pgppacket.c

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#include "config.h"
#include <stdbool.h>
#include <stdio.h>
#include "mutt/lib.h"
#include "pgppacket.h"
 
#define CHUNK_SIZE 1024 
 
static unsigned char *PacketBuf = NULL; 
static size_t PacketBufLen = 0;         
 
static int read_material(size_t material, size_t *used, FILE *fp)
{
  if ((*used + material) >= PacketBufLen)
  {
    PacketBufLen = *used + material + CHUNK_SIZE;
 
    mutt_mem_realloc(&PacketBuf, PacketBufLen);
  }
 
  if (fread(PacketBuf + *used, 1, material, fp) < material)
  {
    mutt_perror("fread");
    return -1;
  }
 
  *used += material;
  return 0;
}
 
unsigned char *pgp_read_packet(FILE *fp, size_t *len)
{
  size_t used = 0;
  LOFF_T startpos;
  unsigned char ctb;
  unsigned char b;
  size_t material;
 
  startpos = ftello(fp);
  if (startpos < 0)
    return NULL;
 
  if (PacketBufLen == 0)
  {
    PacketBufLen = CHUNK_SIZE;
    PacketBuf = mutt_mem_malloc(PacketBufLen);
  }
 
  if (fread(&ctb, 1, 1, fp) < 1)
  {
    if (!feof(fp))
      mutt_perror("fread");
    goto bail;
  }
 
  if (!(ctb & 0x80))
  {
    goto bail;
  }
 
  if (ctb & 0x40) /* handle PGP 5.0 packets. */
  {
    bool partial = false;
    PacketBuf[0] = ctb;
    used++;
 
    do
    {
      if (fread(&b, 1, 1, fp) < 1)
      {
        mutt_perror("fread");
        goto bail;
      }
 
      if (b < 192)
      {
        material = b;
        partial = false;
      }
      else if (b <= 223)
      {
        material = (b - 192) * 256;
        if (fread(&b, 1, 1, fp) < 1)
        {
          mutt_perror("fread");
          goto bail;
        }
        material += b + 192;
        partial = false;
      }
      else if (b < 255)
      {
        material = 1 << (b & 0x1f);
        partial = true;
      }
      else /* b == 255 */
      {
        unsigned char buf[4];
        if (fread(buf, 4, 1, fp) < 1)
        {
          mutt_perror("fread");
          goto bail;
        }
        material = (size_t) buf[0] << 24;
        material |= buf[1] << 16;
        material |= buf[2] << 8;
        material |= buf[3];
        partial = false;
      }
 
      if (read_material(material, &used, fp) == -1)
        goto bail;
 
    } while (partial);
  }
  else /* Old-Style PGP */
  {
    int bytes = 0;
    PacketBuf[0] = 0x80 | ((ctb >> 2) & 0x0f);
    used++;
 
    switch (ctb & 0x03)
    {
      case 0:
      {
        if (fread(&b, 1, 1, fp) < 1)
        {
          mutt_perror("fread");
          goto bail;
        }
 
        material = b;
        break;
      }
 
      case 1:
        bytes = 2;
        FALLTHROUGH;
 
      case 2:
      {
        if (!bytes)
          bytes = 4;
 
        material = 0;
 
        for (int i = 0; i < bytes; i++)
        {
          if (fread(&b, 1, 1, fp) < 1)
          {
            mutt_perror("fread");
            goto bail;
          }
 
          material = (material << 8) + b;
        }
        break;
      }
 
      default:
        goto bail;
    }
 
    if (read_material(material, &used, fp) == -1)
      goto bail;
  }
 
  if (len)
    *len = used;
 
  return PacketBuf;
 
bail:
 
  (void) mutt_file_seek(fp, startpos, SEEK_SET);
  return NULL;
}
 
void pgp_release_packet(void)
{
  PacketBufLen = 0;
  FREE(&PacketBuf);
}