, sizeof(dateval));
dateval.tm_year = (token[3] - '0') * 1000 + (token[4] - '0') * 100 + (token[5] - '0') * 10 + token[6] - '0' - 1900;
dateval.tm_mon = (token[7] - '0') * 10 + token[8] - '0' - 1;
dateval.tm_mday = (token[9] - '0') * 10 + token[10] - '0';
dateval.tm_hour = (token[11] - '0') * 10 + token[12] - '0';
dateval.tm_min = (token[13] - '0') * 10 + token[14] - '0';
dateval.tm_sec = (token[15] - '0') * 10 + token[16] - '0';
if (token[17] == 'Z')
{
offset = 0;
}
else
{
offset = (token[18] - '0') * 600 + (token[19] - '0') * 60 + (token[20] - '0') * 10 + token[21] - '0';
if (token[17] == '-')
offset = -offset;
}
v->type = PDFIO_VALTYPE_DATE;
v->value.date = mktime(&dateval) + offset;
}
v->type = PDFIO_VALTYPE_DATE;
v->value.date = timeval;
}
else if (token[0] == '(')
{
@ -363,36 +399,6 @@ _pdfioValueRead(pdfio_file_t *pdf, // I - PDF file
*dataptr++ = (unsigned char)d;
}
if (obj && pdf->encryption)
{
// Decrypt the string...
_pdfio_crypto_ctx_t ctx; // Decryption context
_pdfio_crypto_cb_t cb; // Decryption callback
size_t ivlen; // Number of initialization vector bytes
uint8_t temp[32768]; // Temporary buffer for decryption
size_t templen; // Number of actual data bytes
if (v->value.binary.datalen > (sizeof(temp) - 32))
{
_pdfioFileError(pdf, "Unable to read encrypted binary string - too long.");
return (false);
}
ivlen = v->value.binary.datalen;
if ((cb = _pdfioCryptoMakeReader(pdf, obj, &ctx, v->value.binary.data, &ivlen)) == NULL)
return (false);
templen = (cb)(&ctx, temp, v->value.binary.data + ivlen, v->value.binary.datalen - ivlen);
// Copy the decrypted string back to the value and adjust the length...
memcpy(v->value.binary.data, temp, templen);
if (pdf->encryption >= PDFIO_ENCRYPTION_AES_128)
v->value.binary.datalen = templen - temp[templen - 1];
else
v->value.binary.datalen = templen;
}
}
else if (strchr("0123456789-+.", token[0]) != NULL)
{
@ -728,3 +734,76 @@ _pdfioValueWrite(pdfio_file_t *pdf, // I - PDF file
return (false);
}
//
// 'get_date_time()' - Convert PDF date/time value to time_t.
//
static time_t // O - Time in seconds
get_date_time(const char *s) // I - PDF date/time value
{
int i; // Looping var
struct tm dateval; // Date value
int offset; // Date offset
// Possible date value of the form:
//
// (D:YYYYMMDDhhmmssZ)
// (D:YYYYMMDDhhmmss+HH'mm)
// (D:YYYYMMDDhhmmss-HH'mm)
//
for (i = 2; i < 16; i ++)
{
if (!isdigit(s[i] & 255) || !s[i])
break;
}
if (i >= 16)
{
if (s[i] == 'Z')
{
i ++;
}
else if (s[i] == '-' || s[i] == '+')
{
if (isdigit(s[i + 1] & 255) && isdigit(s[i + 2] & 255) && s[i + 3] == '\'' && isdigit(s[i + 4] & 255) && isdigit(s[i + 5] & 255))
{
i += 6;
if (s[i] == '\'')
i ++;
}
}
}
if (s[i])
{
// Just a string...
return (0);
}
// Date value...
memset(&dateval, 0, sizeof(dateval));
dateval.tm_year = (s[2] - '0') * 1000 + (s[3] - '0') * 100 + (s[4] - '0') * 10 + s[5] - '0' - 1900;
dateval.tm_mon = (s[6] - '0') * 10 + s[7] - '0' - 1;
dateval.tm_mday = (s[8] - '0') * 10 + s[9] - '0';
dateval.tm_hour = (s[10] - '0') * 10 + s[11] - '0';
dateval.tm_min = (s[12] - '0') * 10 + s[13] - '0';
dateval.tm_sec = (s[14] - '0') * 10 + s[15] - '0';
if (s[16] == 'Z')
{
offset = 0;
}
else
{
offset = (s[17] - '0') * 600 + (s[18] - '0') * 60 + (s[19] - '0') * 10 + s[20] - '0';
if (s[16] == '-')
offset = -offset;
}
return (mktime(&dateval) + offset);
}